[Federal Register Volume 60, Number 186 (Tuesday, September 26, 1995)]
[Notices]
[Pages 49553-49564]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-23798]
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Notices
Federal Register
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or proposed rules that are applicable to the public. Notices of hearings
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Federal Register / Vol. 60, No. 186 / Tuesday, September 26, 1995 /
Notices
[[Page 49553]]
DEPARTMENT OF AGRICULTURE
Food Safety and Inspection Service
[Docket No. 95-025N]
Comparison of Methods for Achieving the Zero Tolerance Standard
for Fecal, Ingesta, and Milk Contamination of Beef Carcasses: Notice of
Conference
AGENCY: Food Safety Inspection Service, USDA.
ACTION: Notice.
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SUMMARY: The Food Safety and Inspection Service (FSIS) will host a
conference to consider ``Achieving the Zero Tolerance Standard for
Fecal, Ingesta and Milk Contamination on Beef Carcasses'' on October 23
and 24, 1995, from 8:30 a.m. to 5 p.m., at the United States Department
of Agriculture in Washington, DC. The conference will consist of two
sessions on consecutive days. At the first day's session, participants
will discuss available scientific and technical data comparing the
efficacy of the methods for achieving the zero tolerance standard for
fecal, ingesta, and milk contamination of beef carcasses. Participants
are invited to make presentations regarding this scientific and
technical data during this first session. At the second day's session,
participants will discuss relevant public policy issues, including
public heath, regulatory, and economic issues.
The input provided at this conference will be taken into account by
FSIS in deciding whether to approve any methods in addition to trimming
for achieving the zero tolerance standard.
ADDRESSES: The conference will be held at the U.S. Department of
Agriculture, in the back of the South Building Cafeteria, (between the
2nd and 3rd wings), 14th Street and Independence Avenue, SW., in
Washington DC. Persons wishing to make presentations at the first
session of the conference are requested to submit in advance brief
statements describing the general topics of their presentations. Send
descriptions to Dr. William James, Director, Slaughter Inspection
Standards and Procedures Division, FSIS, USDA, Room 202 Cotton Annex,
300 12th Street, SW., Washington, DC 20250.
FOR FURTHER INFORMATION CONTACT: For further information, contact Dr.
William James at (202) 720-3219.
SUPPLEMENTARY INFORMATION:
Background
Effective prevention and removal of fecal, ingesta, and milk
contamination are among the most important steps companies must take to
ensure the safety of beef carcasses. Such contamination may harbor E.
coli 0157:H7, Salmonella, and other enteric pathogenic microorganisms.
FSIS has a zero tolerance standard for fecal, ingesta, and milk
contamination of beef carcasses, and is continually seeking the most
effective, scientifically supportable means of implementing this
standard.
The policy of FSIS has been to require the physical removal of all
feces, ingesta, and milk from beef carcasses by trimming. Before
February 1993, however, ambient temperature washes were sometimes used
to remove small flecks of contaminants. Use of ambient temperature
water washes for this purpose varied across the country and among
inspection personnel. A distinction between flecks of contamination as
to their source was not always made, i.e., determinations were not made
about whether flecks were fecal contamination or rail dust, and, in
some localities, whether they could be removed by washing.
In February 1993, after an outbreak of E. coli 0157:H7 in several
Western States, FSIS reinforced that trimming was to be the only means
of removing feces, ingesta, and milk contamination from beef carcasses.
The trim-only policy was based on the judgment that trimming was more
effective for removing fecal contamination than alternative approaches.
At the time, there were no scientific data available to the Agency
comparing the efficacy of trimming and alternative procedures.
Trimming, if performed properly, is an effective means of
physically removing from beef carcasses the visible contamination and
any accompanying microbial contamination. A primary conceptual
advantage of trimming over ambient temperature washing is that it
physically removes visibly contaminated tissue (which is more likely to
be microbiologically contaminated) rather than relying on a wash to
remove bacteria that, depending on the circumstances, may be firmly
attached. Also, trimming, when properly performed, is presumed to have
less potential than ambient temperature washing for spreading
contamination to other parts of the carcass. On the other hand, if
trimming is performed incorrectly, it has the potential to cause cross-
contamination as the knife moves from areas contaminated with bacteria
to newly exposed uncontaminated areas. The effectiveness of trimming
also depends on the skill of the operator in visually detecting and
effectively removing contamination, while avoiding further
contamination by handling the carcass during this process.
Strict enforcement of the policy requiring that trimming be the
only means to achieve zero tolerance, following the 1993 E. coli
0157:H7 outbreak in the Western States, was also based on the Agency's
need to directly and aggressively remove any potential source of
pathogenic contamination. FSIS believes that strict enforcement of the
trim-only approach was appropriate, based on the information available
at the time.
Since 1993, numerous other approaches to removing contamination
have been devised and studied to assess their potential as effective
alternatives or supplements to carcass trimming to achieve the zero
tolerance standard. FSIS is now considering whether to permit the use
of some or all of these alternative approaches. The following material
reviews current scientific data concerning different approaches to
achieving the zero tolerance standard for fecal, ingesta, and milk
contamination on beef carcasses, as they would apply under commercial
conditions.
Data Review
I. Condition of the Animal on Arrival at the Abattoir
Any discussion of the sources of pathogen contamination on beef
carcasses must consider animal husbandry practices and the farm
environment (Hancock et al., 1994), the possibility of cross-infection
during transport (Gronstol et al., 1974 a, b), and
[[Page 49554]]
lairage of the animals before slaughter (Anderson et al., 1961; Grau et
al., 1968). The practice of regularly cleaning and disinfecting
transport vehicles and holding facilities reduces the level of
bacterial contamination in the environment and decreases the risk of
pathogens being spread between live animals (ICMSF, 1988).
Soil, feces, and moisture present on the hides and feet/hooves of
animals entering the slaughterhouse pose a considerable challenge to
hygienic slaughtering practices (Troeger, 1995). Seasonal and
geographical factors, together with animal management systems, have a
tremendous effect on the cleanliness of live animals presented for
slaughter.
Although it would be desirable to exclude grossly contaminated
animals from the slaughterhouse, Mackey and Roberts (1991) concluded
that such an action could be difficult to rationalize and enforce. Data
from Finland, however, indicate that exclusion of cattle carrying
excessive loads of soil and manure can be accomplished, with resulting
improvements in meat hygiene (Ridell and Korkeala, 1993). As a result
of imposing regulations requiring that excessively dirty cattle either
be slaughtered at a ``casualty'' abattoir or processed separately at
the end of the day using extra care (with any extra costs being
incurred by the farmer), the number of ``excessively dungy'' animals
presented at slaughter in Finland has decreased dramatically. Exclusion
of grossly contaminated cattle is deemed justifiable since such animals
yield more highly contaminated carcasses, even when slaughtered with
extreme care and using reduced line speeds. Carcasses from
``excessively dungy'' cattle had, on average, 5-fold more
microorganisms per cm\2\ than carcasses from ``control'' cattle despite
the added precautions.
Attempts have been made to clean live animals following arrival at
the slaughterhouse. In general, however, these efforts have not been
regarded as effective (Empey and Scott, 1939; Roberts, 1980). Though
Empey and Scott estimated that a cold water wash reduced the bacterial
levels present on cattle by approximately one-half, such treatments
have to be applied in such a manner as to restrict later potential
microbial growth on a wet hide and reduce practical difficulties
associated with handling wet, slippery hides. These investigators also
conducted small-scale experiments on the effects of hot water and
chlorine on microbial loads of hide-on cattle feet (not live animals).
