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Controlling Listeria in Processing and Retail Environments, Part II: Preventing Cross Contamination
By Beth McKew
Although Listeria monocytogenes isn't the cause of the most common
foodborne illness in the United States, it is the most deadly. Approximately 500 people die every year
from ingesting food contaminated with this type of
bacterium, the highest fatality rate among all foodborne pathogens. Listeria
monocytogenes is killed by pasteurization and cooking; however, there are
greater challenges. In certain ready-to-eat (RTE) foods such as hot dogs and
deli meats, contamination may occur after cooking, but before packaging.
Also, consumers usually do not reheat many RTE products to a high enough
temperature to kill Listeria. In Small Plant News, Vol. 3, No. 11, the first part of
this special two-part series on controlling Listeria focused on plant sanitation. In
Part II, Small Plant News looks at preventing cross contamination.
For many of us, our first lesson on the importance of cross contamination came at a very
early age, when as a child you rushed to the dinner table, only to be sent
away with orders to "Wash your hands!" This fundamental lesson that
we all learned as children takes on even greater importance when dealing
with ready-to-eat (RTE) meat and poultry products.
RTE products are processed to kill bacteria during a "kill step," but
subsequent exposure of the product to the processing environment may
permit contamination with bacteria. This is a unique problem with RTE
products such as sliced deli meats, hot dogs, deli salads, patés, and meat
spreads because these RTE products are rarely reheated by consumers to
temperatures high enough to kill the bacteria before they're consumed.
Of special concern in this regard is Listeria monocytogenes. As noted in
Small Plant News, Vol. 3, No. 11, this bacterium presents a very high risk of
serious illness (listeriosis) and death to older adults, the fetuses of pregnant
women, newborns, and adults with weakened immune systems.
Listeria is sometimes transferred to RTE products after the lethality
processing step when the product is exposed to the environment during
handling or storage, most often when the surface of the product contacts a
contaminated surface. This is known as cross contamination, and the importance of preventing it cannot be overstated.
In order to evaluate potential sources of cross contamination in your establishment, you must understand
the variety of ways that Listeria monocytogenes makes its way into your plant and is spread within the processing and
retail environments. You should consider that:
- Incoming materials, such as raw food products, may be contaminated with Listeria monocytogenes;
- Contaminated equipment can readily spread Listeria monocytogenes; and
- Employees, as well as customers, vendors, or anyone entering your plant, can contaminate food with Listeria
monocytogenes by acting as vectors, transferring bacteria from product to product as well as throughout the establishment.
With these considerations in mind, let's take a closer look at four areas — incoming materials, people,
equipment, and facilities — and how you can better prevent cross contamination.
Incoming Materials. A key to preventing cross contamination is a separation between raw and fully
cooked product. If possible, dedicate separate areas of your establishment to working with raw product, and other areas
for RTE product. If complete separation is not possible in your facility, use separate equipment for raw and RTE
products whenever possible and always follow your plant's sanitation controls when cleaning up.
The importance of separating raw and RTE products extends well beyond preparation areas and should also
include receiving, storage, and display areas. Separating raw from RTE product during preparation accomplishes
little if the products are stored in a way that enables cross contamination to occur in the cooler or display case.
If separate coolers and display cases are not an option, physical separation with a plastic barrier, for example, will
reduce the risk of cross contamination.
People. Raw and RTE product need not be in close contact for cross contamination to occur. Employees can
very efficiently carry foodborne pathogens throughout the retail or processing areas of your plant. Consider traffic
patterns that will minimize employees walking from areas with raw product into areas with RTE product. This can also
be accomplished by restricting employees who work with raw product from working with RTE product.
Attention to employee hygiene, such as changing outer garments before handling RTE product, hand washing,
and using designated, clean utensils when handling RTE products, will minimize the risks of cross contamination.
Employee hygiene policies are just the beginning. All employees should be properly trained and retrained as
needed in your hygiene policies.
Customers and outside vendors entering your establishment also can bring Listeria monocytogenes inside
your plant and spread it throughout the interior. Consider posting instructions for "outsiders" to
follow when entering your facility.
