Water Binding in Whey Protein Concentrates

Abstract

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 solu- tions containing lactose and salts varied between .5 and 1.2 g water/g solids, with unfreezable water increasing as the con- centrations of lactose and salts were in- creased. 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 de- naturatiort 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.