Growth response and modeling of the effects of selected factors on the time-to-detection and probability of growth initiation of Salmonella typhimurium

To predict some growth kinetics of Salmonella typhimurium, time-to-detection (time-to the nearest visible growth detection) (TTD) and log probability percentage (log P%) of growth initiation were used to measure the effects of pH (5.0-7.4), sodium chloride (NaCl, 0.5-3%), potassium sorbate (KS, 0.0-0.3%) and temperature (T, 15-35degreesC) on the growth response of this organism. For the prediction of log P%. another variable, storage time (D, up to 43 days) also was used as an additional factor. The TTD of S. typhimurium was affected significantly (p < 0.05) by the values of KS, pH and T, but not by NaCl concentration within the studied limits. The log P% of S. tyhimurium was affected significantly (P < 0.001) by KS, pH, T, D and also NaCl in this study. Regression equations were derived relating TTD to KS, T and pH and log P% to KS, NaCl, T, pH and D. From these models the values of predicted TTD and log P% of S. typhimurium can be calculated by any combination of KS, NaCl, pH and T within the limits studied. However, between two models obtained in this study (TTD and log P%), the TTD model showed better prediction (R-2 = 0.91) than the log P% model of growth (R-2 = 0.73). (C) 2003 Elsevier Ltd. All rights reserved.