While chlorine showed some potential, application of hot water was
thought by the authors to have practical limitations for live animals
as water temperatures of 75 to 80 deg.C were necessary to achieve
significant microbial inactivation. Animal welfare concerns and the
effect on meat and hide quality may complicate or preclude application
of such antimicrobial treatments to the live animal.
II. Bacterial Contamination During Slaughter
It is generally agreed that deep muscle tissue of healthy live
animals is essentially sterile (Gill, 1979, 1982; Zender, et al.,
1958). During slaughter and dressing procedures, the surfaces of
livestock carcasses become contaminated with microorganisms. The extent
of this contamination varies depending on the condition of the animal
upon arrival at the establishment and methods used during slaughter and
dressing (Roberts, 1980). Contamination of carcasses is undesirable,
but cannot be completely avoided, even under the most hygienic
conditions (NRC, 1985; Roberts, 1980; Roberts et al., 1984; Grau, 1987;
Dixon et al., 1991).
When meat is produced under hygienic conditions, numbers of
pathogens contaminating the surface of the carcass are usually small,
and the micro-flora consists primarily of saprophytic bacteria, such as
Pseudomonas. Results from beef carcasses sampled for pathogens and
other bacteria of interest, reported in Nationwide Beef Microbiological
Baseline Data Collection Program: Steers and Heifers, reflect low
numbers of pathogens contaminating the surface of beef carcasses.
Staphylococcus aureus and Listeria monocytogenes were recovered from
approximately 4% of 2,000 beef carcasses. Salmonella and Escherichia
coli 0157:H7 were recovered from 1% and 0.2%, respectively, of more
than 2,000 beef carcasses. Only 3.6% of the carcasses had coliform
counts greater than 100 colony-forming units (CFU)/cm\2\ (2.0 logs) and
6.9% of the carcasses had aerobic plate counts of over 10,000 CFU/cm\2\
(4.0 logs). Although raw meat containing over 10,000 CFU/cm\2\ of non-
pathogenic spoilage bacteria does not present a health risk, it is
generally considered aesthetically undesirable, has reduced shelf-life,
and is often viewed as having been produced unhygienically.
Good hygienic practices during the slaughter and dressing of
livestock are critical to safeguard the microbiological safety and
quality of meat (Empey and Scott, 1939; Ayres, 1955; ICMSF, 1988).
Adherence to good hygienic practices, however, does not preclude the
presence of pathogenic bacteria on the final dressed carcass.
Salmonella, E. coli 0157:H7, Listeria monocytogenes, and Campylobacter
jejuni have all been recovered from hygienically-slaughtered beef
carcasses (Stolle, 1981; Weissman and Carpenter, 1969; Chapman et al.,
1993; Loncarevic et al., 1994; Stern, 1981; Gill and Harris, 1982).
Feces, ingesta, and milk from infected cows may contain Salmonella,
E. coli 0157:H7, and other pathogens (Grau et al., 1968; Munroe et al.,
1983; Martin et al., 1986). Accidental carcass contamination with
feces, ingesta, and milk is thought to be the primary route by which
pathogens enter the food chain (Chapman et al., 1993). Removing such
visible contamination from carcasses should reduce the risk to
consumers but is unlikely to produce pathogen-free carcasses.
Slaughter Floor Contamination
The main direct sources of carcass microbial contamination on the
slaughter floor include the animal (especially the hide and feet/
hooves), dressing equipment and tools, personnel and their clothing,
and the plant environment. Water is sometimes mentioned as a possible
source of microorganisms, but this association is largely historical
since contemporary abattoirs use exclusively potable water (or
reconditioned water of equivalent microbiological quality). Similarly,
the contribution of airborne microbes to carcass contamination on the
slaughter floor has been mentioned, but Roberts (1980) concluded that,
``air deposits only tens or hundreds of microorganisms per cm\2\ per
hour, where operatives and equipment carry tens or hundreds of
thousands--or even millions.''
Although some microbial contamination of deep-muscle tissues may
occur during stunning and bleeding processes when intact skin is
broken, thus allowing bacteria to enter the bloodstream, these actions
do not generally introduce significant numbers of bacteria (Roberts and
Hudson, 1986). The primary source of bacterial contamination of the
carcass is generally the hide (Empey and Scott, 1939; Ayres, 1955;
Newton et al., 1978; Smeltzer et al., 1980a). During the initial stages
of hide and leg removal, microorganisms present on the hide are
transferred to subcutaneous tissue by the skinning knife. Additional
microbes may be directly transferred to the subcutaneous tissues from
the hide when a loose outer flap of the hide contacts the carcass
surface during hide pulling (Mackey and Roberts, 1991). Contamination
may also be transferred indirectly from the
[[Page 49555]]
tools, hands/arms, and clothing of workers (Mackey and Roberts, 1991).
A classic example is a worker holding the carcass with an unwashed hand
that previously had been in contact with the outer surface of the hide.
Studies have shown that workers handling hide-on beef carcasses are
more likely to have a higher incidence and prevalence of salmonellae on
their hands than are personnel performing other on-line tasks (Smeltzer
et al., 1980b). Similarly, knives and other equipment used for hide
removal are more likely to be contaminated with Salmonella than are
implements used for other operations (Peel and Simmons, 1978; Smeltzer
et al., 1980a). Grau (1979) found that Salmonella contamination was
especially likely to occur when a knife was used to free the rectum and
anal sphincter during hide removal. Studies have shown that knife
decontamination in hot water is often an inadequate means of
inactivating Salmonella and other bacteria on the knife surface,
usually because of insufficient exposure time (Peel and Simmons, 1978).
Greater than 10 seconds exposure was necessary for microbial
inactivation when a contaminated knife was dipped in 82 deg.C water.
Cross-contamination is reduced when knives and other implements are
frequently decontaminated, and hands, arms, and aprons are washed and
sanitized regularly (Norval, 1961; Childers et al., 1973; Peel and
Simmons, 1978; Roberts, 1980; Smeltzer et al., 1980a and b; de Wit and
Kampelmacher, 1982; Grau, 1987).
After the removal of hide, hooves, and head, most subsequent
microbial contamination is attributable to the hygienic practices of
the workers or technical errors, such as puncturing the animal's
gastrointestinal tract (Roberts, 1980). Knives and other equipment used
for evisceration are generally less contaminated than tools used for
hide and leg removal (Smeltzer et al., 1980a). The incidence of
Salmonella on beef carcasses, knives, and aprons increases at the stage
of evisceration, but to a lesser degree than during hide and leg
removal (Stolle, 1981; Smeltzer et al., 1980a). Thorough training and
careful evisceration practices (especially closing off the ends of the
gastrointestinal tract and removing the intestines from the body
cavity) are necessary to prevent carcass contamination with ingesta or
feces (Grau, 1987; ICMSF, 1988; Mackey and Roberts, 1991).
