THERMAL INACTIVATION OF SALMONELLA ENTERITIDIS PT 30 AND ENTEROCOCCUS FAECIUM IN EGG POWDERS AT DIFFERENT WATER ACTIVITIES

Thesis (Ph.D.), Biological and Agricultural Engineering, Washington State UniversityEgg powders have seen an increasing demand in the food market, because their functional properties, and less storage space requirements. However, industrial egg powders processing consists of several unit operations, where they can be contaminated with Salmonella. The objectives of this research were to: study the impact of the temperature and composition on the aw of the egg powders; develop a prediction model of aw at elevated temperatures; obtain the D80°C-values of Salmonella Enteritidis PT30 and E. faecium in the egg powders; assess the impact of aw on the quality of egg white powder after thermal treatment. The changes of aw in the egg powders with temperatures between 20 and 80°C were measured using a Vapor Sorption Analyzer and a High-Temperature Cell (HTC). A model-based on Cassius Clapeyron equation was developed, which allows getting the moisture sorption isotherms of egg powders at different temperatures. The D80°C-value of S. Enteritidis PT30 and E. faecium inoculated in the egg powders preconditioned to three aw levels (0.3, 0.45, 0.6) at 20°C were determined using aluminum thermal death test cells. The results showed a significant increase (P