Enhancement of Thermal Inactivation of Foodborne Pathogenic Bacteria at Mild Heating Temperatures with Inclusion of Butyl Paraben and the Application on Foods

Abstract

Title of Thesis: ENHANCEMENT OF THERMAL INACTIVATION OF FOODBORNE PATHOGENIC BACTERIA AT MILD HEATING TEMPERATURES WITH INCLUSION OF BUTYL PARABEN AND THE APPLICATION ON FOODS Zhujun Gao Master of Science (M.S.), 2019 Thesis Directed By: Dr. Robert L. Buchanan Department of Nutrition and Food Science Center for Food Safety and Security Systems Thermal processing is widely used in food industry to ensure the microbial safety, however, there is increasing demand on reducing the processing temperature and duration. This study specifically focused on mild heating temperatures (<60 °C) with inclusion of low level (≤ 125 ppm) of the approved preservative butyl-parahydroxy-benzoate (BPB). In a BHI model matrix, four pathogens were studied with submerged coil apparatus: Cronobacter sakazakii 607, Salmonella enterica serotype Typhimurium, attenuated Escherichia coli O157:H7 and Listeria monocytogenes. The results indicated that low concentrations of BPB combined with temperatures < 60 °C achieved 5 – 6 log reductions in less than 15 minutes with tested gramnegative microorganisms, whereas reductions without BPB were only 1 – 2 logs. We further extended the study to food applications: powdered infant formula, non-fat dry milk, and apple juice. The results indicate BPB will be inhibited by proteins, but apple juice is a suitable application. ENHANCEMENT OF THERMAL INACTIVATION OF FOODBORNE PATHOGENIC BACTERIA AT MILD HEATING TEMPERATURES WITH INCLUSION OF BUTYL PARABEN AND THE APPLICATION ON FOODS By Zhujun Gao Thesis submitted to the Faculty of the Graduate School of the University of Maryland, College Park, in partial fulfillment of the requirements for the degree of Master of Science 2019 Advisory Committee: Dr. Robert L. Buchanan, Chair Dr. Rohan V. Tikekar Dr. Abani K. Pradhan Dr. Shirley Micallef © Copyright by Zhujun Gao 2019