Equipment. Food contact surfaces are always potential sites for cross contamination. The importance
of well developed and implemented sanitation programs was discussed in Small Plant News, Vol. 3, No. 12. If a deli
meat slicer is contaminated with Listeria monocytogenes, the slicer will likely contaminate other foods that come in
contact with it.
Food preparation tables and utensils will have the same effect if they come in contact with Listeria monocytogenes,
potentially passing the bacteria onto each product with which they come in contact. In addition to every product
they touch, a contaminated cutting table or utensil may also contaminate other surfaces. For example, a contaminated
knife set down on the counter will contaminate the counter.
Cracks in equipment and utensils can also be major harborage sites for bacteria. Any non-smooth surface
provides opportunities for bacteria to hide, often evading cleaners and sanitizers, and potentially contaminating other
products and surfaces. Frequent cleaning and sanitizing as described in written Standard Operating Procedures (SOP)
during processing will minimize contaminated RTE product.
Facilities. Non-food contact surfaces can also harbor Listeria monocytogenes and potentially contaminate RTE
product or other surfaces in your plant. Drains have been shown to be a collection area or "reservoir" where Listeria
monocytogenes collects. During high-pressure cleaning, spray from hoses may spread the bacteria to other surfaces
or into the environment, such as in the ventilation system, potentially circulating Listeria monocytogenes throughout
your facility. Leaky roofs and floors, and other places in your facility where water collects can also become potential
Attentiveness to plant sanitation, time, and temperature controls (explained below ),
and a conscientious effort to prevent cross contamination are three critical factors in protecting RTE products from
Listeria monocytogenes. Incorporating these principles when dealing with RTE products is your best defense for the
prevention of Listeria monocytogenes — much like sitting
down with freshly washed hands was your best defense for not being sent away from the dinner table all those years ago.
(For more information and to obtain resources on Listeria control, contact the Small Plant Help Desk at
1-877-FSISHelp (1-877-374-7435) or send an email to
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Controlling Listeria: Time and Temperature Matter
The United States Food and Drug Administration's (FDA) Food Code guidelines recommend that refrigerated
food be kept at 41 °F or colder. This is because most foodborne pathogens do not multiply well at temperatures below 41 °F.
Unfortunately, Listeria monocytogenes is still able to multiply at this temperature, although its rate is
slowed down. If a RTE product is contaminated with Listeria monocytogenes during processing or handling,
the bacteria will multiply slowly while the product is refrigerated. Danger arises when the bacteria continues to
multiply to levels high enough to cause foodborne illness. This temperature guideline of 41 °F or colder applies to
receiving food, as well as storage.
The FDA Food Code provides that these foods are to be held no longer than 7 days after opening. Adherence
to the first-in, first-out rule, also referred to as "FIFO," will ensure that the oldest product is used. All RTE food
should be properly labeled with "use by" or discard dates, and these dates should be honored, even on unopened products.
A program detailing your plant's regular temperature monitoring and recording procedures should be developed
and implemented. Finally, be aware of the recommended capacity of your display case. Overfilling the case will
affect airflow and could prevent products from being maintained at the desired temperature.
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SBA's National Ombudsman Can Work for You
By Jeff Tarrant, CDR, U.S. Public Health Service
Have you ever questioned or appealed a U.S. Department of Agriculture's (USDA) Food Safety and Inspection Service (FSIS) regulatory or
enforcement action and received a response not to your liking, but weren't sure where to go to next? If so, then the
U.S. Small Business Administration (SBA), Office of the National Ombudsman, may be what you're looking for as your next step.
The National Ombudsman's primary mission is to assist small businesses when they experience excessive or
unfair federal regulatory actions, such as repetitive audits or investigations, excessive fines, penalties, threats, retaliation,
or other unfair enforcement action by a federal agency.
Since 1996, the National Ombudsman has received comments from small business owners and acted as a
liaison between them and more than 35 federal agencies. Comments received from small businesses are forwarded
to federal agencies for a high-level review and request to consider the fairness of their enforcement action.
