Write the procedure of testing and grading of raw milk at primary milk collection centre.

Testing Procedures at Primary Milk Collection Centres

The testing process at PCCs is multi-faceted, encompassing physical, chemical, and biological assessments. These tests are crucial to determine the milk's suitability for processing and consumption.

1. Physical Tests

• Temperature Test: Milk temperature is checked immediately upon arrival. Ideal temperature range is 4-10°C. Lower temperatures indicate chilling, while higher temperatures suggest inadequate preservation.
• Appearance Test: Visual inspection for color, clarity, and any visible adulterants (e.g., water, starch).
• Sediment Test: Milk is allowed to stand, and the sediment volume is measured. Excessive sediment indicates poor hygiene during milking and storage.
• Foreign Matter Test: Checks for the presence of hair, dirt, or other extraneous matter.

2. Chemical Tests

• pH Test: The pH of milk is measured. The normal range is 6.5-6.7. Deviations may indicate adulteration or bacterial activity.
• Fat Content Test (Gerber Method): This is a crucial test to determine the percentage of fat in milk. A minimum fat content is required for different grades of milk.
• Solids-Not-Fat (SNF) Test: Determines the amount of protein, lactose, and minerals in milk. The ratio of fat to SNF is also assessed.
• Adulterant Tests: Tests are conducted to detect common adulterants like sugar, starch, urea, and detergents. These tests often involve chemical reactions that produce characteristic colors or precipitates. For instance, the presence of urea can be detected using the Erlich's reagent test.

3. Biological Tests

• Plate Count Test (Standard Plate Count – SPC): This test estimates the total bacterial load in milk. High bacterial counts indicate contamination and potential spoilage. The limit is generally < 50,000 CFU/ml (Colony Forming Units per milliliter) as per FSSAI standards.
• Phosphatase Test: This test checks for the presence of alkaline phosphatase, an enzyme naturally present in raw milk. Its absence indicates that the milk has been improperly heated (HTST pasteurization).
• MMP (Methylene Blue Reduction) Test: This test assesses the reductase activity of microorganisms in milk, indicating the level of microbial spoilage.

Milk Grading System

Based on the test results, raw milk is graded according to a predefined system. The grading system varies slightly between states, but generally follows a similar pattern. The table below provides a typical grading system:

Grade	Fat (%)	SNF (%)	SPC (CFU/ml)	Remarks
Grade 1	≥ 6.0	≥ 8.5	≤ 30,000	Excellent Quality
Grade 2	5.5 – 5.9	8.2 – 8.4	≤ 50,000	Good Quality
Grade 3	5.0 – 5.4	8.0 – 8.1	≤ 100,000	Average Quality
Grade 4	< 5.0	< 8.0	> 100,000	Rejected – Not Suitable for Processing

Quality Control and Traceability

Beyond the testing and grading procedures, PCCs maintain quality control records. These records track the source of the milk (farmer/cooperative), test results, and grade assigned. Traceability is crucial for identifying the origin of any quality issues and taking corrective actions. Many states have implemented milk procurement and processing schemes, like the National Dairy Development Board’s (NDDB) Dairy Entrepreneurship Development Scheme (DEDS), which promote quality improvement and traceability.

Case Study: Operation Flood Operation Flood, launched in 1970, revolutionized the Indian dairy industry. It focused on establishing a national milk grid, improving milk production, and ensuring quality. The program involved setting up chilling centers and primary milk collection centers, implementing quality control measures, and providing training to farmers and milk handlers. This led to a significant increase in milk production and improved the livelihoods of millions of dairy farmers.