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Title of Research:
Lethality of Commercial Whole-Muscle Beef Jerky
Manufacturing Processes Against Salmonella serovars and
Escherichia coli O157:H7 |
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Place:
University of Wisconsin - Madison
Authors:
Drs. Dennis R. Buege, Gina Searls, and Steven C. Ingham
Purpose:
- To develop and validate sufficiently lethal processes for use by commercial jerky manufacturers in heating and drying whole-muscle beef jerky.
- To develop a simple method for commercial processors of whole-muscle beef jerky to evaluate the lethality of new processes using a commercially available lactic acid bacterial starter culture as a surrogate for
Salmonella serovars and E. coli O157:H7.
Summary:
A standardized process was used to inoculate beef strips
with 5-strain cocktails of either Salmonella serovars or
Escherichia coli O157:H7, marinade the strips in pH 5.3
marinade for 22-24 hours at 5ْ C, and then convert the strips to
jerky using various heating/drying regimes. The number of surviving
organisms was determined during and after the heating/drying. In
some trials a commercial lactic acid starter culture was also
evaluated as a potential surrogate for the pathogens. 1. A 5-log
reduction for both Salmonella and E. coli. O157:H7
was best achieved by ensuring that high wet-bulb temperatures were
reached and maintained early in the process (51.7ْ C or 54.4ْ C for
60 minutes, 57.2ْ C for 30 minutes, or 60ْ C for 10 minutes)
followed by drying at 76.7ْ C (dry-bulb temperature). 2. Processes
that met the USDA guideline with smaller safety margins were: a)
heating and drying at 76.7ْ C (dry-bulb) within 90 minutes of
beginning the process, b) heating for successive hourly intervals at
48.9, 54.4, 60, and 76.7ْ C (dry-bulb), or c) heating at 51.7ْ C
(dry-bulb), followed by 76.7ْ C (dry-bulb) drying started before the
product water activity was < 0.86. Achieving a ≥ 3.0 log reduction
in the starter culture is a possible standard for validating process
lethality.
Benefits:
The results of the study clearly shows the importance of wet-bulb
temperature in achieving mandated lethality, thus it is strongly
recommended that processors use a wet-bulb thermometer for use in
processing or use a hygrometer to monitor humidity and then use a
commercial available slide rule to determine wet-bulb temperature
from known dry-bulb temperature and % RH values. Reductions in
Salmonella serovars and E. coli O157:H7 of ≥ 5.0 log
CFU can be achieved in the production of whole-muscle beef jerky by
ensuring that high enough wet-bulb temperatures are reached and
maintained early in the process or that high dry-bulb temperatures
heating and drying is done before the beef strip water activity has
fallen below 0.86. This research should help minimize their
operating cost while helping them to ensure food safety and public
health protection. Plants will, however, need to validate that their
methodology achieves these parameters.
The full report on this research can be found on the Fiscal Year 2004 table under the column Food Safety Technologies - Additional Information.
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