Heat Resistance of Spores of Non-Proteolytic Type B Clostridium botulinum

Abstract

The heat resistance of spores of non-proteolytic type B Clostridium botulinum was compared to that of type E and proteolytic type B spores. Spore suspensions were produced in a biphasic medium consisting of beef heart agar overlaid with a liquid phase containing trypticase, peptone, glucose, starch and cysteine. Thermal death time curves were established for seven strains heated in phosphate buffer. In general, spore suspensions of non-proteolytic type B strains had greater thermal resistance than type E strains. Decimal reduction times at 82.2°C, established by linear regression analyses of data, ranged from 1.49 to 32.3 min, but the higher heat resistances were not obtained consistently, even with different spore suspensions of the same strain. None of the spore suspensions of non-proteolytic, type B C. botulinum demonstrated heat resistance comparable to that of the proteolytic type B spores.