EFFECT OF TEMPERATURE AND RELATIVE HUMIDITY ON GROWTH BEHAVIOR OF ESCHERICHIA COLI O157:H7 ON SPINACH USING RESPONSE SURFACE METHODOLOGY

Abstract

ABSTRACTIn this study, response surface methodology (RSM) was used to model the growth of Escherichia coli O157:H7 on spinach as a function of temperature (15–35C) and relative humidity (60–80%). The growth data were collected under different conditions, and were then fitted by the modified Gompertz model to estimate the maximum growth rate (GR), lag time (LT) and maximum population density (MPD) at each condition with high coefficients of determination (R2 > 0.98). Moreover, the secondary models were developed for the GR, LT and MPD values obtained from the primary model using RSM quadratic polynomial equation. Model validation was conducted based on the additional experimental data not used for the model development. The results showed that the overall predictions had slight deviation with the observations for its acceptable ranges of bias and accuracy factors as well as lower standard errors of predictions, indicating success at predicting the growth of E. coli O157:H7 on spinach.PRACTICAL APPLICATIONSThe impact of environmental factors including temperature and relative humidity on the response of Escherichia coli O157:H7 on spinach were investigated using response surface methodology. The methodology was successfully applied to E. coli O157:H7 on spinach and the developed models based on the experimental data at simulated conditions exhibited a satisfactory performance. The model developed in this study could be applied during the vegetable distribution chain from farm to retail to predict the growth of E. coli O157:H7 and provide sufficient information for the development of microbiological risk assessment related to E. coli O157:H7 on spinach.