INFLUENCE OF THE INTRINSIC-PROPERTIES OF FOOD ON THERMAL INACTIVATIONOF SPORES OF NONPROTEOLYTIC CLOSTRIDIUM-BOTULINUM - DEVELOPMENT OF A PREDICTIVE MODEL

The effects and interactions of heating temperature (70-90C), pH (5-6. 5), sodium chloride (0-3%), and sodium pyrophosphate (0-0.3%) on the h eat resistance of a six strain mixture of spores of nonproteolytic Clo stridium botulinum type B and type E in turkey were examined. Thermal death times were determined in submerged vials heated using a water ba th. Heated spores were recovered on Reinforced Clostridial Medium (RCM ) supplemented with lysozyme (10 mu g/ml). Decimal reduction times (D- values) were calculated by fitting a survival model to the data with a curve fitting program. The D-values were analyzed by second order res ponse surface regression for temperature, pH, salt (sodium chloride) a nd sodium pyrophosphate levels. The four variables interacted to effec t the inactivation of spores. Confidence intervals (95%) predicted hea t resistance of spores in turkey. The data suggest that the effect of reduced pH in increasing the inactivation was more pronounced at high temperatures and may provide an adequate degree of protection from non proteolytic C. botulinum spores in minimally processed foods, particul arly if employed in conjunction with combinations of salt and sodium p yrophosphate.