Microbiological contamination acquired during the slaughter and
dressing process of livestock is not spread evenly over the carcass,
and may be expected to vary between sides of the same carcass, between
different carcasses processed on the same day at an abattoir, between
carcasses produced on different days at an abattoir, and between
carcasses produced at different establishments (Empey and Scott, 1939;
Kotula et al., 1975; Ingram and Roberts, 1976; Roberts 1980; Johanson
et al., 1983). This variability can be due to a number of factors, such
as differences in dressing methods, worker skill, application of
washing or other carcass treatments, season of the year, and weather.
III. Attachment of Bacteria
The rate of attachment, growth, and multiplication of bacteria on
carcasses is dependent on the structure, composition, and water
activity of the exposed tissues, the acidity of the surface, the
temperature of air and the carcass, the bacterial strain, and various
bacterial attachment mechanisms (Lillard, 1985). The skinned ``hot''
beef carcass provides an ideal environment for bacterial survival and
multiplication. Surfaces of chilled carcasses, especially those that
have experienced significant dehydration, may be less attractive sites
for bacterial attachment.
The process by which bacteria attach to meat surfaces is believed
to consist of two stages. The first stage is where bacteria are either
attached by weak physical forces or freely floating in the water film
that covers the meat surface. The second stage is characterized by a
stronger attachment mechanism involving, in part, the formation of
polysaccharides over time (Firstenberg-Eden, 1981). This consolidation
stage is followed by colonization or growth of the microbes on the meat
tissue. Once attachment and colonization have occurred, it is very
difficult to completely remove pathogenic microorganisms from meat or
poultry surfaces by normal processing methods (Benedict et al., 1991).
There is considerable variability among bacteria in their ability
to attach to different surfaces. This is likely to be a reflection of
the different mechanisms (including pili, flagella, extracellular
polymers) used by different bacteria. It has been suggested that
bacteria from feces attach more strongly and in higher numbers than the
same bacteria grown in laboratory media or meat surfaces (Notermans et
al., 1980). Enhanced binding by bacteria present in feces may have to
be considered when evaluating the efficacy of carcass decontamination
treatments.
It appears that specific bacterial binding sites (receptors) exist
on animal cells. Collagen, in particular, seems to be a target for
bacterial attachment (Mattila and Frost, 1988; Benedict et al., 1991).
Notermans and Kampelmacher (1983) concluded that attachment cannot be
completely prevented by manipulating water sprays or baths through the
addition of chemicals or manipulating pH. Therefore, the only way to
absolutely prevent attachment is to prevent contact between bacteria
and meat. While bacteria are still freely floating in the water film,
they can be displaced using clean water (Notermans and Kampelmacher,
1983). Measures designed to block attachment should be applied as soon
as possible following contamination. Two points on the slaughter line
that appear to be likely sites for the application of carcass sprays
are following hide removal and following evisceration.
IV. Methods To Decrease Carcass Contamination
In addition to trimming as a means of removing bacteria associated
with visible contamination, bacteria are removed from carcasses by
several recommended methods, such as rinsing or washing with water
(both hot and ambient temperatures), either with or without one of
several approved food-grade organic acids (lactic, acetic, or citric)
or chemical sanitizers, such as chlorine. Each of these factors is
reviewed in the following sections for its relevance to beef carcass
decontamination.
A. Water Rinsing
Rinsing a carcass can remove physical contamination (dirt, hair,
fecal matter, etc.) to a varying degree, carrying with it some of the
resident microorganisms. As indicated above, interventions of this type
or others that physically remove bacteria should be used as early as
possible after likely introduction of contamination (e.g., after hide
removal) to prevent or retard bacterial attachment and growth. Various
factors associated with rinsing carcasses can be manipulated,
increasing the effectiveness of this approach. Major factors include
water temperature, water pressure, line speed, and method of
application (Anderson et al., 1979; Crouse et al., 1988). While
numerous studies have examined the efficacy of washing techniques, most
investigations have been conducted under research conditions, and only
a few have directly evaluated effectiveness in production settings.
The use and timing of hot water (95 deg. C) application during
processing were investigated by Barkate et al. (1993) to determine
effectiveness in reducing the numbers of naturally
[[Page 49556]]
occurring bacteria on beef carcass surfaces. They found a 1.3
log10 CFU/cm2 reduction in aerobic plate counts (APCs) for
samples sprayed with hot water before the final carcass rinse as
compared to a 0.8 log10 CFU/cm2 reduction in samples sprayed
with hot water after the final rinse. The fact that fewer bacteria were
removed from the samples sprayed with hot water after the final rinse
may have been due to the length of time (approximately 15 to 20
minutes) that elapsed before hot water was applied. In this connection,
the authors interpreted Butler et al. (1979) as indicating that the
time lapse may have allowed more bacteria to become attached and more
resistant to the lethal effects of hot water.
Anderson et al. (1979) reported that under laboratory conditions,
bacterial counts were reduced 1.0 and 2.0 log10 CFU/cm2 when
beef plates were treated with cold (15.6 deg. C) and hot (76-80 deg. C)
water, respectively. During subsequent storage at 3.3 deg. C, the time
to reach microbial spoilage (108 CFU/cm2) was 6 days with cold
water and 12 days with hot water. The untreated controls took 7 days to
reach spoilage levels.
Smith and collaborators (Smith and Graham, 1978; Smith, 1992; and
Smith and Davey, 1990, and Smith et al., 1995) have investigated the
effectiveness of hot water (140 deg. F) washes versus a more commonly
used wash temperature (100 deg. F). Hot water was effective against
pathogens such as E. coli 0157:H7, Salmonella, Yersinia enterocolitica,
and L. monocytogenes. Quantitative studies assessing the effect of hot
water treatment on the survival of E. coli 0157:H7 indicated that
levels on artificially inoculated carcasses are reduced by 84-99.9%
(Smith, 1992; Smith and Davey, 1990; Smith et al., 1995) Other studies
have reported reductions in E. coli biotype 1 as great as 99-99.9%
(Davey and Smith, 1989).
Hot water sprays are most effective when the water film on the
carcass surface is raised to 82 deg. C (180 deg. F) for at least 10
seconds. If beef tissue is exposed to this temperature for more than 10
seconds, the surface of the fat and lean tissues can become gray to a
depth of about 0.5mm. These carcasses, however, regain their normal
color after chilling (Smith and Graham, 1978; Barkate et al., 1993;
Patterson, 1969). Carcass bloom, however, is permanently and adversely
affected if exposed for 20 seconds to temperatures above 81.4 deg. C-
82 deg. C (Davey, 1989, 1990; Barkate et al., 1993). Lower temperatures
applied for longer periods of time also have been found (Davey and
Smith, 1989) to permanently affect bloom.
Similar results have been reported by investigators worldwide.
Patterson (1970) sprayed beef carcasses with steam and hot water at
176-204.8 deg. F (80-96 deg. C) for two minutes, applying in the case
of water 18.9 liters to each carcass at a distance of one foot (25cm),
to determine the effectiveness of hot water in reducing carcass
contamination. Although some discoloration of the carcass occurred
initially, cooling for 24 hours restored normal color. Approximately a
log reduction in total plate count was observed; however, there was no
significant reduction in fecal streptococci. A differential in
bacterial counts between treated and untreated carcasses was still
evident after 48 hours of refrigerated storage. Smith and Graham (1974)
used beef and mutton samples inoculated with E. coli to compare the
effectiveness of hot water treatment, steam chamber, steam injection,
or washing with water at 37 deg. C (91 deg. F) on microbial levels and
carcass color changes. Water temperatures below 60 deg. C (140 deg. F)
produced no significant color change. As temperatures rose above
85 deg. C (176 deg. F), there was permanent and marked color change.
