Thermal Resistance of Spores of Two Species of the Genus Bacillus

Abstract

Parameters that increased the thermal resistance of spores of Bacillus coagulans and Bacillus macerans, two common spoilage organisms in canned acid and acidified foods, were studied. Spores of these organisms were produced on solid media with various concentrations of added manganese, calcium chloride, or both, and at different pH values, and incubated at different temperatures. They were then heated in boiling water and decimal reduction times (D values) calculated. Results indicated that growing the organisms in nutrient agar modified with 50 p/m of MnSO₄, pH 6.8 and incubation temperature of 50° C produced spores with greatest heat resistance in both B. coagulans and B. macerans.