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S. N. ALBRIGHT¹, J. N. Sofos², P. A. Kendall¹, and G. R. Schmidt². (1) Department of Food Science and Human Nutrition, Colorado State University, Gifford Building, Fort Collins, CO 80523-1571, (2) Department of Animal Sciences, Colorado State University, Fort Collins, CO 80523

A 5-log reduction in Escherichia coli O157:H7 is recommended during the drying of beef jerky. However, there are discrepancies in the literature as to whether current practices for home dried jerky can achieve such destruction.

The objective was to determine survival of E. coli O157:H7 populations during preparation of beef jerky with and without marinade and drying at two temperatures.

Jerky preparation methods evaluated included: (a) no marinade, dried at 62.5° C; (b) marinade, dried at 62.5°C; and (c) marinade, dried at 68.3°C. Slices (8.7 x 4.0 x 0.6 cm) were inoculated with a four-strain composite of E. coli O157:H7 (6.2 to 7.4 log CFU/cm²), stored overnight (4°C) and prepared according to one of the three methods. Samples were analyzed (bacterial enumeration with selective and nonselective agar media, pH, and a_w) prior to marinating (methods b and c), and at 0, 4, 6, 8 and 10 h of drying. The study was replicated twice with three samples analyzed per replication.

Differences in bacterial counts between selective and nonselective agar media during initial stages of drying indicated bacterial injury. However, at the end of the drying period (10 h) counts of surviving bacteria were similar among agar media. None of the three methods examined achieved a 5-log reduction in bacteria after 10 h of drying. The two treatments dried at the traditional temperature of 62.5° C resulted only in log reductions of 2.2 to 3.4 CFU/cm². Drying at 68.3° C achieved log reductions of 3.0 to 4.6 CFU/cm².

Based on the results of this study, it was concluded that use of a marinade and drying at 62.5 and 68.3°C for 10 h were not adequate treatments for inactivation of 5-logs of inoculated E. coli O157:H7 in home dehydrated beef jerky.