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From: Food Quality & Safety magazine, April/May 2008

Be Ready to Beat Listeria

Ready-to-eat plants must know their options when fighting this persistent pathogen

by Charles Giambrone, MS

The foodborne pathogen Listeria monocytogenes has remained a major concern in all food markets but is especially problematic for ready-to-eat (RTE) products. Its high level of morbidity—nearly 30% in those at greatest risk (pregnant woman, the elderly, young children, and the immunocompromised)—makes it a high priority in RTE plants.

A major Listeria monocytogenes outbreak in fall 2002, triggered by an RTE luncheon meat processor in the Northeast, served as a catalyst for the U.S. Department of Agriculture’s Food Safety and Inspection Service (FSIS) to bolster its control measures.

This enhancement includes validation-verification programs to prevent contamination by Listeria monocytogenes and generic Listeria. The revised versions of these guidelines—10,240.4 Rev. 1 and 10,240.5, dated March 15, 2006—delineate three “alternative control” programs available to RTE FSIS plants, along with the enforcement measures FSIS field inspectors must implement.

Federal Oversight

The first key legislative directive that resulted in mandated federal regulations was the 2002 “Microbial Sampling of Ready-To-Eat (RTE) Products for the FSIS Verification Testing Program.” This document details FSIS’ rationale for implementation, as well as key terminology. The three parts of this document provide decision-making criteria for FSIS-regulated RTE plants.

The first part differentiates high-, medium-, and low-risk products, taking into account products that have undergone so-called post-lethality treatment. It classifies RTE products into four groups:

  • not heat treated and shelf stable;
  • heat treated and shelf stable;
  • fully cooked and not shelf stable; and
  • product with secondary inhibitors and not shelf stable.

These categories are further defined in 9 CFR Part 430. FSIS includes frozen products in the RTE foods category.

The second part is the nuts and bolts of the 2002 directive. This statement of policy focuses on enforcement levels in programs testing for Listeria monocytogenes in finished products, in food contacts, and on environmental surfaces.

Plants that have a science-based Listeria monocytogenes control program and share data with FSIS will be tested under a targeted verification program. Producers of high to medium-risk products that have no science-based control program and don’t provide data to FSIS will undergo an intensified verification program—FSIS will take more samples from more products. Further, if a Listeria monocytogenes positive is found either in product, in food contacts, or on environmental surfaces at any enforcement level, the FSIS can put a plant under the most rigorous scrutiny.

The last part of the directive deals with regulatory actions and sampling when a product or surface sample is found to have any of the “big three” (Listeria monocytogenes, Salmonella, and E. coli 0157:H7). For example, if a food contact is found to have Listeria monocytogenes, the FSIS will most likely request a recall for a product that has been shipped. This, of course, puts pressure on plant sanitation programs, emphasizing the need for both internal and external support, for the following reasons:

  • If an environmental surface is found to have Listeria monocytogenes, the RTE plant must adhere to the corrective actions described in the plant’s hazard analysis and critical control point (HACCP) program and sanitation standard operating procedures documents.
  • The section on food contact surface testing for indicator organisms focuses on corrective actions if indicator microbe levels are present.
  • The FSIS expects the plant to “take additional steps to thoroughly clean and sanitize potentially contaminated food surfaces and increase the number of food contact surface samples that it takes.”

This directive has required RTE food plant quality assurance and sanitation programs and their technical resources to double their focus on these programs, utilizing a multi-pronged control strategy with Listeria monocytogenes but also targeting Salmonella spp. and E. coli 0157:H7. This is most acute for post-lethal treatment production processes, where recontamination with Listeria monocytogenes after a heat kill step threatens RTE products.

RTE Alternatives

This RTE directive was codified as an Interim Final Rule on June 6, 2003 (“Control of Listeria monocytogenes in RTE Meat and Poultry Products;” Final Rule as 9 CFR Part 430) and revised on January 1, 2006.

There are three FSIS alternatives (Rule 430.4: Control of Listeria monocytogenes in post-lethality exposed ready-to-eat products).

