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.