High pressure effects on the colloidal calcium phosphate and the structural integrity of micellar casein in milk

Temperature and pressure affect the conformation of the (globular) whey proteins as well as the structure of the colloidal casein aggregates - casein micelles but also the equilibrium state of dissolved and colloidal (casein-bound) calcium phosphate in milk. The relations between temperature- and pressure-induced changes of calcium phoshate equilibria were evaluated in original and ultra-high-temperature treated milks, in corresponding ultrafiltration retentates and permeates and in synthetic milk salt solutions. By high pressure treatment the heat-induced changes of calcium phosphate can be largely reversed to their original values. These changes can be related to the pressure-induced structural changes of the micellar casein and to interactions of casein with temperature- or pressure-denaturated whey proteins.