Effect of pH of the recovery medium on the apparent heat resistance of three strains of Bacillus cereus.

The influence of pH of the recovery medium, in the range 7.6-5.4, on the apparent heat resistance of three strains of Bacillus cereus (ATCC 4342, 7004 and 9818) has been investigated. The highest counts of heat-injured spores were obtained at pH near neutral, decreasing markedly as pH was reduced, especially with longer heating times. When the media were acidified, the apparent D-values tended to decrease, although some exceptions related to the strain and the nature of the medium were observed. z-Values determined were not affected by the pH of the medium.