Very high temperatures of 95 deg. C (194 deg. F) for three minutes
changed the surface coloration to a depth of no more than 0.5mm below
the surface. Temperatures equal to or greater than 70 deg. C (158 deg.
F) produced a 2 log10 (99%) reduction of E. coli.
Water can be applied to a carcass, by either hand or machine, using
washing, spraying, or dipping. Hand and machine washing were compared
by Anderson et al. (1981). Hand-washed carcasses had reductions of 0.99
log10 CFU/cm2, while an experimental beef carcass washing
unit yielded a 1.07 log10 CFU/cm2 reduction, a non-
significant difference.
The angle of water impact has been shown to be an important factor
in bacterial removal. When water pressure is normal, a 30 deg. angle is
more effective at removing bacteria than a 90 deg. angle (Anderson
1975). When line pressure is increased, the angle degree is less
important.
Since bacterial attachment affects the ease of removing bacteria,
the point during slaughter and dressing at which water is applied has
been deemed significant in retarding or inhibiting attachment.
Notermans et al (1980) concluded that control of Enterobacteriaceae and
salmonellae was more effective when carcasses were spray-cleaned with
water at multiple stages during evisceration than when washing occurred
only after evisceration.
Water pressure can influence the effectiveness of carcass washing
treatments. De Zuniga et al (1991) investigated the effect of increased
water pressure on the penetration of bacteria into tissue using Blue
Lake dye. As the pressure of the water increased, the dye penetrated to
a correspondingly greater depth in the tissue. They recommended an
optimal water pressure for washing beef carcasses between 100 psi to
300 psi. They cautioned that higher pressures may drive the organisms
deeper into the tissues, while pressures less that 100 psi were less
effective at reducing bacterial counts. Kotula (1974) found that water
containing 200 ppm chlorine, sprayed at a pressure of 355 psi and at
temperatures ranging from 55-125 deg. F, effectively removed bacteria
from market beef forequarters. Kotula et al. (1974) concluded that
water pressure was a more important variable than pH or water
temperature for removing bacteria by spray washing. These beef samples,
however, were not freshly slaughtered, and may have required more
intense pressures. Jerico et al. (1995), concluded that washing beef
carcasses with water at 200-400 psi at 38 deg.C (100.4 deg.F) did not
significantly change the level of bacteria on the carcass. They noted
that other investigators (Anderson, 1981; Kotula et al., 1974; Crouse
et al., 1988) did not statistically validate the sample size to adjust
for variation in counts and sample size, and did not collect samples
immediately after washing.
Increasing water pressures has been found to have certain
operational disadvantages. For example, greater pumping pressure is
required, thus requiring more energy and special equipment, less heat
energy can be recovered from the outlet water steam, and the nozzle is
more likely to become blocked if water is recirculated (Graham et al.,
1978).
B. Beef Carcass Trimming vs. Washing Treatment Studies
Only three studies directly compare hand trimming vs. washing as
methods to remove fecal and bacterial contamination from beef
carcasses. Hardin et al. (1995) conducted an FSIS-supported research
project designed to compare traditional hand trimming procedures to
washing of beef carcasses for removal of feces and associated bacteria.
Paired cuts from four carcass regions (inside round, outside round,
brisket, and clod) were removed from hot, split carcasses, then
contaminated with a fecal suspension containing either E. coli 0157:H7
or S. typhimurium (10 \6\ CFU/ml). Inoculated meat cuts
[[Page 49557]]
(400 cm\2\ area) were treated by one of four treatments either
immediately or 20-30 min post-contamination. One paired contaminated
surface region from each carcass side was trimmed of all visible fecal
contamination. The remaining paired carcass surface region was then
washed either with water (35 deg.C/95 deg.F), water wash with 2% lactic
acid (55 deg.C/131 deg.F), or water wash with 2% acetic acid (55 deg.C/
131 deg.F). Samples for microbiological analyses were collected pre-
and post-treatment from within and outside the defined area
contaminated with the fecal suspension.
All treatments significantly reduced levels of pathogens; however,
decontamination was affected by carcass surface region. The inside
round region was the most difficult carcass surface to decontaminate,
regardless of treatment. Washing followed by organic acid treatment
performed better than trimming or washing alone on all carcass region
surfaces except the inside round, where organic acid treatments and
trimming performed equally well. Overall, 2% V/V lactic acid reduced
levels of E. coli 0157:H7 significantly better than 2% V/V acetic acid;
however, differences between the abilities of the acids to reduce
Salmonella were less pronounced. All treatments caused minimal spread
of pathogens outside the initial area of fecal contamination. Recovery
after spreading was reduced by the use of organic acid treatments.
This study is limited in relation to evaluating commercial
conditions due to the experimental design, which deliberately added
inoculated feces to the carcass. A rather large area (400 cm\2\) was
inoculated and deliberate placement on the meat surface allowed the
trimmer to know exactly where fecal contamination occurred. Under
commercial situations, fecal contamination must first be visually
located and the borders of contamination subjectively evaluated. This
subjectiveness may allow the trimmer to inadvertently touch the knife
to areas of fecal contamination that are not obviously visible, thereby
cross-contaminating the freshly trimmed areas as the knife blade is
drawn across. Knife trimming was highly controlled in these
experiments, whereas knife trimming under commercial conditions might
be expected to yield more variable results. Secondly, although this
study was performed in an abattoir, the treatments were performed in an
adjacent laboratory setting rather than on a slaughter line where
deliberate inoculation of carcasses with pathogens is not allowed by
FSIS.
The second direct comparison of trimming vs. washing involved work
performed by scientists from four universities. This study was
conducted in four phases, and is commonly referred to as the National
Livestock and Meat Board study, for the organization that funded the
project.
Phase I trials sought to define the proper parameters for the
washing experiments (Gorman et al., 1995, submitted for publication;
Smith et al., 1995, submitted for publication; Smith, 1995). Results of
Phase I suggested that higher pressures of 20.68 bar (300 psi) and
27.58 bar (400 psi) during spray-washing were more effective (P<0.05)
than lower pressures of 2.76 bar (40 psi) or 13.79 bar (200 psi) bar
for removal of fecal material and for reducing bacterial numbers. Phase
II compared the efficacy of hand-trimming and six potential carcass
decontamination treatments: hot water (74 deg.C), ozone, trisodium
phosphate, acetic acid, hydrogen peroxide, and a commercial sanitizer
(Smith, 1995; Gorman et al., submitted for publication).
Data from Phase II revealed that application of hot water (74 deg.C
at the meat surface) for spray-washing reduced total plate counts and
E. coli (ATCC 11370) counts exceeding 3.0 log10 CFU/cm2. The
best combination and sequence of interventions for reducing bacteria
counts on beef brisket samples were: (a) Use 74 deg.C water in the
first wash with water pressure at 20.68 bar, and (b) if colder
(<35 deg.C) water is used in the first wash, spray-wash with hydrogen
peroxide or ozone in the second wash. Trimming alone or trimming
followed by a single spray-washing treatment of plain water (16-
74 deg.C; 20.68 bar; 12 or 36 sec) significantly (P<0.05) reduced the
microbiological counts compared to the untreated, inoculated control.
