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The effects of sodium benzoate and potassium sorbate added to the recovery medium, at different pH values (6.5, 6.0 and 5.0), on the recovery rates and heat resistance of Bacillus stearothermophilus spores (ATCC 12980, 7953, 15951 and 15952) were investigated. Heated spores of strains 12980 and 7953 were inhibited by sorbate concentrations over 0.05%. Potassium sorbate at concentrations as low as 0.025%, and sodium benzoate at 0.1%, were very effective inhibitory agents for heat-damaged spores. Their effectiveness always increased at pH 5.0, at which no growth occurred, with sodium benzoate for strains 7953, 15951 and 15952, and with potassium sorbate for strains 15951 and 15952. Decimal reduction times, whenever recovery was possible, were not significantly (P > 0.05) affected. None of these compounds modified the z-values obtained for the spores of the four strains, which had a mean value of 7.53 ± 0.28.