Effects of the heating medium pH on heat resistance of Bacillus cereus spores

摘要

The influence of the pH of the heating medium (which-included several foods and buffers) on the thermal resistance (D and z-values) of spores of three Bacillus cereus strains was studied. Acidification from pH 7.0 to 4.0 produced a 5-fold decrease in D-values. Plots of log D vs pH gave straight lines, which made it possible to develop an equation to approximately predict the changes in heat sensitivity of B. cereus spores which occurred with changing pH. z-Values for two of the strains studied were not affected by acidification. On the other hand, with the strain ATCC 9818, a clear and statistically significant increase in z-value was observed as the pH decreased.