This chapter introduces the importance and necessity of milk testing in the dairy industry. It explains how testing ensures the quality, safety, and fairness in trade of milk and milk products. The chapter highlights the objectives of milk testing, such as detecting adulteration, assessing nutritive value, and meeting regulatory standards.
Overview:
· The role of milk testing in protecting consumer health and building trust.
· Historical development of milk quality control practices.
· Types of tests (physical, chemical, microbiological, and instrumental).
· The significance of milk testing in payment systems at collection centres and in quality assurance programs.
This introduction sets the foundation for understanding the subsequent chapters, which detail the methods, procedures, and interpretation of various milk tests.
Milk testing is critical for ensuring the safety, quality, and nutritional value of milk and dairy products. It plays a vital role in public health, regulatory compliance, and maintaining consumer trust in the dairy industry. Below, I outline the importance of milk testing, its key aspects, and provide references to recent books and journals for further reading.
1. Ensuring Food Safety:
Milk is a nutrient-rich medium, making it susceptible to microbial contamination (e.g., Escherichia coli, Salmonella, Listeria). Testing identifies pathogens, preventing foodborne illnesses.
Detects chemical contaminants like antibiotics, pesticides, or aflatoxins, which can pose health risks if present above permissible limits.
Ensures pasteurization efficacy by testing for alkaline phosphatase activity, confirming the destruction of harmful bacteria.
2. Quality Assurance:
Tests for compositional attributes (fat, protein, lactose, and total solids) ensure milk meets industry standards and consumer expectations.
Detects adulteration (e.g., water, urea, or detergents), which compromises quality and nutritional value.
Sensory and physical tests (e.g., pH, titratable acidity) assess freshness and shelf-life stability.
3. Regulatory Compliance:
Milk testing ensures compliance with national and international standards, such as those set by the FDA, Codex Alimentarius, or FSSAI (India).
Verifies labelling claims (e.g., organic, low-fat) and prevents fraudulent practices.
Facilitates export/import by meeting stringent safety and quality requirements of global markets.
4. Economic Impact:
Accurate testing supports fair pricing by determining milk composition (fat and solids-not-fat content), which influences farmer payments.
Prevents economic losses due to spoilage or rejection of contaminated batches.
Enhances consumer confidence, boosting market demand and brand reputation.
5. Public Health and Nutrition:
Ensures milk is free from zoonotic pathogens (e.g., Mycobacterium bovis) that can transmit diseases like tuberculosis.
Verifies nutritional content, ensuring milk delivers essential nutrients like calcium, vitamin D, and protein.
Monitors residues of veterinary drugs, protecting consumers from potential long-term health effects.
6. Environmental and Ethical Considerations:
Testing for antibiotic residues supports responsible use of antimicrobials, reducing the risk of antimicrobial resistance (AMR).
Detects environmental pollutants, ensuring sustainable dairy farming practices.
7. Technological Advancements in Testing:
Modern methods like PCR, ELISA, and infrared spectroscopy enable rapid, accurate testing, improving efficiency in large-scale dairy operations.
Emerging technologies, such as biosensors and AI-driven analytics, enhance real-time monitoring of milk quality.
Milk quality control in India is critical due to the country's position as the world's largest milk producer, contributing over 20% of global milk production, and the significant role dairy plays in the economy, nutrition, and livelihoods. The objectives of milk quality control in India are driven by public health, economic, and regulatory needs, addressing challenges like adulteration, contamination, and inconsistent standards.
Key objectives of Milk Quality Control:
1. Ensuring Public Health and Safety:
Milk is a staple in Indian diets, consumed by millions daily. Poor quality or adulterated milk (e.g., with water, detergents, urea, or harmful chemicals) poses health risks, including foodborne illnesses and long-term toxicity.
Quality control ensures milk is free from pathogens (e.g., E. coli, Salmonella), antibiotics, pesticides, and aflatoxins, protecting consumers, especially vulnerable groups like children and the elderly.
Example: The Food Safety and Standards Authority of India (FSSAI) set standards to detect and prevent adulteration, such as through tests for neutralizers or synthetic milk.
2. Preventing Adulteration and Fraud:
Adulteration is a widespread issue in India due to high demand, supply chain gaps, and economic incentives for dilution or substitution. Common adulterants include water, starch, or vegetable fats, which reduce nutritional value.
Quality control aims to detect and deter such practices through rigorous testing (e.g., lactometer tests for density, fat content analysis) and enforce compliance with standards.
Example: The 2018 FSSAI National Milk Safety and Quality Survey found 41% of milk samples non-compliant, highlighting the need for stringent controls.
3. Enhancing Nutritional Value:
Milk is a key source of protein, calcium, and vitamins in India, where malnutrition remains a concern. Quality control ensures milk retains its nutritional integrity, free from dilution or contamination that could reduce its value.
Objective: Maintain prescribed standards for fat (e.g., 3.5% for cow milk) and solids-not-fat (SNF) content (e.g., 8.5%) as per FSSAI norms.
4. Supporting Economic Growth and Farmer Livelihoods:
Dairy supports over 80 million rural households in India, with cooperatives like Amul playing a major role. Poor milk quality can lead to rejection of supplies, reduced prices, and economic losses for farmers.
Quality control ensures fair pricing based on milk composition (fat and SNF content), encouraging farmers to maintain high standards and boosting trust in the supply chain.
Example: Milk collection centres use automated analysers to test quality, ensuring transparency and fair payments.
5. Promoting Export Potential and Global Competitiveness:
India exports dairy products like skimmed milk powder and ghee, but global markets demand high safety and quality standards. Quality control aligns Indian milk with international norms (e.g., Codex Alimentarius), enhancing export opportunities.
Objective: Meet stringent requirements for microbial safety, residue limits, and packaging to compete in markets like the EU or Middle East.
6. Strengthening Consumer Confidence and Market Trust:
Frequent reports of milk adulteration erode consumer trust, impacting dairy sales. Quality control, backed by certifications and testing, reassures consumers about safety and authenticity.
Example: Brands and cooperatives use quality certifications (e.g., FSSAI’s “A1” mark) to build trust and differentiate their products.
7. Regulatory Compliance and Standardization:
India’s diverse dairy sector, with unorganized (70%) and organized (30%) segments, faces inconsistent quality practices. Quality control enforces uniform standards across the supply chain, from farm to table.
Objective: Ensure compliance with FSSAI’s Food Safety and Standards (Milk and Milk Products) Regulations, 2011, covering raw, pasteurized, and processed milk.
Example: Mandatory pasteurization and testing for microbial load at dairy plants.
8. Reducing Economic Losses from Spoilage:
India lacks adequate cold chain infrastructure, leading to spoilage and quality degradation, especially in rural areas. Quality control includes monitoring storage, transport, and processing to minimize losses.
Objective: Implement tests for acidity, temperature stability, and shelf-life to ensure milk remains safe and usable.
Challenges Specific to India:
Unorganized Sector: Small-scale vendors and lack of testing facilities make quality enforcement difficult.
Adulteration Incentives: High milk prices and supply shortages drive unethical practices.
Infrastructure Gaps: Limited access to chilling units and testing labs in rural areas.
Awareness: Farmers and consumers often lack knowledge about quality standards.
Milk quality testing is essential to ensure safety, nutritional value, and compliance with standards, particularly in India, where adulteration and contamination are significant concerns. Tests for milk quality can be classified based on their purpose, such as detecting adulteration, assessing microbial safety, evaluating chemical composition, or determining physical properties. Below is a comprehensive classification of milk quality tests, categorized by their objectives and types, with relevance to the Indian context (e.g., FSSAI standards).
Classification of Milk Quality Tests
1. Organoleptic Tests
These tests evaluate the sensory attributes of milk using human senses to detect basic quality issues.
Purpose: Assess appearance, smell, taste, and texture to identify spoilage or abnormalities.
Examples:
Visual Inspection: Checks for colour (e.g., creamy white for cow milk), presence of clots, or foreign particles.
Odour Test: Detects off-odours (e.g., sour, rancid, or chemical smells) indicating spoilage or adulteration.
Taste Test: Identifies abnormal flavours (e.g., bitterness due to bacterial growth).
Relevance in India: Used at milk collection canters for initial screening but limited by subjectivity.
2. Physical Tests
These tests measure physical properties of milk to assess quality and detect dilution or adulteration.
Purpose: Evaluate density, temperature, and other physical characteristics.
Examples:
Lactometer Test: Measures specific gravity (density) to detect water adulteration (normal range: 1.028–1.032 g/cm³ for cow milk).
Freezing Point Depression Test: Detects added water by measuring the freezing point (normal: -0.520 to -0.550°C).
Temperature Check: Ensures milk is stored at safe temperatures (below 4°C) to prevent spoilage.
Clot-on-Boiling Test: Checks for heat stability and acidity; clotting indicates high acidity or microbial activity.
Relevance in India: Lactometer tests are widely used in cooperatives (e.g., Amul) to detect water adulteration, a common issue.
3. Chemical/Compositional Tests
These tests analyse the chemical composition of milk to ensure nutritional quality and detect adulterants or contaminants.
Purpose: Measure fat, solids-not-fat (SNF), protein, lactose, and detect chemical adulterants or residues.
Subcategories:
Proximate Analysis:
Fat Content Test: Uses Gerber or Babcock methods to measure fat percentage (FSSAI standard: min. 3.5% for cow milk).
SNF Test: Determines solids-not-fat (e.g., proteins, lactose) using gravimetric methods or lactometers (FSSAI: min. 8.5% for cow milk).
Protein Content: Kjeldahl method or infrared spectroscopy to measure protein levels.
Lactose Content: Polarimetry or enzymatic methods to quantify lactose.
Adulterant Detection:
Urea Test: Detects added urea using p-dimethyl-amino-benzaldehyde (DMAB) reagent (colour change indicates presence).
Starch Test: Iodine test to detect starch adulteration (blue colour confirms starch).
Sugar/Sucrose Test: Resorcinol test for added sugars (red colour indicates presence).
Neutralizer Test: Rosalic acid test to detect sodium hydroxide or carbonates used to mask acidity.
Detergent Test: Methylene blue or turbidity tests to identify detergent residues.
Formalin Test: Hehner’s test for formalin preservation (violet ring formation).
Hydrogen Peroxide Test: Paraphenylenediamine test for peroxide additives.
Contaminant Analysis:
Aflatoxin M1 Test: ELISA or HPLC to detect aflatoxin M1 from contaminated feed (FSSAI limit: 0.5 µg/kg).
Antibiotic Residue Test: Charm ROSA or LC-MS to detect residues like tetracycline or beta-lactams.
Pesticide Residue Test: Gas chromatography-mass spectrometry (GC-MS) for organophosphates or organochlorines.
Heavy Metal Test: Atomic absorption spectroscopy for lead, cadmium, or arsenic.
Relevance in India: FSSAI’s 2018 Milk Survey highlighted the need for tests like aflatoxin M1 and antibiotic residue analysis due to non-compliance. Gerber method is common in dairy plants for fat testing.
4. Microbiological Tests
These tests assess microbial load to ensure milk safety and shelf-life.
Purpose: Detect pathogens, spoilage organisms, or total bacterial count.
Examples:
Total Plate Count (TPC): Measures total viable bacteria (FSSAI limit for pasteurized milk: <30,000 CFU/mL).
Coliform Count: Detects faecal contamination using violet-red bile agar (FSSAI limit: <10 CFU/mL for pasteurized milk).
Pathogen Detection:
E. coli Test: Selective media (e.g., MacConkey agar) or PCR for Escherichia coli.
Salmonella Test: Enrichment culture or ELISA for Salmonella spp.
Listeria Test: Selective media or PCR for Listeria monocytogenes.
Staphylococcus aureus Test: Baird-Parker agar for coagulase-positive staphylococci.
Somatic Cell Count (SCC): Measures white blood cells to detect mastitis in cows (high SCC indicates infection).
Methylene Blue Reduction Test (MBRT): Assesses microbial load by measuring dye reduction time (faster reduction indicates higher bacterial activity).
Relevance in India: High microbial loads due to poor cold chain infrastructure necessitate TPC and coliform tests. Mastitis detection via SCC is critical for farmer-level quality control.
5. Biochemical Tests
These tests evaluate milk’s biochemical properties to assess freshness, spoilage, or processing quality.
Purpose: Measure acidity, enzyme activity, or spoilage indicators.
Examples:
Titratable Acidity Test: Measures lactic acid content to assess freshness (normal: 0.13–0.16% lactic acid).
pH Test: Determines milk acidity (normal: 6.6–6.8); lower pH indicates bacterial fermentation.
Phosphatase Test: Checks pasteurization efficiency by detecting alkaline phosphatase (inactive in properly pasteurized milk).
Peroxidase Test: Verifies high-temperature pasteurization (e.g., UHT milk).
Alcohol Test: Assesses milk stability for processing; precipitation indicates high acidity or salt imbalance.
Relevance in India: Phosphatase tests are mandatory under FSSAI to ensure proper pasteurization, addressing public health concerns.
6. Instrumental/Analytical Tests
These advanced tests use specialized equipment for precise quality assessment, often for regulatory compliance or export.
Purpose: Provide accurate, automated analysis of composition, contaminants, or authenticity.
Examples:
Infrared Spectroscopy (e.g., Milko Scan): Simultaneously measures fat, protein, lactose, and SNF content.
High-Performance Liquid Chromatography (HPLC): Detects aflatoxins, antibiotics, or vitamins.
Gas Chromatography-Mass Spectrometry (GC-MS): Identifies pesticide or volatile compound residues.
Polymerase Chain Reaction (PCR): Detects specific pathogens or species authenticity (e.g., cow vs. buffalo milk).
Electronic Nose/Tongue: Detects off-flavours or adulterants through chemical profiling.
Relevance in India: Used in large dairy plants (e.g., Mother Dairy) and FSSAI-accredited labs for export compliance and contaminant testing.
7. Shelf-Life and Stability Tests
These tests assess milk’s durability and quality during storage and transport.
Purpose: Ensure milk remains safe and palatable until consumption.
Examples:
Keeping Quality Test: Incubates milk at controlled temperatures to predict shelf-life.
Mosely Test: Measures microbial growth in pasteurized milk over time.
Rancidity Test: Detects lipid oxidation (e.g., peroxide value) affecting flavours.
Relevance in India: Critical due to limited cold chain infrastructure, especially in rural areas.
Sampling techniques and precautions for milk quality testing are critical to ensure accurate, representative, and uncontaminated samples, especially in India, where milk quality control addresses issues like adulteration, microbial contamination, and compliance with Food Safety and Standards Authority of India (FSSAI) regulations. Proper sampling ensures the reliability of test results, which are used to assess milk safety, nutritional quality, and regulatory compliance. Below, I provide a detailed explanation of the sampling techniques and precautions for milk, followed by authentic and recent references from books, journals, and authoritative sources.
Sampling Techniques for Milk
Sampling techniques for milk are designed to obtain a representative portion from a bulk quantity (e.g., cans, tanks, or retail packages) while minimizing contamination and preserving the sample’s integrity. The techniques vary based on the milk source, container type, and testing purpose (e.g., chemical, microbiological, or physical). Below are the key sampling techniques:
1. Single Sampling from Small Containers (e.g., Cans, Bottles)
Description: A single, well-mixed sample is taken from a small container (e.g., milk can, retail bottle) after thorough mixing to ensure homogeneity.
Procedure:
Stir or shake the container vigorously (manually or mechanically) to distribute fat and solids evenly.
Use a clean, sterile dipper, pipette, or sampling tube to collect 100–250 mL of milk.
Transfer to a sterile, airtight container (e.g., glass or food-grade plastic bottle).
Application: Common at milk collection centres in India for testing fat and solids-not-fat (SNF) content.
Example: Used for milk cans delivered by farmers to cooperatives like Amul.
2. Composite Sampling from Bulk Containers (e.g., Tanks, Silos)
Description: Multiple subsamples are taken from different parts of a large container and combined to form a composite sample, ensuring representation of the entire batch.
Procedure:
Agitate the milk tank mechanically (e.g., using a stirrer) for 5–10 minutes to ensure uniformity.
Collect subsamples (e.g., 50–100 mL each) from top, middle, and bottom layers using a sterile sampling tube or dipper.
Mix subsamples in a sterile container to create a composite sample of 250–500 mL.
Application: Used in dairy plants for testing raw or processed milk in large storage tanks.
Example: Applied in dairy processing units to comply with FSSAI’s microbiological and chemical testing requirements.
3. Continuous Sampling (e.g., During Milking or Processing)
Description: Samples are collected at regular intervals during milking, transportation, or processing to monitor quality over time.
Procedure:
Use an automated inline sampler or manual sampling valve to collect small volumes (e.g., 10–20 mL) at fixed intervals.
Combine samples in a sterile container to form a representative sample.
Ensure equipment is sanitized before and after sampling.
Application: Used in large-scale dairies to monitor milk quality during pasteurization or UHT processing.
Example: Implemented in modern dairy plants like Mother Dairy for real-time quality control.
4. Aseptic Sampling for Microbiological Testing
Description: A specialized technique to collect samples without introducing microbial contamination, critical for pathogen or total plate count (TPC) testing.
Procedure:
Sterilize sampling equipment (e.g., needles, syringes, or valves) with 70% ethanol or heat.
Collect 100–200 mL of milk directly into a pre-sterilized container under aseptic conditions (e.g., using a laminar flow hood if feasible).
Seal the container immediately to prevent airborne contamination.
Application: Essential for detecting pathogens like E. coli or Salmonella in raw or pasteurized milk.
Example: Mandated by FSSAI for microbiological compliance in dairy plants.
5. Random Sampling for Retail Milk
Description: Random samples are taken from retail packages (e.g., pouches, tetra packs) to assess quality at the consumer level.
Procedure:
Select packages randomly from different batches or lots in a retail setting.
Use a sterile syringe or cut the package aseptically to extract 100–250 mL.
Store samples in sterile containers under refrigerated conditions (below 4°C).
Application: Used by FSSAI during market surveillance or festive season drives (e.g., Deepavali) to check adulteration or microbial safety.
Example: Applied in FSSAI’s 2018 National Milk Safety and Quality Survey.
Precautions for Milk Sampling
Precautions are critical to prevent contamination, ensure sample integrity, and obtain accurate test results. The following precautions are standardized based on FSSAI guidelines, Codex Alimentarius, and industry best practices:
1. Use of Sterile Equipment
All sampling tools (e.g., dippers, pipettes, syringes, containers) must be sterilized using autoclaving (121°C for 15 minutes), 70% ethanol, or boiling water.
For microbiological sampling, use pre-sterilized, single-use containers to avoid cross-contamination.
Rationale: Prevents introduction of extraneous microbes or chemicals that could skew results (e.g., false positives in TPC tests).
2. Proper Mixing Before Sampling
Thoroughly mix milk (manually or mechanically) to ensure uniform distribution of fat, SNF, and potential contaminants.
Avoid excessive agitation that could introduce air or cause foaming, which may affect chemical tests.
Rationale: Ensures the sample is representative, especially for fat and SNF testing, as fat tends to separate.
3. Temperature Control
Maintain milk samples at 0–4°C immediately after collection to prevent microbial growth or chemical degradation.
Use insulated coolers with ice packs for transport to testing labs, ensuring analysis within 24 hours (or 6 hours for microbiological tests).
Rationale: High temperatures can increase bacterial load or alter acidity, affecting microbiological and biochemical test results.
4. Aseptic Handling
Wear sterile gloves and, if possible, work in a clean environment (e.g., near a flame or in a laminar flow hood) for microbiological sampling.
Avoid touching the inner surfaces of sampling containers or tools.
Rationale: Minimizes contamination, critical for detecting pathogens like Salmonella or Listeria.
5. Correct Labelling and Documentation
Label samples with details like date, time, source (e.g., farm, tank, retail), batch number, and collector’s name.
Maintain a chain-of-custody record to ensure traceability.
Rationale: Prevents mix-ups and ensures compliance with FSSAI’s traceability requirements.
6. Avoiding Cross-Contamination
Use separate sampling tools for each batch or container to avoid cross-contamination.
Clean and sanitize sampling valves or ports in tanks before and after use.
Rationale: Prevents carryover of adulterants, microbes, or residues between samples.
7. Sample Size and Storage
Collect sufficient sample volume (e.g., 250–500 mL for chemical tests, 100–200 mL for microbiological tests) to allow repeat testing if needed.
Store samples in airtight, food-grade containers (glass or high-density polyethylene) to prevent leakage or contamination.
Rationale: Ensures enough material for multiple tests and preserves sample integrity.
8. Compliance with Regulatory Standards
Follow FSSAI’s sampling protocols as outlined in the Manual of Methods of Analysis of Foods: Milk and Milk Products (2025).
Adhere to Codex Alimentarius guidelines for export-oriented testing to ensure international compliance.
Rationale: Ensures legal and regulatory validity of test results.
9. Training of Personnel
Train samplers on proper techniques, hygiene, and safety protocols to minimize errors.
Conduct regular audits of sampling procedures at collection canters and dairy plants.
Rationale: Human error is a major source of sampling inaccuracies, especially in India’s unorganized sector.
10. Avoiding Adulteration During Sampling
Monitor sampling to prevent intentional adulteration (e.g., adding water or chemicals) by farmers or handlers.
Use tamper-proof containers and seals for sample transport.
Rationale: Addresses India’s prevalent adulteration issue, as highlighted in the 2018 FSSAI survey (41% non-compliant samples).
This chapter deals with the physical methods of testing milk, which are quick and simple techniques used to assess its quality, purity, and freshness. Physical tests are often the first line of evaluation at milk collection canters and laboratories.
The chapter covers:
· Organoleptic examination – assessing colour, taste, odour, and appearance.
· Temperature measurement – for checking freshness and storage conditions.
· Specific gravity/density test (Lactometer test) – for detecting adulteration and assessing composition.
· Viscosity and consistency checks – indicating changes in quality.
· Freezing point test – for detecting dilution with water.
These tests provide preliminary information on whether milk meets quality standards and whether further chemical or microbiological analysis is required.
Organoleptic evaluation is typically performed by trained personnel under controlled conditions to ensure consistency and reliability. The process involves four main sensory assessments: appearance, smell, taste, and texture. Below are the detailed steps, precautions, and considerations for each.
1. Preparation for Organoleptic Evaluation
Trained Evaluators: Use personnel trained in sensory analysis to recognize normal and abnormal milk characteristics. Training should include exposure to fresh, spoiled, and adulterated milk samples.
Controlled Environment: Conduct evaluations in a clean, well-lit, odour-free room with a temperature of 20–25°C to avoid external sensory interference.
Sample Preparation:
Collect a representative sample (100–250 mL) using proper sampling techniques (e.g., single or composite sampling, as described in previous responses).
Store samples at 4–7°C and evaluate within 6 hours of collection to prevent spoilage.
Warm samples to 15–20°C before evaluation to enhance sensory perception (especially for smell and taste).
Equipment: Use clean, odour-free glass or stainless-steel containers for sample presentation. Avoid plastic containers, which may impart odours.
Precautions:
Ensure evaluators avoid strong perfumes, smoking, or consuming spicy foods before testing to prevent sensory bias.
Cleanse the palate with water or plain crackers between samples to avoid carryover flavours.
2. Sensory Assessment Procedures
The organoleptic evaluation is conducted systematically, assessing each sensory attribute in sequence to detect deviations from expected milk quality.
a. Appearance (Visual Inspection)
Procedure:
Pour 50–100 mL of milk into a transparent glass container or hold the sample against a white background under good lighting (preferably natural or neutral light).
Observe for:
Colour: Fresh cow milk should be creamy white; buffalo milk is slightly whiter. Abnormal colours (e.g., yellowish, bluish, or reddish tints) may indicate spoilage, adulteration, or contamination.