Trimming alone decreased total aerobic plate counts by 2.5 CFU/cm2
and trimming with plain water (<35 deg.C) wash decreased total aerobic
plate counts by 1.44-2.3 CFU/cm2. These data indicated that
trimming reduces microbiological contamination after carcasses are
contaminated with fecal material but a significant amount of
contamination remained on samples after trimming or trimming with spray
washing. It was concluded that washing at 300 psi was as effective as
trimming and washing combinations for reducing bacterial counts on the
tissues. When water was 74 deg.C, reductions were greater than 3.0 log
CFU/cm2, irrespective of the presence or absence of chemical
sanitizer.
Spray-washing with hot water resulted in less variability in
bacterial counts obtained after treatment compared to hand-trimming
and/or spray-washing with water of lower temperatures. The authors
concluded that this greater variability in bacterial counts for hand-
trimming treatments indicated the potential for cross-contamination
during the process.
Phase IIIA consisted of field studies in six commercial plants and
concluded that: (a) Compared to inoculated controls (no trim; no wash),
every combination of washing--with or without trimming and with and
without chemical agents--lowered (P<0.05) total plate counts and E.
coli counts; (b) compared to the treatment combining trimming plus
washing, washing (without trimming) with 74 deg.C water achieved
(P<0.05) equal reductions in total plate counts and E. coli counts;
and, (c) washing (without trimming) with 74 deg.C water--based upon
comparative standard deviations--achieved more consistent lowering of
total plate counts and of E. coli counts than did trimming plus washing
(Smith, 1995).
Phase IIIB further investigated the effects of hot water washing
under commercial slaughter conditions, as the hot water washing trials
in Phase III were conducted in only two of the six plants, the number
of samples was small, and the parameters of hot water application
(temperature, pressure, etc.,) were not consistent (Smith, 1995). The
results of Phase IIIB were consistent with Phase IIIA in demonstrating
that trimming and washing are effective in reducing the microbial loads
on carcasses. Of the several treatments tested, however, the most
effective in reducing microbial numbers was combined trimming, washing,
and rinsing with hot water for 8 seconds. Other treatments tested
included: control (no trimming, no washing), trimming/washing (current
``zero tolerance'' procedure), no trimming/hot water rinse for 2.5
seconds, and no trimming/hot water rinse for 8 seconds.
The use of hot water alone (no trimming) in this study effectively
reduced the microbial contamination on carcasses, but the average
reduction in counts was slightly less than that achieved by trimming
and washing or trimming and washing combined with hot water rinsing.
These findings suggest that the application of hot water at 20 pounds
per square inch (psi) for 2.5 or 8 seconds is not as effective as the
hot water washing system used in Phase IIIA of the studies, i.e., the
application of a fine spray at psi's ranging from 150 to 260 and
temperatures of 60 deg.C to 75 deg.C (140 deg.F to 175 deg.F).
[[Page 49558]]
The third study that evaluated the effectiveness of carcass
trimming and/or washing on the microbiological quality of beef
carcasses in a commercial slaughter plant was conducted by Prasai et
al. (1995). The inside rounds of 48 beef carcass sides were evaluated
using four treatments: (1) Untreated (no trim, no wash), (2) trim
alone, (3) trim plus wash, or (4) wash alone. Samples for aerobic plate
counts, E. coli, and coliform counts were collected post treatment.
Significant differences (P< 0.05) were observed in aerobic plate counts
(APC) when treatments were compared to controls. E. coli and coliform
counts were too low to show statistical significance between
treatments; however, the mean E. coli and coliform counts were higher
in control samples (P< 0.05) than in other treatments. The greatest
reduction in APC counts were observed in trimmed samples (3.0 log CFU
reduction vs. control), followed by trim and wash (0.9 log CFU
reduction vs. control), and wash alone (0.3 log CFU reduction vs
control) samples. Samples receiving trim and wash treatments had APC
counts approximately 2 logs higher than trimmed samples, suggesting
that washing spreads bacterial contamination. All washed samples,
however, had mean reductions of 0.3-0.9 log CFU vs. control samples.
The investigators concluded that trimming can be effective in reducing
bacterial contamination during slaughter and that additional bacterial
reductions can be obtained if trimming instruments are sanitized
between trim sites. The authors further concluded, however, that the
type of trimming used in the study--i.e., use of sterile instruments
and trimming of entire sample surface--is unlikely on a typical
slaughter line, and that, under commercial conditions, a combination of
trimming and washing could be practical and effective.
C. Organic Acid Sprays
Organic acids, such as lactic, acetic, and citric, reduce
pathogenic and spoilage microbial organism populations by altering the
environmental pH and by direct bactericidal action (Osthold, 1984). The
immediate effect of organic acids on bacteria is to reduce numbers
approximately one log10 when the initial aerobic plate count (APC)
is less than or equal to 104 CFU/cm2. A few investigators have
reported a two or three log reduction (Snijders, 1979; Smulders and
Woolthius, 1983; Netten, 1984). Overall, the available scientific data
indicate that treating carcasses with an organic acid rinse, spray, or
dip can achieve a 90-99.9% (1-3 log10) reduction in the level of
spoilage organisms such as Pseudomonas fluorescens (Dickson and
Anderson, 1992; Prasai et al., 1991; Frederick et al., 1994).
Decontaminating carcasses with lactic or acetic acid can extend the
shelf life of treated product (Smulders and Woolthuis, 1985; Woolthius
and Smulders, 1985). In addition, organic acid sprays and dips have
been shown to decrease the levels of specific pathogens, such as
Salmonella spp., Staphylococcus aureus, C. jejuni, Yersinia
enterocolitica, and L. monocytogenes (Osthold et al., 1984; Bell, et
al., 1986; Smulders, et al., 1986; Anderson, et al., 1987; Siragusa and
Dickson, 1992; and Cutter and Siragusa, 1994). Reductions in the number
of pathogenic bacteria on carcasses reduce the risk of food-borne
disease.
Each organic acid differs in its ability to reduce the bacterial
population on tissue surfaces. The concentration of the organic acid
affects not only bacterial survival, but also the color and odor of the
meat, especially if the concentration is 2% or greater. Bleaching and
discoloration of tissue have been reported, and may occur at 1%
concentrations for lactic and acetic acid (Smulders and Woolthuis,
1985, and Hamby et al., 1987). Balancing antimicrobial activity with
organoleptic impact, the practical concentration for use of lactic or
acetic acids appears to be 0.5 to 2.5%.
Prasai et al. (1991) examined the effect of lactic acid (1.5%,
55 deg.C) applied to beef carcasses at various locations in processing
and found that the greatest reduction in APCs occurred on carcasses
treated immediately after hide removal and again after evisceration.
These reductions, however, were not significantly better than spraying
only after evisceration. After 72 hours of storage (1 deg.C), the
number of bacteria per cm2 on treated carcasses was lower than on
comparable control carcasses. Decontamination with acids is more
effective when employed as soon after slaughter as feasible (Acuff et
al., 1987) and at elevated temperatures (53-55 deg.C).
