Insolubility of milk powder products – A minireview

In this paper, the formation of insolubility in milk powder is described, and the factors affecting the reaction are discussed. The zone in which casein proteins are most sensitive to heat is in the moisture range that occurs during spray drying. The rate of reaction has been determined and shows differences of orders of magnitude with the moisture content. The effect of chemical reagents on the extent of reaction gives insights into the chemical bonds that inhibit hydration. Information on the drying of casein products and individual proteins is used to infer that the withdrawal of moisture from casein proteins and the concentration of divalent cations during drying lead to alterations in the conformation of proteins that have an adverse effect on their rehydration during reconstitution. Further work to fully characterise these effects is required