Consumer demand for ready-to-eat (RTE) products has grown significantly over the past few years due to changing lifestyles and the convenience of the products. Although RTE foods provide us with a convenient meal option, RTE facilities are particularly at risk for Listeria. As consumers continue to value RTE products and are also turning to shelf-stable foods more than ever in the wake of COVID-19, it’s all the more critical to prioritize food safety and sanitation in your plant to prevent outbreaks of Listeriosis.
Why RTE Products are at Higher Risk of Contamination
While Listeria should be a major concern for any food processor, it’s essential that producers of RTE products adopt an aggressive seek and destroy program. Products such as fresh meat or juices usually have kill steps at the manufacturer and/or the consumer level (cooking and pasteurization), but RTE products typically have only a single kill step at the manufacturer level—opening the door for the product to be recontaminated between the kill step and packaging. These products usually come back into contact with processing equipment before leaving a facility, and products such as lunch meats and produce are generally eaten as purchased, meaning the consumer isn’t creating an additional lethality step. And, while many consumers do heat RTE meals like soups, even then the products may not reach a temperature effective in killing Listeria.
Because Listeria can thrive in a wide range of temperatures (including freezing) and in almost any environment, it can be a tough pathogen to combat. Listeria is a persistent pathogen—whole genome sequence testing has documented the ability of Listeria to persist in the plant environment for many years despite regular cleaning and sanitation.
So, what can you do? Here’s what to consider if you’re looking to implement or revamp your Listeria seek and destroy program.
Environmental Monitoring
If you haven’t already adopted an environmental monitoring program, doing so is a crucial first step in Listeria contamination prevention. It can provide you with critical insights about where pathogens hide, which can help you develop a plan to eliminate them (and prevent them from reemerging in the future).
Environmental monitoring programs offer a targeted approach to eliminating Listeria and other pathogens. They involve pre-defined points at which samples are collected and tested, allowing you to create a microbiological map of the pathogens in your facility so you can target areas of concern more effectively.
Whether you are just starting to consider an environmental monitoring program or already have one in place, it’s important to go above and beyond the standard monitoring practices, as each facility has a unique situation. Take photographs of specific areas of concern or use a geomap to digitally identify trends within your plant. Considering where pathogens may be hiding out in areas specific to your facility, products and equipment is a critical part of environmental monitoring that you won’t want to skip.
Where to Start: The Zones
Listeria doesn’t discriminate against many environments—it can thrive on several surfaces. So, it’s important to adopt a “seek and destroy” mentality and zero in on every area of your plant, from processing equipment to breakrooms and restrooms.
Use the following zones defined by the FDA as your starting point in your efforts to seek and destroy listeria:
- Zone 1: Direct Contact Areas
Equipment with direct contact to products, including conveyors, tables, cooling racks, food storage, mixing vessels, filler nozzles and pipes that transport food.
- Zone 2: Indirect Contact Areas
Floors, overhead equipment, control panels, maintenance tools or other objects and areas that may come into contact with food or contaminate Zone 1.
- Zone 3: Noncontact Areas
Floors, walls, drains and other areas that don’t come into direct contact with products but could harbor Listeria and contaminate your plant.
- Zone 4: Auxiliary Areas
Break rooms, restrooms, locker rooms, warehouses, loading docks or other areas between which employees move, which can potentially contaminate other zones.
While your initial instinct may be to focus your Listeria prevention efforts on direct contact surfaces, if you produce RTE foods, you’ll want to prioritize contact surfaces that follow the lethality step. It’s also equally important to consider the other zones for random testing to protect your entire facility—and thus, your products—from potential contamination.
Seek—Hard-to-Reach Areas, Scratches and Seams
As you’re deciding where to swab, you won’t just want to consider direct surface areas or swab all in the same place. You’ll also want to look at areas such as the sides, undersides or overheads of equipment as potential testing sites. Scratches, dings, O-rings, seams and areas out of reach are easy to overlook since they don’t usually come into direct contact with products or aren’t noticeable. But, these are places to which you want to pay extra attention.
While these areas may seem microscopic to us, they provide a good niche for an organism, as it’s hard to ensure full physical removal of left-behind product matter, which provides a food source for the pathogen. So, even a small scratch can result in cross-contamination or recontamination of a product.
The more often you check and sanitize these areas, the better. Since different equipment gets used throughout the day or can vary between shifts, you’ll want to monitor these areas at all times, on every shift, and change out old parts like O-rings or replace dated equipment on a regular schedule.
Destroy—Conducting a Root Cause Analysis and Eliminating Pathogens
So, you’ve implemented a rigorous monitoring program, and now you’ve found a sample testing positive for Listeria. While positives are concerning, it’s nearly impossible to keep pathogens out of your plant. The key is destroying them once they make it into your plant, which means a positive test gives you a starting point. Before you start testing, make sure you have a plan for what action to take when you do find a positive.
Once you have a positive, you’re able to minimize the risk of Listeria contamination by analyzing the source of it. With a root cause analysis, you can identify whether a Listeria positive originated from within your facility or was brought in by an employee, contractor or something else from the outside, allowing you to eliminate Listeria at its source and prevent it from reaching your consumers.
The Takeaway
Developing a robust seek and destroy program for Listeria comes down to two things: strategy and aggressiveness. Using a targeted approach (rather than simply increasing the frequency of testing) and ramping up your sanitation in every area surface—and scratch, and drain, and ceiling—is your best bet at protecting your products and your consumers against an outbreak.
The FDA and commodity specific trade organizations have developed some excellent guidance documents to help you seek, destroy and control Listeria in your facility. View their resources here.
