The influence of elevated temperatures and composition on the water activity of egg powders

Abstract

This study aimed to investigate water activity (aw) changes in different egg powders (egg white, egg yolk, and whole egg) as influenced by temperature between 20°C and 80°C. A high‐temperature test cell was used to measure the aw in egg powders of different moisture contents (2 to 30% wet basis) during heating in a closed environment. Then, the net isosteric heat of sorption (qst) of the egg powders was calculated. The qst values were used in the Clausius–Clapeyron equation to generate the isotherms of the egg powders at 40°C and 80°C. The results showed that at fixed moisture content and temperature, egg yolk powder had higher aw than whole egg and egg white powders. In addition, aw of the three egg powders in closed containers all increased with temperature. Egg white powder had stronger binding capacity to water, as reflected by the higher qst, compared to the other two egg powders. Practical applications An important determinant for the survival of microorganisms during thermal treatments is food water activity (aw), which changes with temperature. Currently, there is no scientific data regarding aw changes in egg powders at elevated temperatures. Therefore, this study aimed to determine the aw changes in egg powders as a function of temperature and composition. Data produced by this study regarding aw changes provide useful information for designing effective heat treatments to control pathogens in egg powders. The isosteric data should also help estimate the energy efficiency of egg powder drying operations.

A simple method to measure the isosteric energy of adsorption

“…First, it should be mentioned that the approach presented here is not new; contrary to what the authors initially thought. A similar approach has recently been proposed [28,29] and used for the study of food products [30][31][32][33]. It may be possible that other similar studies have been published, and especially in other scientific fields, although no other papers could be found by the authors.…”