Food Engineering Laboratory, School of Engineering, University of Guelph, Guelph, Canada
Dr. Gauri S. Mittal
Mathematical heat and mass (moisture and fat) transfer models for the single-sided pan-frying of frozen hamburger patties were developed and validated against experimental data. The slowest microbial inactivation point within a patty was predicted using transport and microbial inactivation models. The simulation results demonstrated the inactivation of E. coli O157:H7, Listeria innocua, and Salmonella serotypes within patties during cooking. The effects of various turning intervals, patty thickness, initial patty temperature and D (thermal death time) values on safe process time were analyzed. Increasing the number of overturns by reducing flipping interval reduced the process time considerably at lower pan temperature. Small variations of D had significant differences on process time also at lower pan temperature. E. coli can be satisfactorily inactivated at required final cooking temperature but not Salmonella and Listeria where higher process times are needed for the same temperature.
Increase in heating temperature resulted in higher rates of patty center temperature increase and moisture and fat losses, and decreased the process time for 12 log reductions of microorganisms. An increase in the thickness of the patty resulted in an increased process time. Increasing the number of overturns considerably reduces the process time at lower pan temperature (140ºC). A small variation in the Dr value of E. coli O157:H7 had little effect on the process time, but resulted in a significant difference for lower heating temperature (140ºC) during the cooking. The three-dimensional plots provide a method to estimate the process time when other conditions are known.