Beef Jerky: Viability of Food-Poisoning Microorganisms on Jerky during its Manufacture and Storage

Abstract

Beef jerky was made from slices of flank steak inoculated with Staphylococcus aureus, vegetative cells of Clostridium perfringens as well as Bacillus subtilis and a two species-composite of Salmonella. Slices were placed in a domestic food dehydrator for 4 h at 52.9±0.8°C (127.2°F) followed by 4 h at 48.2±0.4°C (118.8°F). Meat slices dried rapidly, reaching an a_w of 0.86 and a shelf-stable moisture-protein ratio of ≤1.6 within the first 2.5–3 h of drying. Samples originally contained about 68% moisture, but this dropped to about 30% by 4 h and 20% by 8 h. Some growth of inoculated S. aureus occurred initially but total numbers of all other added microorganisms decreased rapidly from the start of drying and although significantly reduced in numbers at the end of 8 h treatment, they survived processing. C. perfringens cells were not detected at the end of the heated-drying regimen but were recovered later in an inoculated sample stored at 2.5°C for a month. Contaminated jerky stored at 20°C and high relative humidity (RH) for 26–28 d did not contain detectable added bacteria, whereas identical samples stored at 2.5°C and low RH contained viable S. aureus and B. subtilis as well as C. perfringens. Domestic preparation of jerky from beef of normal retail quality would involve little risk provided initial drying is done rapidly at temperatures equal to or greater than those used in the present study.