ABSTRACT Fully cooked chicken leg quarters (160 g to 300 g) were injected to contain 107 to 108 colony‐forming units (CFU)/g of a 5‐strain Listeria monocytogenes culture. The inoculated leg quarters were vacuum‐packaged in 0.08‐mm‐thick packaging films and then pasteurized at 96°C via steam. The heat transfer coefficient was about 760 W/m2 K in the steam cooker. Seven log10 (CFU/g) reduction of L. monocytogenes was achieved in about 22 min of steam treatment. Results from the inoculation tests agreed with the process lethality model prediction using the kinetic values that were obtained for the same product. This information helps industry to validate the lethality of L. monocytogenes in similar products during postcook pasteurization.

Studies were conducted to determine thermal inactivation D- and z-values of Salmonella and Listeria innocua in fully cooked and vacuum-packaged chicken breast meat. Fully cooked chicken breast meat products that were obtained from three different sources with differing formulations were uniformly inoculated with a cocktail of Salmonella (including Senftenberg, Typhimurium, Heidelberg, Mission, Montevideo, and California) or L. innocua at approximately 10(7) cfu/g. The inoculated meat samples were vacuum-packaged and then heat-treated at a temperature of 55 to 70 C for 5 to 90 min. After heat treatment, the samples were immediately cooled in an ice-water bath. Survivors of Salmonella and L. innocua were enumerated for each sample. D- and z-values of Salmonella and L. innocua were determined for each product and compared among the products. Source and formulation did not cause significant differences in the D- and z-values of Salmonella or L. innocua among the three fully cooked and vacuum-packaged chicken breast meat products.

Fully cooked chicken breast strips were surface inoculated to contain 9 log(10) (CFU/g) Salmonella Senftenberg or Listeria innocua. The inoculated products were vacuum packaged. in 0.2-mm-thick barrier bags (241 by 114 mm), then steam pasteurized at 88 degreesC in a continuous process for 26 to 40 min or in a batch process for 33 to 41 min. After the treatments, the products were analyzed for the survivors of Salmonella or Listeria. The models were developed to correlate the surviving rate of Salmonella and Listeria with cooking time for both continuous and batch processes. A cooking time of 34 min was needed to achieve 7 logs of the reduction in a batch process. To achieve the same log reduction, a longer (6 min) cooking time was needed in a batch process than in a continuous process. The results from this study will be useful for processors to evaluate postcooking treatment procedures for ready-to-eat meat products.