Milk Handling and Quality
This domain tests whether you can keep milk safe from the udder to the buyer, and whether you can interpret simple quality tests.
Core rules
- Clean utensils: stainless steel or food-grade plastic, washed with hot water and detergent, sanitised and dried upside down. Never use copper or galvanised containers.
- Cool quickly: bring milk to 4 °C within two hours; every hour at ambient temperature multiplies bacteria.
- No preservatives: formalin, hydrogen peroxide and boric acid are illegal adulterants.
- Strain and cover: filter through muslin, cover the container, keep out of sunlight and strong smells, because milk picks up odours.
- Separate abnormal milk: colostrum, mastitis milk and milk from treated cows must not enter the bulk tank.
Quality tests
- Specific gravity 1.028–1.032; low gravity suggests added water, high gravity suggests skimming or added starch.
- Fat 3.5–4.5% cow, 6–7% buffalo; SNF minimum 8.5% cow and 9% buffalo.
- MBRT or resazurin: reduction in 5 hours or more indicates good keeping quality; fast reduction means a heavy bacterial load.
- Clot-on-boiling and alcohol test: detect acidity from souring.
- Adulteration: iodine test for starch, glucose test for added sugar, sedimentation for dirt.
Worked example
A sample shows specific gravity 1.019, fat 3.2% and SNF 7.9%. Reasoning: all three are low together, the classic picture of added water rather than skimming, because skimming lowers fat but raises gravity and leaves SNF near normal. Check the water source and the supplier's practice; record and report.
Traps
- Judging quality by colour or thickness.
- Storing milk in open buckets overnight.
- Adding preservative to hide poor hygiene.
- Mixing colostrum or mastitis milk with bulk milk.