Keeping the pathogen out of the plant is essentially what sanitarians preach. Sanitarians focus on minimizing the use of sanitizing chemicals. This strategy reduces costs and exposure to toxic chemicals, and by definition focuses attention on control strategies. These include identifying and studying hygienic zones, personnel hygiene, traffic patterns in the plant, and the array of sanitation steps taken over all shifts. An article by Dr. Bob Powitz describes this approach.
Eradicating Listeria when it is found is usually the result of a find it and kill it approach–often called “seek out and destroy”, an aphorism coined over a decade ago by Dr. John Butts. The principles and techniques outlined in these mini-articles are very much aligned with this kind of approach. They are also the ones employed by most food companies in their management of Listeria risk. And that is mainly because Listeria can still find a way into a plant, in spite of best efforts to the contrary.
It is beyond the scope of this mini-article to go into all of the different chemicals that can be used to attack Listeria. Common chemicals include peroxyacetic acid, often used in plants for which an organic sanitizer must be used. Chlorine dioxide gas is used when companies want to introduce a sanitizing chemical across the entire plant, essentially as a “fumigation” technique. This can be useful since the gas can reach areas in which liquid sanitization techniques are ineffective.
The most common chemicals used against Listeria are the “quats”, mixtures of quaternary ammonium compounds. Not only are these compounds effective sanitizers, but it is generally believed that quats have a substantive property which allows them to remain on surfaces for a time. Thus they can have an ongoing effect against Listeria.
Highly experienced food plant chemical companies are well versed in sanitation chemicals and procedures. They are the best source for determining which chemicals are the most effective for your situation, at what concentrations (e.g., to achieve a no-rinse level on equipment), and with best-practice standard sanitation procedures. Highly reputable chemical companies understand sanitation, sanitization, and disinfection–and they can teach these concepts, and solve contamination issues.
FDA (“draft guidance for industry”) and USDA (“compliance guideline”) provide guidance on what corrective actions (e.g., sanitization) are required when Listeria is found. Regardless of which actions are decided upon, their effectiveness must be verified and validated. This requires well thought out statistical sampling and risk assessment, and continued testing.
Constant vigilance is very important. Use checklists that are centered on GMPs (Good Manufacturing Practices) as a start, using these to ensure that areas are sampled appropriately. But make sure that you are not solely relying on checklists (see this article on checklists that can be traps). Too often, companies find Listeria, throw some sanitizer on the area in question, sample, get a negative (the pathogen is no longer found in that location)–and then move on, convinced that they have solved the problem.
This is rarely the real outcome unless you have determined definitively that the root source has been eliminated. In addition, you have to be convinced that the transfer points around the root source are no longer in play. They have to be eliminated or highly controlled.
Said another way, you are rarely done. As frustrating as this might seem, constant microbiological vigilance is what keeps your products safe. Not doing so can end up being very costly to the company in insurance costs, recall costs, and legal costs, and in brand image to customers and consumers. All are avoidable.
It is much better to maintain and improve your environmental monitoring programs to constantly protect public health. So keep sampling and testing!
This is the 5th in a series of 6 Listeria in Food Plants articles. See the Related Articles below to read the series.
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