THERMAL INACTIVATION OF SALMONELLA AGONA IN LOW-MOISTURE FOOD SYSTEMS AS INFLUENCED BY WATER ACTIVITY

Salmonella can survive in low-moisture, high-protein and high-fat foods for several years. Despite nationwide recalls for Salmonella in low-moisture products, information on survival of Salmonella during high-protein and high-fat food processing is limited. This project evaluated Salmonella enterica serovar Agona 447967 thermal inactivation kinetics in a high-protein and a high-fat matrix using a defined matrix composition, varying water activities and process conditions. A high-protein matrix, composed of 60:6:25 weight ratio of flour: oil: protein, and a high-fat matrix, composed of 60:25:6 weight ratio of flour: oil: protein was studied. Each matrix was inoculated with Salmonella enterica serovar Agona 447967 at activities of 0.5, and 0.9. Samples were packed in aluminum test cells and heat treated over a range of temperatures and time intervals. Survival of Salmonella Agona was detected on trypticase soy agar with 0.6% yeast extract. The average z-values for the high-protein matrix at the water activity (aw) of 0.5 and 0.9 were 9.01ºC, and 7.51ºC, respectively. The average z-values for the high-fat matrix was 11.91ºC at aw 0.5, and 7.08ºC at aw 0.9. Results showed that the z-value at aw 0.5 was significantly different from the z-value at aw 0.9 (p < 0.05) in both the highprotein and high-fat matrices. Critical process factors associated with pathogen destruction were identified during thermal treatments in this project. Results indicated that a correlation existed between temperature and water activity and must be accounted for when predicating inactivation of Salmonella enterica in these model matrices under dynamic process conditions.M.S. in Food Process Engineering, July 201