Colorado State University Extension
SafeFood Rapid Response Network


SAFEFOOD NEWS - Summer 1999 - Vol 3 / No. 3

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New Recommendations for Home Dried Jerky that Minimize the Risk of E. coli O157:H7

Escherichia coli O157:H7 is a unique challenge to food processors, as well as the food consumer. An estimated 725,000 cases of foodborne illness occur each year due to this pathogen at a cost of 2.4 million dollars (Altekruse, et al., 1997). E. coli O157:H7 is particularly dangerous because of the severe consequences of infection that can affect all age groups. The pathogen has a very low infectious dose, thus raising concern for food products consumed raw or with inadequate cooking. In addition, E. coli O157:H7 has been found to survive many weeks at a limited water activity, particularly at refrigerated temperatures. Thus, there is a strong indication for the potential risk of E. coli O157:H7 surviving certain dried foods (Zhao and Doyle, 1994).

There are discrepancies in research conducted involving beef and deer jerky, resulting in consumers and the public receiving mixed messages about the safety of home drying methods. Through research involving jerky made from whole muscle beef inoculated with E. coli O157:H7, we established that the drying methods we had been recommending for meat jerky in the CSU Extension fact sheet 9.311 did not provide adequate destruction of E. coli O157:H7. The traditional methods recommended in 9.311 (marinating raw strips and then drying in an oven set at 60-65 degrees C (140-150 degrees F) for up to 10 hours (or until chewy and leathery) resulted in a log reduction of 2.3 when dried for 10 hours at 62.5 degrees C (145 degrees F) and a log reduction of 4.0 when dried for 10 hours at 68.3 degrees C (155 degrees F).

The U.S. Food Safety and Inspection Service (FSIS) recommends a 5-log reduction in E. coli O157:H7 populations in order for processed food systems such as beef jerky to be considered safe. (This is equivalent to destroying 99.999% of the bacterial cells present.) Their current recommendation for achieving this is to pre-cook the meat to 160 degrees F, then dry at 130-140 degrees F. (FSIS, 1998).

While safe, many jerky connoisseurs object to the cooked flavor of jerky prepared in this manner. We worked with Master Food Preserver (MFP) volunteers in Larimer, Boulder, and Weld counties to develop alternative treatment methods that would likely be acceptable to consumers who dry meat jerky, yet produce a safe product. Preliminary taste panels conducted last summer with Extension agents and MFP volunteers and at the February 1999 In-Service meetings with Extension and Colorado State Forestry personnel helped guide the treatment methods chosen for the inoculation studies. We completed inoculation studies on three of the more promising alternative treatment methods developed, plus three traditional methods (no marinade, dried 10 hours at 145 degrees F; marinade, dried 10 hours at 145 degrees F; marinade, dried 10 hours at 155 degrees F). Of these six treatment methods, none of the traditional methods achieved a 5-log reduction of bacteria. The hot pickle cure method achieved greater than a 5-log reduction (5.95) and the two pre-dip methods (boiling water and warm vinegar/water) reached near 5-log reductions (4.65 and 4.98 respectively). See Table 1 below.

We also evaluated the palatability of a commercially prepared jerky product and the three alternative treatments with 120 consumers recruited at 3 central locations on the CSU campus. Although the commercial product was rated significantly higher than the three home treatment methods for most sensory characteristics, the differences were modest and the mean overall acceptability scores for all three alternative treatment methods were in the lower mid range (3.4-3.9 on a 7 point scale with 7 being highly acceptable and 1 being highly unacceptable).

Recommendations

For the greatest reduction in E. coli O157:H7, we recommend the Hot Pickle Cure method from You and Your Wild Game, University of Wyoming Agricultural Extension Service. For those who do not like the Hot Pickle Cure method, the two dipping methods (boiling water and warm vinegar/water) provide safer products than the traditional method. A more complete summary is available from the authors. See attached enclosure for recipes.

Investigators:

Susan Albright, Ph.D. Candidate, Jennifer Burnham, M.S. Candidate, Pat Kendall, Ph.D., R.D., John Sofos, Ph.D.

References:

• Altekruse, S. F., Cohen, M. L., and Swerdlow, D. L. 1997. Emerging foodborne pathogens. Centers for Disease Control, Emerging Infectious Diseases, 3:417-479.
• FSIS. 10/98. Food Safety of Jerky. http://www.fsis.usda/ OA/pubs/jerky.htm
• Zhao, T., and Doyle, MP. 1994. Fate of enterohemorrhagic Escherichia coli O157:H7 in commercial mayonnaise. J. Food Prot. 57:780-783.

Updated Monday, August 29, 2011