Radio frequency heating of comminuted meats - considerations in relation to microbial challenge studies

Bacillus cereus and Clostridium perfringens vegetative cell and spore cocktails in maximum recovery diluent (MRD) were inoculated into pork luncheon meat to challenge a previously developed radio frequency (RF) cooking protocol. After RF cooking and cooling microbial enumeration results showed a reduction in B. cereus vegetative cell and spores of 5.4 and 1.8 log10 cfu g−1, respectively while the corresponding reduction for C. perfringens vegetative cells and spores were 6.8 and 4.1 log10 cfu g−1, respectively. However, post cooking temperatures within the product were lower than anticipated. Subsequent analysis of product thermal and dielectric properties indicated that MRD addition and compositional variations within meat ingredients altered thermal and dielectric properties which in turn contributed to reduced and less uniform temperatures. The study shows that for RF microbial challenge studies, adjustment of product formulation prior to MRD addition is critical to ensure a similar composition to the normal product and a true picture of microbial inactivation.