Impact of Operational Parameters on Pathogen Lethality in Dry and Semi-dry Uncooked Fermented Sausages

The safety of uncooked fermented, dried sausages relies upon controlled fermentation and drying that inactivates pathogenic bacteria. Current guidelines for the production of fermented sausages by the United States Department of Agriculture (USDA) Food Safety Inspection Services (FSIS) and related research highlight specific safety parameters. The confidence that processing steps, which do not include cooking, inherently mitigate microbial risks, is challenged by the resilience of pathogens in the dry and acidic environments of these food products. The aim of this work was to examine the length of drying required to achieve a target pathogen reduction across a range of sausage diameters. This study investigated the relationship between product diameter and time required to achieve target reductions of Escherichia coli O157:H7, Salmonella enterica, and Listeria monocytogenes, as well as the attainment of specific water activity (a_w). The research utilized salami and summer sausage with diameters of 18 mm, 30 mm, 60 mm, 90 mm, and 110 mm. Sausage batter was inoculated with 5 strains each of E. coli O157:H7, L. monocytogenes, and S. enterica. Inoculated sausages were processed with fermentation and drying protocols for each sausage type. Smaller diameter sausages reached both the desired pathogen reduction and target a_w of 0.85 sooner than larger ones. However, the time to achieve the target a_w did not align with the time to achieve the pathogen reduction targets, suggesting that a_w alone is not a reliable indicator of safety. Another finding was larger sausages achieved the target pathogen reduction without reaching the target a_w, suggesting complex relationship between a_w, diameter, and pathogen inactivation. These data support the need for food safety guidelines that consider drying duration, a_w, and pathogen behavior for varying sausage diameters. This research contributes to developing more precise safety protocols for producing dry and semi-dry fermented sausages.