Heat-induced changes in milk salts: A review

Although milk salts are classified as micronutrients, they strongly affect the behaviour of the proteins and the physical stability of milk and dairy products. This review focuses on heat-induced changes in milk salts, with particular emphasis on salt speciation, precipitation and association with proteins. In milk and other dairy liquids at neutral pH, heating results in precipitation of calcium phosphates. These precipitates may become stabilised by caseins and casein-derived (SerP-containing) peptides, with limited observable instability; in the absence of stabilising protein, precipitates can lead to notable instability. Increasing temperature reduces solubility of calcium phosphate, but, perhaps more importantly, also accelerates precipitate formation. In milk, heat-induced changes in salts are reversible, but only slowly, if heat-treatment is of moderate intensity. After treatment at temperatures >90 °C and/or for >20 min reversal may be incomplete. Heat-induced changes in milk salts are crucial for retaining functionality and stability during and after heating of milk.