To measure spore inactivation in BHI broth, aliquots (1 ml) obtained at various times were placed in an ice-water bath, serially dilutedin25 mMphosphate buffer (pH7.4), plated on BHIagarplates, and incubated overnight at 37 C. Results were expressed in terms of decimal reduction (DR, DR ¼ log10[final count/ml BHI] log10[ initial count/ml BHI]), where initial counts refer to counts from the heatactivated sample prior to incubation for spore germination.