Treating beef carcasses with acids does not completely inactivate
all pathogens, particularly E. coli 0157:H7, which is relatively acid
tolerant. Cutter and Siragusa (1992) reported that there are
differences among E. coli 0157:H7 isolates in relation to their acid
tolerances. Salmonella spp., L. monocytogenes, and Pseudomonas
fluorescens are more sensitive to acids than E. coli 0157:H7 (Dickson,
1991; Greer and Dilts, 1992; Cutter and Siragusa, 1994; Bell et al.,
1986); while E. coli biotype 1, particularly E. coli 01257:H7, appears
to be among the more resistant enteric bacteria to the effects of
organic acids (Woolthuis et al., 1984; Woolthuis and Smulders, 1985;
Van Der Marel et al., 1988; Bell et al., 1986; Anderson and Marshall,
1990, 1989; Acuff et al., 1994).
The extent of reduction of E. coli 0157:H7 achieved has varied
among studies. For example, Dickson (1991) found that the reduction of
E. coli 0157:H7 was similar to that observed for Salmonella and L.
monocytogenes, with up to a 99.9% reduction in the levels of all three
bacteria from inoculated tissues. A number of other studies have
reported reductions in E. coli and in Enterobacteriaceae (which belongs
to the same family as E. coli) of 46 to 99.9% on tissues treated with
1.2% to 2% acid (Bell et al., 1986; Anderson and Marshall, 1990, 1989;
Cutter and Siragusa, 1994; Greer and Dilts, 1992; Acuff et al., 1994).
Anderson and Marshall (1990) found that although lactic acid exerted a
significant antimicrobial effect on some Enterobacteriaceae, it did not
appreciably affect E. coli or S. typhimurium on beef issue samples.
Conversely, Brackett et al. (1993) reported that up to 1.5% acid
treatments did not appreciably reduce E. coli 0157:H7, whether at 20C
or 55C, and was ``of little value in disinfecting beef of EC 0157.''
Dickson (1991) concluded that an acetic acid carcass sanitizer could be
used as an effective method to control bacterial pathogens. Cutter and
Siragusa (1992) reported that the reduction of E. coli 0157:H7 on meat
by acid treatment is dependent on acid concentration (5% giving the
greatest reduction) and tissue type (greater reduction on fat tissue
than lean). They found lactic acid to be more effective than acetic or
citric acid against E. coli. This has been reported by Hardin et al.,
1995, as well. Cutter and Siragusa (1992) suggested that the two
primary determinants of effectiveness are the pH achieved at the
surface of the carcass and the corresponding period of exposure.
A number of other studies have reported reductions in E. coli or
Enterobacteriaceae ranging from 46 to 99.9% on tissues treated with
1.2% to 2% acid (Bell et al. 1986; Anderson and Marshall, 1990, 1989;
Cutter and Siragusa, 1994; Greer and Dilts, 1992; Hardin et al., 1995).
Anderson and Marshall (1990) found that concentration and temperature
of lactic acid solutions had significant but independent effects on
reduction in numbers of inoculated microorganisms (aerobes,
Enterobacteriaceae, and E. coli) on the surface of lean beef muscle. E.
coli cells, however, were
[[Page 49559]]
comparatively resistant to the effects of temperature and concentration
of lactic acid. Further, Brackett et al. (1993) reported that up to
1.5% acid treatments did not appreciably reduce E. coli 0157:H7,
whether at 20 deg. or 55 deg.C and ``was of little value in
disinfecting beef of EC O157.'' Brackett (1994) also concluded that E.
coli (Biotype I) and E. coli 0157:H7 are quite resistant to the effects
of organic acids, particularly lactic acid. Hardin et al. (1995)
observed that E. coli 0157:H7 was more resistant than S. typhimurium to
the effects of both 2% lactic and 2% acetic acid applied to beef
carcass surface regions. Reductions in levels of E. coli 0157:H7 were
0.6-1.5 log10 CFU/cm2 greater with lactic acid than acetic
acid, depending on the carcass surface tested. Both lactic and acetic
acid, however, were equally effective in reducing levels of S.
typhimurium.
Both acid concentration and temperature have been studied for their
effects on reducing bacterial numbers on beef tissue. Anderson and
Marshall (1989) observed that both concentration and temperature
produced significant, but independent, reductions in numbers of E. coli
and S. typhimurium on beef semitendinosus muscle dipped in an acetic
acid solution. Acid concentration (1, 2, 3%) was found to be
insignificant at the higher temperature (70 deg.C), but caused
significant reduction in numbers of microorganisms at lower
temperatures (22, 40, and 55 deg.C). Anderson and Marshall (1989)
reported that the most effective treatment was dipping pieces of lean
meat in 3% acetic acid at 70 deg.C. They suggested that some direct
effects from heat may have contributed to the increased reduction of
bacterial numbers in samples treated at this higher temperature. The
numbers of surviving organisms were reduced as the temperature of the
acid was increased from 25 to 70 deg.C, with acid concentration being
less significant at higher temperatures. These researchers later
reported similar results for treatments using 3% lactic acid at
70 deg.C (Anderson and Marshall, 1990). Anderson et al. (1987) observed
a greater reduction in levels of indigenous E. coli, Enterobacteriaceae
and APC with hot (52 deg.C) acetic acid when compared to cool
(14.4 deg.C) acetic acid.
In a more recent study, Anderson et al. (1992) reported an
increased removal of bacteria as either the concentration or
temperature of the acid solution was increased, with the acids
performing differently at different temperatures. Lactic acid was
reported to be significantly more effective than acetic acid for all
bacterial types (aerobes, Enterobacteriaceae, S. typhimurium, E. coli)
at both 20 and 45 deg.C, and more effective on S. typhimurium at
70 deg.C. Cutter and Siragusa (1994) reported that of three
concentrations evaluated (1, 3, and 5%), 5% acid (acetic, lactic, or
citric) resulted in the greatest reduction in numbers of both E. coli
0157:H7 and P. fluorescens from beef carcass tissue.
Evaluation of the overall effectiveness of organic acids is
confounded by the fact that the various studies have employed different
acid types, applied at different concentrations and temperatures to
varying types of meat tissue surfaces. Each of these factors has an
effect on the removal of bacteria from carcasses. Several studies have
evaluated the effect of tissue type (fat and lean) on the effectiveness
of organic acids to reduce the number of bacterial cells from beef
tissue surfaces. Cutter and Siragusa (1994) reported that the magnitude
of bacterial reductions from beef surfaces treated with organic acids
was consistently greater when spray treatments were applied to bacteria
attached to adipose tissue. Log reductions for E. coli 0157:H7 and P.
fluorescens were 1 and 2 log10 greater on adipose vs. lean beef
carcass tissue. These findings agree with Dickson and Anderson (1991),
who reported significant reductions in S. california from use of
distilled water and 2% acetic acid with beef fat tissue, whereas no
significant differences were observed between treated and untreated
lean tissues. Dickson (1991, 1992) reported similar findings for S.
typhimurium, L. monocytogenes, and E. coli 0157:H7 attached to fat
surfaces of beef trim. Acid treatment resulted in an immediate
sublethal injury of approximately 65% of S. typhimurium (Dickson, 1992)
remaining on lean and fat tissue. A residual effect from the acid was
observed with the fat tissue, resulting in an additional 1 log \10\
decrease over four hours. The author suggested that the differences
observed in the effects of acid for lean and fat tissue were due to the
increased water content of lean tissue and the presence of water-
soluble components that may neutralize the acid and its effect on the
bacterial cell. In a comparison of methods for the removal of S.
typhimurium and E. coli 0157:H7 from various beef carcass surfaces,
Hardin et al. (1995) found a significant difference in the type of
surface evaluated. The researchers observed that the inside round was
the most difficult carcass surface to decontaminate and attributed this
to a substantial amount of exposed lean on the meat surface, as well as
a pronounced collar of fat at the edge of the lean.
