Process Humidity Affects Salmonella Lethality at the Surface and Core of Impingement-Cooked Meat and Poultry Products

Abstract

Recent revisions to U.S. Department of Agriculture, Food Safety and Inspection Service (FSIS) compliance and safe harbor guidelines for ready-to-eat meat and poultry products addressed process humidity requirements. Given the lack of prior data for impingement-cooked products, the present study was conducted to evaluate the impact of process humidity on Salmonella lethality at the product core and surface and compliance of the results with FSIS lethality performance standards. Whole muscle beef strips, ground beef patties, whole muscle chicken breast fillets, and breaded ground chicken patties were inoculated with an eight-serovar cocktail of Salmonella. Beef and chicken samples were cooked in a pilot-scale moist-air impingement oven to a core temperature of 70.0 and 72.8°C, respectively, immediately quenched in liquid nitrogen, and dissected to obtain core and surface samples. Variables included oven temperature (218 and 232°C), air velocity (0.7 and 2.8 m/s), and oven humidity (0.7, 15, 30, or 70% moisture by volume [%, v/v]). Additional treatments were performed to examine the impact of supplemental critical control processes such as increased endpoint temperature, postoven carryover time, and pre- or postoven steam treatments. Salmonella reductions of >7 log units were reliably achieved in chicken patties regardless of the processing variables; however, none of the treatments reliably ensured >6.5-log reductions of Salmonella in ground beef. A majority of whole-muscle samples failed to meet the required performance lethality when processed at 0.7% (v/v) humidity; however, Salmonella inactivation was significantly improved (P < 0.05) at oven humidities of ≥30% (v/v). Dry oven conditions achieved greater Salmonella lethality at the core than at the surface for multiple products (P < 0.05). The efficacies of minimal and supplemental critical controls were dependent on product, process, and humidity (P < 0.05). Overall, process humidity and product variability should be considered in regulatory requirements and process validations.