A PREDICTIVE MODEL TO DESCRIBE SENSITIZATION OF HEAT-TREATED BACILLUS-STEAROTHERMOPHILUS SPORES TO NACL

The effect of different concentrations of sodium chloride (NaCl) in th e recovery medium on the apparent thermal resistance of Bacillus stear othermophilus spores (strain ATCC 12980) was studied. Spores were heat ed at different temperatures (115-125 degrees C) and subcultured in me dium with different NaCl concentrations [1, 2, 3 and 3.5% (w/v)]. The results indicate that increasing NaCl levels decreases the apparent he at resistance of the spores, over a temperature range of 115-125 degre es C. No significant difference was found between 3 and 3.5% (w/v) NaC l although both reduced B. stearothermophilus heat resistance consider ably. A second-order polynomial equation provided a good description o f the spores' D value, as influenced by the temperature and NaCl conce ntration. Predictions from the model compared well with published data , and therefore the model is suitable for predicting the effect of NaC l concentration on thermal inactivation of B. stearothermophilus.