The overall goal of this thesis was to evaluate phenomenological similarity in bacterial pathogen inactivation under different thermal treatments of two very different food products (cooked bacon and dried apples) with similarly wide changes in moisture during processing. As ready-to-eat (RTE) products, both must comply with specific food safety regulations, under the United States (US) Department of Agriculture – Food Safety Inspection Service and the Food Safety Modernization Act Preventive Controls for Human Foods Rule, respectively. Therefore, there is a need for pathogen inactivation data to validate commercial pathogen control processes for both products. Both conventional and microwave oven cooking of bacon to the required 40% cooking yield achieved >6.5 log reduction of Salmonella. However, when humidity was reduced (dew point ≤25°C), microwave cooking of bacon yielded <6.5 log reduction. When drying apples to a standard moisture content (<24% wet basis), lower Listeria monocytogenes inactivation (1.8 and 2.8 log CFU) was achieved when drying at 60°C, under the studied air velocities (0.7 and 2.1 m/s) (P < 0.05), compared to 80°C, at which Listeria decreased by 5 log reduction by the end of drying. Despite the use of different pathogens, similar inactivation response patterns were observed during both apple drying and bacon cooking, especially microwave cooked bacon under dry conditions, reflecting the simultaneous counter-effects of dynamically increasing product temperature and decreasing product moisture. Therefore, results from this study suggest that it is theoretically possible to develop one model form for bacterial inactivation in widely changing moisture products.
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