Clarity: Check for homogeneity and absence of foreign particles, clots, or sediments. Cloudy milk may indicate microbial growth or adulteration (e.g., starch).
Consistency: Note if the milk appears watery (possible water adulteration) or overly thick (possible additives like starch or flour).
Expected Characteristics:
Cow milk: Creamy white, opaque, no visible particles.
Buffalo milk: Slightly whiter, creamier texture.
Abnormalities:
Yellowish tint: Oxidation or bacterial growth.
Bluish hue: Water adulteration or Pseudomonas contamination.
Clots/Sediments: Microbial spoilage or physical contaminants.
Precautions:
Use clean containers to avoid false positives from container residues.
Avoid direct sunlight, which may alter perceived colour.
b. Smell (Odour Assessment)
Procedure:
Pour 50 mL of milk into a clean glass or cup, warmed to 15–20°C for optimal odour release.
Gently swirl the sample to release volatiles, then sniff the headspace immediately above the milk surface.
Note the odour intensity and character:
Normal Odour: Fresh milk has a mild, slightly sweet, or creamy odour.
Abnormal Odours:
Sour/acidic: Lactic acid from bacterial fermentation (e.g., Lactobacillus).
Rancid: Lipolysis due to lipase activity or improper storage.
Chemical: Adulterants like detergents, formalin, or urea.
Burnt: Overheating during pasteurization.
Feed-like: Strong feed odours (e.g., silage) from cow diet.
Precautions:
Avoid prolonged exposure to air, which may mask odours or introduce external smells.
Evaluate each sample quickly (within 10–15 seconds) to capture initial impressions.
Use a separate container for each sample to prevent cross-contamination of odours.
c. Taste
Procedure:
Take a small sip (5–10 mL) of milk, warmed to 15–20°C, and roll it over the tongue for 5–10 seconds before swallowing or spitting out.
Assess the taste profile:
Normal Taste: Fresh milk is mildly sweet, creamy, and slightly rich, with no aftertaste.
Abnormal Tastes:
Sour: High acidity from microbial growth.
Bitter: Proteolysis or rancidity due to bacterial enzymes.
Salty: High mineral content or mastitis in cows.
Chemical: Adulterants like urea, neutralizers, or detergents.
Metallic: Contamination from equipment or oxidation.
Rinse the mouth with water between samples to reset the palate.
Precautions:
Taste testing is optional and should only be conducted if the milk is confirmed safe (e.g., free from pathogens or harmful adulterants) via prior microbiological or chemical tests.
Avoid taste testing in cases of suspected spoilage or chemical adulteration to prevent health risks.
Limit the number of samples per session (e.g., 5–10) to avoid sensory fatigue.
d. Texture (Mouthfeel)
Procedure:
During taste evaluation, assess the milk’s texture or mouthfeel by noting its consistency and smoothness.
Expected characteristics:
Normal Texture: Smooth, creamy, and slightly viscous (varies by fat content; buffalo milk is creamier than cow milk).
Abnormal Textures:
Watery: Dilution with water or low fat/SNF content.
Gritty: Presence of undissolved adulterants (e.g., starch, flour).
Slimy: Microbial growth (e.g., Pseudomonas or coliforms).
Curdled: High acidity or protein denaturation.
Precautions:
Ensure the sample is well-mixed to avoid false impressions of texture due to fat separation.
Combine texture assessment with visual inspection to confirm findings (e.g., watery texture with cloudy appearance).
3. Scoring and Interpretation
Scoring System:
Assign scores (e.g., 1–5 or 1–10) for each attribute based on intensity and acceptability:
Appearance: 1 (unacceptable, e.g., clots) to 5 (ideal, creamy white).
Smell: 1 (strong off odour) to 5 (mild, creamy).
Taste: 1 (bitter/chemical) to 5 (sweet, creamy).
Texture: 1 (slimy/watery) to 5 (smooth, creamy).
Total scores can be used to classify milk as acceptable, borderline, or rejected.
Interpretation:
High scores (e.g., >80% of maximum) indicate fresh, high-quality milk.
Low scores or specific abnormalities (e.g., sour smell, watery texture) trigger further testing (e.g., microbiological for spoilage, chemical for adulteration).
Indian Context:
FSSAI’s Manual of Methods of Analysis of Foods: Milk and Milk Products (2025) recommend organoleptic evaluation as a preliminary step before advanced testing.
Common issues in India include watery appearance (water adulteration), chemical odours (urea, detergents), and sour tastes (poor cold chain).
4. Precautions and Considerations
Hygiene: Ensure all containers and tools are cleaned and sanitized to avoid introducing odours or contaminants.
Sample Integrity: Evaluate samples promptly after collection and maintain cold storage (4°C) to prevent spoilage before testing.
Evaluator Health: Exclude evaluators with colds, allergies, or other conditions that impair sensory perception.
Subjectivity: Use multiple evaluators (e.g., 3–5) to reduce bias and average scores for consistency.
Safety: Avoid taste testing if preliminary tests (e.g., visual, smell) suggest spoilage or adulteration, as per FSSAI guidelines.
Documentation: Record observations with details (e.g., sample ID, date, evaluator name) for traceability, as required by FSSAI.
Limitations: Organoleptic evaluation is subjective and should be complemented by objective tests (e.g., lactometer for adulteration, TPC for microbial load).
5. Applications in India
Milk Collection Centres: Used by cooperatives (e.g., Amul, Mother Dairy) to quickly screen raw milk for freshness and adulteration before acceptance.
Dairy Processing: Employed to check pasteurized or processed milk for off-flavours or processing defects (e.g., burnt flavours from overheating).
Regulatory Surveillance: FSSAI uses organoleptic evaluation during market surveys (e.g., 2018 National Milk Safety and Quality Survey) to identify substandard milk.
Consumer Protection: Helps detect adulteration (e.g., water, starch) and spoilage, addressing public health concerns in India’s dairy sector.
Temperature measurement is a straightforward but essential physical test to assess milk’s storage conditions, freshness, and safety. It is typically conducted at various stages of the dairy supply chain, including collection, transport, storage, and processing. The goal is to ensure milk is maintained at safe temperatures (e.g., below 4°C for raw milk, 4–7°C for pasteurized milk) to prevent microbial proliferation and spoilage.
1. Equipment for Temperature Measurement
The choice of equipment depends on the setting (e.g., farm, collection canter, dairy plant) and required precision. Common tools include:
Digital Thermometers: Portable, battery-operated devices with a probe for quick and accurate readings (accuracy: ±0.1°C).
Infrared Thermometers: Non-contact devices that measure surface temperature, suitable for rapid checks but less accurate for bulk milk.
Glass Mercury or Alcohol Thermometers: Traditional, less common due to safety concerns (mercury) but still used in some rural settings (accuracy: ±0.5°C).
Thermocouples: Advanced sensors used in automated dairy systems for continuous monitoring (accuracy: ±0.1°C).
Data Loggers: Devices that record temperature over time, used in transport or storage tanks to ensure compliance with cold chain standards.
Automated Inline Sensors: Integrated into milking machines or processing lines for real-time temperature monitoring in large dairies.
Indian Context: Digital thermometers and thermocouples are widely used in cooperatives (e.g., Amul, Mother Dairy) and FSSAI-accredited labs, while glass thermometers are still prevalent in rural collection canters due to cost-effectiveness.
2. Procedure for Measuring Milk Temperature
The procedure varies slightly based on the milk source (e.g., cans, tanks, retail packages) and equipment used. Below is a standardized method for measuring temperature using a digital thermometer, the most common tool in India.
a. Preparation
Calibrate the Thermometer: Verify the thermometer’s accuracy by placing the probe in a known temperature standard (e.g., ice water at 0°C or boiling water at 100°C, adjusted for altitude). Calibration should be done monthly or as per FSSAI guidelines.
Sterilize the Probe: Clean the thermometer probe with 70% ethanol or a food-grade sanitizer and rinse with sterile water to prevent contamination.
Sample Collection:
Collect a representative milk sample (e.g., 100–500 mL) using proper sampling techniques (e.g., single or composite sampling, as described in previous responses).
For bulk milk (e.g., tanks), agitate the milk mechanically for 5–10 minutes to ensure uniform temperature distribution.
Environment: Conduct measurements in a clean area to avoid external heat sources (e.g., direct sunlight) affecting readings.
b. Measurement Process
Insert the Probe:
For small containers (e.g., cans, bottles): Insert the digital thermometer probe at least 5–10 cm into the milk, ensuring it is submerged in the canter of the sample.
For bulk tanks: Use a long probe to reach the middle of the tank, avoiding contact with tank walls, which may have different temperatures.
For retail packages (e.g., pouches): Open the package aseptically and insert the probe or use an infrared thermometer for surface measurement (less accurate).
Stabilize the Reading:
Wait 10–30 seconds for the digital thermometer to stabilize and display a consistent reading (most modern devices beep when stable).
Record the temperature in degrees Celsius (°C) to one decimal place (e.g., 4.2°C).
Repeat for Accuracy: Take 2–3 readings from different parts of the sample (e.g., top, middle, bottom) and calculate the average to account for temperature gradients.
Inline Measurement (for automated systems):
Use thermocouples or inline sensors installed in milking machines, transport tanks, or processing lines to continuously monitor temperature.
Record data via a digital interface or data logger for compliance documentation.
c. Interpretation
Expected Temperatures (per FSSAI and Codex standards):
Raw Milk: Below 4°C immediately after milking and during transport/storage to prevent microbial growth.
Pasteurized Milk: 4–7°C during storage and retail to maintain shelf-life.
UHT Milk: Room temperature (20–25°C) if unopened but refrigerated (4–7°C) after opening.
Abnormal Readings:
Above 4°C for raw milk: Indicates inadequate cooling, risking bacterial proliferation (e.g., coliforms, psychrotrophs).
Above 7°C for pasteurized milk: Suggests cold chain failure, reducing shelf-life.
Below 0°C: Indicates freezing, which may damage milk’s protein structure and texture.
Action: If temperatures exceed safe limits, reject the milk for processing or conduct further tests (e.g., total plate count, titratable acidity) to assess spoilage.
3. Precautions and Considerations
Sterility: Always sterilize the probe before and after use to avoid introducing microbes or contaminants, critical for microbiological safety in India’s warm climate.
Calibration: Regularly calibrate thermometers to ensure accuracy, as per FSSAI’s Manual of Methods of Analysis of Foods: Milk and Milk Products (2025).
Probe Placement: Avoid contact with container walls or air pockets, which may give false readings.
Rapid Measurement: Measure temperature immediately after sampling to prevent warming or cooling of the sample during handling.
Cold Chain Monitoring: Use data loggers or inline sensors for continuous monitoring during transport, especially in India’s rural areas with limited refrigeration.
Documentation: Record temperature readings with sample details (e.g., date, time, source) for traceability, as required by FSSAI.
Environmental Factors: Avoid measuring near heat sources (e.g., machinery, sunlight) or in humid conditions that may affect equipment performance.
Equipment Maintenance: Store thermometers in protective cases and replace batteries regularly to ensure reliability.
Indian Challenges:
Limited access to advanced equipment (e.g., thermocouples) in rural areas necessitates reliance on portable digital thermometers.
Frequent power outages in India require backup cooling systems to maintain safe temperatures during measurement and storage.
4. Applications in India
Milk Collection Centres: Temperature checks are mandatory to accept raw milk from farmers, ensuring it is below 4°C to prevent spoilage (common in cooperatives like Amul).
Transport and Storage: Data loggers monitor milk temperature during transport to dairy plants, addressing India’s cold chain gaps.
Processing: Inline sensors verify milk temperature during pasteurization (e.g., 72°C for 15 seconds) and cooling (below 4°C).
Regulatory Compliance: FSSAI’s 2018 National Milk Safety and Quality Survey used temperature measurements to assess cold chain adherence.
Public Health: Proper temperature control prevents microbial growth, critical in India where 41% of milk samples were non-compliant in the 2018 FSSAI survey.
The sedimentation test is a simple physical test used to check the cleanliness of raw milk by detecting visible dirt, dust, and other extraneous matter. It does not measure microbial quality but gives an indication of hygienic conditions during milking, handling, and transport.
Principle
When a measured volume of milk is passed through a filter medium (sediment pad or cotton disk), suspended particles such as hairs, dirt, feed residues, and dung remain on the filter surface. The quantity and appearance of the sediment reflect the cleanliness of milk.
Materials Required
Sedimentation tester (sediment testing apparatus).
Measured milk sample (usually 500 ml or 1 litre).
Filter discs or pads (standard cotton wool, absorbent cotton, or special sediment pads).
Funnel or filtration holder.
Graduated cylinder or measuring flask.
Procedure
Preparation
Assemble the sediment tester with a filter disc fixed securely in place.
Mix the milk sample thoroughly by gentle inversion (do not froth).
Filtration
Measure a fixed volume of milk (usually 500 ml).
Pour the milk slowly through the tester, allowing it to pass through the filter disc.
Observation
After filtration, remove the filter disc.
Observe the nature, amount, and colour of sediment retained on the disc.
Grading
Compare with standard sediment charts (Grades: Excellent, Good, Fair, Poor).
Clean milk will show little or no visible dirt, while unhygienic milk will leave dark deposits.
Interpretation
Clean milk → Very little or no visible sediment.
Dirty milk → Considerable dark or fibrous particles on the filter.
The result helps dairy staff to assess farm hygiene practices and the suitability of milk for processing.
The COB test is a rapid test to check the stability of milk proteins (mainly casein) against heat. It is widely used in milk collection canters to detect developed acidity or poor-quality milk before processing.
Principle
Fresh, good-quality milk has a pH of about 6.6–6.8 and its proteins remain stable when heated.
If milk has developed high acidity (pH < 6.4) due to bacterial fermentation of lactose → casein precipitates (curdles) when boiled.
COB test therefore indicates unsuitable milk for heat processing (pasteurization, sterilization, or drying).
Materials Required
Clean, dry test tubes.
Water bath or spirit lamp (for heating).
Pipette or small measuring cylinder.
Fresh milk sample (well-mixed).
Procedure
Mix the milk sample thoroughly.
Take about 5 ml of milk in a clean test tube.
Heat the test tube in a boiling water bath or directly over a small flame.
Continue heating for about 2–3 minutes, observing closely.
Observation
No coagulation (smooth milk) → Milk passes the test (good quality, low acidity).
Clotting/curdling observed → Milk fails the test (developed acidity, unsuitable for processing).
Interpretation
Negative COB test: Milk is fresh, fit for processing.
Positive COB test: Milk has high developed acidity (usually >0.17% lactic acid), poor keeping quality, not suitable for heat treatment.
Applications
Used as a routine screening test in milk collection canters.
Quick indicator of milk freshness before bulk transport.
Helps in preventing processing losses in dairy plants.
Principle
The specific gravity (density) of milk is a measure of its weight compared to the same volume of water at a standard temperature (usually 27°C in India, 20°C in some other countries).
Normal cow/buffalo milk has a specific gravity between 1.028 and 1.034.
Adulteration with water lowers the value, while addition of skim milk powder, starch, or sugar may increase it.
A lactometer is a hydrometer specially calibrated for milk to measure its specific gravity quickly.
Materials Required
Lactometer (Quevenne type is commonly used).
Lactometer jar (tall glass cylinder).
Milk sample (well-mixed, free from foam).
Thermometer.
Procedure
Mix the milk sample gently to ensure uniformity.
Pour the milk into the lactometer jar, avoiding froth.
Insert the clean and dry lactometer vertically into the milk.
Ensure it floats freely without touching the sides.
When the lactometer settles, note the reading at the lower meniscus of milk.
Record the temperature of milk simultaneously with a thermometer.
Temperature Correction
Lactometers are usually calibrated at 27°C (India).
If the milk temperature differs:
Add 0.2 lactometer degree for every 1°C above 27°C.
Subtract 0.2 lactometer degree for every 1°C below 27°C.
Calculation
The corrected lactometer reading (CLR) is obtained after applying the temperature correction.
To get the specific gravity (SG):
SG=1+(CLR/1000)
Interpretation
Normal cow milk: 1.028 – 1.032
Normal buffalo milk: 1.030 – 1.034
Low value → Possible addition of water or removal of fat.
High value → Possible removal of cream or addition of solids.
Applications
Routine test at milk collection canters for detecting adulteration.
Quality control in dairy plants.
Used along with fat % test to calculate Solids-Not-Fat (SNF) content of milk.
Calculation of Solids-Not-Fat (SNF) and Total Solids (TS) in Milk
1. Corrected Lactometer Reading (CLR)
Since lactometer is calibrated at 27°C, apply temperature correction:
CLR=LR±(0.2×ΔT)
Subtract if sample temp is below 27°C
Add if sample temp is above 27°C
2. Solids-Not-Fat (SNF) %
SNF%=CLR/4+(Fat%X2.5) +0.44
3. Total Solids (TS) %
TS%=SNF%+Fat%
Example Calculation
Suppose:
Lactometer Reading (LR) = 30
Milk temperature = 29°C → 2°C above standard
Fat % = 4.5
Step 1: CLR
CLR=30+(0.2×2) =30.4
Step 2: SNF %
SNF=30.4/4+(4.5X2.5) +0.44
SNF%=7.6+1.125+0.44=9.165
Step 3: TS %
TS=9.165+4.5=13.665%
Interpretation
Cow milk: SNF ≈ 8.2–9.0% and TS ≈ 12–14%
Buffalo milk: SNF ≈ 9–10% and TS ≈ 15–17%
Lower SNF → possible water addition.
Higher SNF → possible adulteration with solids.
Determining the freezing point of milk is an important quality test, as it helps detect adulteration with water. Here’s a detailed step-by-step guide:
Principle
Pure milk has a freezing point around −0.512°C (slightly below 0°C).
Addition of water raises the freezing point (makes it less negative).
The test is usually done using a cryoscope.
Materials/Equipment Needed
Cryoscope or Freezing Point Determination Apparatus
Test tubes
Thermometer
Milk sample (fresh and properly mixed)
Distilled water (for calibration)
Procedure
Sample Preparation
Mix the milk thoroughly to get a uniform sample.
Remove any cream layer if necessary, depending on the method.
Calibration (if needed)
Use distilled water to check the cryoscope is functioning correctly. Distilled water should freeze at 0°C.
Filling the Apparatus
Pour the milk sample into the cryoscope sample tube.
Make sure no air bubbles are trapped.
Freezing Process
Cool the milk sample slowly under controlled conditions.
The milk starts to form ice crystals at its freezing point.
Observation
The temperature at which ice crystals first appear is noted as the freezing point.
Typically, pure cow milk has a freezing point around −0.512°C.
Deviations toward higher temperatures (closer to 0°C) may indicate added water.
Interpretation
Freezing Point
Interpretation
~−0.512°C
Normal, pure milk
>−0.505°C
Possible dilution with water
Significantly higher
Adulterated milk
Notes
Temperature should be precise; even small changes indicate dilution.
Avoid contamination and ensure milk is well mixed.
Cow, buffalo, and goat milk have slightly different standard freezing points.
Simple field methods
1. Using a Freezing Point Osmometer Substitute (Chemical Method)
This involves using a refractometer or freezing point test strips, if available commercially.
These strips give a rough estimate of freezing point or indicate if the milk is diluted.
Steps:
Dip the strip into well-mixed milk.
Wait for the recommended time (usually 30–60 seconds).
Compare the colour change with the standard chart provided.
2. Simple Ice Bath Method
This is a rudimentary method that works for educational purposes:
Fill a small test tube with milk.
Prepare an ice-salt mixture in a beaker (crushed ice + table salt).
Immerse the milk sample in the ice-salt bath.
Stir gently and monitor for the formation of ice crystals.
The milk will start to freeze slightly below 0°C. If ice forms at a temperature much higher than −0.5°C, the milk is likely diluted.
Chemical testing of milk involves analysing its composition and chemical properties to assess quality, purity, and safety. These tests help determine important constituents such as fat, protein, lactose, and solids-not-fat (SNF), and detect adulteration with water or other substances. Common chemical tests include acidity determination to check freshness, alcohol test for spoilage, fat estimation using Gerber or Babcock methods, and detection of adulterants like detergents, starch, or synthetic milk. Such testing is essential for ensuring that milk meets nutritional and safety standards, helps dairy processors maintain quality, and protects consumers from contaminated or adulterated milk.
Three methos are used to determine fat content of milk:
(1) Gerber Method (2) Babcock Method (3) Mojonnier Method
1. Gerber Method
Principle:
Milk fat is separated from milk using sulfuric acid, which dissolves proteins and releases fat.
Fat is measured volumetrically in a calibrated butyrometer after centrifugation.
Materials/Equipment:
Gerber butyrometer (calibrated glass tube)
Sulfuric acid (conc. 90–92%)
Amyl alcohol (or isoamyl alcohol)
Centrifuge (Gerber centrifuge)
Milk sample
Procedure:
Add 10.75 mL of milk with milk pipette into 10 mL of sulfuric acid in the butyrometer.
Add 1 mL of amyl alcohol to facilitate fat separation.
Seal the butyrometer, mix and centrifuge for 5 minutes at ~1200 rpm.
After centrifugation, the fat rises to the top as a clear layer.
Read the fat percentage directly from the graduated scale of the butyrometer.
Advantages:
Quick and accurate
Suitable for routine milk testing
Limitations:
Uses concentrated sulfuric acid (hazardous)
2. Babcock Method
Principle:
Like the Gerber method, milk fat is separated using sulfuric acid, which digests proteins.
Fat content is then measured volumetrically in a special Babcock bottle after centrifugation.
Materials/Equipment:
Babcock bottle (graduated)
Sulfuric acid (conc. 90–92%)
Water bath (for heating)
Centrifuge
Milk sample
Procedure:
Pour 10 mL of milk into the Babcock bottle.
Add 17.5 mL of concentrated sulfuric acid carefully along the walls to avoid contact with fat.
Mix gently and allow the acid to dissolve proteins.
Add water to bring the liquid to the graduated mark.
Centrifuge the bottle for 5 minutes.
The fat layer floats at the top; read the percentage on the bottle scale.
Advantages:
Reliable and widely used
Low cost
Limitations:
Sulfuric acid is corrosive
Slightly slower than Gerber method
3. Mojonnier Method
Principle:
Milk fat is extracted using ether and petroleum ether, avoiding concentrated sulfuric acid.
Fat is then weighed after evaporation of solvents.
Materials/Equipment:
Mojonnier flask
Solvent mixture (ether + petroleum ether)
Centrifuge
Water bath
Analytical balance
Procedure:
Add a measured quantity of milk into the Mojonnier flask.
Add ammonium hydroxide to digest proteins and alcohol to release fat.
Add ether-petroleum ether mixture to extract fat.
Centrifuge to separate the fat layer.
Evaporate the solvent in a water bath, leaving pure fat.
Weigh the fat residue to calculate fat percentage.
Advantages:
Accurate and suitable for dairy products with higher fat content (cheese, cream)
No concentrated sulfuric acid
Limitations:
More time-consuming
Requires organic solvents and careful handling
Summary Table
Method
Principle
Measurement Type
Advantages
Limitations
Gerber
Acid + centrifuge
Volumetric
Quick, accurate
Uses conc. sulfuric acid
Babcock
Acid + centrifuge
Volumetric
Reliable, cheap
Acid is corrosive
Mojonnier
Solvent extraction
Gravimetric
Accurate, no strong acid
Time-consuming, solvent use
1. Solids-Not-Fat (SNF) of Milk
Definition:
SNF includes all milk solids except fat, such as proteins, lactose, minerals, and vitamins.
It is an important indicator of milk quality and nutritional value.
Methods to Determine SNF
A. Calculation Method
Formula using fat content and specific gravity (lactometer reading):
SNF (%) = CLR/4 +(Fat%×0.25) +0.44
Fat % is determined using Gerber/Babcock method.
