Cream, Butter, Ghee and Other Fat-Rich Products
Cream, Butter, Ghee and Other Fat-Rich Products tests centrifugal separation, churning, moisture control and clarification. The exam focuses on fat balance, yield and defects.
Cream and butter
A cream separator uses centrifugal force; cream fat is typically 35-40% for market cream and higher for manufacturing. Butter is made by churning cream, draining buttermilk, washing, salting and working. Table butter is about 80% fat, with moisture about 16%, salt about 2% and curd not more than about 2%. Good working disperses moisture finely and limits free moisture.
Ghee
Ghee is clarified butterfat made by melting butter or cream, removing moisture and curd, and heating to develop flavour. It has very low moisture and high fat. Overheating causes burnt flavour; poor clarification causes grainy or rancid ghee.
Worked example
1,000 kg milk at 4.0% fat is separated with 90% fat recovery into 40% cream. Fat to cream = 1,000 × 0.04 × 0.90 = 36 kg. Cream mass = 36 / 0.40 = 90 kg. If butter contains 80% fat and 99% of cream fat is recovered, butter fat = 36 × 0.99 = 35.64 kg; butter mass = 35.64 / 0.80 = 44.55 kg. The remaining fat leaves in skim milk and buttermilk.
Traps
Do not use milk fat percentage as butter yield without accounting for cream fat and losses. Do not confuse overrun in ice cream with butter yield. Excess moisture shortens butter shelf life. Lipase causes rancidity even at low temperature.