Viability of Escherichia coli O157:H7 in ground and formed beef jerky prepared at levels of 5 and 20% fat and dried at 52, 57, 63, or 68°C in a home-style dehydrator

Beef jerky batter was prepared to fat contents of about 5 and 20% and inoculated with about 108 cfu g−1 of a five-strain inoculum of Escherichia coli O157:H7. Pathogen numbers were determined in the raw batter and in the strips formed from it after drying at 52, 57, 63, and 68°C for times that ranged from 2 to 20 h. For both the high and low fat products, pathogen numbers were reduced by about 5 log10 cfu g−1 within 4 h drying at 68°C and within 8 h drying at 63°C. At 57°C, a 5-log10-unit reduction was achieved within 10 h drying for the 5% fat product and within 16 h drying for the 20% fat product. At 52°C, a 5-log10-unit reduction was achieved within 10 h drying for the 5% fat product and within 20 h drying for the 20% fat product. In at least one of the three trials for all four drying temperatures tested, the pathogen was present following enrichment of the samples in synthetic media. The calculated D values decreased from 2.59, 2.48, 1.23, and 1.17 as the temperature increased from 52, 57, 63, and 68°C and as the fat content decreased from 20 to 5%. However, there was no direct correlation between the moisture-to-protein ratio and either the doneness of the strips or the viability of the pathogen. These data indicate that the fat content and the time and temperature at which strips are dried directly impact the viability of E. coli O157:H7 in ground and formed beef jerky.