Physico-chemical characterization of phosphate-added skim milk

The addition of potassium phosphate (KH2PO4) to milk is a common practice in the dairy industry but the changes resulting from such addition have not been fully elucidated. Physico-chemical changes were evaluated after addition of KH2PO4 at concentrations from 0 to 160 mm with or without adjustment of pH. At pH adjusted to 6.8, the addition of phosphate to milk-induced formation of insoluble calcium phosphate salt, decrease in lightness and solubilization of casein molecules. As a result of these biochemical changes, especially at high phosphate concentrations (about 120 mm and more), the formation of large aggregates occurred. At the same time, the amount of water combined with the modified casein strongly increased. When the pH was not adjusted, the same biochemical changes occurred but they were quantitatively lower. In this case, no destabilization of casein micelles occurred.