Lactometer reading measures specific gravity of milk.
The formula gives SNF % approximately.
Advantages:
Quick and simple
Requires only fat content and lactometer
B. Chemical Method
Involves precipitation of fat and determination of remaining solids.
Fat is separated by solvent or acid, and the residue is weighed to calculate SNF.
More accurate but time-consuming, mainly used in laboratories.
2. Total Solids (TS) of Milk
Definition:
Total solids include fat + SNF, i.e., all solids present in milk.
Important for standardization, pricing, and quality control.
Methods to Determine TS
A. Gravimetric (Evaporation) Method
Take a measured quantity of milk (e.g., 10 mL) in a pre-weighed dish.
Evaporate the water content by drying in an oven at 100–105°C until constant weight is obtained.
Weigh the residue.
Total Solids % = (Weight of residue ÷ Weight of milk sample) × 100
Advantages:
Accurate and direct
Measures all solids
Limitations:
Time-consuming
Requires precise oven and balance
B. Calculation Method
If Fat % and SNF % are known:
TS (%) =Fat %+SNF %
Quick and commonly used in dairy labs.
Summary Table
Component
Method
Principle / Formula
Notes
SNF
Lactometer & Fat
SNF % = (0.25 × Fat %) + (0.22 × LR) + 0.72
Quick, approximate
1. Protein Content of Milk
Definition:
Milk protein includes casein, whey proteins, and minor proteins.
Protein content is important for nutritional quality, cheese yield, and dairy product standardization.
Methods of Protein Estimation
A. Kjeldahl Method
Principle:
Measures total nitrogen in milk.
Milk protein is calculated using a conversion factor (generally 6.38 for milk).
Procedure:
Digest known volume of milk with concentrated sulfuric acid and a catalyst (e.g., K₂SO₄ + CuSO₄) to convert nitrogen to ammonium sulphate.
Neutralize with NaOH and distil the released ammonia into boric acid.
Titrate with standard acid (HCl or H₂SO₄) to determine nitrogen content.
Calculate protein content:
Protein (%) =Nitrogen (%) ×6.38
Advantages:
Accurate and widely accepted.
Limitations:
Time-consuming
Uses strong acids and requires lab setup
B. Lowry or Biuret Method (Colourimetry)
Proteins react with reagents to produce a colour, and absorbance is measured spectrophotometrically.
Mainly used in research or for whey protein estimation.
2. Casein Content of Milk
Definition:
Casein is the main milk protein, forming 80% of total protein in cow’s milk.
Important for cheese and dairy product production.
Methods of Casein Estimation
A. Precipitation Method (Acid or Enzymatic)
Precipitate casein by adding acid (e.g., acetic acid, HCl) or rennet to milk.
Allow the casein curd to form and separate by filtration or centrifugation.
Wash the precipitate to remove whey proteins.
Dry and weigh the casein.
Casein % = (Weight of dried casein ÷ Volume of milk) × 100
B. Calculation from Total Protein
If total protein is known, casein can be estimated using:
Casein (%) =Total Protein (%) ×0.8
Approximation assumes casein is 80% of milk protein.
Summary Table
Component
Method
Principle
Notes
Protein
Kjeldahl
Total nitrogen × 6.38
Accurate, standard method
Protein
Biuret/Lowry
Colourimetry measurement
Laboratory/research use
Casein
Precipitation
Acid/rennet precipitation, weight
Direct determination
Casein
Calculation
Casein ≈ 80% of total protein
Quick estimate
Definition:
Ash represents the total mineral content of milk, including calcium, potassium, sodium, phosphorus, magnesium, and trace elements.
It is determined by complete combustion of milk solids.
Importance:
Indicates the mineral quality of milk.
Useful for nutritional labelling and quality control.
Method: Gravimetric (Incineration) Method
Principle:
Milk is heated at high temperature to burn off all organic matter.
The remaining inorganic residue is the ash, which is weighed to determine content.
Materials/Equipment
Porcelain crucible or silica dish
Muffle furnace or hot air oven (500–600°C)
Analytical balance
Milk sample
Procedure
Pre-weigh a clean, dry crucible (weight = W₁).
Place a known volume of milk (e.g., 10 mL) in the crucible and dry it at 100–105°C to remove water.
Place the dried sample in a muffle furnace at 500–600°C for 4–6 hours until all organic matter is burnt.
Cool the crucible in a desiccator to room temperature and weigh it (weight = W₂).
Calculate ash content:
Ash (%) =(W2−W1)/Weight of milk sample×100
Notes
Avoid contamination from crucible or surroundings.
Ensure complete combustion to get accurate results.
Typical ash content of cow milk: 0.7–0.8%.
High ash may indicate added salts or adulteration.
1. Acidity of Milk
Definition:
Acidity measures the lactic acid content in milk, indicating freshness and microbial activity.
Method: Titratable Acidity (TA)
Principle:
Milk is titrated with a standard alkali (0.1 N NaOH) using phenolphthalein as an indicator.
Procedure:
Take 10 mL of well-mixed milk in a conical flask.
Add 2–3 drops of phenolphthalein.
Titrate with 0.1 N NaOH until a permanent light pink colour appears.
Calculate % lactic acid:
Acidity (% lactic acid) = (mL of NaOH used×N×0.009)/ Volume of milk taken (mL) ×100
Normal Range (Cow Milk): 0.13–0.17% lactic acid
2. pH of Milk
Definition:
pH measures the hydrogen ion concentration, reflecting milk’s freshness and spoilage.
Methods:
pH Meter (Accurate)
Calibrate with pH 4.0 & 7.0 buffers.
Immerse the electrode in well-mixed milk and record the reading.
Normal cow milk pH: 6.6–6.8
Litmus Paper (Approximate)
Blue litmus turns red in acidic milk (pH < 6.6).
Red litmus remains unchanged in fresh milk.
Quick, but less accurate.
Summary Table
Parameter
Method
Principle
Normal Range (Cow Milk)
Acidity
Titration (NaOH)
Lactic acid neutralized by alkali
0.13–0.17% lactic acid
pH
pH meter / Litmus
Hydrogen ion concentration
6.6–6.8
Detection of Neutralizers in Milk
Definition:
Neutralizers are chemicals added to increase the pH of sour or acidic milk, making it appear fresh.
Common neutralizers include sodium carbonate, sodium bicarbonate, potassium carbonate, sodium hydroxide, and ammonia.
Their addition is illegal and hazardous, as they can mask spoilage and affect milk quality.
Purpose of Detection:
To identify adulteration and ensure milk safety and freshness.
Methods for Detection of Neutralizers
1. Using Phenolphthalein Indicator
Principle:
Phenolphthalein changes colour in the presence of alkaline substances.
Procedure:
Take 5–10 mL of milk in a test tube.
Add 2–3 drops of phenolphthalein.
Observe the colour:
Pink colour appears → milk contains alkaline neutralizer
No colour change → milk is free from neutralizers
Notes:
Quick and simple field test.
Only detects strong or moderate alkalinity.
2. Using Methylene Orange Indicator
Principle:
Methylene orange changes colour with alkaline substances, useful for detecting added neutralizers.
Procedure:
Add a few drops of methylene orange to milk.
Observe the colour change:
Red to orange/yellow shift indicates the presence of neutralizers.
3. Commercial Neutralizer Test Kits
Rapid test kits are available for on-site detection.
Typically based on colourimetric reaction, giving a visible colour change if neutralizers are present.
Suitable for milk collection canters or dairy plants.
4. Laboratory Confirmation
pH measurement: Milk with high pH (>6.8) may indicate neutralizers.
Chemical analysis: Specific detection of carbonate, bicarbonate, or hydroxide ions using titration or spectrophotometric methods.
Precautions
Test fresh milk immediately.
Use clean glassware to avoid false results.
Milk naturally has a slightly acidic pH (6.6–6.8); any significant alkalinity is suspicious.
Summary Table
Method
Principle
Observation / Result
Notes
Phenolphthalein
Alkalinity indicator
Pink colour indicates neutralizer
Quick, simple
Methylene Orange
Alkalinity indicator
Colour change indicates neutralizer
Field use
pH Measurement
High pH indicates neutralizer
pH > 6.8
Preliminary check
Commercial Test Kits
Colourimetry reaction
Colour change indicates neutralizer
Rapid, convenient
Laboratory Analysis
Titration / Chemical detection
Confirms type and amount of neutralizer
Accurate, for labs
Detection of Preservatives in Milk
Definition:
Preservatives are chemicals added to milk to inhibit microbial growth and extend shelf life.
Commonly used preservatives (illegal in many countries) include formalin (formaldehyde), hydrogen peroxide, boric acid, benzoates, and hypo chlorites.
Their use is illegal and can be hazardous to health, as they may mask spoilage.
Purpose of Detection:
To identify adulteration and ensure milk safety.
Protect consumers from toxic effects of chemical preservatives.
Common Methods for Detection of Preservatives
1. Detection of Formalin (Formaldehyde)
Principle:
Formalin reacts with Schiff’s reagent (fuchsin-sulphurous acid solution) to produce a violet colour.
Procedure:
Take 5–10 mL of milk in a test tube.
Add a few drops of Schiff’s reagent.
Observe colour change:
Violet or pink colour → indicates the presence of formalin.
Notes:
Simple, rapid, and commonly used in field testing.
2. Detection of Hydrogen Peroxide
Principle:
Hydrogen peroxide reacts with potassium iodide (KI) in acidic solution to release iodine, producing a yellow-brown colour.
Procedure:
Mix milk sample with KI and starch solution.
Add a few drops of dilute acid.
Observe colour:
Blue-black or brown colour → indicates presence of hydrogen peroxide.
3. Detection of Boric Acid
Principle:
Boric acid reacts with curcumin in acidic medium to produce a red-coloured complex.
Procedure:
Add curcumin reagent to the milk sample.
Acidify with concentrated H₂SO₄.
Observe:
Red layer formation indicates boric acid.
4. Detection Using Commercial Preservative Test Kits
Rapid kits are available for formalin, hydrogen peroxide, and other preservatives.
They are colourimetric and provide visual results within minutes.
Useful in milk collection canters and dairy plants.
Precautions
Use clean glassware to avoid false positives.
Test milk freshly collected, as natural enzymes may interfere with reactions.
Compare with control sample of fresh milk.
Summary Table
Preservative
Test / Reagent
Observation / Result
Notes
Formalin
Schiff’s reagent
Violet/pink colour
Rapid, simple
Hydrogen Peroxide
KI + Starch + Acid
Blue-black or brown colour
Field or lab test
Boric Acid
Curcumin + H₂SO₄
Red layer formation
Specific test
Commercial Kits
Colourimetric kits
Colour change indicates presence
Rapid and convenient
Detection of Adulterants in Milk
Definition:
Adulterants are substances added to milk intentionally or unintentionally to increase volume, mask poor quality, or alter appearance.
Common adulterants include water, starch, detergents, synthetic milk, sugar, salts, urea, neutralizers, and preservatives.
Adulteration can reduce nutritional quality, pose health risks, and violate legal standards.
Purpose of Detection:
Ensure milk quality, purity, and safety.
Prevent health hazards and economic fraud.
Common Adulterants and Detection Methods
1. Water
Detection Methods:
Specific Gravity (Lactometer Test): Lower density indicates added water.
Freezing Point Test: Freezing point rises if water is added.
Boiling Test: Milk boils faster and forms less cream if diluted.
2. Starch
Detection Methods:
Iodine Test:
Add iodine solution to milk.
Blue-black colour indicates presence of starch.
3. Detergents / Soap
Detection Methods:
Foaming Test:
Shake milk vigorously.
Persistent froth or foam indicates detergents.
Dilute HCl Test:
Add a few drops of HCl; soap scum formation confirms detergent.
4. Synthetic Milk / Urea / Salts
Detection Methods:
Urea Test: Using urease enzyme or chemical reagents; presence of urea may indicate synthetic milk.
Salt Detection: Excessive sodium or potassium can be detected by chemical tests.
Milk Adulteration Kits: Rapid kits can detect synthetic milk, urea, and other chemicals.
5. Neutralizers
Detection Methods:
Phenolphthalein Test: Pink colour indicates alkaline neutralizer.
Methylene Orange Test: Colour change indicates neutralization.
6. Preservatives
Detection Methods:
Formalin: Schiff’s reagent → violet colour.
Hydrogen Peroxide: KI + Starch → blue-black colour.
Boric Acid: Curcumin + Acid → red layer.
Precautions
Use clean glassware to avoid contamination.
Test freshly collected milk.
Compare results with control sample of pure milk.
Some adulterants may interfere with other tests; confirm with specific detection methods.
Summary Table
Adulterant
Detection Method
Observation / Result
Water
Lactometer / Freezing point
Low density / Raised freezing point
Starch
Iodine test
Blue-black colour
Detergent / Soap
Foaming test / Dilute HCl
Persistent froth / soap scum
Synthetic milk / Urea
Urease test / Chemical kits
Colour change or reaction
Neutralizers
Phenolphthalein / Methylene Orange
Pink / Colour change
Preservatives
Schiff, KI-starch, Curcumin tests
Violet / Blue-black / Red layer
Microbiological testing of milk involves the examination and quantification of microorganisms present in milk to assess its hygienic quality, safety, and shelf life. Milk, being highly nutritious, can harbor bacteria, yeasts, and molds if not handled properly, leading to spoilage or foodborne diseases. Common tests include total bacterial count, coliform count, detection of specific pathogens (e.g., E. coli, Salmonella, Listeria), and somatic cell count, which also reflects animal health. These tests help in monitoring milk hygiene, evaluating processing efficiency, and ensuring compliance with legal and quality standards. Regular microbiological testing is essential for protecting consumers, preventing outbreaks of milk-borne illnesses, and maintaining the overall quality of dairy products.
Definition:
The Standard Plate Count (also called Total Viable Count) measures the total number of viable (live) bacteria in milk.
It is a key indicator of milk quality, hygiene, and shelf life.
Principle:
Milk is serially diluted and inoculated on a nutrient agar medium.
After incubation, colonies formed by individual bacteria are counted.
Each colony represents a colony-forming unit (CFU).
Materials/Equipment
Nutrient agar plates or Plate Count Agar (PCA)
Sterile Petri dishes
Sterile pipettes and tips
Dilution tubes (sterile)
Incubator (35–37°C)
Milk sample
Procedure
1. Preparation of Dilutions
Take 1 mL of milk and add it to 9 mL of sterile diluent (e.g., 0.85% NaCl solution) → 10⁻¹ dilution.
Prepare serial dilutions (10⁻², 10⁻³, etc.) as required.
2. Plating
Transfer 1 mL of the selected dilution into a sterile Petri dish.
Pour 15–20 mL of molten nutrient agar (cooled to 45°C) into the dish.
Mix gently by rotating the plate to distribute the sample evenly.
Allow the agar to solidify.
3. Incubation
Incubate plates inverted at 35–37°C for 48 hours.
4. Colony Counting
After incubation, select plates with 30–300 colonies for accuracy.
Count the number of colonies.
Calculate CFU/mL of milk using:
SPC (CFU/mL) =Number of colonies × Dilution factor
Interpretation
CFU/mL (Cow Milk)
Quality Indicator
<50,000
Excellent / Very good
50,000–200,000
Good / Acceptable
200,000–500,000
Fair / Marginal
>500,000
Poor / Unsuitable for consumption
Precautions
Use aseptic techniques to avoid contamination.
Mix milk properly before sampling.
Select plates with countable colonies (30–300) for reliability.
Handle molten agar carefully to avoid burns and maintain sterility.
Definition:
MBRT is a rapid test to assess the bacterial quality of milk.
It measures the time taken for methylene blue dye to lose its colour due to bacterial activity (reduction by milk bacteria).
The faster the dye decolourizes, the higher the bacterial load, indicating lower milk quality.
Principle:
Methylene blue is a redox dye.
Bacteria in milk consume oxygen and produce reducing compounds (enzymes, metabolites).
These reducing substances convert methylene blue to a colourless form.
Materials/Equipment
Fresh milk sample
1% Methylene Blue solution
Test tubes
Water bath (optional, 35–37°C)
Timer or stopwatch
Pipettes
Procedure
Take 10 mL of milk in a sterile test tube.
Add 1 mL of 1% methylene blue solution and mix gently.
Invert the tube to mix thoroughly.
Place the tube at room temperature or in a water bath at 35°C.
Observe colour change:
Record the time taken for the blue colour to completely disappear (turn colourless).
Interpretation
Time for Decolourization
Quality of Milk
Bacterial Load
>6 hours
Excellent / Fresh
Low bacteria
4–6 hours
Good
Moderate bacteria
2–4 hours
Fair
High bacteria
<2 hours
Poor / Spoiled
Very high bacteria
Notes:
The test is qualitative and indicates milk hygiene, not exact bacterial count.
Works best on fresh, unheated milk.
Temperature affects the test; higher temperatures accelerate reduction.
Precautions:
Use fresh milk for accurate results.
Avoid contamination from hands or utensils.
Mix the dye gently to prevent oxygen introduction, which may delay decolourization.
Definition:
The Resazurin Test is a rapid microbiological quality test for milk.
It indicates the bacterial load by measuring the reduction of resazurin dye by milk bacteria.
Fresh milk retains a blue colour longer, whereas milk with high bacterial activity turns pink or colourless quickly.
Principle:
Resazurin is a redox dye that is blue in its oxidized form.
Bacteria in milk reduce the dye to resorufin (pink) and then to hydro resorufin (colourless) as they metabolize lactose and consume oxygen.
The rate of colour change reflects microbial activity and milk quality.
Materials/Equipment
Fresh milk sample
0.01% Resazurin solution
Test tubes or sterile bottles
Water bath (optional, 35–37°C)
Timer or stopwatch
Pipettes
Procedure
Take 10 mL of well-mixed milk in a sterile test tube.
Add 1 mL of 0.01% resazurin solution.
Mix gently by inverting the tube.
Incubate at room temperature or in a water bath at 35°C.
Observe the colour change at regular intervals:
Blue → Pink → Colourless.
Record the time taken for colour changes to occur.
Interpretation
Colour Change
Milk Quality / Bacterial Load
Blue
Excellent / Very low bacteria
Blue → Light Pink
Good / Moderate bacteria
Pink
Fair / High bacteria
Colourless
Poor / Very high bacteria
Notes:
The test is qualitative and semi-quantitative, providing a rapid estimate of microbial quality.
Works best on fresh, unpasteurized milk.
Temperature and storage conditions affect results.
Precautions
Use fresh milk and clean glassware.
Mix gently to avoid oxygen introduction.
Perform the test soon after milk collection for accuracy.
Definition:
Coliforms are a group of Gram-negative, rod-shaped bacteria that indicate fecal contamination and poor hygienic quality of milk.
Coliform count reflects the sanitary quality of milk and milk handling practices.
Principle:
Coliform bacteria are lactose-fermenting, producing acid and gas.
The Most Probable Number (MPN) method or direct plating on selective media is used to estimate coliforms.
Materials/Equipment
Milk sample
Sterile dilution tubes
MacConkey broth or Lauryl Sulphate Tryptose (LST) broth
Brilliant Green Lactose Bile (BGLB) broth (for confirmation)
Sterile pipettes and tips
Incubator (35–37°C)
Test tubes with Durham tubes (for gas detection)
Procedure (MPN Method – Most Common)
1. Sample Preparation
Take 10 mL of well-mixed milk.
Prepare serial dilutions using sterile diluent (e.g., 10⁻¹, 10⁻², 10⁻³).
2. Inoculation in LST Broth
Add 1 mL, 0.1 mL, and 0.01 mL of each dilution into LST broth tubes containing Durham tubes.
Incubate at 35–37°C for 24–48 hours.
Observe gas production in Durham tubes.
Gas formation = presumptive coliform presence.
3. Confirmation Test
Transfer a loopful from positive LST tubes to BGLB broth.
Incubate at 35–37°C for 24–48 hours.
Confirm coliforms by gas formation in BGLB broth.
4. Calculation
Use MPN table based on the number of positive tubes at different dilutions.
Express as coliforms per mL of milk.
Interpretation
Coliform Count (CFU/mL)
Milk Quality
0–10
Excellent / Very hygienic
10–100
Good
100–1,000
Fair / Moderate contamination
>1,000
Poor / Unsuitable for consumption
Precautions
Use aseptic techniques to avoid contamination.
Handle milk samples freshly collected.
Confirm positive tubes to avoid false positives.
Maintain incubation temperature strictly.
Definition:
Somatic cells are white blood cells and epithelial cells present in milk.
High somatic cell counts indicate mastitis (udder infection) and poor milk quality.
SCC is an important indicator of animal health and milk hygiene.
Purpose:
Detect subclinical mastitis in dairy animals.
Assess milk quality for processing and safety.
Methods for Detection
1. Direct Microscopic Method (Direct Somatic Cell Count – DSCC)
Principle:
Somatic cells are stained and counted under a microscope.
Materials/Equipment:
Milk sample
Microscope slides and cover slips
Staining solution (e.g., Newman-Lampert stain or acetic acid–methylene blue solution)
Light microscope
Procedure:
Mix milk thoroughly and place a drop on a slide.
Add a staining solution to highlight somatic cells.
Cover with a cover slip.
Count cells in 10–20 fields under 400× magnification.
Calculate somatic cells per mL of milk using standard formulas.
Interpretation:
Healthy cow milk: <200,000 cells/mL
Mild infection: 200,000–500,000 cells/mL
Mastitis: >500,000 cells/mL
2. California Mastitis Test (CMT) – Rapid Field Test
Principle:
Detects somatic cells based on gel formation when milk is mixed with a reagent containing sodium hydroxide and a dye.
Materials/Equipment:
CMT paddle or plastic cup
CMT reagent (commercial kit)
Fresh milk sample
Procedure:
Place milk from each quarter of the udder in separate cups of the CMT paddle.
Add an equal volume of CMT reagent to each milk sample.
Mix gently by swirling for 10–15 seconds.
Observe gel formation and colour change:
No gel, watery → Negative (healthy)
Slight gel → Weak positive (subclinical mastitis)
Distinct gel, thick → Strong positive (mastitis)
Advantages:
Quick, simple, and can be performed on the farm.
Detects subclinical mastitis early.
3. Automated Electronic Counters
Modern dairy labs use Fossomatic or DeLaval cell counters.
Milk is analysed electronically for somatic cell concentration.
Provides rapid and accurate results for large samples.
Precautions
Mix milk properly before testing.
Test fresh milk; storage can affect SCC.
Use clean, sterile equipment to avoid contamination.
Interpret results in context of animal health and milk quality standards.
Definition:
Pathogens are disease-causing microorganisms that can contaminate milk.
Common pathogens include E. coli, Salmonella, Listeria monocytogenes, and Staphylococcus aureus.
Detecting them ensures milk safety and public health.
Purpose:
Prevent milk-borne illnesses.
Ensure compliance with food safety standards.
Evaluate hygiene during milking, handling, and storage.
General Procedure for Pathogen Detection
1. Sample Collection
Collect aseptically 25–50 mL of fresh milk in a sterile container.
Keep refrigerated (4°C) during transport.
Test as soon as possible to avoid microbial growth or death.
2. Pre-enrichment
To recover stressed or low-number bacteria:
Add milk to a non-selective broth (e.g., Buffered Peptone Water for Salmonella, Tryptic Soy Broth for Listeria).
Incubate at 30–37°C for 18–24 hours.
3. Selective Enrichment
Transfer pre-enriched sample to selective enrichment media to favor pathogen growth:
E. coli: MacConkey broth or E. coli enrichment broth
Salmonella: Rappaport-Vassiliadis (RV) broth
Listeria: Fraser broth
Incubate under appropriate temperature and time to allow target bacteria to multiply.
