The Influence Of Elevated Temperatures And Composition On The Water Activity Of Egg Powders

This study aimed to investigate water activity (a(w)) changes in different egg powders (egg white, egg yolk, and whole egg) as influenced by temperature between 20 degrees C and 80 degrees C. A high-temperature test cell was used to measure the a(w) 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 (q(st)) of the egg powders was calculated. The q(st) values were used in the Clausius-Clapeyron equation to generate the isotherms of the egg powders at 40 degrees C and 80 degrees C. The results showed that at fixed moisture content and temperature, egg yolk powder had higher a(w) than whole egg and egg white powders. In addition, a(w) 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 q(st), compared to the other two egg powders.Practical applications An important determinant for the survival of microorganisms during thermal treatments is food water activity (a(w)), which changes with temperature. Currently, there is no scientific data regarding a(w) changes in egg powders at elevated temperatures. Therefore, this study aimed to determine the a(w) changes in egg powders as a function of temperature and composition. Data produced by this study regarding a(w) 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.