Organic acids have been reported to be more effective in reducing
bacterial levels when applied during, or shortly after, slaughter and
dressing. Acuff et al. (1987) and Dixon et al. (1987) reported no
significant difference in reduction of aerobic populations from beef
steaks and subprimals treated post-fabrication with various organic
acids and their controls. They suggested that the application of acid
decontamination would be most effective as soon as possible after
slaughter, before bacteria have had a chance to attach firmly to meat
surfaces. This was supported by Brackett et al. (1994), who recently
reported that hot acid sprays were ineffective in reducing levels of E.
coli 0157:H7 inoculated onto the surface of sirloin tips purchased from
local butchers. Snijders et al. (1985) reported an increase in the
bactericidal effect of lactic acid sprayed on hot carcasses (45 minutes
postmortem) when compared to spraying on chilled carcasses. They
suggested that on hot carcass surfaces, increased reductions may be due
to higher levels of bacteria present in the water film and not yet
attached to the carcass surface. Van Netten et al. (1994) described an
in vitro model to evaluate the inactivation kinetics of bacteria from
meat surfaces treated with lactic acid. A rapid reduction in bacterial
numbers due to the replacement of the fluid (water film) on a warm meat
surface by a film containing lactic acid was referred to as ``immediate
lethality.'' They proposed that organisms on chilled meat are less
accessible to lactic acid and are better protected by meat buffering
effects than those in the fluid film of hot meat surfaces.
D. Chlorine and Chlorine Compounds
Chlorine, chlorine dioxide, sodium hypochlorite, and hypochlorous
acid all have been sprayed onto beef carcasses in an effort to reduce
microbial populations.
Chlorine and chlorine dioxide were compared for chickens by Lillard
(1979) to determine their relative bactericidal effect. Chlorine
dioxide was found to be more potent than chlorine and required only
one-seventh as much to produce the same bactericidal effect. Further,
chlorine dioxide maintained its effectiveness when both pH and the
level of organic matter increased. Chlorine is less effective when the
pH or organic load is increased. Kotula et al. (1974) treated beef
forequarters with chlorinated water (200 ppm) and found initial
reductions (45 min post-treatment) in APCs for duplicate testing days
of 1.5 and 2.3 log10 CFU/cm2, respectively. Temperature (12.8
vs 51.7 deg.C) and pH (4 to 7) were found to
[[Page 49560]]
significantly affect efficacy, with the greatest reductions observed at
a temperature of 51.7 deg. and pH values of 6 and 7.
Anderson et al., (1979) compared the effectiveness of several
treatments to reduce APCs on previously frozen beef plate stripes. Meat
was washed and sanitized with cold water (15.6 deg.C [60 deg.F]), hot
water (76-80 deg.C [168-176 deg.F]) (14kg/cm2), sodium
hypochlorite (200-250g/ml), or acetic acid (3%)--all at 14kg/
cm2; and at 17 kg/cm2 steam at 95 deg.C (194 deg.F). They
found that the sodium hypochlorite and cold water treatments reduced
counts by about one log. Steam reduced the count by only 0.06 log. Hot
water reduced counts by 2.0 log and acetic acid reduced counts by 1.5
log. Over time, samples treated with hypochlorite had rates of
bacterial re-growth that exceeded those of the untreated controls.
Steam and cold water treated samples exceeded APCs on controls after
five days, presumably due to greater surface moisture from the
treatment. Growth rates associated with the hot water samples were
similar to the untreated controls, but, because of the initial 2.0 log
reduction in microbial levels, it took nearly five additional days
before counts reached 108/cm2. Acetic acid, applied to
samples after a cold water wash, provided a 14-16 day delay before
counts returned to initial levels, and it took a full 23-24 days before
the bacteria reached 108/cm2.
V. Other Technologies
Several other approaches or technologies have been suggested as
additional alternative means for decontaminating beef carcasses, such
as rinsing with trisodium phosphate (TSP), steam pasteurization of
carcasses, steam vacuuming, and chemical dehairing. These approaches
have not been as extensively investigated and reported in the
scientific literature to date, relative to their use with beef
carcasses. A brief discussion of each method follows.
A. Trisodium Phosphate
Trisodium phosphate (TSP) has been shown to reduce Salmonella on
processed poultry carcasses. In a 1991 patent, Bender and Brotsky
presented the claim that trisodium phosphate (Na3PO4) could
successfully reduce Salmonella on processed poultry carcasses. Since
then, industry, university, and USDA Agricultural Research Service
researchers have conducted studies that demonstrate reductions in
Salmonella levels on poultry carcasses ranging from 90 to greater than
99.9% (1.2 to 8.3 log10). Dickson et al. (1994) studied the effect
of TSP on beef tissue dipped in TSP after inoculation with both Gram
positive (L. monocytogenes) and Gram negative (S. typhimurium and E.
coli 0157:H7) pathogens. They reported reductions of 1 to 1.5
log10 for the Gram-negative pathogens, and a maximum reduction of
less than one log10 for L. monocytogenes on lean tissue. Reduction
of L. monocytogenes was greater on fat tissue: 1.2 to 1.5 log10. A
reduction of 2 to 2.5 log10 for S. typhimurium and E. coli 0157:H7
on fat tissue was reported.
In-plant testing of TSP on beef carcasses (Rhone-Poulenc) showed a
greater than 1.5 log10 reduction of E. coli (biotype I). Further,
they found that incidence rates for E. coli fell from 51.3% on
untreated carcasses to 1.3% on TSP-treated carcasses. The level of
Enterobacteriaceae was reduced by one log10, and the incidence
rates fell from 75% on untreated carcasses to 8.8% on treated
carcasses. Salmonella was not detected on any carcasses.
B. Steam Pasteurization
A patent-pending process developed by Frigoscandia for steam
pasteurization of meat and poultry has been tested at Kansas State
University and has received approval by FSIS for in-plant evaluation;
the process is applied at the end of beef dressing operations on
inspected and passed carcasses. A request by Frigoscandia to evaluate
and test the process as an antimicrobial reduction intervention is
being considered by FSIS.
Tests of a prototype unit at Kansas State University showed that
the process consistently reduces pathogenic bacteria, including E. coli
0157:H7, by 99.9% (Frigoscandia, 1995). The process uses pressurized
steam applied uniformly to the entire carcass surface, producing
surface meat temperatures of 77-93 deg.C (170-200 deg.F) and a uniform
bacterial reduction on the entire carcass. Since the steam reaches all
exposed surfaces, the reduction is more uniform and operator-
independent. The process is reported to not affect the color of the
carcass, and to use less energy than is required for a comparable hot
water system. Furthermore, the use of a 2% lactic acid cooling spray
immediately after steam application appeared to act synergistically to
inactivate surface bacteria. It should be noted that the intended use
of the steam pasteurization is not the direct physical removal of
visible contamination, but the technology has the potential to be
integrated into pathogen control systems to enhance their
effectiveness.