4. Isolation on Selective Agar
Streak enriched samples on selective agar plates:
E. coli: MacConkey agar or Eosin Methylene Blue (EMB) agar → metallic green sheen colonies indicate E. coli
Salmonella: XLD (Xylose Lysine Deoxycholate) agar → red colonies with black centres
Listeria: Oxford or PALCAM agar → small grey-green colonies with black halos
Incubate at 35–37°C for 24–48 hours.
5. Confirmation
Perform biochemical tests or molecular methods (PCR) to confirm pathogen identity:
E. coli: IMViC tests (Indole, Methyl Red, Voges-Proskauer, Citrate)
Salmonella: Triple Sugar Iron (TSI) test, urease test
Listeria: Catalase test, motility test, CAMP test
Rapid commercial kits and PCR-based assays can also provide faster and specific confirmation.
6. Interpretation
Presence of colonies with characteristic morphology and positive confirmatory tests indicates contamination.
Results are usually reported as presence/absence in 25 mL milk or CFU/mL if quantitative methods are used.
Precautions
Use aseptic techniques to prevent contamination.
Handle pathogens in a biosafety level 2 lab.
Store samples cold but do not freeze, as freezing can kill some bacteria.
Follow manufacturer instructions for commercial detection kits.
Summary Table
Pathogen
Selective Media / Broth
Colony Characteristics
Confirmation Test
E. coli
MacConkey / EMB
Pink colonies / Metallic green sheen
IMViC, Biochemical tests
Salmonella
XLD / RV broth
Red colonies with black centres
TSI, Urease, Serological tests
Listeria
Oxford / PALCAM
Gray-green colonies, black halos
Catalase, Motility, CAMP test
Milk, being a highly nutritious and perishable food, is often subjected to adulteration and contamination, which pose serious health risks to consumers. Adulteration refers to the intentional addition of substances such as water, starch, detergents, synthetic milk, or preservatives to increase volume or shelf life, thereby reducing its quality and safety. Contamination, on the other hand, occurs unintentionally due to poor handling, unhygienic practices, or environmental factors, leading to the presence of harmful microorganisms, pesticides, heavy metals, or antibiotic residues. Detection of adulteration and contamination in milk involves both simple rapid tests (such as lactometer reading, clot-on-boiling test, methylene blue reduction test) and advanced analytical techniques (like chromatography, spectrophotometry, and molecular assays) to ensure authenticity and safety. Regular monitoring and strict quality control are essential to protect consumer health, maintain nutritional value, and uphold public confidence in dairy products.
1. Water
Purpose of Addition: To increase the volume and hence profit.
Effect on Milk: Reduces nutritional value, dilutes proteins, fats, and minerals.
Health Hazards: If contaminated water is used, it may introduce pathogens and cause water-borne diseases like diarrhoea, typhoid, or cholera.
2. Starch
Purpose of Addition: To increase the thickness of diluted milk and mask adulteration.
Effect on Milk: Gives a false impression of higher solids.
Health Hazards: Can cause indigestion and is harmful for diabetic patients.
3. Detergents
Purpose of Addition: To give milk a frothy appearance like natural milk fat.
Effect on Milk: Alters taste and stability of milk.
Health Hazards: Causes gastro-intestinal irritation, food poisoning, and even damage to organs in severe cases.
4. Urea
Purpose of Addition: To artificially increase non-protein nitrogen (SNF – solids-not-fat) content and mask dilution.
Effect on Milk: Makes milk appear rich in protein.
Health Hazards: Excess urea affects kidney function, may cause indigestion, vomiting, or kidney damage.
5. Formalin (Formaldehyde solution)
Purpose of Addition: Used as a preservative to extend milk shelf life.
Effect on Milk: Prevents bacterial growth but makes milk unsafe.
Health Hazards: Highly toxic, carcinogenic, and can cause severe damage to digestive tract, liver, and kidneys.
6. Synthetic Milk
Composition: Made from soap, detergent, urea, starch, and synthetic fat.
Effect on Milk: Looks like natural milk but has no nutritional value.
Health Hazards: Extremely harmful, causes gastroenteritis, food poisoning, and long-term organ damage.
7. Sugar / Glucose
Purpose of Addition: To increase solids-not-fat (SNF) content in diluted milk.
Effect on Milk: Increases density, masking adulteration.
Health Hazards: Harmful to diabetic patients, may cause metabolic stress.
8. Salt (Common Salt / Sodium chloride)
Purpose of Addition: To enhance density and mask dilution.
Effect on Milk: Alters taste.
Health Hazards: In excess, can cause hypertension and kidney strain.
9. Neutralizers (Sodium carbonate, sodium bicarbonate, caustic soda)
Purpose of Addition: To neutralize acidity and increase shelf life of spoiled milk.
Effect on Milk: Prevents curdling during transport/storage.
Health Hazards: Causes gastrointestinal irritation, alkalosis, and long-term health issues.
10. Skimmed Milk Powder or Reconstituted Milk
Purpose of Addition: To standardize fat and SNF levels in diluted milk.
Effect on Milk: Alters natural composition.
Health Hazards: Not very toxic but reduces nutritional authenticity.
Summary:
Common adulterants like water, starch, urea, detergents, and preservatives are used mainly for profit or shelf-life extension. While some (like water or sugar) reduce nutrition, others (like detergents, urea, and formalin) pose serious health hazards, including gastrointestinal problems, kidney damage, and cancer risk.
1. Starch
Principle: Starch turns blue with iodine.
Procedure: Add 2–3 drops of iodine solution to 2–3 mL of milk.
Observation: Blue colouration indicates presence of starch.
2. Cane Sugar (Sucrose)
Principle: Sucrose, when hydrolysed, produces reducing sugars that react with resorcinol in HCl.
Procedure (Seliwanoff’s test): Add a few drops of resorcinol solution and concentrated HCl, heat in boiling water bath.
Observation: Red colour indicates sucrose adulteration.
3. Glucose
Principle: Glucose acts as a reducing sugar.
Procedure: Use diacetic strip (glucose strip) and dip in milk.
Observation: Change of strip colour (green to brown) shows glucose adulteration.
4. Urea
Principle: Urea reacts with p-dimethylaminobenzaldehyde to give yellow colour.
Procedure: Mix milk with a few drops of the reagent.
Observation: Yellow colour indicates urea.
5. Detergents
Principle: Detergents form stable lather.
Procedure: Shake 5 mL of milk vigorously.
Observation: Persistent foamy lather indicates detergent adulteration.
6. Neutralizers (e.g., Sodium carbonate, Sodium bicarbonate, Ca (OH)₂)
Phenolphthalein Test:
Add a few drops of phenolphthalein indicator to milk.
Observation: Pink colouration indicates neutralizers.
Rosalic Acid Test:
Add rosalic acid reagent.
Observation: Rose-red colour indicates presence of carbonate/ bicarbonate.
7. Formalin (Formaldehyde)
Hehner’s Test:
Carefully add concentrated H₂SO₄ along the sides of the milk test tube.
Observation: A violet/blue ring forms at junction, indicating formalin.
8. Hydrogen Peroxide
Principle: Hydrogen peroxide oxidizes paraphenylene diamine.
Procedure: Add a few drops of paraphenylene diamine reagent.
Observation: Blue colour indicates hydrogen peroxide.
9. Boric Acid / Borax
Turmeric Paper Test:
Dip turmeric paper in milk and dry.
Observation: Red colouration, turning green with ammonia, confirms boric acid/borax.
10. Salt (NaCl)
Principle: Salt with silver nitrate produces white precipitate.
Procedure: To 5 mL milk, add 1 mL potassium chromate, then silver nitrate.
Observation: Yellow colour turning brick-red shows salt presence.
11. Ammonium Sulphate
Principle: Ammonium salts release ammonia with alkali, giving brown colour with Nessler’s reagent.
Procedure: Add 1 mL of Nessler’s reagent after treating with NaOH.
Observation: Brown colouration indicates ammonium sulphate.
12. Starch-based Synthetic Milk
Characteristic test: On boiling, it gives a soapy texture, unpleasant odour, and may show lather like detergent.
These qualitative tests are widely used in dairy labs, teaching labs, and by regulatory authorities as quick screening methods. They do not quantify the amount of adulterant but confirm its presence.
Qualitative Tests for Adulterants in Milk:
Adulterant
Test / Reagent
Observation (Positive Result)
Starch
Add iodine solution
Blue colouration
Cane Sugar (Sucrose)
Seliwanoff’s test (Resorcinol + HCl, heat)
Red colour
Glucose
Dip glucose/diacetic strip
Colour change (green → brown)
Urea
p-Dimethylaminobenzaldehyde reagent
Yellow colour
Detergents
Shake vigorously
Persistent foamy lather
Neutralizers (Na₂CO₃, NaHCO₃, lime)
- Phenolphthalein test
- Rosalic acid test
Pink colour (phenolphthalein)
Rose-red colour (rosalic acid)
Formalin (HCHO)
Hehner’s test (conc. H₂SO₄ along tube side)
Violet/blue ring at junction
Hydrogen Peroxide
Paraphenylene diamine reagent
Blue colour
Boric Acid / Borax
Turmeric paper test
Red colour (turns green with NH₃)
Salt (NaCl)
Potassium chromate + AgNO₃
Yellow → brick-red colour
Ammonium Sulphate
Nessler’s reagent after NaOH treatment
Brown colouration
Synthetic Milk
Boiling / observation
Soapy texture, lather, bad odour
Unlike qualitative tests, which only confirm the presence of adulterants, quantitative estimation determines their actual concentration. These tests are used in food testing laboratories and regulatory analysis.
1. Estimation of Added Water
Method: Freezing Point Depression (Cryoscopic Method)
Principle: Pure milk has a freezing point around –0.54 °C. Addition of water raises it closer to 0 °C.
Procedure: Freezing point is measured with a cryoscope and compared with standard value.
Result: % Added water = (Observed FP–Standard FP)/ (Standard FP–0) × 100.
2. Estimation of Cane Sugar (Sucrose)
Method: Polarimetric Method
Principle: Sucrose rotates plane-polarized light.
Procedure: Milk is clarified, then tested in a polarimeter.
Result: The degree of rotation corresponds to sucrose content (expressed as % w/v).
3. Estimation of Glucose
Method: Glucose Oxidase–Peroxidase (GOD–POD) Colourimetric Method
Principle: Glucose oxidase converts glucose → gluconic acid + H₂O₂; peroxidase with chromogen produces coloured compound.
Procedure: Measure absorbance in spectrophotometer at 505 nm.
Result: Glucose concentration obtained from calibration curve.
4. Estimation of Starch
Method: Iodometric Method
Principle: Starch forms a blue complex with iodine; absorbance intensity is proportional to starch concentration.
Procedure: Add iodine solution, measure absorbance at 620 nm.
Result: Starch quantified by comparing with standard starch solutions.
5. Estimation of Urea
Method: Diacetyl Monoxime Method
Principle: Urea reacts with diacetyl monoxime under acidic conditions to form a pink-coloured complex.
Procedure: Treat milk filtrate with reagent, heat in water bath, measure absorbance at 540 nm.
Result: Urea concentration determined using a standard curve.
6. Estimation of Detergents
Method: MBAS (Methylene Blue Active Substances) Method
Principle: Detergents (anionic surfactants) form a coloured complex with methylene blue, extractable in chloroform.
Procedure: Shake milk with reagent, extract, measure absorbance at 652 nm.
Result: Detergent content calculated (mg/L).
7. Estimation of Neutralizers (Carbonates / Bicarbonates)
Method: Acid-Base Titration
Principle: Neutralizers increase alkalinity of milk.
Procedure: Titrate milk with standard acid using phenolphthalein as indicator.
Result: Amount of alkali (mg Na₂CO₃ / 100 mL milk) calculated.
8. Estimation of Formalin (Formaldehyde)
Method: Chromotropic Acid Method
Principle: Formaldehyde reacts with chromotropic acid in presence of concentrated H₂SO₄, giving violet colour.
Procedure: Measure absorbance at 570 nm.
Result: Formalin content (mg/L) from calibration curve.
9. Estimation of Hydrogen Peroxide
Method: Colourimetric (Titanium Sulfate Method)
Principle: H₂O₂ oxidizes titanium (IV) to form yellow pertitanic acid.
Procedure: Treat milk with reagent and measure absorbance at 410 nm.
Result: H₂O₂ concentration calculated.
10. Estimation of Boric Acid / Borax
Method: Titrimetric Method
Principle: Boric acid can be titrated with NaOH using phenolphthalein indicator after complexing with mannitol.
Result: Boric acid content expressed as mg/100 mL milk.
11. Estimation of Salt (NaCl)
Method: Mohr’s Method (Argentometric titration)
Principle: Chloride ions are precipitated with AgNO₃ in presence of K₂CrO₄ indicator.
Result: Salt concentration calculated as % NaCl.
12. Estimation of Ammonium Sulphate
Method: Nesslerization
Principle: Ammonium salts release NH₃ with alkali, which gives a brown complex with Nessler’s reagent.
Procedure: Compare intensity with ammonium sulphate standards at 420 nm.
Result: Expressed as mg/100 mL milk.
Quantitative Estimation of Adulterants in Milk:
Adulterant
Method
Principle
Measurement / Result
Added Water
Cryoscopic method (Freezing point)
Added water raises milk’s freezing point (–0.54 °C normally)
% Water = ΔFP × 100 / Std FP
Cane Sugar (Sucrose)
Polarimetry
Sucrose rotates plane-polarized light
% sucrose from optical rotation
Glucose
GOD–POD colourimetric assay
Glucose oxidase → gluconic acid + H₂O₂; peroxidase + chromogen → colour
Absorbance at 505 nm vs std curve
Starch
Iodometric method
Starch forms blue complex with iodine
Absorbance at 620 nm vs standards
Urea
Diacetyl monoxime method
Urea reacts with diacetyl monoxime → pink colour
Absorbance at 540 nm vs std curve
Detergents
MBAS method
Detergents form complex with methylene blue, extractable in chloroform
Absorbance at 652 nm (mg/L)
Neutralizers (Na₂CO₃, NaHCO₃, lime)
Acid–base titration
Neutralizers increase alkalinity of milk
mg Na₂CO₃ / 100 mL milk
Formalin (HCHO)
Chromotropic acid method
Formaldehyde + chromotropic acid + H₂SO₄ → violet colour
Absorbance at 570 nm (mg/L)
Hydrogen Peroxide
Titanium sulphate method
H₂O₂ oxidizes Ti(IV) → yellow pertitanic acid
Absorbance at 410 nm (mg/L)
Boric Acid / Borax
Titration with NaOH (mannitol aid)
Boric acid titrated after forming mannitol–borate complex
mg/100 mL milk
Salt (NaCl)
Mohr’s argentometric titration
Cl⁻ precipitated by AgNO₃, K₂CrO₄ used as indicator
% NaCl in milk
Ammonium Sulphate
Nesslerization
Ammonia from ammonium salts + Nessler’s reagent → brown complex
Absorbance at 420 nm vs std curve
Qualitative and Quantitative Tests for Common Milk Adulterants, showing detection and estimation:
Adulterant
Qualitative Test / Observation
Quantitative Test / Principle / Measurement
Added Water
Freezing point rise on observation
Cryoscopic method: ΔFP → % water added
Cane Sugar (Sucrose)
Seliwanoff’s test (Red colour on heating with resorcinol + HCl)
Polarimetry: Optical rotation → % sucrose
Glucose
Glucose strip (colour change green → brown)
GOD–POD colourimetric assay → Absorbance at 505 nm → mg/dL
Starch
Iodine solution (Blue colour)
Iodometric method → Absorbance at 620 nm → mg/dL
Urea
p-Dimethylaminobenzaldehyde (Yellow colour)
Diacetyl monoxime method → Absorbance at 540 nm → mg/100 mL
Detergents
Persistent lather on shaking
MBAS method → Absorbance at 652 nm → mg/L
Neutralizers (Na₂CO₃, NaHCO₃, lime)
Phenolphthalein (Pink) / Rosalic acid (Rose-red)
Acid–base titration → mg Na₂CO₃ / 100 mL milk
Formalin (HCHO)
Hehner’s test (Violet/blue ring)
Chromotropic acid method → Absorbance at 570 nm → mg/L
Hydrogen Peroxide
Paraphenylene diamine (Blue colour)
Titanium sulphate method → Absorbance at 410 nm → mg/L
Boric Acid / Borax
Turmeric paper (Red → green with NH₃)
Titration with NaOH (mannitol complex) → mg/100 mL
Salt (NaCl)
Silver nitrate + K₂CrO₄ (Yellow → brick-red)
Mohr’s argentometric titration → % NaCl
Ammonium Sulphate
Nessler’s reagent (Brown colour with alkali)
Nesslerization → Absorbance at 420 nm → mg/100 mL
Synthetic Milk
Boiling → soapy texture, unpleasant odour
Not precisely quantifiable; lab tests for starch, detergents, proteins
Definition:
Rapid test kits or strip tests are ready-to-use, easy, and quick diagnostic tools to detect common adulterants, contaminants, or quality parameters in milk. They are designed for field testing or routine quality checks without sophisticated laboratory equipment.
Advantages:
Quick results (usually in 1–10 minutes).
Simple to use; minimal training required.
Portable; suitable for dairy farms, collection centres, or retail.
Can detect multiple adulterants simultaneously in some kits.
1. Strip Tests
Principle: Paper or plastic strips impregnated with reagents that change colour or intensity when they react with a specific adulterant.
Examples:
Adulterant / Parameter
Test Strip
Observation / Result
Urea
Urea strip impregnated with DMAB reagent
Pink colour indicates urea presence
Detergents
MBAS strip (methylene blue active substances)
Blue colour or lather indicates detergent
Starch
Iodine strip
Blue colour indicates starch
Neutralizers / Alkali
Phenolphthalein or pH strip
Pink colour indicates alkalinity
Formalin
Chromotropic acid strip
Violet colour indicates formalin
Water Addition
Cryoscope strip / refractometer strip
FP or refractive index deviation indicates added water
Adulterated Milk
Multiparameter strip kits
Different coloured pads for urea, starch, neutralizer, detergent
2. Rapid Test Kits
Definition: Ready-to-use kits, often with colour charts, vials, and reagents, allowing semi-quantitative or qualitative detection of one or more adulterants.
Examples:
Kit Name / Type
Adulterants Detected
Principle / Observation
Urea Test Kit
Urea
Pink colour indicates presence; intensity may give rough concentration
Starch Test Kit
Starch
Blue colour with iodine; compare with colour chart
Detergent Test Kit
Detergents
Foaming or colour change; MBAS-based kits
Neutralizer Test Kit
Alkali (NaHCO₃, Na₂CO₃)
Phenolphthalein or rosalic acid; colour intensity indicates alkalinity
Formalin Test Kit
Formaldehyde
Violet colour formation; comparison with colour chart for semi-quantitative estimation
Milk Adulteration Multiparameter Kit
Urea, Detergent, Starch, Neutralizer
Pads with different reagents; colour comparison with chart
How They Work (General Procedure):
Collect 2–5 mL of milk in a test tube or container.
Dip the strip or add milk to kit reagent well.
Wait for 1–10 minutes depending on the kit.
Compare colour change with the supplied colour chart to confirm presence or approximate concentration.
Applications:
On-farm milk quality checks.
Milk collection centres to prevent adulteration.
Quick screening by regulatory authorities.
Educational labs and training purposes.
Notes:
Rapid kits are qualitative or semi-quantitative; they cannot fully replace laboratory quantitative analysis.
They are most useful for screening, after which positive samples are confirmed in lab using standard chemical methods.
Comparative table for Qualitative Tests, Rapid Test Kits / Strip Tests, and Quantitative Estimation of common milk adulterants:
Adulterant
Qualitative Test
Rapid Test / Strip Kit
Quantitative Estimation
Added Water
Freezing point rise (cryoscopic observation)
Refractometer strip / FP strip
Cryoscopic method → % water added
Cane Sugar (Sucrose)
Seliwanoff’s test (Red colour)
Sugar test strip (colour change)
Polarimetry → % sucrose
Glucose
Glucose strip (green → brown)
Glucose strip / kit
GOD–POD colourimetric assay → mg/dL
Starch
Iodine solution (Blue colour)
Iodine strip / starch kit
Iodometric method → mg/dL
Urea
DMAB reagent (Yellow / Pink)
Urea test strip / kit
Diacetyl monoxime method → mg/100 mL
Detergents
Shake test (persistent foam)
MBAS strip / detergent kit
MBAS method → mg/L
Neutralizers (Na₂CO₃, NaHCO₃, lime)
Phenolphthalein (Pink) / Rosalic acid (Rose-red)
pH / neutralizer strip
Acid–base titration → mg Na₂CO₃ / 100 mL
Formalin (HCHO)
Hehner’s test (Violet/blue ring)
Chromotropic acid strip / kit
Chromotropic acid method → mg/L
Hydrogen Peroxide
Paraphenylene diamine (Blue)
H₂O₂ test strip
Titanium sulfate method → mg/L
Boric Acid / Borax
Turmeric paper (Red → green with NH₃)
Boric acid strip / kit
Titration with NaOH (mannitol complex) → mg/100 mL
Salt (NaCl)
AgNO₃ + K₂CrO₄ (Yellow → brick-red)
Salt test strip
Mohr’s argentometric titration → % NaCl
Ammonium Sulphate
Nessler’s reagent (Brown)
Nessler strip / kit
Nesslerization → mg/100 mL
Synthetic Milk
Boiling → soapy texture, unpleasant odour
Multi-adulterant kit
Lab tests for starch, detergents, proteins
Notes:
Qualitative Tests: Quick, simple, confirm presence only.
Rapid Test / Strip Kits: Field-friendly, 1–10 min, semi-quantitative or qualitative.
Quantitative Estimation: Lab-based, accurate measurement of concentration.
Milk is a highly perishable and essential food commodity, so its quality, safety, and legality are strictly regulated. Detecting adulteration and contamination is critical to protect public health, ensure fair trade, and maintain consumer trust.
1. Legal Framework in India
a) Food Safety and Standards Act, 2006 (FSSAI)
Governing Authority: Food Safety and Standards Authority of India (FSSAI).
Milk Regulations:
Maximum permissible limits for adulterants (e.g., urea, detergents, neutralizers, formalin).
Mandatory labelling for milk fat, SNF (solids-not-fat), and other components.
Legal Implications:
Selling adulterated milk is an offense punishable with fines and imprisonment.
Milk failing quality tests may be seized, destroyed, or recalled.
b) Prevention of Food Adulteration Act (PFA), 1954 (now merged under FSSAI)
Earlier law regulating food adulteration.
Classified adulteration into:
Unsafe food: injurious to health
Sub-standard food: does not meet prescribed standards
Provides penalties for manufacturers, distributors, and retailers.
c) BIS Standards (IS 1169, IS 1479)
Specifies chemical, physical, and microbiological standards for milk.
Milk should meet parameters like:
Fat content
SNF
Freezing point
Absence of harmful adulterants
2. Safety and Public Health Aspects
a) Health Hazards of Milk Adulteration
Adulterant
Health Risks
Water
Dilution, microbial growth → diarrhoea, gastroenteritis
Starch / Synthetic milk
Digestive issues, nutrient imbalance
Urea / Neutralizers
Kidney damage, metabolic disturbances
Detergents
Gastrointestinal irritation, nausea, chronic toxicity
Formalin / Hydrogen Peroxide
Carcinogenic, organ toxicity
Boric acid / Borax
Liver/kidney damage, reproductive toxicity
Microbial contamination
Foodborne illnesses: E. coli, Listeria, Salmonella
b) Microbiological Safety
Milk must be free from pathogenic microbes.
Tests include: SPC, coliform count, MBRT, resazurin test.
Rapid detection kits can identify contaminated batches to prevent outbreaks.
3. Regulatory and Enforcement Mechanisms
Sampling & Testing:
Dairy farms, collection centres, and retail outlets are regularly sampled.
