Dairy products: cream, butter, ghee, curd, paneer, khoa, milk powder, ice cream
What this domain tests
This domain checks the manufacture, composition and defects of cream, butter, ghee, curd, paneer, khoa, milk powder and ice cream. Expect calculation questions on yield, overrun and moisture/fat balance.
Core rules
- Cream is classified by fat content; butter is a water-in-oil emulsion with at least 80% milk fat, moisture about 16% and some SNF.
- Ghee is clarified milk fat with very low moisture, typically not more than 0.5%, and a characteristic cooked flavour.
- Curd/dahi is fermented by lactic acid bacteria; yoghurt specifically uses Streptococcus thermophilus and Lactobacillus delbrueckii subsp. bulgaricus.
- Paneer is made by coagulating hot milk with citric acid, lemon juice or a permitted coagulant, then pressing the curd.
- Khoa is made by continuous evaporation of milk to a plastic mass; milk powder is made by evaporation followed by spray drying.
- Ice cream is a frozen foam; overrun is the air incorporated, expressed relative to the volume of mix.
Worked example
20 kg cream contains 40% fat, so fat = 8 kg. Butter is 80% fat, so theoretical butter = 8/0.80 = 10 kg. If 2% of the fat is lost, available fat = 7.84 kg and butter = 7.84/0.80 = 9.8 kg. The reasoning is a fat balance, not a volume balance.
Traps
Overrun % = (volume of ice cream − volume of mix) ÷ volume of mix × 100; dividing by ice cream volume is a common error. Ghee is not simply unstandardized butter. Paneer yield depends on milk casein, calcium and coagulation temperature, not only on fat.