Inactivation kinetics and reduction of bacillus coagulans spore by the combination of high pressure and moderate heat

Abstract

The combination effect of high pressure (400, 500 and 600 MPa) and moderate heat (70 and 80C) on the inactivation kinetics and reduction of Bacillus coagulans spore in phosphate buffer and ultra-high temperature (UHT) whole milk was investigated. The pressure come-up time and corresponding logarithmic reduction of spore inactivation were considered during pressure-thermal treatment. B. coagulans spore had a much higher resistance to pressure in UHT whole milk than in phosphate buffer. Survival data were modeled using the linear, Weibull and log-logistic models to obtain relevant kinetic parameters. The tailing phenomenon occurred in all survival curves, indicating the linear model was not adequate for describing these curves. The mean square error and regression coefficient suggested that the log-logistic model produced best fits to all survival curves, followed by the Weibull model. PRACTICAL APPLICATIONS It becomes increasingly apparent that high-pressure treatment combined with moderate heat treatment for low acid and acid products is often required for effective bacterial spores' inactivation. Consequently, the prediction model of microbial survival curves is essential. Bacillus coagulans is a slightly pressure-resistant and relatively heat-resistant spoilage bacterium of considerable concern during the processing of acid foods. Spore inactivation effect during the pressure come-up time is sometimes considerable and should not beignored. The use of mathematical models to predict inactivation for spores could help the food industry further to develop optimum process conditions.