Screening using rapid kits → qualitative tests → quantitative confirmation.
Penalties for Adulteration:
Fines, imprisonment, license cancellation.
Mandatory product recall for contaminated milk.
Quality Certification:
Milk suppliers may require FSSAI license and compliance certification.
Adherence to HACCP (Hazard Analysis & Critical Control Points) is recommended for large-scale dairies.
4. Safety Protocols During Testing
Wear gloves and lab coat when handling milk samples.
Dispose of contaminated milk according to biohazard rules.
Avoid inhalation or ingestion of reagents (e.g., phenol, formaldehyde, acids).
Follow standard lab practices to prevent cross-contamination.
5. Global Standards and Guidelines
Codex Alimentarius: International guidelines for milk quality and adulteration limits.
WHO & FAO: Recommend strict monitoring for microbial and chemical contamination.
Summary
Milk adulteration is illegal and hazardous.
FSSAI standards govern acceptable limits of chemicals, additives, and microbial counts.
Rapid tests, lab confirmation, and quantitative estimation are legally recognized methods for enforcement.
Dairy operators and regulators must follow safety protocols to protect public health.
Table combining Adulterant → Health Risks → Legal Status → Detection Method for milk, useful for exam notes or practical reference:
Adulterant / Contaminant
Health Risks
Legal Status / Regulation
Detection Method
Water (excess / added)
Dilution, supports microbial growth → diarrhoea, gastroenteritis
Illegal if it exceeds permissible dilution; FSSAI standards on SNF & fat
Freezing point depression, cryoscope, refractometer strip
Starch / Synthetic milk
Digestive issues, nutrient imbalance
Illegal; milk must meet FSSAI composition standards
Iodine test, starch strip, quantitative iodometric method
Urea
Kidney damage, metabolic disturbances
Illegal; maximum limit set by FSSAI
DMAB qualitative test, strip test, diacetyl monoxime method
Detergents
Gastrointestinal irritation, chronic toxicity
Illegal; FSSAI prohibits use in milk
Shake test, MBAS strip / kit, MBAS quantitative method
Neutralizers (NaHCO₃, Na₂CO₃, lime)
Metabolic disturbances, kidney issues
Illegal; neutralizers above permissible limit
Phenolphthalein / rosalic acid test, pH strip, acid-base titration
Formalin / Formaldehyde
Carcinogenic, organ toxicity
Illegal; strictly prohibited
Hehner’s test, chromotropic acid strip/kit, chromotropic acid quantitative method
Hydrogen Peroxide
Irritation, organ toxicity at high doses
Illegal; FSSAI prohibits use as preservative
Paraphenylene diamine test, H₂O₂ strip, titanium sulfate method
Boric Acid / Borax
Liver/kidney damage, reproductive toxicity
Illegal; strictly prohibited
Turmeric paper test, boric acid strip/kit, titration method
Salt (NaCl)
High intake risks (hypertension)
Permissible up to standard levels; excess is illegal
AgNO₃ + K₂CrO₄ qualitative, strip, Mohr’s titration
Ammonium Sulphate
Toxic to kidneys/liver
Illegal; FSSAI prohibits
Nessler’s reagent test, Nessler strip/kit, quantitative Nesslerization
Microbial Contamination
Foodborne illnesses: E. coli, Salmonella, Listeria
Unsafe milk banned; must meet FSSAI microbial limits
Standard Plate Count (SPC), coliform count, MBRT, resazurin test
Key Points:
All chemical adulterants above permissible limits are illegal under FSSAI.
Health risks range from mild digestive issues to serious organ toxicity or carcinogenicity.
Detection uses a tiered approach: rapid kits / strip tests → qualitative confirmation → quantitative lab methods.
Microbial contamination is considered unsafe even without chemical adulteration.
Milk Adulteration & Contamination – Rapid Reference Sheet:
Adulterant
Qualitative Test
Rapid / Strip Test
Quantitative Estimation
Health Risks
Legal Status
Added Water
Freezing point rise
Refractometer / FP strip
Cryoscopic method → % water
Dilution, microbial growth → diarrhoea, gastroenteritis
Illegal if exceeds permissible dilution; FSSAI standards on SNF & fat
Cane Sugar (Sucrose)
Seliwanoff’s test (Red colour)
Sugar test strip
Polarimetry → % sucrose
Excess sugar intake → metabolic disturbances
Illegal if added for adulteration
Glucose
Glucose strip (green → brown)
Glucose strip / kit
GOD–POD colourimetric → mg/dL
Digestive issues, hyperglycemia
Illegal if added as adulterant
Starch / Synthetic milk
Iodine solution (Blue colour)
Iodine strip / starch kit
Iodometric method → mg/dL
Digestive issues, nutrient imbalance
Illegal; violates FSSAI composition standards
Urea
DMAB reagent (Yellow/Pink)
Urea strip / kit
Diacetyl monoxime method → mg/100 mL
Kidney damage, metabolic disturbances
Illegal; FSSAI sets maximum limit
Detergents
Shake test (persistent foam)
MBAS strip / kit
MBAS method → mg/L
Gastrointestinal irritation, chronic toxicity
Illegal; prohibited in milk
Neutralizers (NaHCO₃, Na₂CO₃, lime)
Phenolphthalein (Pink) / Rosalic acid
pH strip / neutralizer kit
Acid–base titration → mg Na₂CO₃ / 100 mL
Metabolic disturbances, kidney issues
Illegal above permissible limits
Formalin / Formaldehyde
Hehner’s test (Violet/Blue ring)
Chromotropic acid strip / kit
Chromotropic acid method → mg/L
Carcinogenic, organ toxicity
Strictly prohibited; illegal
Hydrogen Peroxide
Paraphenylene diamine (Blue)
H₂O₂ strip
Titanium sulfate method → mg/L
Irritation, organ toxicity at high doses
Illegal; FSSAI prohibits as preservative
Boric Acid / Borax
Turmeric paper (Red → Green with NH₃)
Boric acid strip / kit
Titration with NaOH (mannitol complex) → mg/100 mL
Liver/kidney damage, reproductive toxicity
Strictly prohibited; illegal
Salt (NaCl)
AgNO₃ + K₂CrO₄ (Yellow → Brick-red)
Salt test strip
Mohr’s titration → % NaCl
Excess intake → hypertension
Permissible within standards; illegal if excessive
Ammonium Sulphate
Nessler’s reagent (Brown)
Nessler strip / kit
Nesslerization → mg/100 mL
Toxic to kidneys/liver
Illegal; prohibited in milk
Microbial Contamination
MBRT, Resazurin test
Multiparameter microbial kits
Standard Plate Count, Coliform count → CFU/mL
Foodborne illnesses: E. coli, Salmonella, Listeria
Unsafe milk banned; must meet microbial limits
Notes
Screening: Start with Rapid / Strip tests for quick detection in the field.
Confirmation: Use qualitative lab tests to confirm suspected adulterants.
Quantification: Apply laboratory quantitative methods to determine concentration.
Legal Action: Samples exceeding FSSAI limits are rejected, recalled, and suppliers penalized.
Safety: Always use gloves, lab coat, and proper disposal for contaminated milk and reagents.
Instrumental methods in milk testing are modern analytical techniques that provide rapid, accurate, and sensitive detection and quantification of milk components, adulterants, and contaminants. These methods include spectroscopic techniques like UV-Visible and infrared spectroscopy for measuring fat, protein, lactose, and detecting added water or chemicals; chromatographic methods such as HPLC and GC for separating and quantifying sugars, preservatives, antibiotics, or volatile compounds; electrochemical methods using pH meters and ion-selective electrodes for detecting neutralizers and salts; and immunological methods like ELISA and lateral flow assays for antibiotics, hormones, or pathogens. Additionally, microbiological instruments like automated microbial counters and flow cytometry can rapidly assess bacterial load and somatic cells, while physical and sensor-based methods such as lactometers, refractometers, and electronic noses detect density changes, off-flavours, or spoilage. These instrumental techniques are widely used in quality control, regulatory compliance, and research, offering high precision and reproducibility, though they require trained personnel and specialized equipment.
1. Milko-Tester
Definition:
Milko-Tester is a portable, semi-automatic electronic milk analyser used for rapid determination of milk composition and quality parameters.
Parameters Measured:
Fat (%)
Solids-not-fat (SNF %)
Density
Added water detection
Lactose (in some models)
Principle:
Works on electronic conductivity, density, and temperature correction.
Some models also use infrared or ultrasonic sensors to measure fat and SNF.
Advantages:
Rapid results (within 1–2 minutes per sample)
Portable and suitable for field use or milk collection centres
Requires minimal training
Can detect adulteration like added water indirectly via density/SNF
Limitations:
Less precise than full laboratory instruments like Lactoscan or FTIR analysers
Needs calibration and temperature correction
Cannot detect chemical adulterants (e.g., urea, detergents)
2. Lactoscan
Definition:
Lactoscan is a high-precision electronic milk analyser, commonly used in laboratories and milk collection centres, for accurate milk composition analysis.
Parameters Measured:
Fat (%)
Solids-not-fat (SNF %)
Lactose (%)
Protein (%)
Density
Added water detection
Freezing point (in advanced models)
Principle:
Based on Ultrasound / Infrared technology for fat, protein, lactose, and SNF determination.
Measures sound velocity or infrared absorption through milk sample.
Temperature compensation and calibration ensure high accuracy.
Advantages:
Accurate and reproducible results
Suitable for bulk testing in laboratories and collection centres
Can detect added water precisely
Measures multiple parameters simultaneously
Some models can store data electronically for quality monitoring
Limitations:
Less portable than Milko-Tester
Expensive and requires trained personnel
Not designed for direct chemical adulterant detection (requires separate kits)
Comparison Table: Milko-Tester vs Lactoscan
Feature
Milko-Tester
Lactoscan
Use
Field, collection centres
Laboratory, collection centres
Parameters
Fat, SNF, density, added water
Fat, SNF, lactose, protein, density, freezing point, added water
Technology
Conductivity, density, ultrasonic
Ultrasound / Infrared
Accuracy
Moderate
High
Portability
Portable
Semi-portable / Lab-based
Training Required
Minimal
Moderate to high
Adulterant Detection
Indirect (water via density/SNF)
Indirect (water via density/SNF)
Summary:
Milko-Tester: Quick, portable, for field screening of milk quality.
Lactoscan: High-precision analyser for lab and collection centre use, measuring multiple milk components accurately.
Both are essential for routine milk quality monitoring, but neither detects chemical adulterants directly—for that, rapid kits or lab tests are required.
Definition:
Infrared (IR) spectroscopy is an analytical technique that measures absorption of infrared light by milk components. Different molecules absorb IR radiation at characteristic wavelengths, allowing detection and quantification of fat, protein, lactose, and other constituents, as well as some adulterants.
Principle:
Molecules in milk vibrate and rotate, absorbing infrared light at specific frequencies.
The absorption pattern (spectrum) is unique for different functional groups:
C–H stretching → fat
N–H / C=O stretching → protein
O–H / C–O stretching → lactose and water
The intensity of absorption is proportional to concentration, allowing quantitative estimation.
Types of IR Used in Milk Testing:
Mid-Infrared (MIR) Spectroscopy
Most common in commercial milk analysers.
Measures fat, protein, lactose, SNF, urea, and added water.
Rapid, non-destructive, and requires minimal sample preparation.
Near-Infrared (NIR) Spectroscopy
Used for bulk milk analysis and portable devices.
Slightly less precise than MIR but fast and suitable for field applications.
Applications in Milk Testing:
Parameter / Adulterant
Detection Using IR
Fat
C–H bond absorption in triglycerides
Protein
N–H, C=O vibrations in casein and whey proteins
Lactose
O–H and C–O stretching vibrations
Solids-not-Fat (SNF)
Calculated from protein, lactose, and mineral content
Added Water
Dilution reduces absorption intensity; detected via calibration
Urea / Some Adulterants
Specific absorption peaks can indicate presence (semi-quantitative)
Advantages:
Rapid and non-destructive: Only a few minutes per sample.
Simultaneous multi-component analysis: Fat, protein, lactose, SNF, urea.
High accuracy and reproducibility for routine quality control.
Minimal sample preparation: Milk can be analysed directly.
Limitations:
Cannot detect all chemical adulterants (e.g., detergents, formalin) directly.
Requires calibration with standard samples for accurate results.
Expensive equipment and trained personnel needed.
Typical Workflow in Milk Labs:
Collect milk sample and filter/bring to uniform temperature.
Introduce milk into IR analyser (cuvette or flow cell).
Measure absorption spectrum.
Use software calibration to calculate fat, protein, lactose, SNF, and check for added water.
Record results and compare with regulatory standards (FSSAI / ISO).
Summary:
Infrared spectroscopy, especially MIR, is a cornerstone of modern milk testing. It enables rapid, accurate, and multi-component analysis, making it essential for milk quality control, adulteration detection (like water addition), and regulatory compliance.
Comparative table of MIR, NIR, and Classical Methods in Milk Testing:
Feature
Mid-Infrared (MIR) Spectroscopy
Near-Infrared (NIR) Spectroscopy
Classical / Conventional Methods
Principle
Absorption of mid-IR light by functional groups (C–H, N–H, O–H)
Absorption of near-IR light (overtones of molecular vibrations)
Chemical / physical reactions (gravimetric, titration, colourimetry)
Parameters Measured
Fat, Protein, Lactose, SNF, Added Water, Urea
Fat, Protein, Lactose, SNF (semi-quantitative)
Fat (Gerber), SNF (gravimetric), Lactose (polarimetry), Added Water (freezing point)
Speed / Time
Very fast (1–2 min per sample)
Very fast (seconds to 1 min)
Slower (10–30 min per test depending on parameter)
Accuracy / Precision
High
Moderate to high
Moderate; operator dependent
Sample Preparation
Minimal; milk can be analysed directly
Minimal; portable devices usable
Moderate; may require reagents, heating, centrifugation
Detection of Adulterants
Indirect (added water, urea, some others)
Indirect (added water)
Direct for some (urea, starch, detergents)
Portability
Laboratory / collection centre
Portable / field-compatible
Generally, lab-based; some field kits available
Cost
High
Moderate to high
Low to moderate
Training Required
Moderate to high
Moderate
Low to moderate
Advantages
Rapid, multi-component, accurate, reproducible
Rapid, portable, good for field screening
Simple, inexpensive, widely established
Limitations
Expensive, cannot detect all chemical adulterants directly
Less precise than MIR, limited adulterant detection
Time-consuming, less reproducible, more labor-intensive
Summary:
MIR: Best for lab-based, high-accuracy multi-component analysis.
NIR: Good for rapid field screening and bulk milk monitoring.
Classical methods: Still useful for small labs, teaching, and detecting certain adulterants not detectable by IR.
This table is ideal for exam notes, practical reference, or comparative study of milk testing methods.
Definition:
Ultrasonic milk analysers are electronic instruments that measure milk composition and detect adulteration by analysing the velocity of ultrasonic waves passing through the milk. These analysers provide rapid, non-destructive, and accurate estimation of fat, protein, solids-not-fat (SNF), density, and added water.
Principle:
Milk is a liquid medium through which sound waves can travel.
The velocity of ultrasonic waves depends on:
Fat content
Protein concentration
Solids-not-fat (SNF)
Water content
Temperature
Higher solids content → faster sound velocity; added water → slower velocity.
The instrument measures sound velocity and uses calibrated correlations to estimate milk components.
Parameters Measured:
Fat (%)
Protein (%)
Solids-not-fat (SNF) (%)
Density
Added water detection (indirect)
Some advanced models measure lactose (%) and freezing point.
Procedure / Workflow:
Collect 10–20 mL of milk sample in a clean container.
Pour the sample into the ultrasonic analyser chamber.
The instrument emits ultrasonic pulses through the milk.
Sensors measure the velocity and attenuation of the waves.
The analyser calculates fat, protein, SNF, and water content using pre-programmed calibration curves.
Results are displayed digitally within 1–2 minutes.
Advantages:
Rapid and accurate; results in 1–2 minutes.
Non-destructive; milk can be reused after testing.
Portable and suitable for milk collection centres, laboratories, and field use.
Detects added water indirectly through density and sound velocity.
Requires minimal sample preparation.
Limitations:
Cannot detect chemical adulterants (e.g., urea, formalin, detergents) directly.
Accuracy depends on proper calibration and temperature control.
Equipment is relatively expensive compared to classical methods.
Cannot measure microbial contamination.
Applications:
Routine quality control in dairy farms and milk collection centres.
Screening for added water and checking milk composition.
Monitoring milk for processing plants to standardize fat and protein content.
Summary:
Ultrasonic milk analysers are modern, rapid, and reliable instruments for analysing milk composition (fat, protein, SNF, and density) and detecting water adulteration indirectly. They are particularly useful in collection centres and laboratories, complementing chemical tests and instrumental methods like infrared spectroscopy.
Comparative table of Ultrasonic Milk Analyser, Milko-Tester, and Lactoscan:
Feature
Ultrasonic Milk Analyser
Milko-Tester
Lactoscan
Principle
Measures ultrasonic wave velocity through milk; sound speed correlates with fat, protein, SNF, and water
Electronic density/conductivity; some use ultrasonic sensor
Infrared (MIR) absorption; measures fat, protein, lactose, SNF
Parameters Measured
Fat, Protein, SNF, Density, Added Water (indirect)
Fat, SNF, Density, Added Water (indirect)
Fat, Protein, Lactose, SNF, Density, Freezing Point, Added Water
Accuracy / Precision
High
Moderate
Very High
Speed
1–2 minutes per sample
1–2 minutes per sample
1–2 minutes per sample
Portability
Portable / Field & Lab use
Portable / Field use
Semi-portable / Lab use
Sample Preparation
Minimal; milk at uniform temperature
Minimal
Minimal
Detection of Added Water
Indirect via velocity/density
Indirect via density/SNF
Indirect via IR calibration
Detection of Chemical Adulterants
No
No
No
Cost
Moderate to high
Low to moderate
High
Training Required
Moderate
Minimal
Moderate to high
Advantages
Rapid, non-destructive, accurate, portable
Quick, portable, easy to use
Highly accurate, multi-component analysis
Limitations
Cannot detect chemical adulterants; calibration needed
Moderate accuracy; limited parameters
Expensive; lab or collection centre use; no chemical detection
Summary:
Ultrasonic Milk Analyser: Best for rapid, non-destructive, portable milk composition analysis; detects added water indirectly.
Milko-Tester: Simple and portable; suitable for field screening; moderate accuracy.
Lactoscan: High-precision lab analyser; measures multiple milk components accurately; more expensive.
1. pH Meter in Milk Testing
Definition:
A pH meter is an electronic device used to measure the hydrogen ion concentration in milk, which reflects its acidity or alkalinity. Milk pH is a key indicator of freshness, spoilage, and quality.
Principle:
Works on electrochemical measurement using a glass electrode immersed in milk.
The electrode develops a potential difference proportional to the hydrogen ion concentration (pH).
A digital display shows the pH value, usually ranging from 0–14.
Applications in Milk Testing:
Freshness assessment: Fresh milk pH ~6.6–6.8; decrease indicates microbial spoilage (acid production).
Detection of adulteration: Neutralizers (like baking soda) increase pH artificially.
Process monitoring: pH changes are monitored during fermentation (curd/yogurt) and processing.
Procedure:
Calibrate pH meter using standard buffer solutions (pH 4.0 and 7.0).
Immerse electrode in milk sample at room temperature.
Wait for reading to stabilize and record pH.
Rinse electrode with distilled water after measurement.
Advantages:
Rapid, accurate, and reproducible.
Useful for detecting spoilage and improper handling.
Limitations:
Does not detect chemical adulterants directly.
Electrode requires regular calibration and cleaning.
2. Conductivity Meter in Milk Testing
Definition:
A conductivity meter measures the ability of milk to conduct electric current, which depends on the ionic content (salts, minerals, and added chemicals) of milk.
Principle:
Milk contains ions like Na⁺, K⁺, Cl⁻, Ca²⁺ that conduct electricity.
Conductivity increases with added salts, neutralizers, or water dilution.
The meter applies a small voltage across electrodes in milk and measures current to calculate conductivity (µS/cm).
Applications in Milk Testing:
Detection of neutralizers or salts added to milk.
Freshness monitoring: Spoiled milk shows changes in ionic content and conductivity.
Process control: Used in dairy plants to monitor composition and quality.
Procedure:
Calibrate conductivity meter with standard KCl solution.
Immerse electrodes in milk sample.
Record conductivity once reading stabilizes.
Clean electrodes after use.
Advantages:
Quick and easy to detect changes in milk ionic content.
Helps identify adulteration with neutralizers or salts indirectly.
Limitations:
Cannot detect all adulterants (like starch, urea, or detergents).
Readings influenced by temperature and ionic composition of milk naturally.
Summary Comparison: pH vs Conductivity Meter
Feature
pH Meter
Conductivity Meter
Measures
Hydrogen ion concentration
Ionic content / electrical conductivity
Indicates
Acidity / freshness / spoilage
Added salts / neutralizers / spoilage
Principle
Electrochemical (glass electrode)
Electrical conduction through ions
Applications
Freshness, spoilage, neutralizer detection
Neutralizer/salt adulteration, process control
Advantages
Accurate, rapid
Rapid, easy, non-destructive
Limitations
Cannot detect chemical adulterants
Temperature-sensitive, cannot detect non-ionic adulterants
Conclusion:
pH meters are ideal for monitoring milk freshness and spoilage.
Conductivity meters are useful for screening ionic adulterants and quality monitoring.
Both are complementary tools in routine milk testing and quality control in dairies.
6. Instrumental Methods in Milk Testing
Definition:
An Automatic Milk Collection Unit (AMCU) is a technologically advanced system installed at milk collection centres to automatically weigh, measure, and analyse milk samples from individual farmers. It ensures accurate milk quality assessment, rapid payment, and prevention of adulteration.
Principle:
AMCUs integrate electronic milk analysers, flow meters, and sensors.
Milk is passed through the system, where the volume, fat, SNF, and other components are measured using infrared spectroscopy or ultrasonic sensors.
Data is stored digitally and linked to individual farmer IDs for automated billing.
Optional adulteration detection sensors (conductivity, density) can flag suspicious milk.
Components of AMCU:
Milk Inlet and Weighing System
Measures milk quantity in liters or kilograms.
Milk Analyser Module
Determines fat, SNF, protein, lactose, density.
Commonly uses Infrared (MIR) or Ultrasonic technology.
Sensors for Adulteration Detection
Conductivity or density sensors to detect added water or salts.
Optional pH monitoring for freshness.
Farmer Identification System
RFID card or biometric scan to identify milk source.
Data Processing Unit
Stores milk quality and quantity for automated payment and reporting.
Cooling & Storage System
Maintains milk at 4–6°C before transportation to processing plants.
Parameters Measured / Tested:
Milk volume (weight/flow)
Fat (%)
Solids-not-fat (SNF) (%)
Protein (%)
Lactose (%) (in advanced models)
Density and specific gravity
Added water (indirect)
pH / acidity (optional)
Milk temperature
Advantages:
Rapid and automated: Reduces human error in weighing and quality testing.
Accurate farmer payments: Based on milk quantity and quality.
Integrated quality control: Immediate detection of substandard milk.
Digital record keeping: Supports traceability and reporting.
Reduces adulteration risk: Sensors detect added water, neutralizers, or other anomalies.
Hygienic and efficient: Minimizes handling and contamination.
Limitations:
High initial investment and maintenance cost.
Requires trained operators and electricity supply.
Some chemical adulterants (urea, formalin, detergents) may require separate testing kits.
Periodic calibration and cleaning are essential to maintain accuracy.
Applications:
Milk collection centres for cooperatives or private dairies.
Bulk milk analysis and farmer payment systems.
