THE EFFECT OF TRANSIENT TEMPERATURES ON THE GROWTH OF SALMONELLA-TYPHIMURIUM LT2 .1. CYCLING WITHIN THE GROWTH REGION

The effect of fluctuating temperatures on microbial growth is importan t in the passage of foods through the food chain. Suspensions of Salmo nella typhimurium were subjected to sinusoidally time-varying temperat ures of periods from 40 to 480 min within their growth temperature ran ge. The change in the numbers of viable bacteria was measured with tim e and the experimental growth curves and average generation times comp ared with predictions based on isothermal growth data. The experimenta l average generation times exceeded the predictions by less than 30%, although the discrepancy increased with cycle frequency. Instantaneous growth rates obtained for the 480 min cycles were in agreement with t hose predicted from isothermal behaviour.