Growth of Spoilage Bacteria in Broth and Vacuum-Packed Bologna-Type Sausage at Fluctuating Temperatures and Low Temperature Storage

Abstract

The influence of fluctuating temperatures on some important spoilage bacteria, i.e., Brochothrix thermosphacta, Serratia liquefaciens and a Lactobacillus sp., as well as Vibrio sp. and Yersinia enterocolitica was determined in broth culture and in vacuum-packed Bologna-type sausage. Temperatures used were −2.0, 2.0 and 5.0°C. The influence of fluctuating temperatures varied considerably among the organisms studied. B. thermosphacta grew irrespective of temperature, numbers of S. liquefaciens decreased each time the product was stored at −2°C but grew at temperatures above 0°C. The effect on the Lactobacillus sp., depended on the initial storage temperature, whereas no significant difference in numbers of Y. enterocolitica were observed during fluctuating temperature storage. Generally the time-temperature combination was important and was the determining factor in the number of bacteria present after equivalent periods at the incubation temperatures above and below 0°C. The study indicated that with short periods of 2 to 3 d at each temperature, B. thermosphacta was favored. For long periods of 5 or 7 d at each temperature, lactics, S. liquefaciens and Vibrio sp. also increased to high numbers. B. thermosphacta, but neither S. liquefaciens nor Y. enterocolitica grew at a constant temperature of −2°C.