Integration with milk transport and processing plants.
Quality assurance and traceability in the dairy supply chain.
Summary:
AMCU testing systems are modern, automated milk collection and quality assessment units that combine volume measurement, milk composition analysis, adulteration detection, and farmer identification in one system. They ensure rapid, accurate, and hygienic milk collection, support fair payment, and enhance overall milk quality control in dairy operations.
Quality standards and regulatory requirements for milk testing are established to ensure that milk is safe, nutritious, and free from adulteration or contamination. Regulatory bodies, such as FSSAI in India, Codex Alimentarius, and ISO, specify limits for milk composition, including fat, protein, solids-not-fat (SNF), lactose, and microbial counts, as well as permissible levels of chemical additives or contaminants. Milk must meet these standards during collection, transportation, and processing, and routine testing is conducted using physical, chemical, microbiological, and instrumental methods. Parameters such as pH, density, freezing point, fat, protein, microbial load, and the presence of adulterants are monitored to ensure compliance. Adherence to these standards safeguards public health, ensures fair trade practices, and maintains the quality of dairy products across the supply chain.
1. BIS Standards for Milk
BIS (Bureau of Indian Standards) sets specifications for different types of milk under the standard IS 1168: 1991 (for cow and buffalo milk) and related amendments.
Key Parameters:
Parameter
Cow Milk (IS 1168)
Buffalo Milk (IS 1168)
Remarks
Fat (%)
≥ 3.0
≥ 6.5
Minimum required for whole milk
Solids-Not-Fat (SNF %)
≥ 8.5
≥ 9.0
Ensures nutritive value
Protein (%)
≥ 2.8
≥ 3.5
Quality and nutritional content
Lactose (%)
4.8–5.2
4.8–5.2
Naturally occurring sugar
Density / Specific Gravity
1.028–1.032 g/mL
1.028–1.032 g/mL
Detects dilution with water
Freezing Point (°C)
−0.515 ± 0.005
−0.515 ± 0.005
Detects added water
Added Water
Not permitted
Not permitted
Milk should be natural
Urea / Neutralizers
Not permitted
Not permitted
Must meet chemical safety standards
Microbial Limits (SPC)
≤ 5×10⁵ CFU/mL
≤ 5×10⁵ CFU/mL
Standard Plate Count for hygiene
Coliform Count
≤ 100 CFU/mL
≤ 100 CFU/mL
Ensures safety for consumption
Notes: BIS standards focus primarily on milk composition, physical quality, and microbial limits, and are often used for industry quality control.
2. FSSAI Standards for Milk
FSSAI (Food Safety and Standards Authority of India) sets legal standards for milk under FSS (Food Products Standards and Food Additives) Regulations, 2011, specifically Part IX – Milk and Milk Products.
Key FSSAI Requirements:
Parameter
Requirement
Remarks / Limits
Fat (%)
Cow: ≥ 3.0
Buffalo: ≥ 6.5
Minimum fat content
Solids-Not-Fat (SNF %)
Cow: ≥ 8.5
Buffalo: ≥ 9.0
Ensures nutritional value
Protein (%)
Cow: ≥ 2.8
Buffalo: ≥ 3.5
Required for nutritional labelling
Lactose (%)
Naturally 4.8–5.2
Optional test in routine QC
Density / Specific Gravity
1.028–1.032 g/mL
Used to detect dilution
Freezing Point
−0.515 ± 0.005 °C
Confirms absence of added water
Added Water
Not permitted
Adulteration is illegal
Urea / Neutralizers
Maximum 70 mg/100 mL (urea)
Adulteration detection
Formalin / Hydrogen Peroxide / Boric Acid
Strictly prohibited
Any detectable amount is illegal
Microbial Limits
SPC: ≤ 5×10⁵ CFU/mL
Coliform: ≤ 100 CFU/mL
Ensures safety for consumption
Somatic Cell Count (SCC)
≤ 5×10⁵ cells/mL
Indicator of udder health and milk quality
Additional Requirements under FSSAI:
Milk must be free from adulterants and contaminants.
Must comply with packaging, labelling, and hygiene standards.
Periodic testing at collection centres, transport, and processing plants is mandatory.
Comparison: BIS vs FSSAI Standards
Feature
BIS
FSSAI
Focus
Physical, chemical composition, microbial quality
Legal compliance, safety, labelling, adulteration limits
Regulatory Status
Voluntary (industry standard)
Mandatory (law under FSS Act, 2006)
Microbial Limits
SPC ≤ 5×10⁵ CFU/mL
SPC ≤ 5×10⁵ CFU/mL; Coliform ≤100 CFU/mL
Adulterants
Not explicitly enforced
Strict prohibition, legal action for violation
Scope
Quality and grading of milk
Safety, composition, hygiene, traceability, and labelling
Summary:
BIS standards provide guidelines for milk composition and quality control in the dairy industry.
FSSAI standards are legally binding and ensure milk safety, hygiene, and consumer protection, including limits on chemical adulterants, microbial quality, and composition.
Both standards are complementary, with BIS providing technical specifications and FSSAI enforcing regulatory compliance.
Combined table showing BIS and FSSAI standards side by side for cow and buffalo milk, useful for quick reference:
Parameter
BIS (Cow Milk)
FSSAI (Cow Milk)
BIS (Buffalo Milk)
FSSAI (Buffalo Milk)
Remarks / Testing Methods
Fat (%)
≥ 3.0
≥ 3.0
≥ 6.5
≥ 6.5
Gerber / Babcock, IR, Ultrasonic
Solids-Not-Fat (SNF %)
≥ 8.5
≥ 8.5
≥ 9.0
≥ 9.0
Gravimetric, Lactoscan, IR spectroscopy
Protein (%)
≥ 2.8
≥ 2.8
≥ 3.5
≥ 3.5
Kjeldahl, IR spectroscopy, Ultrasonic
Lactose (%)
4.8–5.2
4.8–5.2 (natural)
4.8–5.2
4.8–5.2 (natural)
Polarimetry, IR spectroscopy
Density / Specific Gravity
1.028–1.032 g/mL
1.028–1.032 g/mL
1.028–1.032 g/mL
1.028–1.032 g/mL
Lactometer, Ultrasonic Analyser
Freezing Point (°C)
−0.515 ± 0.005
−0.515 ± 0.005
−0.515 ± 0.005
−0.515 ± 0.005
Cryoscope / Freezing point apparatus
Added Water
Not permitted
Not permitted
Not permitted
Not permitted
Freezing point depression, IR, Ultrasonic
Urea / Neutralizers
Not permitted
Max 70 mg/100 mL
Not permitted
Max 70 mg/100 mL
DMAB test, Conductivity, IR spectroscopy
Formalin / Hydrogen Peroxide / Boric Acid
Prohibited
Strictly prohibited
Prohibited
Strictly prohibited
Chemical tests, Rapid kits
Microbial Limits (SPC)
≤ 5×10⁵ CFU/mL
≤ 5×10⁵ CFU/mL
≤ 5×10⁵ CFU/mL
≤ 5×10⁵ CFU/mL
Standard Plate Count, MBRT
Coliform Count
Not specified
≤ 100 CFU/mL
Not specified
≤ 100 CFU/mL
Coliform count test
Somatic Cell Count (SCC)
Not specified
≤ 5×10⁵ cells/mL
Not specified
≤ 5×10⁵ cells/mL
Microscopic count, Flow cytometry
Key Points:
BIS provides technical specifications mainly for milk composition and quality control.
FSSAI provides legally enforceable limits for safety, hygiene, and adulteration.
Both standards cover fat, SNF, protein, density, freezing point, and microbial quality, but FSSAI additionally enforces coliform limits, somatic cell count, and legal compliance.
Testing methods include a combination of physical (lactometer), chemical (Kjeldahl, DMAB), microbiological (SPC, coliform), and instrumental (IR, ultrasonic) methods.
Definition:
The Codex Alimentarius Commission (CAC), established by FAO and WHO, develops internationally recognized standards, guidelines, and codes of practice for foods, including milk and milk products. The guidelines ensure safety, quality, and fair trade in the global dairy sector.
Scope:
Raw milk (cow, buffalo, goat, sheep, camel, etc.)
Processed milk (pasteurized, UHT, sterilized)
Milk composition and hygiene standards
Limits on contaminants and additives
Key Parameters for Milk Testing
Parameter
Codex Guidelines / Standards
Purpose
Fat (%)
Cow milk ≥ 3.25%
Ensure nutritive value and standard composition
Solids-Not-Fat (SNF %)
Minimum 8.25%
Maintain nutritional quality and prevent dilution
Protein (%)
Typical cow milk 3.0–3.5%
Nutritional and compositional standard
Lactose (%)
Naturally occurring 4.8–5.2%
Quality marker
Density / Specific Gravity
1.028–1.032 g/mL
Detect added water
Freezing Point (°C)
−0.515 ± 0.005
Detect milk dilution
Added Water
Not permitted
Prevent adulteration
Urea / Neutralizers
Not permitted
Prevent adulteration and chemical contamination
Formalin / Hydrogen Peroxide / Boric Acid
Strictly prohibited
Safety and chemical compliance
Microbial Limits
Standard Plate Count ≤ 5×10⁵ CFU/mL
Ensure hygiene and safety
Coliform Count
≤ 100 CFU/mL
Indicator of sanitary handling
Somatic Cell Count (SCC)
≤ 4×10⁵ cells/mL
Indicator of udder health and milk quality
Key Points of Codex Guidelines:
International benchmark: Ensures milk quality and safety for global trade.
Composition standards: Fat, SNF, protein, and lactose are standardized for nutritional adequacy and product labelling.
Microbiological limits: SPC and coliform limits ensure hygiene and prevent foodborne illnesses.
Adulteration prevention: Guidelines prohibit added water and chemical adulterants.
Analytical methods: Milk testing may include:
Physical: Lactometer, density, freezing point
Chemical: Kjeldahl (protein), Gerber/Babcock (fat), DMAB (urea)
Instrumental: IR spectroscopy, ultrasonic analysers
Microbiological: Standard Plate Count, coliform count, somatic cell count
Harmonization: Codex standards are aligned with ISO and national standards, such as BIS and FSSAI, facilitating international trade.
Applications of Codex Milk Guidelines
Regulatory compliance for international milk trade
Quality assurance in milk processing and packaging
Benchmarking milk composition for farmers and cooperatives
Guidance for milk testing laboratories to ensure safe and standardized products
Summary:
Codex Alimentarius provides globally accepted standards for milk composition, safety, and hygiene, focusing on fat, protein, SNF, lactose, microbial quality, and adulteration control. These guidelines serve as a reference for national regulations (like FSSAI and BIS) and facilitate safe, high-quality milk production and trade worldwide.
Comparative table of Codex, FSSAI, and BIS milk standards:
Parameter
Codex Alimentarius
FSSAI (India)
BIS (India)
Remarks / Testing Methods
Fat (%)
Cow milk ≥ 3.25%
Cow: ≥ 3.0%, Buffalo: ≥ 6.5%
Cow: ≥ 3.0%, Buffalo: ≥ 6.5%
Gerber / Babcock, IR, Ultrasonic
Solids-Not-Fat (SNF %)
≥ 8.25%
Cow: ≥ 8.5%, Buffalo: ≥ 9.0%
Cow: ≥ 8.5%, Buffalo: ≥ 9.0%
Gravimetric, Lactoscan, IR spectroscopy
Protein (%)
Typical cow milk 3.0–3.5%
Cow: ≥ 2.8%, Buffalo: ≥ 3.5%
Cow: ≥ 2.8%, Buffalo: ≥ 3.5%
Kjeldahl, IR spectroscopy, Ultrasonic
Lactose (%)
4.8–5.2 (natural)
Naturally 4.8–5.2
4.8–5.2 (natural)
Polarimetry, IR spectroscopy
Density / Specific Gravity
1.028–1.032 g/mL
1.028–1.032 g/mL
1.028–1.032 g/mL
Lactometer, Ultrasonic Analyser
Freezing Point (°C)
−0.515 ± 0.005
−0.515 ± 0.005
−0.515 ± 0.005
Cryoscope / Freezing point apparatus
Added Water
Not permitted
Not permitted
Not permitted
Freezing point depression, IR, Ultrasonic
Urea / Neutralizers
Not permitted
Max 70 mg/100 mL (urea)
Not permitted
DMAB test, Conductivity, IR spectroscopy
Formalin / Hydrogen Peroxide / Boric Acid
Strictly prohibited
Strictly prohibited
Prohibited
Chemical tests, Rapid kits
Microbial Limits (SPC)
≤ 5×10⁵ CFU/mL
≤ 5×10⁵ CFU/mL
≤ 5×10⁵ CFU/mL
Standard Plate Count, MBRT
Coliform Count
≤ 100 CFU/mL
≤ 100 CFU/mL
Not specified
Coliform count test
Somatic Cell Count (SCC)
≤ 4×10⁵ cells/mL
≤ 5×10⁵ cells/mL
Not specified
Microscopic count, Flow cytometry
Key Insights:
Codex standards provide international benchmarks for milk composition, microbial quality, and adulteration control.
FSSAI standards are legally binding in India, closely aligned with BIS and Codex, with additional enforcement on adulterants, coliform count, and somatic cell count.
BIS standards focus primarily on composition and quality control, widely used in industry.
Testing methods include a combination of physical (lactometer), chemical (Kjeldahl, Gerber), microbiological (SPC, coliform), and instrumental (IR, ultrasonic) techniques.
Harmonizing Codex, BIS, and FSSAI standards ensures safety, quality, and international trade compliance.
Definition:
The International Organization for Standardization (ISO) develops globally recognized standards for food quality, safety, and testing methods, including milk and dairy products. ISO standards ensure uniformity, reliability, and comparability of milk testing results across laboratories worldwide.
Relevant ISO Standards for Milk:
ISO Standard
Scope / Purpose
ISO 6731
Determination of milk density (lactometer method)
ISO 7218
Microbiological examination of milk – general rules
ISO 5764
Milk – Determination of fat content (Gerber method)
ISO 8968-1 / 2
Determination of milk protein content (Kjeldahl method / calculation of true protein)
ISO 1736
Determination of freezing point of milk (cryoscopic method)
ISO 6611
Determination of lactose in milk and milk products (polarimetric method)
ISO 21543
Detection of adulteration – added water
ISO 16649
Enumeration of coliforms in milk
ISO 4833
Enumeration of microorganisms (Standard Plate Count)
ISO 14154
Somatic cells count in milk
Key Parameters Covered by ISO Standards
Parameter
Typical ISO Specification / Range
Purpose / Testing Method
Fat (%)
Cow: ~3.0–4.0%
Gerber method, Babcock method, IR spectroscopy
Solids-Not-Fat (SNF %)
8.0–9.0%
Gravimetric or IR methods
Protein (%)
Cow: 3.0–3.5%
Kjeldahl, IR spectroscopy
Lactose (%)
4.8–5.2%
Polarimetry, IR spectroscopy
Density / Specific Gravity
1.028–1.032 g/mL
ISO 6731 – lactometer
Freezing Point (°C)
−0.515 ± 0.005
ISO 1736 – cryoscopic method
Added Water
Not permitted
Freezing point depression, ISO 21543
Urea / Neutralizers
Not specifically set
Chemical / instrumental tests
Microbial Limits
SPC ≤ 5×10⁵ CFU/mL; Coliform ≤ 100 CFU/mL
ISO 4833, ISO 16649
Somatic Cell Count (SCC)
≤ 5×10⁵ cells/mL
ISO 14154 – microscopic or flow cytometry
Key Features of ISO Standards for Milk:
Global comparability: Ensures milk quality and testing results are consistent across countries.
Comprehensive: Covers physical, chemical, microbiological, and instrumental testing methods.
Adulteration detection: Provides methods for detecting added water and monitoring milk composition.
Traceability and reproducibility: Standardized procedures allow laboratories worldwide to generate reliable results.
Integration with national regulations: ISO standards often guide BIS, FSSAI, and Codex-aligned testing protocols.
Applications:
Milk collection and processing centres for quality control.
Dairy laboratories for routine analysis.
Export and trade compliance, ensuring milk meets international safety and quality benchmarks.
Research and development for new dairy products.
Summary:
ISO standards provide globally recognized guidelines for milk testing, including composition analysis, microbiological quality, adulteration detection, and somatic cell count. They are widely used in laboratories and dairy industries to ensure safety, quality, and international trade compliance, complementing national standards like BIS and FSSAI and international guidelines like Codex Alimentarius.
Comparative table of ISO, Codex, BIS, and FSSAI milk standards:
Parameter
ISO Standards
Codex Alimentarius
FSSAI (India)
BIS (India)
Testing Methods / Notes
Fat (%)
Cow: 3.0–4.0%
Cow: ≥ 3.25%
Cow: ≥ 3.0%, Buffalo: ≥ 6.5%
Cow: ≥ 3.0%, Buffalo: ≥ 6.5%
Gerber / Babcock, IR, Ultrasonic
Solids-Not-Fat (SNF %)
8.0–9.0%
≥ 8.25%
Cow: ≥ 8.5%, Buffalo: ≥ 9.0%
Cow: ≥ 8.5%, Buffalo: ≥ 9.0%
Gravimetric, Lactoscan, IR spectroscopy
Protein (%)
Cow: 3.0–3.5%
3.0–3.5%
Cow: ≥ 2.8%, Buffalo: ≥ 3.5%
Cow: ≥ 2.8%, Buffalo: ≥ 3.5%
Kjeldahl, IR spectroscopy, Ultrasonic
Lactose (%)
4.8–5.2%
4.8–5.2%
Naturally 4.8–5.2
4.8–5.2 (natural)
Polarimetry, IR spectroscopy
Density / Specific Gravity
1.028–1.032 g/mL
1.028–1.032 g/mL
1.028–1.032 g/mL
1.028–1.032 g/mL
Lactometer, Ultrasonic Analyser
Freezing Point (°C)
−0.515 ± 0.005
−0.515 ± 0.005
−0.515 ± 0.005
−0.515 ± 0.005
Cryoscope / Freezing point apparatus
Added Water
Not permitted
Not permitted
Not permitted
Not permitted
Freezing point depression, IR, Ultrasonic
Urea / Neutralizers
Not specifically set
Not permitted
Max 70 mg/100 mL (urea)
Not permitted
DMAB test, Conductivity, IR spectroscopy
Formalin / Hydrogen Peroxide / Boric Acid
Strictly prohibited
Strictly prohibited
Strictly prohibited
Prohibited
Chemical tests, Rapid kits
Microbial Limits (SPC)
≤ 5×10⁵ CFU/mL
≤ 5×10⁵ CFU/mL
≤ 5×10⁵ CFU/mL
≤ 5×10⁵ CFU/mL
Standard Plate Count, MBRT
Coliform Count
≤ 100 CFU/mL
≤ 100 CFU/mL
≤ 100 CFU/mL
Not specified
Coliform count test
Somatic Cell Count (SCC)
≤ 5×10⁵ cells/mL
≤ 4×10⁵ cells/mL
≤ 5×10⁵ cells/mL
Not specified
Microscopic count, Flow cytometry
Key Insights:
ISO standards provide internationally recognized methods for milk testing, enabling global trade and lab comparability.
Codex standards serve as a global benchmark for composition, safety, and adulteration control.
FSSAI standards are legally binding in India, with additional enforcement on adulterants, coliforms, and SCC.
BIS standards focus on milk composition and quality control, widely used in Indian industry.
Testing methods across all standards include a combination of physical, chemical, microbiological, and instrumental techniques, ensuring accuracy and reliability.
Definition:
Legal Metrology refers to the system of laws, regulations, and standards that govern the measurement of goods to ensure accuracy, fairness, and transparency in trade. In the context of milk, it ensures that milk sold by volume or weight is measured correctly and that consumers are not shortchanged.
Governing Laws in India:
Legal Metrology Act, 2009 – provides the legal framework for units of measurement, verification, and certification of weighing and measuring instruments.
Legal Metrology (Packaged Commodities) Rules, 2011 – specifies standards for packaged milk, labelling, and quantity declaration.
State-specific rules – local authorities may regulate milk vendors, collection centres, and cooperatives.
Key Requirements for Milk Measurement:
Aspect
Requirement / Standard
Units of Measurement
Liters (L) or milliliters (mL) – standard SI units
Accuracy of Measuring Instruments
Milk meters, volumetric tanks, and milk cans must be calibrated and certified periodically
Packaging and Labelling
Packaged milk must indicate:
• Net quantity
• Manufacturing date
• Expiry / Best before date
• Name and address of manufacturer / packer
• MRP
Certification of Instruments
Milk collection units, electronic milk meters, and weighing scales must be verified by Legal Metrology Department
Inspection & Penalties
Authorities conduct random inspections; non-compliance may result in penalties, fines, or license cancellation
Temperature Considerations
For bulk milk, measurements must consider temperature correction, as milk density changes with temperature
Transparency & Consumer Protection
Ensures fair trade practices; consumers get the declared volume and quality
Milk Measurement Methods under Legal Metrology:
Volumetric Measurement:
Using calibrated milk cans, tanks, or jars with standard markings.
Common in village-level milk collection centres.
Electronic Milk Meters / Milk Collection Units (AMCU):
Measure volume and weight electronically.
Must be verified, calibrated, and certified under Legal Metrology rules.
Weighing Scales (if milk sold by weight):
Scales must be verified periodically and marked with certification seal.
Importance of Legal Metrology in Milk Trade:
Consumer protection: Ensures buyers receive the exact quantity of milk.
Fair trade: Prevents short-weighing or adulteration claims in the market.
Standardization: Harmonizes measurement practices across dairy cooperatives, private dairies, and vendors.
Compliance for packaged milk: Mandatory for milk brands, retail packaging, and exports.
Integration with quality control: Works alongside FSSAI and BIS standards to ensure both quantity and quality.
Summary:
Legal Metrology in milk measurement ensures that milk sold or collected is measured accurately, instruments are verified and certified, and consumers receive the quantity declared. It complements milk quality regulations (FSSAI, BIS) by focusing on trade fairness, transparency, and compliance with standard units of measurement.
Definition:
Laboratory accreditation is the formal recognition that a laboratory is technically competent to perform specific tests, calibrations, or analyses, following international standards. Accreditation ensures accuracy, reliability, and global acceptance of test results.
Relevant Accreditation Standards for Milk Testing:
ISO/IEC 17025:2017 – General requirements for competence of testing and calibration laboratories.
NABL (National Accreditation Board for Testing and Calibration Laboratories) – India’s official body providing accreditation to food testing labs, including milk.
FSSAI-recognized labs – Laboratories accredited for food safety, quality, and compliance testing.
Key Aspects of Accreditation:
Technical Competence: Lab personnel must be trained in milk testing methods (chemical, microbiological, instrumental).
Equipment Calibration: Instruments like Lactoscan, Milko-Tester, IR analysers, pH meters, and cryoscopes must be calibrated and maintained.
Standard Operating Procedures (SOPs): Tests are performed following documented procedures for repeatability.
Quality Assurance: Regular internal audits, proficiency testing, and validation of methods are mandatory.
Traceability: Test results must be traceable to standard reference materials and certified methods.
Reporting: Test reports should include test method, results, uncertainty, and accreditation status.
Benefits of Accreditation:
Ensures reliable milk quality and safety assessment.
Enhances consumer confidence and trade compliance.
Facilitates recognition in domestic and international markets.
Helps in regulatory compliance with FSSAI, BIS, and Codex standards.
2. Good Laboratory Practices (GLP) for Milk Testing
Definition:
GLP is a set of principles and procedures to ensure quality, integrity, and reproducibility of laboratory testing. While originally developed for research, GLP is applied to analytical and food testing laboratories, including milk testing labs.
Key Principles of GLP in Milk Testing:
Organization and Personnel:
Defined roles for lab manager, analysts, and quality officers.
