Cook/chill foodservice system with a microwave oven: Injured aerobic bacteria during food product flow

Summary

This study determined how processing in cook/chill foodservice systems affected the quantity of sublethally injured bacteria in food. Beef loaf and frozen green beans were each prepared three times in a laboratory simulation following time-temperature recommendations of the Hazard Analysis Critical Control Point model. Beef loaf (15 kg) was initially cooked (1 kg/loaf) to a mean and temperature of 66°C; stored 24 h at 6°C and sliced, 100 g/poriton. Beans (4.5 kg) were removed from the freezer, stored 24 h at 6°C, and portioned, 100 g/ portion. Portions were helds at 6°C for 2 h and then were microwave-heated individually for 20, 50, 80, or 110s. Samples were then plated using Plate Count Agar (PCA) to obtain aerobic plate count (APC) and PAC plus 3.0% (beans) or 4.5% (beaf loaf) sodium chloride. The difference in results between the two counts (APC less PCA + NaCl) was defined as a measure of sublethally injured bacteria in the sample. The proportion of injured cells in beef loaf before microwave-heating was larger than that in green beans before microwave-heating probably because the beef loaf was initially cooked. Lenghtening the time of microwave-heating increased the proportion of injured cells in all microwave treatments of beef loaf and also in green beans when the time was 50 or more seconds.