Inactivation Effect of Infrared Radiation Heating on Bacterial Spores Pretreated at Various Water Activities

Abstract

Bacillus subtilis spores pretreated at various water activities (a_w, from 0.005 to 0.996) were inactivated by infrared radiation heating (IRH) at 0.5 and 1.0 kW of electric power under dry conditions in an open system. The resistance of B. subtilis spores to IRH was greater in the range of 0.25 to 0.874 a_w, and had the maximum value when a_w was 0.796 at 0.5 kW and 0.688 at 1.0 kW. Markedly lower IRH resistance of B. subtilis spores was observed at the lower or higher levels of a_w.