Dairy Products Manufacture (Butter, Ghee, Curd, Paneer, Cheese, Milk Powder)
Domain 5 covers the unit operations and composition rules for butter, ghee, curd, paneer, cheese and milk powder. Questions often ask for yields, culture types or process sequence.
Core rules
- Butter is made by churning cream, washing and salting; moisture is at most 16% and fat at least 80%.
- Ghee is clarified butter fat with moisture at most 0.5%; avoid scorching and keep FFA low.
- Curd/dahi uses a lactic starter; paneer is acid-coagulated milk at 70-75°C, then pressed; cheese uses rennet and starter, with whey expulsion; milk powder uses evaporation and spray drying. Cheddar has lower moisture than cottage cheese.
Worked example
20 kg cream at 40% fat contains 8 kg fat. If butter is 80% fat and fat recovery is 97%, butter yield = (8 × 0.97) / 0.80 = 9.7 kg. The reasoning is that the fat in cream becomes the fat in butter; yield is adjusted for fat recovery and butter's fat content.
Traps
- Over-acidification makes paneer hard and crumbly.
- Unwashed butter retains buttermilk and spoils faster.
- Scorching ghee raises FFA and gives a burnt flavour.
- Using the wrong starter or a contaminated culture can ruin curd and cheese.