Presently, FSIS-inspected establishments have the ability to appeal any inspection decision through the formal
Agency appeals process. In fact, FSIS encourages plant owners and operators to appeal decisions they believe
are unfair or are not consistent with applicable regulatory standards. Use of the appeals process ensures that any
disagreements between plant owners or operators and FSIS inspectors are reviewed.
If you've already gone through the formal FSIS appeals process and feel that it did not work to your satisfaction, then
you may want to consider filing a comment or complaint with the National Ombudsman. It's important to note
that the National Ombudsman cannot change, stop, or delay a federal agency enforcement action, nor assist
with comments of a non-regulatory nature. The National Ombudsman can, however, serve as a liaison between the
FSIS-regulated owner/operator and the Agency to discuss the fairness of regulatory action, hold follow-up meetings,
report on significant enforcement issues, and reflect all concerns in their report to Congress.
For more information on the Small Business Administration's Office of National Ombudsman,
feel free to contact them via their toll-free number at 1-888-REGFAIR (888-734-3247), or send a fax to (202)
or view their Web site at www.sba.gov/ombudsman.
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Commonly Asked Questions & Answers
Q. A plant produces post-lethality exposed beef brisket applicable to 9 Code of Federal
Regulations (CFR) Part 430. Would this product be considered a deli product?
A. In order to determine whether the product is classified as a deli product under 9 CFR
Part 430, inspection personnel would need to consider the intended use of the product. For
example, if the product is produced as a deli log for slicing or is pre-packaged as thin slices to be used in
sandwiches, the product would be considered a deli product. However, if it's packaged as an intact brisket
intended to be served as a family entrée, it would not be considered a deli product under the 9 CFR 430
rule. If the intended use of the product is unknown or uncertain, the product should be considered a deli
product by default and assigned a higher risk.
Q. Is reimbursable inspection coverage required if the plant transfers fully labeled and inspected
consumer sized packages from one properly labeled shipping container to another properly labeled shipping container
after the official hours of operation?
A. Yes, even though the fully labeled consumer size packaged product bears the mark of
inspection, when the plant transfers the consumer size package from one size shipping container to another size shipping container, they
are "applying the mark of inspection" so inspection coverage is required.
Q. Is an icehouse considered a food contact surface that must be addressed in the Sanitation SOP?
A. A food contact surface is any surface that may come in direct contact with exposed product.
Examples of food contact surfaces include conveyor belts, table tops, saw blades, augers,
and stuffers. If the interior surfaces of an icehouse do not directly contact product, the plant would not
be required to address them in the Sanitation SOP. Regardless, FSIS verifies Sanitation Performance
Standard regulatory compliance. FSIS expects the plant will prevent the creation of insanitary conditions
within the icehouse that could result in product contamination with filth or that may render the product
injurious to health.
Q. Can a "use-by" or "sell-by" date be used in lieu of the slaughter date required on "dressed"
poultry as described in 9 CFR 381.126(b). "Dressed poultry," for the application of this section of the regulations, means slaughtered,
defeathered, eviscerated whole birds with the head and feet removed, i.e., a ready-to-cook whole bird?
A. No, a "use-by" or "sell-by" date may not be used in lieu of the slaughter date. However,
the regulations do permit the use of a code to identify the slaughter date.
Q. What is the general rule about pack dates on poultry food products produced in a federally inspected facility?
A. FSIS requires all immediate containers or shipping containers of poultry food products
to be clearly and permanently marked by code or otherwise with the date of packing. If
a calendar date is used, it must be accompanied by a statement explaining the meaning of the date. The
calendar date must include the month of the year and the day of the month for all products and also the year
in the case of products hermetically sealed, dried, or frozen products, for example, "packed on May 22,
2005." For further information, see the regulations at 9 CFR 381.126 (b) and 381.129 (c) (1).
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Small Plant NEWS
Editor: Keith Payne
Production: Joan Lindenberger, Sally Fernandez
Design: Gordon Wilson
Contact: Small Plant News, USDA/FSIS, Aerospace Building,
3rd Floor-Room 405, 14th and Independence Ave., SW, Washington,
DC 20250. 1-800-336-3747