Milk Production, Clean Milk Handling and Milk Testing
Domain 7: Milk Production, Clean Milk Handling and Milk Testing
This domain tests milk composition, clean milk production, cooling and the common platform tests. Numerical questions on fat-based pricing and lactometer correction are common.
Composition and clean milk
Cow milk averages about 87 percent water, 3.5 to 4.5 percent fat and 8.5 percent solids-not-fat. Buffalo milk has more fat, often 6 to 7 percent, and slightly higher solids-not-fat. Clean milk means a low bacterial count: healthy udder, clean utensils, potable water, rapid cooling to 4 degrees Celsius, and no adulteration.
Tests
- Lactometer: specific gravity normally 1.028 to 1.032; correct for temperature, usually 27 degrees Celsius in India.
- Gerber: fat by sulphuric acid digestion in a butyrometer; read the fat column.
- Acidity: fresh milk about 0.14 to 0.16 percent lactic acid; higher values suggest souring.
- MBRT: methylene blue reduction time; a shorter time means more bacteria.
- Adulteration: iodine for starch, resorcinol for cane sugar, DMAB for urea, and lactometer plus freezing point for added water.
Worked example
A milk sample reads 5.0 percent fat and the society pays 700 rupees per kg fat. Price per litre = (5.0 divided by 100) multiplied by 700 = 35 rupees. Reason: fat percentage is converted to kg fat per litre, then multiplied by the rate. Check solids-not-fat separately if the society uses a two-axis formula.
Traps
Reading the lactometer without temperature correction; assuming a high lactometer reading always means pure milk; and confusing MBRT, which tests bacterial quality, with the alcohol test, which tests stability.