Water Binding in Whey Protein Concentrates

Measurements of the heat of fusion of free water in concentrated solutions of purified whey proteins showed that .5 g water/g whey protein would not freeze at --40 C. This water was defined as bound. Total bound water in protein solutions containing lactose and salts varied between .5 and 1.2 g water/g solids, with unfreezable water increasing as the concentrations of lactose and salts were increased. Bound water values observed with several whey protein products agreed with values computed from data both for high and low molecular weight fractions of these products. Thermal denaturatiort did not cause significant changes in water binding. Water vapor sorption by a concentrated whey protein product was an additive process at all relative pressures, with the amount of sorbed water, as P/Po approached unity, equal to the unfreezable water in the corresponding suspension of the same product.