THE EFFECT OF TRANSIENT TEMPERATURES ON THE GROWTH OF SALMONELLA-TYPHIMURIUM LT2 .2. EXCURSIONS OUTSIDE THE GROWTH REGION

The effect of fluctuating temperatures on microbial growth is importan t in the passage of foods from production to consumption. Suspensions of Salmonella typhimurium have been subjected to sinusoidally time-var ying temperatures of periods from 60 to 240 min between 4 degrees and 22 degrees C, that is within and below the growth temperature range, T he suspensions were prepared with two concentrations of sodium chlorid e and adjusted to two different values of pH, The change in the number s of viable bacteria was measured with time and the experimental growt h curves and average generation times compared with predictions based on isothermal growth data. Generally, the experimental average generat ion times exceeded the predictions by not more than 10%, In enumeratin g viable bacteria in the suspensions containing 3.5% (w/v) sodium chlo ride it was necessary to use sodium chloride in the diluent and recove ry medium in order to recover the bacteria quantitatively.