Solving Food Safety Problems in Muscle Foods
What major problems or issues are being
resolved by our research and how are we resolving it?
CDC has reported that outbreaks of food borne illnesses caused by Campylobacter,
Escherichia coli O157:H7 (EHEC), Listeria monocytogenes (LM), Salmonella, and
Yersinia enterocolitica have declined. Although incidences have decreased,
controlling these pathogens remains to be a primary goal for the meat industry.
The consumer’s demand for minimally processed safe foods encourages food
processors to explore non-thermal, novel food preservation systems to control
food borne pathogens associated with meats and meat products. Consumer aversion
to traditional chemical preservatives has left food processors with less
flexibility in choosing preservation methods. Some of these methods include
pulsed electric field, pulsed light, irradiation, heating processes, and high
hydrostatic pressure, however, they do not satisfy industry and consumer
requirements. The goal of this research is to explore non-thermal emerging
pressure technologies to reduce/eliminate pathogens associated with meats.
Hydrodynamic pressure processing (HDP) is a preservation technology being
developed to determine the effect of this method on pathogenic and indigenous
spoilage microorganisms found on fresh meats (pork, beef, poultry) and meat
products. Investigations will be done to determine microorganisms and pathogens
in meats that are susceptible or resistant to HDP. Bacterial intracellular
proteins will be examined to determine possible bacterial target sites of HDP.
At the request of a regulatory agency (FSIS), a funded project will be conducted
to determine the accuracy, reliability, and cross-contamination potential of
temperature devices. The information will provide FSIS with suggestions for
guidelines to consumers for purchasing temperature devices and using them
properly when cooking hamburgers and chicken breasts.
How serious are the problems? Why does it matter?
 The CDC estimates that food borne diseases are responsible for approximately 76
million illnesses, 325,000 hospitalizations, and 5,000 deaths per year. Meats
and meat products are vehicle foods for 5 million cases of food borne illnesses.
Pathogens such as Salmonella, Campylobacter jejuni, LM, and EHEC are the primary
causative agents of illness in muscle foods. These pathogens contribute to
billions of dollars spent for medical costs and productivity losses. Recent
outbreaks and recalls involving ConAgra in which 19 million pounds of ground
beef were recalled due to EHEC contamination emphasize the urgency confronting
the meat industry. HDP could improve meat product safety by inhibiting pathogen
proliferation. Improving product safety leads to a decrease in cases of food
borne illnesses, deaths, and financial losses. The meat industry would profit
from this novel non-thermal technology by fewer recalls of contaminated product
and increased sales derived from consumer confidence in higher quality, safe
meat products.
Our most significant accomplishments
Research was done to identify microorganisms that are resistant or susceptible
to HDP. Preliminary results have shown that Gram-negative indigenous spoilage
(Pseudomonas, Serratia) microorganisms in ground beef are more susceptible to
HDP than Gram-positive microorganisms (Streptococcus, Bacillus). This should
lead to an extended shelf-life of the meat product. Identification of
susceptible/resistant microorganisms will provide information for using
additional preservation treatments (antimicrobials) that may increase inhibition
or decrease resistance to enhance pressure treatment.
[picture of distribution of predominant microorganisms recovered after
HDP]
Microorganisms isolated from ground beef treated with the combination of HDP and
diacetyl were identified. Individual treatments using diacetyl or HDP inhibited
Gram- negative microorganisms. The additive effect of the combination treatment
was due to the inhibition of predominant Gram-negative spoilage bacteria
(Pseudomonas) by diacetyl and HDP. Diacetyl inhibits microorganisms by
inhibiting the utilization of arginine by the bacterium. Future research will
determine the bacterial target site of HDP. This information could lead to
combining HDP with other preservation methods to enhance microbial inhibition.
Normal spoilage microorganisms in portions of fresh and temperature abused meats
(ground beef, beef round rump roast) were reduced (2-3 logs) by HDP technology,
and HDP treatment significantly increased the microbiological shelf-life of
refrigerated ground beef and bottom round sections. These accomplishments
provide the basis for further investigations which include determining the
action of HDP on bacterial cells, the effect of HDP in combination with approved
food additives (antimicrobials) and other processing (in particular,
non-thermal) technologies on food borne pathogens.
 Controlling (eliminating) pathogens from meat products and reducing spoilage
microorganisms are primary goals for the meat industry. Research by the Food
Technology and Safety Lab to identify microorganisms, such as Pseudomonas and Serratia in ground beef, are more susceptible to HDP than Gram-positive
microorganisms, such as Streptococcus and Bacillus. This should lead to an
extended shelf-life of the ground beef meat product. Identification of
susceptible/resistant microorganisms will provide information for using
additional preservation treatments (antimicrobials) that may increase inhibition
or decrease resistance to enhance pressure treatment. A comparison was done
using HDP technology to determine the relationship between microbial reduction
and tenderness improvement in beef strip loins. The experiments were
conducted in both the winter and spring using two different shaped explosives
(rectangular vs.
 cylindrical) and fresh (never frozen) of frozen then thawed
meat samples. Results indicated that HDP using either shape of explosive
instantaneously reduced (2-3 log CFU/g) Gram negative and lactic acid bacteria
when experiments were performed in the winter regardless of the state of the
meat (fresh vs. frozen/thawed). However, when HDP was performed in the spring,
there was no bacterial reduction on the surface of the meat using either shape
of the explosive or state of the meat. Initial numbers of microbial populations
were lower in the spring than in the winter months, and this along with the
possibility of different types of bacteria present during those seasons might
explain the differences in HDP performance. It was also determined that
tenderness improvement as a response to HDP treatment could not be used as an
indicator for successful microbial reduction resulting from HDP treatment.
 In 2003 FSIS requested FTSL perform a comprehensive project to determine the
accuracy, reliability, and potential for cross-contamination of temperature
indicating devices. The information will be used by FSIS to provide guidelines
to consumers for using disposable and non-disposable temperature devices when
cooking ground beef patties and chicken breasts by different cooking methods.
Other Significant Accomplishments
Package survival during HDP processing is critical for conducting successful
microbiological tests. Efforts by FTSL to improve the packaging system (films,
sealing methods) have resulted in a flexible and reasonably suitable vacuum
package that reliably maintains its integrity during and after HDP treatment. At
the present time, more than 80% of the package survive the HDP pressure
treatment.
Significant Activities that Support Special Target Populations
FSIS provided funding to the FTSL for a study to determine the accuracy,
reliability, and cross-contamination of temperature devices. The information
will be used by FSIS to provide guideline to consumers for using disposable and
non-disposable temperature devices when cooking ground beef patties and chicken
breasts by different cooking methods.
Current FTSL food safety research projects:
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