Personnel trained in milk testing protocols and safety.
Facilities and Equipment:
Proper lab infrastructure, clean and controlled environment.
Calibration and maintenance of Lactoscan, Milko-Tester, ultrasonic analysers, IR spectroscopy equipment, pH/conductivity meters.
Standard Operating Procedures (SOPs):
Documented methods for physical, chemical, microbiological, and instrumental milk tests.
Includes sample collection, handling, analysis, and reporting.
Test and Calibration Methods:
Use of validated methods for fat, SNF, protein, lactose, microbial counts, and adulterant detection.
Quality Assurance and Control:
Regular internal audits, control samples, proficiency testing, and corrective actions for deviations.
Data Recording and Reporting:
Complete and accurate lab notebooks, electronic records, and test reports.
Ensures traceability, transparency, and legal defensibility.
Safety and Waste Management:
Proper handling of chemicals, biological samples, and waste.
Compliance with occupational safety standards.
Importance of Accreditation and GLP in Milk Testing
Ensures high-quality, reliable, and legally defensible milk test results.
Promotes consumer safety and confidence in dairy products.
Facilitates regulatory compliance with FSSAI, BIS, and international standards (Codex, ISO).
Supports international trade and export of dairy products.
Reduces errors, improves laboratory efficiency, and maintains scientific integrity.
Summary:
Laboratory accreditation (ISO/IEC 17025, NABL) and GLP together ensure that milk testing laboratories are competent, reliable, and safe, following standardized procedures, validated methods, and documented quality assurance practices. This ensures accurate milk quality assessment, supports regulatory compliance, and safeguards consumer health.
Sample Collection and Laboratory Practices in Milk Testing involve standardized procedures to ensure the accuracy, reliability, and safety of test results. Milk samples are collected using clean, sterilized containers, labeled with unique identifiers, date, time, and source information, and stored at 4–6°C to prevent microbial growth or compositional changes. During laboratory analysis, Good Laboratory Practices (GLP) are followed, including the use of calibrated instruments (e.g., Lactoscan, Milko-Tester, IR analysers), adherence to Standard Operating Procedures (SOPs) for physical, chemical, and microbiological tests, and proper handling of chemicals and biological materials. Quality control is maintained through duplicate testing, control samples, and periodic instrument verification. Accurate documentation, traceability, and reporting are ensured to meet ISO/IEC 17025, NABL accreditation, and regulatory compliance (FSSAI, BIS, Codex), providing trustworthy results for milk quality, safety, and payment determination.
Milk testing laboratories handle different types of milk samples, depending on the stage of the supply chain and the purpose of analysis. Each type requires specific handling and testing methods to ensure accuracy.
1. Raw Milk
Definition: Milk collected directly from the udder of cows, buffaloes, goats, or other dairy animals without any heat treatment.
Purpose of Testing:
Determining basic composition: fat, protein, solids-not-fat (SNF), lactose.
Detecting adulterants: water, neutralizers, chemicals.
Assessing microbial quality: Standard Plate Count (SPC), coliforms, pathogens.
Monitoring somatic cell count (SCC) for udder health.
Handling: Collected in sterile, cooled containers, transported at 4–6°C to the laboratory.
2. Pasteurized Milk
Definition: Milk that has been heat-treated (usually 63–65°C for 30 minutes or 72°C for 15 seconds) to kill pathogenic microorganisms.
Purpose of Testing:
Verifying compliance with pasteurization standards (thermal treatment).
Checking microbiological quality, including spore-forming bacteria.
Monitoring composition and adulteration, as some chemical adulterants may survive pasteurization.
Handling: Must be stored under refrigeration (4°C) and tested promptly to avoid post-pasteurization contamination.
3. Sterilized / UHT Milk
Definition: Milk processed at ultra-high temperatures (135–150°C for 2–5 seconds) to achieve commercial sterility.
Purpose of Testing:
Ensuring sterility and absence of microbial growth.
Verifying composition and shelf-life stability.
Detecting any chemical adulterants or packaging-related contaminants.
Handling: Can be stored at room temperature before opening; samples for testing should be taken under aseptic conditions.
4. Packaged Milk
Definition: Milk sold in tetra packs, bottles, or pouches, which may be raw, pasteurized, or UHT.
Purpose of Testing:
Compliance with FSSAI labelling and packaging regulations.
Checking composition, microbial quality, and chemical safety.
Assessing adulteration, added water, and shelf-life parameters.
Handling: Samples are tested as-is, maintaining integrity of the packaging until analysis.
5. Milk Powder / Concentrated Milk
Definition: Milk that has been evaporated, spray-dried, or condensed to reduce water content.
Purpose of Testing:
Verifying reconstitution properties (solubility, taste, colour).
Determining composition: fat, protein, lactose, minerals.
Testing for adulterants and microbial contamination.
Handling: Stored in airtight containers, tested after proper reconstitution if required.
6. Mixed / Bulk Milk Samples
Definition: Composite milk collected from multiple animals or farms, often at milk collection centres or dairy plants.
Purpose of Testing:
Determining average quality and composition.
Detecting batch adulteration or contamination.
Used for payment determination in cooperatives.
Handling: Mixed thoroughly, representative sample collected using standard protocols to ensure accuracy.
Key Points Across All Sample Types
Temperature control: Essential to prevent microbial growth or chemical changes.
Sterility and hygiene: Avoid contamination during collection and transport.
Proper labelling and documentation: Ensures traceability and regulatory compliance.
Testing methods vary depending on milk type: raw milk emphasizes microbial load, while UHT focuses on sterility and shelf-life, etc.
Table summarizing different types of milk samples with their key testing parameters, handling, and purpose:
Milk Type
Definition
Key Testing Parameters
Handling / Storage
Purpose of Testing
Raw Milk
Milk collected directly from the udder, no heat treatment
Fat, SNF, protein, lactose, SPC, coliform, SCC, adulterants
Sterile containers, refrigerated at 4–6°C
Composition, hygiene, adulteration, udder health
Pasteurized Milk
Milk heat-treated (63–65°C for 30 min or 72°C for 15 sec)
Fat, protein, SNF, lactose, SPC, thermophilic bacteria, adulterants
Refrigerated at 4°C, test promptly
Pasteurization compliance, microbial quality, adulteration
UHT / Sterilized Milk
Milk processed at 135–150°C for 2–5 sec for commercial sterility
Fat, protein, SNF, lactose, sterility, adulterants, shelf-life
Room temperature before opening; aseptic sampling
Sterility, composition, shelf-life, chemical safety
Packaged Milk
Milk sold in bottles, pouches, tetra packs (raw/pasteurized/UHT)
Fat, protein, SNF, lactose, SPC, adulterants, labelling compliance
Tested as-is, maintain packaging integrity
Regulatory compliance, composition, microbial and chemical safety
Milk Powder / Concentrated Milk
Evaporated, spray-dried, or condensed milk
Fat, protein, lactose, solubility, minerals, adulterants, microbial load
Airtight containers; reconstitute if needed
Composition, reconstitution properties, adulteration, microbial quality
Mixed / Bulk Milk
Composite milk from multiple animals/farms
Average fat, SNF, protein, lactose, SPC, adulterants
Thorough mixing, representative sampling
Batch quality assessment, detection of adulteration, payment determination
Key Notes:
Temperature control is critical to prevent spoilage or microbial growth.
Sterile collection and proper labelling ensure traceability.
Testing methods vary according to milk type and purpose: e.g., raw milk emphasizes microbial quality, while UHT focuses on sterility and shelf-life.
Mixed/bulk samples are representative of the batch, used for quality monitoring and payment calculations.
Milk is a highly perishable commodity, and its composition and microbial quality can change rapidly after collection. Proper sample preservation and transport are crucial to ensure accurate and reliable laboratory testing results.
1. Preservation Methods
a. Temperature Control
Raw milk:
Must be cooled immediately to 4–6°C after collection.
Prevents microbial growth and chemical changes such as proteolysis or fat separation.
Pasteurized milk:
Maintain at 4°C, avoid prolonged storage before testing.
Limits post-pasteurization contamination.
UHT / Sterilized milk:
Can be stored at room temperature before opening; once opened, refrigerate at 4°C.
b. Chemical Preservatives (if cooling is not possible)
Used to delay microbial growth during transport to distant labs.
Common preservatives:
Potassium dichromate (for microbial tests)
Bronopol
Must be used according to standard protocols to avoid interference with tests.
c. Sterility and Hygiene
Containers must be sterile, clean, and leak-proof.
Avoid contact with hands or contaminated surfaces.
Use airtight lids to prevent exposure to dust, air, or external microbes.
2. Sample Containers
Raw and pasteurized milk: Sterile glass or plastic bottles, preferably graduated for volume measurement.
UHT / Packaged milk: Original packaging can be used; open carefully for testing.
Milk powder / condensed milk: Airtight, moisture-proof containers; reconstitute if required.
Mixed / bulk samples: Large sterile tanks; take representative subsamples in sterile bottles.
3. Transport Guidelines
Time: Samples should reach the laboratory within 24 hours of collection for raw and pasteurized milk.
Cooling: Use ice boxes or refrigerated transport for raw and pasteurized milk.
Labelling: Each sample must have:
Unique ID / batch number
Date and time of collection
Source / farm / cow ID
Type of milk (raw, pasteurized, etc.)
Documentation: Maintain sample logs and chain-of-custody records for traceability and regulatory compliance.
4. Special Considerations
Avoid repeated temperature fluctuations – can cause protein denaturation or fat separation.
Minimize shaking or agitation – prevents foaming or changes in milk solids.
Prevent contamination – ensure clean handling and transport equipment.
Use preservatives only when necessary – may interfere with some chemical or microbiological tests.
Importance of Proper Preservation and Transport
Ensures accurate milk composition analysis (fat, SNF, protein, lactose).
Maintains microbiological integrity for SPC, coliform, and pathogen testing.
Prevents false readings due to spoilage, adulteration, or chemical changes.
Complies with ISO, NABL, FSSAI, BIS, and Codex standards for quality and regulatory testing.
Summary:
Proper sample preservation and transport in milk testing involve cooling, sterile handling, proper containers, timely transport, and documentation. Following these practices ensures that the physical, chemical, and microbiological properties of milk remain intact, providing reliable test results for quality control, safety assessment, and regulatory compliance.
Milk testing involves accurate measurement of physical, chemical, and microbiological parameters. Proper cleaning and sterilization of glassware are essential to avoid contamination, interference, or erroneous results.
1. Cleaning of Glassware
a. Initial Rinsing
Immediately after use, rinse glassware with tap water to remove residual milk and solids.
For sticky residues, soak in cold water briefly to prevent protein coagulation.
b. Washing with Detergent
Use neutral or mild laboratory detergents; avoid strong alkaline or acidic detergents that may react with milk components.
Scrub using a soft brush to reach all internal surfaces.
c. Rinsing
Rinse thoroughly with tap water to remove detergent residues.
Follow with distilled or deionized water to prevent mineral deposits or ionic contamination.
d. Special Considerations
For fat or protein residues, rinse with warm water or a mild solution of alcohol or acetone if necessary.
Avoid abrasive materials that can scratch glassware, as scratches may harbor contaminants.
2. Sterilization of Glassware
a. Dry Heat Sterilization
Place glassware in a hot air oven at 160–180°C for 1–2 hours.
Commonly used for volumetric flasks, pipettes, and beakers that must be completely dry.
b. Autoclaving (Steam Sterilization)
Glassware is placed in an autoclave at 121°C, 15 psi for 15–20 minutes.
Suitable for microbiological work such as SPC, coliform count, or pathogen detection.
c. Chemical Sterilization
For delicate glassware or instruments, sterilization can be done using 70% ethanol or 0.1% sodium hypochlorite.
After chemical sterilization, rinse thoroughly with sterile distilled water to remove residues.
3. Drying and Storage
After cleaning and sterilization, dry glassware in a dust-free area or hot air oven.
Store in closed cabinets to prevent contamination.
Avoid stacking glassware in a way that could cause scratches or breakage.
4. Importance in Milk Testing
Prevents contamination – especially for microbiological and chemical tests.
Maintains accuracy – residues of milk, detergent, or microbes can alter test results for fat, protein, SNF, or microbial counts.
Supports GLP and accreditation – clean and sterilized glassware is required for ISO/IEC 17025 and NABL compliance.
Ensures safety – reduces risk of microbial growth and chemical hazards in the lab.
Summary:
Cleaning and sterilization of glassware in milk testing involve rinsing, detergent washing, thorough rinsing with distilled water, and sterilization via dry heat, autoclaving, or chemicals. Proper procedures maintain accuracy, reproducibility, and hygiene, ensuring reliable results in physical, chemical, and microbiological milk testing.
Milk testing laboratories handle perishable biological samples, chemicals, and microbiological cultures, so proper safety and hygiene are essential to protect personnel, prevent contamination, and ensure accurate results.
1. Personal Hygiene
Lab personnel must:
Wear clean lab coats, gloves, and protective footwear.
Use hair nets or caps to prevent hair contamination.
Wash hands before and after handling milk samples.
Avoid eating, drinking, or smoking inside the laboratory.
Health precautions: Personnel with infections should avoid handling milk samples, as raw milk can carry pathogens.
2. Lab Cleanliness
Work surfaces: Clean and disinfect before and after each use with 70% ethanol or other suitable disinfectants.
Equipment maintenance: Instruments such as Lactoscan, Milko-Tester, IR analysers, and pH/conductivity meters must be cleaned, calibrated, and maintained regularly.
Glassware and tools: Follow strict cleaning and sterilization protocols to prevent contamination.
Floor and environment: Floors, drains, and waste bins must be clean and disinfected daily to avoid microbial growth.
3. Sample Handling Safety
Collection and transport: Use sterile containers, labelled with source and date, and maintain temperature control (4–6°C) for raw and pasteurized milk.
Avoid cross-contamination: Handle each sample separately and use dedicated tools for microbial, chemical, or instrumental analysis.
Spillage management: Clean spills immediately using disinfectants and dispose of contaminated materials safely.
4. Chemical Safety
Handling reagents: Many milk tests use chemicals such as acids, bases, solvents, or preservatives.
Protective gear: Wear gloves, goggles, and lab coats when handling chemicals.
Storage: Store chemicals in labeled, corrosion-resistant cabinets, separated by compatibility.
Disposal: Dispose of chemical wastes according to lab SOPs and environmental regulations.
5. Microbiological Safety
Biosafety levels: Milk testing for pathogens may require BSL-1 or BSL-2 precautions depending on the microorganisms involved.
Use of biosafety cabinets: Handle pathogenic or potentially pathogenic cultures in a Class II biosafety cabinet.
Autoclaving: All microbial waste must be autoclaved before disposal.
6. Waste Management
Solid waste: Glassware, gloves, and disposable containers must be segregated and disposed of in designated bins.
Liquid waste: Chemical and milk waste must be neutralized or treated before disposal.
Biohazard waste: Microbiological waste should be autoclaved or incinerated according to regulatory guidelines.
7. Documentation and Training
Standard Operating Procedures (SOPs): All safety, hygiene, and handling practices must be documented.
Training: Laboratory personnel should be trained in biosafety, chemical safety, spill management, and proper use of PPE.
Incident reporting: Accidents, spills, or exposure incidents must be recorded and corrective actions implemented.
Importance of Safety and Hygiene
Protects laboratory personnel from pathogens and chemical hazards.
Prevents contamination of milk samples, ensuring reliable and accurate test results.
Ensures compliance with GLP, ISO 17025, NABL, and FSSAI/BIS standards.
Promotes efficient laboratory operations and reduces risk of accidents.
Summary:
Safety and hygiene in milk laboratories involve a combination of personal protective measures, clean and disinfected workspaces, careful sample handling, chemical and microbial safety, waste management, and staff training. Proper implementation ensures accuracy in milk testing, regulatory compliance, and protection of personnel from biological and chemical hazards.
Milk Testing in the Supply Chain is a critical process to ensure quality, safety, and fair trade from the point of collection to the consumer. At farm and village collection centres, raw milk is tested for composition (fat, protein, SNF), added water, and microbial quality before pooling or payment. During transport and storage, milk is monitored for temperature and hygiene to prevent spoilage. At processing plants, pasteurized or UHT milk undergoes further testing for microbiological safety, chemical contaminants, and adherence to labelling standards. Quality checks continue during packaging, distribution, and retail, ensuring compliance with FSSAI, BIS, ISO, and Codex standards. Effective milk testing across the supply chain maintains consumer confidence, regulatory compliance, and the integrity of dairy products.
Milk testing at the producer level (farms or small-scale dairy units) is the first and most critical step in ensuring milk quality, safety, and fair payment. Early detection of adulteration, microbial contamination, or poor milk composition helps maintain consumer confidence, animal health, and compliance with regulatory standards.
1. Objectives of Testing at Producer Level
Assess milk composition: Fat, protein, solids-not-fat (SNF), and lactose to determine payment based on quality.
Detect adulterants: Added water, neutralizers, detergents, or chemicals.
Monitor hygiene and microbial quality: Check for bacterial load and udder health indicators (somatic cell count).
Ensure animal health: High SCC or unusual composition can indicate mastitis or other infections.
Maintain traceability: Record the source, date, and batch for compliance and quality tracking.
2. Common Tests at Producer Level
Test Type
Purpose / Parameter
Physical Tests
Clot-on-boiling, lactometer reading, sediment test for adulteration detection
Chemical Tests
Fat (Gerber method), SNF, protein estimation, detection of added water, neutralizers, or preservatives
Microbiological Tests
Methylene blue reduction test, coliform detection, somatic cell count
Rapid / Strip Tests
Commercial kits for urea, starch, detergents, or antibiotics in milk
3. Equipment and Instruments
Lactometer: Measures milk density, indicating added water or poor solids content.
Fat testing equipment (Gerber or digital): Determines fat percentage for payment and quality assessment.
Portable Milko-Tester or Lactoscan: Provides rapid readings of fat, SNF, protein, lactose, and density.
Rapid test kits/strips: Detect common adulterants or antibiotic residues.
4. Sample Collection and Handling
Collect milk directly from the udder into clean, sterilized containers.
Mix thoroughly before taking samples to ensure representative testing.
Label samples with producer ID, date, and batch number.
Cool to 4–6°C if testing is delayed or for transport to a collection centre.
5. Benefits of Producer-Level Milk Testing
Improves milk quality at the source before bulk collection.
Prevents economic loss due to adulteration or poor-quality milk.
Promotes animal health monitoring, detecting early signs of mastitis or infection.
Supports fair trade practices, as payment is often linked to milk quality.
Facilitates compliance with FSSAI, BIS, and cooperative society regulations.
Summary:
Milk testing at the producer level ensures that milk entering the supply chain is safe, wholesome, and of good quality. It involves a combination of physical, chemical, microbiological, and rapid tests, supported by simple instruments and proper sampling practices. Early testing benefits farmers, processors, and consumers by maintaining quality, safety, and fair pricing.
Milk Collection Centres serve as intermediate points between producers (farmers) and processing plants, where raw milk from multiple farmers is pooled, tested, and stored before transportation. Testing at MCCs is crucial to ensure milk quality, safety, and fair payment.
1. Objectives of Testing at MCCs
Assess quality of incoming milk from individual farmers.
Detect adulteration such as added water, neutralizers, or chemicals.
Monitor microbial load to prevent spoilage during storage and transport.
Determine milk composition (fat, SNF, protein, lactose) for payment calculation.
Ensure compliance with FSSAI, BIS, and cooperative society standards.
Provide feedback to farmers for quality improvement.
2. Common Tests at MCCs
Test Type
Purpose / Parameter
Physical Tests
Lactometer (density), Clot-on-Boiling (COB), sediment test
Chemical Tests
Fat (Gerber or digital), SNF, protein, lactose, adulterants (water, neutralizers, detergents)
Microbiological Tests
Methylene Blue Reduction Test, Total Plate Count (TPC), coliform detection, somatic cell count (SCC)
Rapid / Strip Tests
Antibiotic residues, urea, starch, detergents, and other adulterants
Instrumental Testing
Portable Lactoscan, Milko-Tester, or ultrasonic milk analysers for fat, SNF, protein, lactose, density
3. Equipment and Instruments at MCCs
Lactometer: For density check to detect added water.
Gerber or digital fat testers: Quick estimation of fat content.
Milko-Tester / Lactoscan / ultrasonic analysers: Simultaneous measurement of fat, SNF, protein, lactose, density.
Rapid test kits / strips: Detect common adulterants and antibiotic residues.
Cold storage tanks: Maintain milk at 4–6°C before transport.
4. Sample Collection and Handling at MCCs
Collect representative samples from each farmer before pooling.
Label samples with farmer ID, date, and batch number.
Mix the pooled milk thoroughly to ensure uniform composition.
Store milk under refrigeration (4–6°C) until transported to the processing plant.
5. Importance of MCC-Level Milk Testing
Ensures quality of milk entering the dairy plant, preventing downstream issues.
Enables payment based on quality, incentivizing farmers to maintain hygiene and feed standards.
Early detection of adulteration reduces economic loss and protects consumers.
Supports cooperative management by maintaining records and traceability.
Reduces microbial load before transportation, preserving shelf-life and safety.
Summary:
Milk testing at Milk Collection Centres is a critical quality control step in the dairy supply chain. It involves physical, chemical, microbiological, and rapid tests, supported by portable instruments and cold storage, to ensure that pooled milk from multiple producers is safe, high-quality, and compliant with regulatory standards before it reaches the processing plant.
Dairy plants are the central processing units where raw milk from multiple collection points is processed into pasteurized, UHT, or value-added dairy products. Rigorous testing and quality control at this stage ensure consumer safety, compliance with standards, and product consistency.
1. Objectives of Milk Testing at Dairy Plants
Ensure raw milk meets quality standards before processing.
Monitor composition: Fat, SNF, protein, lactose, total solids.
Detect contaminants: Added water, neutralizers, antibiotics, heavy metals, pesticides.
Assess microbial quality: Standard Plate Count, coliforms, pathogens.
Check process efficiency: Pasteurization, homogenization, and storage conditions.
Maintain regulatory compliance: FSSAI, BIS, ISO, Codex standards.
2. Milk Testing Procedures at Dairy Plants
Test Type
Purpose / Parameters
Physical Tests
Lactometer, Clot-on-Boiling, sediment check, freezing point
Chemical Tests
Fat, protein, SNF, lactose, total solids, added water, neutralizers, preservatives
Microbiological Tests
Standard Plate Count (SPC), coliforms, E. coli, Listeria, Salmonella, yeast and molds
Instrumental Testing
Infrared (IR) spectroscopy, ultrasonic milk analysers, Milko-Tester, Lactoscan
Rapid / Strip Tests
Antibiotic residues, urea, starch, detergents, other adulterants
Process Control Tests
Pasteurization verification (PT test), pH monitoring, conductivity, temperature checks
3. Quality Control Measures in Dairy Plants
a. Incoming Milk Inspection
Test milk from collection centres for composition, microbial quality, and adulteration.
Reject substandard milk to prevent contamination in processing.
b. Process Monitoring
Pasteurization: Monitor temperature and holding time; perform PT (Pasteurization Test) or enzyme tests.
Homogenization: Ensure uniform fat distribution.
Storage & Cooling: Milk stored at 4°C, equipment sanitized regularly.
c. Product Testing
Final product analysis: Fat, SNF, protein, lactose, total solids, and microbial quality.
Packaging checks: Labelling, seals, and sterility (for UHT milk).
Shelf-life studies: Periodic testing for microbial growth, pH, and sensory properties.
d. Instrumentation & Automation
Modern dairy plants use IR analysers, ultrasonic milk analysers, Milko-Tester, and Lactoscan for rapid and accurate testing.
Automated sampling and AMCU (Automatic Milk Collection Unit) testing helps in real-time quality assessment.
