|Title of Research:
Evaluation of Non-Pathogenic Surrogate Bacteria As Process Validation
Indicators for Salmonella enterica
Iowa State University, Department of Animal Science
Texas A&M University, Department of Animal Science
S. E. Niebuhr, A. Laury, G. R. Acuff, and J. S. Dickson
To compare the responses of several non-pathogenic Escherichia coli surrogate
bacteria strains to the response of a mixed culture of Salmonella to various
meat processes to determine which, if any, of the non-pathogenic surrogates
could be used for process validation for the reduction of Salmonella on
Pre-rigor lean and adipose beef carcass tissue was artificially
inoculated individually with stationary phase cultures of the five
non-pathogenic E. coli cultures or a mixture of five
Salmonella strains in a fecal inoculum. Each tissue sample was
processed with the following microbial interventions: 90° C water; 90° C
water followed by 55° C 2% lactic acid; 90° C water followed by 20° C 2%
lactic acid; 20° C water followed by 20° C 2% lactic acid; 20° C water
followed by 20° C 20ppm chlorine; 20° C water followed by 20° C 10%
trisodium phosphate. The log10 reductions of the E. coli
isolates were generally not statistically different from the Salmonellae
inoculum within a specific treatment.
Similar inoculation experiments were conducted with ground beef stored
at either 4° C or -20° C. When compared to the Salmonella
inoculum, at least three of the five E. coli strains survived
in a manner which was not statistically different from the Salmonellae.
The E. coli strains and the Salmonellae mixed culture were also
inoculated into summer sausage batter and the population enumerated both
before and after fermentation. Four of the E. coli strains
showed a lower population reduction (higher survival) that the
Salmonella mixed culture. Potentially several of the non-pathogenic
E. coli strains may be used either individually or collectively
for specific process validation indicators for Salmonella.
This study demonstrates that some of the non-pathogenic surrogate E.
coli, either individually or collectively, have the potential to be
used to validate meat processes for the reduction of Salmonella.
These cultures may allow a small or very small processing establishment
to internally validate their own processes for Salmonella
reduction. Potentially, by being able to do this in-house in lieu of
paying for an outside lab to conduct tests may make it cost effective
and thus could be of particular value to small and very small plants.
This research could decrease their operating cost while helping them to
ensure food safety and public health protection. However, plants will
need to validate that their methodology achieves these parameters.
The full report on this research can be found on the
Fiscal Year 2005 table under the column Food Safety Technologies - Additional