Application of nonlinear regression analysis to the estimation of kinetic parameters for two enterotoxigenic strains of Bacillus cereus spores

Two enterotoxigenic Bacillus cereus strains, isolated from cooked chilled foods containing vegetables, were characterized in relation to safe food production by studying their heat resistance characteristics The kinetic parameters of thermal resistance were determined by one-step nonlinear regression and were compared with those calculated by using two linear regressions. Results showed that the new analysis methodology applied in this study can improve the estimation of D- and z- values. Great differences were found in the thermal resistance of the two strains. The D-90 degrees C were 4.04 and 39 min for the AV TZ415 and AV Z421 strains respectively Growth studies indicated that the two strains were able to grow at refrigeration temperatures but the minimum growth temperature for the AV Z421 strain was 10 degrees C, while the less heat-resistant strain, AV TZ415, grew at 5 degrees C. (C) 1999 Academic Press.