Milk Powders, Condensed Milk
Milk Powders, Condensed Milk tests water removal, concentration and preservation principles. The exam expects you to distinguish spray-dried powder, roller-dried powder, evaporated milk and sweetened condensed milk.
Core technology
Milk is preheated, evaporated to concentrate solids, then dried. Spray drying produces fine, readily soluble powder; roller drying gives a cooked flavour and lower solubility. Whole milk powder is typically about 26% fat, while skim milk powder has not more than about 1.5% fat. Powder moisture is usually below about 4%. Sweetened condensed milk uses sugar to lower water activity; evaporated milk is concentrated and sterilised.
Worked example
1,000 kg milk with 12.5% total solids is dried to powder with 97% total solids. Solids input = 1,000 × 0.125 = 125 kg. Powder mass = 125 / 0.97 = 128.9 kg. The difference is mostly water removed. If powder moisture rises, powder mass rises but storage stability falls.
Traps
Do not treat sweetened condensed milk as sterile; it relies on high sugar and low water activity. Do not confuse evaporated milk with sweetened condensed milk. High powder moisture, free fat and scorched particles reduce shelf life. Powder solubility is not the same as whipping ability.