Inactivation of Salmonella enterica, Escherichia coli O157:H7, and Campylobacter jejuni in a Restructured Beef Jerky Developed for Production in Ethiopia

Drying is one of the oldest methods of food preservation, involving the addition of salt and removal of water to generate a shelf-stable and nutrient-dense product. Pathogens have demonstrated the ability to adapt during a slow drying process, making them more resistant to dehydration and heat treatment. In Ethiopia, an inconsistent electrical grid makes refrigeration unreliable, making dried meat products desirable to consumers. The main dried beef product, qwanta, is very labor intensive to produce. It is therefore not well suited for commercial production and drying at ambient temperatures limits inactivation of pathogenic bacteria. This study quantitatively evaluated the inactivation kinetics of foodborne pathogens during the drying of a restructured beef jerky product produced by a heat treatment that could be applied in anEthiopian butcher shop. A secondary objective was to evaluate effects of including 15% (w/w) pureed dates or raisins into the formulation. Challenge studies were performed on 5 serotypes of Salmonella enterica, 3 strains of Escherichia coli O157:H7, and 3 strains of Campylobacter jejuni. Meat formulations were inoculated with stationary phase cultures, formed into strips, and dehydrated for 6 h in a home-style dehydrator. Samples were weighed pre- and post-drying, plated for enumeration of challenge strains each hour, and water activity (aw) was measured at each sampling interval. Nonlinear predictive models were fit to the inactivation data, revealing an inverse sigmoidal curve for S. enterica and concave downward curves for E. coli and Campylobacter. Salmonella and E. coli were reduced 4.56 ± 0.35 and 6.27 ± 0.69 log (CFU/g),respectively, after 6 h of drying, while Campylobacter was reduced below the limit of detection (>4.32 log [CFU/g] reduction) after 3 h of drying. Including dates (15% w/w) into formulation improved the reduction of S. enterica by 0.63 log (CFU/g) compared to the control (P=0.02), whereas the addition of raisins showed a non-significant improvement (0.50 log CFU/g; P=0.07). Modified processes to improve the safety and extend the shelf life of animal-sourced foods in Ethiopia can reduce the incidence of foodborne disease and provide consumers with a more convenient and accessible source of protein as well as reduce food waste. These predictive models and validation studies may be useful for Ethiopian and US jerky producers, giving them the ability to more accurately assess the microbial risk of their products