Microbiology-PTM-OMA_Modules_1-5

Preparation of Inoculum • Raw and cold‐processed foods should be inoculated with unstressed  organisms • Heat‐processed foods should be inoculated with heat‐stressed  organisms • Heat culture at 50˚C for ~10 min  • The heat stress must achieve 50 – 80% injury of the inoculum • The degree of injury is calculated as follows: 1 – ( n select / n nonselect ) x 100 n select = mean number of colonies on selective agar n nonselect = mean number of colonies on nonselective agar