Water Vapor Sorption Properties of Various Dried Milks and Wheys

Abstract

An electronic recording microbalance was incorporated into a gravimetric adsorption apparatus for precise study of adsorption and desorption phenomena on dehydrated dairy products. Data are reported for water sorption by spray-dried whey, skimmilk, and whole milk powders as well as foam-spray-dried whey and milk powders. During the sorption measurements a weight maximum was observed in the area of P/P° ≈ 0.5. The maxima in the adsorption curves are attributed to the occurrence of morphological changes in the sorbent. Evidence for the irreversibility of these morphological effects was obtained from repeated adsorption-desorption studies. The physical changes occurring in the powders may be associated with lactose crystallization, as the magnitude of the weight maxima with their concomitant distortion of the normal sigmoid sorption isotherm was inversely related to the lactose crystallinity in the powders. © 1968, American Dairy Science Association. All rights reserved.