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The Use of Hurdle Technology to Reduce Microorganisms in Ground Beef
F. W. Pohlman, 1 M. R. Stivarius, 2 K. S. McElyea, 1 Z. B. Johnson, 1
and M. G. Johnson 3
Story in Brief
The effectiveness of multiple antimicrobial interventions (hurdle technology) on ground beef microbial characteristics
through simulated retail display was studied. Beef trimmings were inoculated with Escherichia coli (EC) and
Salmonella typhimurium (ST) then treated with either 1) 5% acetic acid followed by 0.5% cetylpyridinium chloride
(AC), 2) 200 ppm chlorine dioxide followed by 0.5% cetylpyridinium chloride (CC), 3) 0.5% cetylpyridinium chloride
followed by 10% trisodium phosphate (CT) or 4) control (C). Trimmings were ground, packaged and sampled on days
0, 1, 2, 3 and 7 of display for EC, ST, coliforms (CO) and aerobic plate count (APC). All treatments reduced (P < 0.05)
all bacterial types monitored. In addition, ST was reduced (P < 0.05) through 7 days of display and APC was held in
check as display progressed. Therefore, the use of hurdle technology was effective for reducing microbial pathogens in
ground beef and would subsequently improve the safety of this product.
Introduction
The meat industry continues to face concerns regarding
the safety of its products. It has been reviewed that the use of
single decontamination interventions are effective for reducing
pathogens on carcass surfaces (Dickson and Anderson
1992; Siragusa, 1995). However, since most carcass decontamination
treatments do not sterilize the carcass, microorganisms
remaining on carcass surfaces can easily become inoculated
onto freshly cut surfaces during carcass fabrication, and
subsequently carried through grinding operations.
Multiple intervention technology utilizes different barriers
or hurdles such as pH changes, oxidizing environments,
or other environmental changes to cause disruption of microbial
cells or cellular metabolism, to either destroy bacterial
cells or retard their growth. Hurdle technology has been more
effective than single interventions for beef carcass decontamination
(Phebus et al., 1997; Graves-Delmore et al., 1998). In
addition, Ellebracht et al. (1999) used 203°F hot water and
2% lactic acid multiple interventions in the production of
ground beef to reduce E. coli, Salmonella typhimurium, and
aerobic plate counts 1.1, 1.8, and 1.5 log colony forming units
(CFU)/g, respectively. Therefore, the objective of this
research was to determine the effects of an organic acid and
other novel decontamination compounds, used in combination,
on the microbial stability of ground beef.
Experimental Procedures
Bacterial preparation and inoculation. Inoculums were
prepared from frozen (-112°F) stock cultures of Escherichia
coli (ATCC #11775; EC) and a nalidixic acid resistant strain
of Salmonella typhimurium (ATTC 1769NR; ST). E. coli was
maintained by brain heart infusion (BHI)(Difco Laboratories,
Detroit, MI) broth with glycerol (20%) and Salmonella
typhimurium was maintained by BHI broth containing
nalidixic acid (Fisher Scientific, Fairlawn, NJ) with glycerol
(20%). Frozen cultures of E. coli and Salmonella typhimurium
were thawed, and 0.1 ml of E. coli suspension was inoculated
into separate 40 ml aliquots of BHI, and 0.1 ml of
Salmonella typhimurium suspension was inoculated into separate
40 ml aliquots of BHI with nalidixic acid. After 18
hours of incubation at 98.6°F, bacteria were harvested by centrifugation
(3649 x g for 20 min @ 98.6°F)(Beckman GS-6
series, Fullerton, CA), re-suspended in the same volume of
0.1% buffered peptone water (BPW) (Difco Laboratories,
Detroit, MI and then pooled together (1600 ml of E. coli and
1600 ml of Salmonella typhimurium) to make a bacterial
cocktail. The cocktail (3200 ml; log 10 7 colony forming units
(CFU)/ml E. coli and log 107 CFU/ml Salmonella typhimurium)
was cooled to 39.2°F and combined with boneless beef
trimmings (28.2 lb) and allowed to attach for 1 hour. The
meat was then drained and separated into 7.9 lb batches and
placed in a 39.2°F cooler for 12 to14 hours to allow further
microbial attachment.
1 Department of Animal Science, Fayetteville.
2 Griffith Laboratories, Griffith Center, Alsip, IL 60658.
3 Department of Food Science, Fayetteville.
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