Antimicrobials inhibit growth of L. monocytogenes in ready-to-eat meats.

L. monocytogenes is ubiquitous in the environment and has the ability to colonize food plants and survive under unfavorable conditions. For these reasons, sanitation and hygienic practices, although important and necessary, may sometimes be insufficient to prevent its presence in meat products.

Accidental post-processing contamination, which may occur when slicing or packaging ready-to-eat (RTE) meats, has become an important safety issue and is a major concern for the meat processing industry. L. monocytogenes has been responsible for certain major fatal outbreaks of illness and recalls of potentially contaminated products in recent years. This has led regulatory authorities, the industry and researchers to undertake efforts aimed at developing and applying effective measures and procedures that would control of the pathogen in RTE meats.

The USDA Food Safety and Inspection Service has issued a final rule for controlling L. monocytogenes in RTE meat and poultry products. These products could be recontaminated after undergoing a lethality treatment and may support growth of the pathogen during storage before they are consumed.

The new rule provides three alternatives that meat processors could use to control the pathogen. The first two of these alternatives allow the use of chemical antimicrobials for reducing the pathogen count or for controlling the growth of bacteria. Researchers at Colorado State University and elsewhere have evaluated the influence of antimicrobials, such as lactates, acetates, diacetates, benzoates, sorbates, nisin and glucono-delta-lactone, on L. monocytogenes population changes during the storage of various meat products inoculated with the bacteria. The inoculation took place after casings were peeled, and before the products were vacuum-packaged. Researchers also examined the resistance of surviving pathogen cells to simulated gastric fluid during product storage.

Scientists found they can control L. monocytogenes by including antimicrobials in the product formulation or applying them to the product as dipping solutions before the product is packaged. However, pathogen cells may become more resistant to acids if storage conditions allow the cells to continue to grow and increase in numbers.

Further information. John Sofos, Department of Animal Sciences, Colorado State University, Fort Collins, CO 80523; phone: [phone]; fax: [phone]; email: [e-mail].