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Effect of marinade and drying temperature on inactivation of Escherichia coli O157:H7 on inoculated home dried beef jerky

Albright, S.N., Kendall, P.A., Avens, J.S., Sofos, J.N.
Journal of food safety 2002 v.22 no.3 pp. 155-167
beef, dried meat, meat cuts, dried foods, home food preparation, food contamination, microbial contamination, Escherichia coli, inactivation, decontamination, mortality, marinating, drying temperature, food storage, plate count, water activity, pH, food safety
Beef slices were inoculated (5.7-7.5 log CFU/cm2) with a 4-strain composite of E. coli O157:H7, stored (4C, 24 h), marinated (4C, 24 h), dried for 10 h at 62.5C or 68.3C, and stored for 90 days at 21C. Unmarinated beef slices dried for 10 h at 62.5C were used to determine the relative contribution of the marinate versus temperature treatment in the 62.5C trials. Samples were analyzed (bacterial enumeration with selective and nonselective agar media, pH, and a(w)) following inoculation, marinating, at 4, 6, 8 and 10 h of drying, and after 30, 60 and 90 days of storage. Marination resulted in slight changes in bacterial populations (-0.3 to + 0.6 log CFU/cm2), but did not enhance bacterial reduction during drying. For all treatments, most bacterial reductions occurred in the first 4 h of drying, with little reduction thereafter. After 10 h of drying, bacterial reductions were 3.2-3.4 log CFU/cm2 for unmarinated beef slices dried at 62.5C. Reductions of 2.2 and 3.0-4.6 log CFU/cm2 were achieved in marinated jerky slices dried at 62.5C and 68.3C, respectively. No treatment resulted in the recommended 5-log reduction at the end of 10 h drying. However, bacteria did become undetectable by direct plating (<10 CFU/cm2) following 30 days of storage in all treatments except the unmarinated beef slices plated on tryptic soy agar (TSA). Additional work is needed to develop procedures for adequate destruction of E. coli O157:H7 during drying of beef jerky.