C. Steam Vacuuming
Alternative methods for removing beef carcass contamination such as
air jets and vacuum systems (without steam) have been shown to be
effective in removing visible as well as microbiological contamination
(Monfort, 1994). Steam vacuuming is a refinement of this approach,
combining physical removal with microbial inactivation. Steam vacuuming
is a process in which steam and hot water are applied through nozzles
to the carcass surface after the hide is removed. This appears to be
particularly useful for opening cuts, which are made in the hide to
facilitate hide removal. These carcass surfaces tend to be contaminated
more frequently than other areas of the carcass. Steam vacuuming treats
these surface areas with hot water (above 160 deg.F) and steam while
vacuuming the removed contamination and any excess water from the
surface. The process of steaming the opening patterns encountered some
difficulty in early trials when the steam nozzle was held 6 to 12
inches from the surface. There was a rapid drop in temperature, and as
a result no significant differences in bacterial levels were noted from
treated areas. These problems were corrected by adjusting the equipment
and placing the head of the vacuum directly on the surface. Testing at
Kansas State University has shown the effectiveness (>99.9% reduction)
of steam vacuuming in decontaminating prerigor meat surfaces that have
been inoculated (approximately 105 CFU/cm2) with the
pathogens L. monocytogenes, E. coli 0157:H7, and S. typhimurium.
Scientists at the U.S. Meat Research Center of USDA's Agricultural
Research Service at Clay Center, Nebraska have reported a 3.0 to 3.5
log (>99.9%) reduction in bacteria on steam vacuum-treated meat.
Preliminary results from an ongoing industry study (ten plants reported
to date) comparing steam vacuuming and knife trimming to remove carcass
contamination indicate that carcasses that have been steam vacuumed
have approximately 90% (0.94 log) less bacteria than trimmed carcasses
in the areas tested. Several inplant trials comparing steam vacuuming
versus traditional trimming are currently underway.
D. Chemical Dehairing
The effects of post-exsanguination (post-bleeding) dehairing on the
microbial load and visual cleanliness of beef carcasses has been
studied by Schnell et al., 1995. Ten grain-fed steers/heifers were
slaughtered and
[[Page 49561]]
dressed without dehairing. The carcasses of these animals were
evaluated for bacterial contamination and visual defects (hair and
specks) and for weight of trimmings made to meet ``zero tolerance.''
Overall, no difference was reported in aerobic plate counts, total
coliform counts, and E. coli counts between samples from dehaired
cattle and those from conventionally-slaughtered cattle. The lack of
difference in bacterial counts was thought to be due to contamination
in the facility from aerosols, and from people and equipment
contaminated by conventionally-slaughtered cattle. An interaction was
noted, however, between treatment and carcass sampling location. E.
coli counts were lower in samples taken from rounds of dehaired
carcasses than in samples from rounds of conventionally-slaughtered
carcasses. The converse was found for samples from briskets, where
higher counts were thought to be due to the additional handling of
dehaired carcasses, i.e., the necessity of cutting the hide to assist
in removal of hides that had become soapy and slippery during the
dehairing process.
The investigators stated the opinion that the microbiological
status of carcasses from dehaired animals should improve in facilities
designed to produce only dehaired carcasses. Dehaired carcasses had
fewer visible specks and fewer total carcass defects before trimming
(but not after trimming) than did conventionally-skinned carcasses. The
average amount of trimmings removed from conventional carcasses to meet
the ``zero tolerance'' specification was almost double (2.7 versus 1.4
kg) that from dehaired carcasses.
Additional tests, conducted in support of an industry petition
(Monfort, 1995), compared the reduction of bacteria from hide to
dehaired hide immediately after the dehairing process. These tests
found a 99% reduction in total plate counts.
VI. The Conference
FSIS is committed to ensuring that the most effective means
available are used to achieve the zero tolerance standard for fecal,
ingesta, and milk contamination of beef carcasses. The Agency's goals
are to protect consumers from harmful contamination and thus reduce
their risk of contracting foodborne illnesses. Given the importance of
these goals, determining the most effective means of implementing the
zero tolerance performance standard is one of FSIS's highest
priorities. FSIS will act on the basis of sound scientific evidence,
discussed in an open public process, to improve the safety of beef
products through effective removal of fecal and associated microbial
contamination.
Accordingly, FSIS is hosting a conference to review the scientific
and technical data and associated public policy issues involved in
achieving the zero tolerance standard and improving beef carcass
microbial safety. The conference will consist of two sessions on
consecutive days. At the first session, participants will discuss
available scientific and technical data comparing the efficacy of
various methods for decontaminating beef carcass surfaces, focusing on
the research summarized above. Participants are invited to make 15-
minute presentations during this first session and are requested to
submit to FSIS, in advance, brief statements describing the general
topics of their presentations (see ADDRESSES above). A panel of
government scientists and managers will participate in this session and
facilitate the discussion; the panel will be moderated by Ms. Patricia
F. Stolfa, Acting Deputy Administrator, Science and Technology, FSIS.
An opportunity will be provided for open discussion of scientific
issues among all participants. Possible scientific and technical
questions for discussion are:
1. Do the studies offered to support the various decontamination
alternatives conform to appropriate scientific standards?
2. Are key results from individual studies reproducible and have
they been replicated in other experiments?
3. How effective is any specific treatment against microbial
pathogens, and against E. coli 0157:H7 in particular?
4. Is a specific treatment bactericidal or bacteristatic?
5. Has a treatment been studied under plant conditions?
6. What are the most effective locations for treatment on the
carcass and on the slaughter line?
7. If water is used, in what amounts? Can water be conserved or
reused?
8. Is there any threat to workers or the environment from residual
treatment fluids, chemical waste, or biological hazards?
9. Does a proposed treatment create an insanitary condition?
10. Does a proposed treatment spread contamination on a carcass or
spread contamination from carcass to carcass?
11. Can - and should - a treatment be combined with other
treatments? What would be the optimum combination?
12. Does a proposed treatment interfere with current inspection
procedures?
13. When all the relevant studies are considered, does a
discernible trend emerge supporting a policy choice?
During the second session, participants will discuss the public
policy issues surrounding beef carcass decontamination. This session
will be moderated by Thomas J. Billy, Associate Administrator, FSIS,
and Dr. Craig Reed, Deputy Administrator, Inspection Operations, FSIS.
Possible policy questions for discussion are:
1. What criteria should be used to decide that an alternative
approach meets the zero tolerance performance standard for visible
fecal contamination and associated microbial contaminants?
2. What amount and quality of scientific data should be required in
order to change current policy?
3. Are alternative approaches equally feasible for all
establishments that may want to use them?
4. Should FSIS prescribe exactly how fecal contamination may be
removed or should there be an organoleptic and microbial performance
standard that companies can achieve as they see fit?
5. What techniques should the FSIS inspection force use to verify
that an alternative approach is functioning effectively?
6. Should preventive measures be made part of this policy decision?
7. What approaches to achieving the zero tolerance performance
standard are consistent with a HACCP approach to process control?
Conference Registration
FSIS is requesting that persons planning to attend the conference
preregister. If you plan to attend, please contact Ms. Mary Gioglio at
(202) 501-7138 to register. Registration will also be available on the
days of the conference on a space-available basis.
Also, if you require a sign language interpreter or other special
accommodations, please contact Mary Gioglio at the number listed above.
Done at Washington, DC on September 20, 1995.
Michael R. Taylor,
Acting Under Secretary for Food Safety.
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