Microbial safety and quality of various types of cooked chilled foods

Refrigerated Processed Foods of Extended Durability (REPFEDs) are a diverse group of food products. Their production process consists of a variable sequence of different processing steps leading to various types of REPFEDs being introduced to the market. To assure microbial safety, the food industry relies on a combination of mild heat treatment (i.e. pasteurization), appropriate product formulation (i.e. pH, water activity, modified atmosphere packaging, preservatives), cold storage and shelf life limitation. In this paper a classification of REPFED food types is presented and their microbiological safety is evaluated. REPFEDs were classified according (i) to the production process and (ii) to the expected consumerʹs reheating practices. To evaluate the microbiological safety, historical data on the microbial contamination of REPFEDS were collected from five companies, 706 analyses on the day of production (T0) and 2912 analyses at the end of shelf life (TEoS). Results demonstrated that the microbial safety of the products is overall satisfactory. The number of samples exceeding the acceptable levels for Bacillus cereus/sulfite reducing Clostridia (T0: 103 CFU/g, TEoS: 105 CFU/g) was 4.07%/1.94% at T0 and 2.04%/0.69% at TEoS. None of the samples exceeded the acceptable levels for Listeria monocytogenes (T0: Absent in 25 g, TEoS: max 102 CFU/g). In addition the temperature of 38 products was monitored during reheating according to instructions of the manufacturer. The pasteurization values obtained during reheating are very heterogeneous, and only 7 products obtained a P70 of 2 min throughout the entire product. To assess the effect of reheating on L. monocytogenes a challenge test (including reheating) of paella with L. monocytogenes was performed. This demonstrated that L. monocytogenes can grow up to 0.63 log CFU/g in 6 days at 4 °C and that reheating the paella according to the instructions on the label does not guarantee absence of L. monocytogenes. These findings demonstrate the microbial food safety of the tested REPFEDs is satisfactory, and that producers should not rely on the reheating at consumer level to eliminate L. monocytogenes.