Effect of Water Vapor Sorption on Porosity of Dehydrated Dairy Products

Marked structural alterations in powder granules of dehydrated dairy products were observed to occur as a result of moisture sorption. These effects were manifested in enhanced rates of gas diffusion into the interior of the powder granules after water sorption. The porosities of powders which had been exposed to various humidity conditions were assessed by determination of true and apparent densities by pycnometric techniques, using He and N 2 as the displaced media. When powders were equilibrated against water vapor at 50% relative humidity, their porosities were so altered as to essentially eliminate any molecular sieve properties. The per cent free fat was also considerably increased after equilibration of the powders against water vapor at 50% relative humidity.