EXPANSION OF THE TIME-TO-TURBIDITY MODEL FOR PROTEOLYTIC CLOSTRIDIUM-BOTULINUM TO INCLUDE SPORE NUMBERS

A model was previously developed to predict the time-so-turbidity of p roteolytic Clostridium botulinum spores placed in broths having variou s pH values, NaCl concentrations and temperatures (Whiting and Call 19 93); however, the model had a constant number of spores (10(4)). This fixed number of spores limits the use of the model and makes inference s to foods more difficult. New data were collected and fitted so the l ogistic model. Regression equations were calculated to provide paramet er estimates for different combinations of temperature, pH, NaCl conce ntration and spore number. The predicted mean times-to-turbidity incre ased with decreasing numbers of spores; at 20 degrees C-pH 7.0-1.0% Na Cl for example, the mean time-to-turbidity was 4.3 and 7.1 days for 10 (4) and 10(0) spores per sample, respectively. (C) 1998 Academic Press .