Alternative 1 (use of post-lethality treatment and an antimicrobial agent/ process). This is the best alternative of the three. Using both intervention strategies means that the RTE processor’s sanitation program faces less of a verification burden than with the second and third alternatives.

Since 2003, many small to medium-sized plants have struggled with implementing this alternative because of plant design and internal resource issues, even though the types of products and their markets are amenable for both measures.

Alternative 2 (use of post-lethality treatment or an antimicrobial agent/ process and sanitation program requirements). As with alternative 1, post-lethality treatment must be in the HACCP plan and must be validated. But if the FSIS plant opts for the antimicrobial agent approach, the same parameters apply here as for alternative 1. In alternative 2, validation of the sanitation program is critical and requires:

  • a microbial swab test of food contact surfaces;
  • identification, holding, and testing of any positives for Listeria or indicator microbes;
  • clear documentation of testing frequency; and
  • clear identification of food and environmental contact sample sites and swab size.

This option puts much greater emphasis on sanitation validation and verification and can stress an RTE plant’s quality assurance, sanitation, production, and distribution personnel and resources. RTE plants opt for this alternative if their products, processes, or plant design are not conducive to using both post-lethality and antimicrobial processes. In most instances, RTE plants choose this alternative because their product and its process cannot support the introduction of an antimicrobial agent or other additive. In some instances, post-lethality intervention may not be effective for the product (e.g., products adhering to religious dietary law or U.S. organic product requirements). These and other mitigating factors may force the plant to use the third alternative.

Alternative 3 (use of sanitation measures only). An FSIS plant manufacturing any type of RTE and/or hot dog or deli-type product must have a sanitation program that adheres to a number of requirements. The FSIS will conduct much more verification testing in a plant that chooses this option than for an RTE plant using one of the first two alternatives. Sanitation rules for this option include those indicated in the second alternative, with the additional requirement that the plant must be able to support testing frequency. Also, plants that produce hot dogs and deli items must:

  • verify corrective actions upon positive identification of food contact swabs;
  • test and hold a product when a second positive is found; and
  • sample and test lots to release or rework them to destroy Listeria monocytogenes.

With this high-maintenance alternative, the burden rests entirely upon the sanitation program. This may be the only option for some plants, however, especially if product type, process, and plant design make post-lethality and antimicrobial interventions awkward or impossible. Smaller processors have chosen this path for lack of resources. But, in many cases, adding a post-lethality intervention is not difficult and would be a far less stressful option than the third alternative.

Some plants that use this alternative may be using cooked product from another facility, then assembling and freezing meals. Or, these facilities may be composite plants, creating a variety of segregation and cross-contamination issues.

I have audited plants using all three alternatives for large, medium, and small RTE FSIS processors. Understandably, the small RTE processors with the most limited resources have had the most formidable task, but some have used the first alternative. Meanwhile, even some large RTE processors choose the second or third options.

Where to Begin

Deciding how to adhere to RTE regulations starts with verified, validated, evolving good manufacturing processes and sanitation programs that feature constant training for both new and veteran employees. This is mandated and is vital to surviving in the RTE FSIS marketplace.

Plants opting for one of the first two alternatives described above must decide how to tackle direct product treatment. Direct intervention treatments should never be viewed as magic bullets to reduce costs.

There are numerous direct treatment modalities involving organic acids (citric, lactic) blended with other adjuvants. Others include acidified chlorite (approved for raw and cooking products) and peracetic acid chemistries (approved for raw products). Key plant decision makers must realize that any intervention chemistry—used correctly and responsibly—is simply another component of the multi-intervention strategy; it will not supplant the vital need for stringent, verifiable personnel and plant processes for all direct, indirect, and environmental food zones in an RTE facility.

Listeria is one of the most formidable pathogen adversaries a food-processing facility encounters. While antimicrobial processes, post-lethality treatments, and even sanitation technologies continue to make rapid advancements, ancient pathogenic foes will continue to adapt to our countermeasures. It is incumbent upon all sectors of the food safety community to keep at least one step ahead.

Giambrone is senior technical support manager at Rochester Midland Corp. Reach him at cgiambrone@ or (800) 762-4448, ext. 7263.



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