Montana State University, Bozeman, MT
Drs. Jane Boles, K.I. Neary, and K. Clawson
- Determine the survivability of E. coli O157:H7, Salmonella spp. and Listeria monocytogenes on whole muscle jerky dried without humidity and stored in a vacuum package.
- Determine the survivability of E. coli O157:H7, Salmonella spp., and Listeria monocytogenes on whole muscle jerky dried with smokehouse dampers closed for the first hour of processing.
- Determine the survivability of Listeria monocytogenes inoculated post-processing on jerky treated with a sodium lactate or hot water dip.
Drying procedures currently used by most small processors will reduce the number of pathogens on the jerky; however, drying does not reduce the number enough to meet the 5-log reduction USDA desires. Closing of the smokehouse dampers for the first hour of processing resulted in a small significant decrease in E. coli and Salmonella survival. Salmonella was more susceptible to the increased moisture during the first hour of drying than were Listeria and E. coli. Use of sodium lactate dip (2%) is not as effective as a 20 second hot water dip or no treatment in decreasing post-processing inoculated Listeria monocytogenes on jerky. Drying and storing in a vacuum package does result in a reduction of pathogens but not to below the detectable limit. The cause of the reduction of pathogens in storage is not clear. Some will be due to the lowered water activity but some may be due to pathogens being injured during drying and not being able to adapt to the vacuum packaged atmosphere. As long as the water activity of jerky is below 0.70, pathogens will not survive vacuum packaged storage at ambient temperature beyond 6 weeks.
This study reinforced the importance of maintaining humidity and controlling the moisture loss from the product in order to achieve an adequate lethality of the three pathogens especially during the initial part of drying. It was demonstrated that closing the oven damper for the first hour of the drying step reduces the amount of Salmonella spp. and E. coli O157:H7 for all successive times of drying except for 12 hours of drying. The results of this study provide reinforcing information on the importance of maintaining humidity during the processing of jerky to control the three pathogens, E. coli O157:H7, Salmonella spp., and Listeria monocytogenes. Something as simple as adjusting the oven damper during processing shows that control of humidity can be easy to achieve and cost effective and thus should be of particular value to small and very small plants that make jerky. Plants will, however, need to validate that their methodology achieves these parameters. This research should decrease their operating cost while helping them to ensure food safety and public health protection.
The full report on this research can be found on the Fiscal Year 2004 table under the column Food Safety Technologies - Additional Information.