Dairy and Milk Product Technology
Dairy and Milk Product Technology
This domain tests milk composition, heat treatment, separation, fermented products and adulteration. Calculations on standardization and yield are common.
Core rules
- Composition: cow milk is roughly 87% water, 3.5–4.5% fat, 3.2–3.5% protein, 4.5–5.0% lactose and 0.7% ash; buffalo milk has more fat.
- Heat treatment: pasteurization kills pathogens; UHT plus aseptic packing gives long shelf life. Boiling changes flavour and destroys some vitamins.
- Separation/homogenization: centrifugation separates cream; homogenization reduces fat globule size and prevents creaming.
- Products: butter is churned cream with salt; ghee is clarified butter with low moisture; cheese uses rennet and starter; curd/yoghurt uses lactic cultures.
- Adulteration: starch detected by iodine, detergent by shaking, urea by colour tests; measure fat, SNF and freezing point.
Worked example
Standardize 100 kg milk at 3.5% fat to 4.5% fat using 40% cream. Let x = kg cream. Fat balance: 3.5(100) + 40x = 4.5(100 + x). 350 + 40x = 450 + 4.5x; 35.5x = 100; x = 2.82 kg cream. Add 2.82 kg cream and mix; the final mass is 102.82 kg.
Traps
Pasteurization is a time–temperature combination, not just heating; homogenization does not sterilize; ghee is not the same as butter; fat is not the only measure of milk quality.