Milk, Meat, Poultry and Fish Processing
8. Milk, Meat, Poultry and Fish Processing
This domain tests the handling and processing of animal foods, where cold chain and hygiene are critical. Expect questions on pasteurisation, product manufacture, rigor mortis and spoilage.
Core rules
- Milk: composition varies by species; pasteurisation (72°C/15 s or 63°C/30 min), homogenisation, separation, standardization, then products such as cream, butter, ghee, paneer, cheese, yoghurt and milk powder.
- Meat: after slaughter, rigor mortis develops; conditioning/tenderisation follows. Chilling slows microbial growth; freezing at −18°C or below preserves.
- Curing uses salt, nitrite and sometimes smoke; nitrite controls C. botulinum but must be within limits.
- Poultry and fish are highly perishable; fish spoilage produces trimethylamine and histamine in some species.
- Cold chain: pre-chilling, refrigerated transport, display at low temperature; avoid temperature abuse.
Worked example
Standardise 100 kg milk at 4% fat to 3% fat using skim milk at 0.1% fat. Let x kg skim milk be added: (4×100 + 0.1x)/(100 + x) = 3. 400 + 0.1x = 300 + 3x; 100 = 2.9x; x = 34.5 kg. Final mass = 134.5 kg at 3% fat. Reasoning: fat is conserved; set up a fat balance, not a total solids balance.
Traps
Homogenisation does not sterilise milk. Pasteurised milk still needs refrigeration. Meat should not be processed immediately before rigor resolution if tenderness matters. Histamine in fish is not destroyed by cooking.