Effect of Different Temperatures on Various Bacteria Isolated from Frozen Meat Piesa

Abstract

SUMMARYThe effect of temperature, particularly storage temperature, is one of the most important factors in controlling microbial populations of frozen foods. Adequate temperature control of frozen foods should limit the growth of microorganisms and insure maintenance of original quality and wholesomeness. This investigation was undertaken to show that correct storage temperature; do inhibit the growth of bacteria which might be considered as the source of potential public health hazard, while certain saprophytic species are able to survive and grow well at the same low temperatures. The cultures were all isolated from chicken pies.Bacterial counts were determined by plating techniques on Brain Heart Infusion (BHI) agar after various time intervals up to 30 days at ‐13°, 0°, 5°, 10°, 20° and 37° C, using both BHI broth and chicken gravy as media. Very similar results were obtained in the two media. Escherichia coli and Streptococcus faecalis had a minimum growth temperature between 5° and 10° C for active reproduction. A minimum growth temperature between 5° and 10° C was observed for the culture of Staphylococcus aureus. Of two cultures representing variants of Pseudomonas fluorescens, one culture followed the growth‐temperature pattern shown by the previously mentioned organisms and failed to grow at or below 5° C. The other P. fluorescens culture grew rapidly at 5° C. Ability to grow at low temperatures is a constitutive characteristic of the organism and is not common to all types of bacteria. At refrigerator temperatures, the growth of the psychrophilic saprophytic species tested completely outstripped the growth of several bacteria of public health significance. This indicates the great likelihood that a frozen food on defrosting, particularly in a refrigerator, would become completely unacceptable, due to the development of off flavors and odors and deteriorated physical appearance before it became a health hazard.