Food Science and Technology Department


Date of this Version

Spring 4-22-2013


A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Food Science and Technology, Under the Supervision of Professor Harshavardhan Thippareddi. Lincoln, Nebraska: May, 2013


Microwave heating instructions for three products (chicken nuggets, turkey pot-pies and mashed potato) were developed and validated based on end point temperatures using two microwave ovens (2,459 MHz; 700 W and 1,350 W). Heating instructions for chicken nuggets were validated using different configuration of product placement (edge or center of the carousel) and number of units (4, 6 and 8). Salmonella spp. reductions of 6.56 log CFU/g (700 W) were observed in chicken nuggets heated in groups of 4 and placed at the center of the carousel with 1 min 26 s of heating time with a target end point temperature of 73.8°C. Longer heating times (2 min 10 s) resulted in total Salmonella spp. reductions (7.22 log CFU/g) when chicken nuggets were placed in groups of 8. Similar Salmonella spp. reductions (p>0.05) were observed when chicken nuggets were placed at the center using shorter heating times (1350 W). Incorporation of standing time (2 min) eliminated Salmonella spp., regardless of the power of the microwave, location and the number of chicken nuggets. Heating instructions for turkey pot-pies were validated using inoculated product (at the geometric center or on the crust). Salmonella spp. reductions of 5.16 log CFU/g were observed following heating times of 9 min 31 s and 7 min 1 s for the low and high power microwave, respectively with a target end point temperature of 73.8°C. For the third product, different amounts of inoculated mashed potato (105 and 205 g) were used to validate the microwave heating instructions. Destruction of Salmonella spp. (8.73 log CFU/g) in mashed potato (105 g) can be achieved with a target end point temperature of 70°C at the geometric center, regardless of the power of the microwave oven. Salmonella spp. destruction (8.73 log CFU/g) was observed in mashed potato (205 g) using the high power microwave oven using an end point temperature of 72.2°C to calculate heating times. Salmonella spp. destruction in mashed potato is dependent on the amount of the product and the power of the microwave oven.

Advisor: Harshavardhan Thippareddi