Growth of Listeria monocytogenes, Aeromonas hydrophila and Yersinia enterocolitica on cooked beef under refrigeration and mild temperature abuse

Abstract

Strains of the cold-tolerant bacteria Listeria monocytogenes, Aeromonas hydrophila and Yersinia enterocolitica were inoculated onto samples of cooked beef and incubated at 5 and 10°C under both aerobic and vacuum-packaged (anaerobic) conditions. These organisms were enumerated over a time course and data were analysed to give values for the generation and lag times. All species grew well under all conditions except for A. hydrophila at 10°C under anaerobic conditions where inhibition by lactic acid bacteria may have occurred. Growth rates were similar for L. monocytogenes and A. hydrophila whether the samples were stored aerobically or anaerobically, but Y. enterocolitica grew more slowly under anaerobic conditions. However, the growth of lactic acid bacteria in samples stored aerobically indicated that metabolic activity resulted in the formation of anaerobic conditions during the incubation period. Growth rates predicted by response surface models and measured growth rates were not in agreement for L. monocytogenes or A. hydrophila, but similar comparisons for Y. enterocolitica showed good agreement.