Purpose: The purpose of this work was to study the effect of temperature and pH on the germination and the growth of spores produced at different sporulation conditions. A global model was proposed based on a single set of parameters, commonly named growth cardinal values.
Methods: The influence of temperature and pH on the bacterial growth, recovery and sporulation abilities of Geobacillus stearothermophilus ATCC 12980 was studied on nutrient agar. Growth cardinal values and heat resistance (D115°C) were estimated at different sporulation and recovery conditions.
Results: Based on experimental results, growth cardinal values were estimated by fitting the cardinal model at 38.52°C, 57.59°C, 68.02°C, 5.27, 7.17 and 8.91 respectively for Tmin, Topt, Tmax, pHmin, pHopt and pHmax. D-values obtained at different temperatures and pH of sporulation and recovery showed that the highest heat resistances are obtained in conditions allowing optimal growth and these D-values decreased at suboptimal growth pHs and temperatures. The current observations revealed also that sporulation and recovery occurred only in the range of temperature and pH allowing the growth, therefore a model was proposed to describe heat recovery using growth cardinal values.
Significance: This work provides a new global approach in food preservation taking into account the sporulation history and the recovery conditions. Growth cardinal values could be the unique set required to model and to predict heat resistance.