4. Documentation and Compliance
Maintain detailed records of incoming milk quality, processing parameters, and final product testing.
Ensure traceability from farm → collection centre → dairy plant → consumer.
Compliance with FSSAI, BIS, ISO 22000, ISO/IEC 17025, and Codex Alimentarius standards.
5. Importance of Dairy Plant Milk Testing and QC
Ensures consumer safety by preventing contaminated or adulterated milk from entering the market.
Maintains product consistency in fat, protein, and other constituents.
Supports regulatory compliance and audit requirements.
Reduces economic losses by preventing spoilage or product recalls.
Provides feedback to upstream supply chain, improving milk quality at the farm and collection centre level.
Summary:
Milk testing and quality control at dairy plants involve comprehensive physical, chemical, microbiological, and instrumental tests across the supply chain. Rigorous QC ensures safe, high-quality, and standardized dairy products, regulatory compliance, and consumer confidence.
Milk and dairy products intended for export must comply with stringent international quality and safety standards. Export-oriented milk testing ensures that products meet the requirements of importing countries, Codex Alimentarius guidelines, ISO standards, and specific buyer specifications.
1. Objectives of Milk Testing for Export
Ensure safety: Free from pathogenic microorganisms, toxins, and harmful chemicals.
Verify composition: Fat, protein, SNF, lactose, and total solids meet international standards.
Detect contaminants and adulterants: Pesticides, heavy metals, antibiotics, and other prohibited substances.
Comply with regulatory standards: Codex Alimentarius, ISO, FSSAI, and importing country requirements.
Maintain traceability: Ensure source-to-export documentation for quality assurance and audits.
2. Key Tests for Export Milk and Dairy Products
Test Type
Purpose / Parameters
Physical Tests
Density, freezing point, sediment, viscosity, organoleptic properties (taste, colour, smell)
Chemical Tests
Fat, protein, SNF, lactose, total solids, moisture content, pH, acidity
Microbiological Tests
Total Plate Count (SPC), coliforms, E. coli, Listeria, Salmonella, yeast & molds, somatic cell count (SCC)
Adulteration Detection
Added water, neutralizers, starch, detergents, synthetic milk, antibiotic residues
Chemical Contaminants
Heavy metals (lead, cadmium), pesticides, mycotoxins, aflatoxins
Instrumental Testing
Infrared spectroscopy, Lactoscan, Milko-Tester, ultrasonic analysers for rapid composition analysis
Shelf-Life & Storage Tests
Stability during transport, temperature monitoring, sensory evaluation
3. Quality Assurance Measures
HACCP Implementation: Identify hazards at critical control points from farm to processing to export.
Traceability Systems: Maintain batch-wise records for raw milk, processing, and final product.
Pre-Export Inspection: Test finished products in certified laboratories before shipment.
Regulatory Certification: Obtain FSSAI Export Registration, ISO 22000, ISO 17025 lab certification, and comply with importing country regulations.
4. Packaging and Transportation Considerations
Milk is exported in UHT, powdered, or condensed forms, requiring strict temperature and humidity control.
Packaging must prevent contamination, spoilage, or chemical migration.
Cold-chain logistics and monitoring systems are critical for maintaining quality during transport.
5. Importance of Export Milk Testing
Ensures international regulatory compliance and smooth customs clearance.
Protects consumers in importing countries from adulterated or contaminated milk products.
Enhances market reputation of the exporting company or country.
Reduces economic losses due to rejected consignments or product recalls.
Encourages good practices across the supply chain, from farm to export packaging.
Summary:
Milk testing for export is more stringent than domestic testing, requiring comprehensive physical, chemical, microbiological, and contaminant analysis. It ensures that exported milk and dairy products are safe, high-quality, and compliant with international standards, safeguarding both consumer health and market access.
Recent Advances and Digital Tools in Milk Testing have revolutionized the monitoring of milk quality, safety, and composition. Modern dairy laboratories increasingly use infrared spectroscopy, ultrasonic analysers, and automated Milko-Tester/Lactoscan systems for rapid, precise, and multi-parameter analysis. Digital milk analysers and Automatic Milk Collection Units (AMCU) enable real-time testing at collection points, integrating fat, SNF, protein, lactose, density, and microbial indicators with digital record-keeping. The use of IoT-enabled sensors, cloud-based data management, and mobile apps allows seamless traceability from farm to processing plant, facilitating quality control, payment calculation, and regulatory compliance. Furthermore, rapid test kits with digital readers and machine-learning-based predictive analytics are enhancing early detection of adulterants, microbial contamination, and deviations in milk composition, supporting efficient decision-making, transparency, and improved supply chain management.
Mobile Milk Testing Units (MMTUs) are transportable laboratories or vehicles equipped with testing instruments that allow milk quality assessment directly at farms, collection centres, or remote locations. These units are designed to enhance milk quality monitoring, reduce delays in testing, and provide rapid feedback to producers and cooperatives.
1. Objectives of MMTUs
On-site testing: Assess milk composition and quality at the producer or collection centre level.
Rapid adulteration detection: Identify added water, neutralizers, detergents, or other adulterants immediately.
Microbial monitoring: Perform microbial tests (SPC, coliforms, somatic cell count) to prevent spoilage.
Support quality-based payment: Ensure fair pricing based on milk quality.
Promote producer awareness: Provide instant feedback and recommendations to farmers.
2. Equipment and Instruments in MMTUs
Physical Testing Tools: Lactometer, pH meter, COB test equipment.
Chemical Analysis Instruments: Gerber or digital fat testers, SNF/protein/lactose analysers.
Microbiological Testing: Portable kits for Methylene Blue Reduction Test, coliform count, somatic cell count.
Rapid/Strip Tests: Antibiotic residue, urea, starch, and detergent detection kits.
Advanced Instruments: Portable Milko-Tester, Lactoscan, or ultrasonic milk analysers for multi-parameter analysis.
Data Integration Tools: Computers or tablets for recording results, linking with cloud or central database for traceability.
3. Operation and Workflow
Arrival at farm or collection centre – set up the mobile unit near milk collection points.
Sample collection – collect representative milk samples from individual farmers.
On-site testing – conduct physical, chemical, and microbial tests, and record results digitally.
Instant feedback – provide quality assessment, adulteration detection, and payment calculation.
Data integration – transmit results to central dairy processing centres for record-keeping and supply chain monitoring.
4. Advantages of Mobile Milk Testing Units
Rapid quality assessment at the source, reducing delays in milk collection and transport.
Early detection of adulteration or contamination, minimizing economic and health risks.
Promotes quality-based payment, encouraging farmers to maintain hygiene and good practices.
Reduces transportation of substandard milk, lowering losses at processing plants.
Enhances traceability and digital record-keeping across the dairy supply chain.
Supports rural and remote dairy operations where fixed labs are not accessible.
Summary:
Mobile Milk Testing Units provide on-site, rapid, and reliable milk testing for physical, chemical, and microbiological parameters. Equipped with portable instruments, rapid test kits, and digital data tools, they enable quality-based payment, producer feedback, and traceability, strengthening the dairy supply chain and consumer safety.
IoT (Internet of Things) and sensor technologies are increasingly transforming milk testing and quality monitoring across the dairy supply chain. These technologies allow real-time, automated, and remote monitoring of milk quality parameters, improving efficiency, traceability, and safety from farm to processing plant.
1. Objectives
Real-time monitoring of milk quality during collection, transport, and storage.
Automation of testing to reduce human error and ensure consistent results.
Early detection of adulteration or contamination.
Traceability of milk from producer to processor.
Data-driven decision-making for quality control, payment, and supply chain management.
2. Types of Sensors in Milk Testing
Sensor Type
Parameters Measured / Purpose
pH Sensors
Monitor acidity to detect spoilage or fermentation.
Conductivity Sensors
Detect mastitis or adulteration with water.
Infrared (IR) Sensors
Measure fat, protein, lactose, and total solids.
Ultrasonic Sensors
Determine milk density, fat content, and solids-not-fat (SNF).
Temperature Sensors
Monitor cooling, transport, and storage conditions.
Optical / Colourimetric Sensors
Detect adulterants, somatic cells, or microbial growth.
Biosensors / Rapid Test Sensors
Detect antibiotics, toxins, urea, starch, or other chemical contaminants.
3. IoT Integration
Automatic Milk Collection Units (AMCUs): Equipped with sensors to measure milk quality at the point of collection, automatically transmitting data to a central system.
Wireless Communication: Bluetooth, Wi-Fi, or GSM modules send data in real-time to cloud-based dashboards.
Data Analytics and Machine Learning: Detect trends, anomalies, or early signs of spoilage and adulteration.
Alerts & Notifications: Immediate feedback to farmers, collection centres, or plant operators if quality falls below thresholds.
4. Applications
Farm-Level Monitoring: Measure milk composition and hygiene immediately after milking.
Milk Collection Centres: Ensure pooled milk quality and detect adulteration before bulk transport.
Transport and Cold Chain: Continuous monitoring of temperature, pH, and density during transport to prevent spoilage.
Processing Plants: Integrate sensors into automated lines for composition checks and process control.
Export Monitoring: Provide traceable digital records for international standards compliance.
5. Advantages
Rapid, accurate, and non-destructive testing of milk quality.
Continuous real-time monitoring, reducing the risk of delayed detection.
Enhanced traceability and digital record-keeping.
Supports quality-based payment systems for farmers.
Reduces reliance on manual sampling and laboratory testing, saving time and labour.
Summary:
IoT and sensor technologies in milk testing enable real-time, automated, and precise monitoring of milk composition, microbial quality, and adulteration. By integrating sensors, cloud computing, and data analytics, the dairy industry can achieve improved quality control, traceability, and efficiency, enhancing both consumer safety and supply chain management.
Modern milk testing increasingly relies on digital data collection, management, and cloud-based integration to ensure accurate quality monitoring, traceability, and regulatory compliance. With sensors, automated analysers, and IoT devices generating large volumes of data, effective data management systems are essential for actionable insights and supply chain optimization.
1. Objectives
Centralized data storage from multiple collection points, farms, and processing units.
Real-time quality monitoring and immediate detection of deviations.
Traceability from producer → collection centre → processing → consumer.
Regulatory compliance with FSSAI, BIS, ISO, and export standards.
Data-driven decision-making for quality-based payment, process optimization, and supply chain management.
2. Data Sources in Milk Testing
Farm and Producer-Level: Milk composition (fat, protein, SNF), microbial quality, temperature, and hygiene records.
Milk Collection Centres (MCCs): Pooled milk quality, adulteration detection, rapid test results, and volume.
Dairy Plants: Incoming milk QC, in-process checks, final product testing, packaging, and storage conditions.
Mobile Milk Testing Units (MMTUs): On-site test data integrated digitally.
IoT Sensors and AMCUs: Continuous real-time data on milk parameters, temperature, conductivity, pH, density, and adulteration indicators.
3. Cloud Integration
Data Transmission: IoT-enabled devices, AMCUs, and digital analysers transmit data via Wi-Fi, GSM, or Bluetooth to cloud servers.
Centralized Dashboards: Real-time visualization of milk quality parameters, alerts, and trend analysis.
Automated Analytics: Machine learning algorithms detect anomalies, predict spoilage, and identify adulteration patterns.
Alerts & Notifications: Instant feedback to farmers, MCC operators, or plant managers if quality thresholds are breached.
Digital Record Keeping: Secure storage of historical data for audits, regulatory compliance, and certification purposes.
4. Benefits
Real-Time Monitoring: Immediate detection of quality deviations or adulteration.
Enhanced Traceability: Full history of milk from producer to consumer.
Data-Driven Decisions: Support for quality-based payments, process optimization, and supply chain planning.
Regulatory Compliance: Easily generate reports for FSSAI, BIS, ISO, and export requirements.
Operational Efficiency: Reduces manual record-keeping, errors, and delays in decision-making.
Predictive Insights: Machine learning identifies trends for preventive measures (e.g., spoilage or mastitis detection).
Summary:
Data management and cloud integration in milk testing enable centralized, real-time, and automated monitoring of milk quality across the supply chain. By combining digital analysers, IoT sensors, AMCUs, and cloud platforms, the dairy industry can achieve traceability, regulatory compliance, early detection of quality issues, and data-driven decision-making, improving both consumer safety and operational efficiency.
Artificial Intelligence (AI) and Machine Learning (ML) are revolutionizing milk testing and quality management by enabling predictive analytics, real-time decision-making, and automated quality control. By analysing large volumes of data collected from farms, collection centres, processing plants, and IoT-enabled devices, AI/ML models can predict milk quality, detect anomalies, and optimize supply chain operations.
1. Objectives
Predict milk quality parameters (fat, protein, SNF, lactose) before laboratory analysis.
Detect adulteration or contamination using pattern recognition.
Forecast microbial growth or spoilage risk based on environmental and handling factors.
Support quality-based payment by predicting composition and hygiene of incoming milk.
Optimize supply chain operations with predictive insights on storage, transport, and processing.
2. Data Sources for AI/ML
Milk Composition Data: Fat, protein, SNF, lactose, density.
Microbiological Data: Standard Plate Count (SPC), coliform counts, somatic cell count (SCC).
Environmental & Handling Data: Temperature, pH, conductivity, storage duration, transport conditions.
Historical Data: Past quality trends, batch records, seasonal variations.
IoT & Sensor Data: Continuous real-time monitoring of milk parameters.
3. Applications of AI/ML in Milk Quality Prediction
Application
Role of AI/ML
Milk Composition Prediction
Predict fat, protein, SNF, lactose from sensor data without full lab testing.
Adulteration Detection
Identify unusual patterns in milk composition or conductivity indicative of water, urea, starch, or detergent.
Microbial Growth Forecasting
Predict spoilage risk based on temperature, storage time, and microbial load trends.
Quality-Based Payment
Automate payment calculations using predicted milk quality scores.
Supply Chain Optimization
Suggest optimal transport routes, cooling schedules, and storage conditions to maintain quality.
Early Disease Detection
Predict potential mastitis or udder infections using SCC and milk conductivity patterns.
4. Benefits
Rapid and accurate prediction of milk quality without relying solely on laboratory testing.
Early detection of adulteration or contamination, reducing economic losses.
Data-driven quality-based payments, incentivizing farmers to improve milk quality.
Optimized storage, transport, and processing, minimizing spoilage and maintaining safety.
Integration with IoT and cloud systems for real-time alerts and decision-making.
Continuous improvement through model learning and adaptation to new data patterns.
Summary:
AI and ML play a critical role in predicting milk quality by leveraging sensor data, historical trends, and environmental factors. These technologies enable real-time quality assessment, early detection of adulteration, predictive spoilage monitoring, and supply chain optimization, improving efficiency, safety, and profitability across the dairy industry.
A1: Standard Operating Procedures (SOPs)
A2: Format for Milk Testing Reports
A3: Troubleshooting Common Test Errors
A4: Glossary of Terms
A5: Reference Values and Conversion Tables
Annexures
Purpose:
Provides structured instructions for consistent, safe, and accurate milk testing.
Contents:
Scope: Raw milk, pasteurized milk, UHT milk, and value-added products.
Responsibilities: Lab technicians, supervisors, QC officers.
Sample Collection: Sterile containers, proper labelling, representative sampling, temperature maintenance (4–6°C).
Equipment and Materials: Lactometer, COB test kit, Gerber/digital fat testers, Milko-Tester/Lactoscan, rapid test kits, microbiological media.
Testing Procedures:
Physical: Lactometer reading, Clot-on-Boiling, sediment test
Chemical: Fat, SNF, protein, lactose, adulterant detection
Microbiological: Standard Plate Count, coliform detection, somatic cell count
Instrumental: IR spectroscopy, ultrasonic analysis, Milko-Tester/Lactoscan
Rapid Tests: Antibiotics, urea, starch, detergents
Safety & Hygiene: PPE, chemical handling, biohazard protocols, lab cleanliness.
Data Recording: Sample ID, date, operator, test results; flag out-of-specification results.
Quality Control: Instrument calibration, internal standards, proficiency testing.
Troubleshooting: Contaminated samples, instrument malfunction, reagent issues.
SOP Review: Annual updates or after technological/regulatory changes.
Purpose:
Standardized reporting ensures clarity, traceability, and regulatory compliance.
Sample Report Layout:
Field
Description
Sample ID
Unique identifier for each milk sample
Source / Producer
Farm name or MCC ID
Collection Date & Time
Date and time of sampling
Sample Type
Raw, pasteurized, UHT, powdered
Physical Tests
Lactometer reading, Clot-on-Boiling, sediment test
Chemical Tests
Fat %, SNF %, protein %, lactose %, added water/adulterants
Microbiological Tests
SPC, coliform count, SCC, Methylene Blue Reduction Test
Instrumental Analysis
Milko-Tester/Lactoscan readings, IR/ultrasonic results
Rapid Test Results
Antibiotic residues, urea, starch, detergents
Observations / Remarks
Any deviations, abnormal findings
Operator / Analyst
Name of lab personnel conducting the test
Supervisor Approval
Signature or digital verification
Date of Report
Final report generation date
Problem
Possible Cause
Corrective Action
Incorrect lactometer reading
Temperature not standardized
Adjust milk to 20°C and re-test
Fat estimation error
Incomplete centrifugation, reagent expired
Re-centrifuge, check reagents
COB test clotting failure
Low protein or contaminated sample
Use fresh sample, verify procedure
Microbial test inconsistencies
Contaminated media or glassware
Sterilize equipment, prepare fresh media
IR/Milko-Tester anomalies
Instrument calibration drift
Calibrate instrument, run standards
Rapid test false positives
Improper sample handling
Follow SOP, repeat test with proper sample
Term
Definition
SNF
Solids-Not-Fat; milk components excluding fat (protein, lactose, minerals)
CC
Somatic Cell Count; indicator of udder health/mastitis
COB
Clot-on-Boiling; simple heat test for milk spoilage/adulteration
SPC
Standard Plate Count; indicator of total viable bacteria
Adulterants
Substances added illegally to milk (water, urea, detergents)
Lactometer
Instrument to measure milk density
IR Spectroscopy
Analytical technique to determine composition using infrared absorption
Milko-Tester
Automated instrument for milk composition analysis
Rapid Test Kits
Portable kits for quick detection of adulterants or residues
AMCU
Automatic Milk Collection Unit; integrates testing and data collection at MCCs
1. Milk Composition Reference Values (for Cow’s Milk)
Component
Typical Range
Fat
3.0–4.5%
Protein
3.0–3.5%
SNF
8.0–9.0%
Lactose
4.5–5.0%
Density
1.028–1.032 g/mL
pH
6.6–6.8
SCC
< 2 × 10^5 cells/mL (healthy cow)
SPC
< 1 × 10^5 CFU/mL (good quality)
2. Common Conversion Factors
Parameter
Conversion
1 mL milk
1.03 g (approx.)
Temperature °F → °C
(°F – 32) × 5/9
Lactometer reading correction
Adjust for temperature: +0.1 per 1°C above 20°C
Fat % (Gerber)
Volume of fat × 0.1 (for calibration standard)
Summary:
These annexures provide a complete supporting framework for milk testing manuals, covering:
A1: SOPs for consistency and safety
A2: Standardized reporting format
A3: Troubleshooting common errors
A4: Glossary of technical terms
A5: Reference values and conversion tables
Walstra, P., Wouters, J. T. M., & Geurts, T. J. (2006). Dairy Science and Technology. CRC Press.
Rangappa, K. S., & Rangappa, S. (2014). Fundamentals of Dairy Science. New Age International.
Fox, P. F., McSweeney, P. L. H., Cogan, T. M., & Guinee, T. P. (2004). Fundamentals of Cheese Science. Springer.
Food Safety and Standards Authority of India (FSSAI). (2020). Manual for Dairy Quality Assurance.
Physical Testing of Milk
ICAR. (2017). Laboratory Manual on Milk and Milk Products Analysis. Indian Council of Agricultural Research.
Rangappa, K. S., & Rangappa, S. (2014). Fundamentals of Dairy Science.
Walstra, P., Wouters, J. T. M., & Geurts, T. J. (2006). Dairy Science and Technology.
Bureau of Indian Standards (BIS). (2010). Methods of Testing Milk (BIS 1479:2010).
Chemical Testing of Milk
Fox, P. F., & McSweeney, P. L. H. (2004). Advanced Dairy Chemistry (3rd ed.). Springer.
Rangappa, K. S., & Rangappa, S. (2014). Fundamentals of Dairy Science.
ICAR. (2017). Laboratory Manual on Milk Analysis.
AOAC. (2019). Official Methods of Analysis (21st ed.). Association of Official Analytical Chemists.
Microbiological Testing
Harrigan, W. F. (1998). Laboratory Methods in Food Microbiology (3rd ed.). Academic Press.
ICAR. (2017). Laboratory Manual on Milk Microbiology.
Jay, J. M., Loessner, M. J., & Golden, D. A. (2005). Modern Food Microbiology (7th ed.). Springer.
FSSAI. (2020). Manual for Dairy Quality Assurance.
Adulteration and Contamination Detection
Rangappa, K. S., & Rangappa, S. (2014). Fundamentals of Dairy Science.
Pundir, C. S., & Narwal, V. (2012). Milk Adulteration Detection: Methods and Kits. Springer.
FSSAI. (2020). Manual for Dairy Quality Assurance.
BIS. (2010). Methods of Testing Milk (BIS 1479:2010).
Instrumental Methods in Milk Testing
Walstra, P., Wouters, J. T. M., & Geurts, T. J. (2006). Dairy Science and Technology.
Rangappa, K. S., & Rangappa, S. (2014). Fundamentals of Dairy Science.
ICAR. (2017). Laboratory Manual on Milk and Milk Products Analysis.
FOSS Analytical AB. (Latest editions). Milko-Tester and Lactoscan User Manuals.
Quality Standards and Regulatory Requirements
FSSAI. (2020). Food Safety and Standards (Food Products Standards and Food Additives) Regulations.
BIS. (2010). Standards for Milk and Milk Products (BIS 1008:2014; BIS 1479:2010).
Codex Alimentarius Commission. (2020). Milk and Milk Products Standards.
International Organization for Standardization (ISO). (2018). ISO 22000:2018 – Food Safety Management Systems.
Sample Collection and Laboratory Practices
ICAR. (2017). Manual on Milk Sampling and Laboratory Practices.
Rangappa, K. S., & Rangappa, S. (2014). Fundamentals of Dairy Science.
FSSAI. (2020). Manual for Dairy Quality Assurance.
Walstra, P., Wouters, J. T. M., & Geurts, T. J. (2006). Dairy Science and Technology.
Milk Testing in the Supply Chain
Rangappa, K. S., & Rangappa, S. (2014). Fundamentals of Dairy Science.
ICAR. (2017). Manual on Milk Collection, Transport, and Quality Control.
FSSAI. (2020). Dairy Quality Assurance Guidelines.
FAO. (2013). Milk and Dairy Products Supply Chain Quality Guidelines.
Recent Advances and Digital Tools
Pundir, C. S., & Narwal, V. (2018). Biosensors and Rapid Detection Techniques in Milk. Springer.
Kumar, R., & Sharma, R. (2020). IoT and Digital Tools in Dairy Quality Monitoring. Dairy Science & Technology Journal.
Singh, J., et al. (2021). Predictive Modelling in Dairy Quality using AI. Journal of Dairy Research.
FOSS Analytical AB. (Latest editions). Digital Milk Analysers and IoT Solutions Manuals.
Annexures (A1–A5)
ICAR. (2017). Laboratory Manuals on Milk Testing and Quality Control.
FSSAI. (2020). Guidelines for Standard Operating Procedures and Record Keeping in Dairy Labs.
Rangappa, K. S., & Rangappa, S. (2014). Fundamentals of Dairy Science.
BIS. (2010). Methods of Testing Milk — Reference Values and C