Inhibition of Listeria monocytogenes on cheese using lactic acid bacteria as a biocontrol system intervention

Obj 1. Quantify the amount of reduction a Lactic Acid Bacteria intervention has on L. monocytogenes on 3 types of artesian soft cheeses (Brie, Blue, and Queso Blanco) and 2 types of commercial hard cheeses (LMPS Mozzeralla). Test the efficacy of 4 types of lactic acid bacteria treatments. Obj 2. Conduct sensory analysis to determine any differences in flavor, texture, or color associated with the application of the multiple LAB on cheese. Obj 3. Evaluate and quantify anti-microbial compounds (lactic acid, acetic acid, butanoic acid, succinic acid, and propionic acid); purify and characterize and bacteriocins Abstract: The United States of America has a zero-tolerance policy for Listeria monoctogenes in ready to eat foods. Soft cheeses (e.g., Queso Fresco, Blue-Veined, Feta, Brie, Camembert and Panela) are at higher risk of supporting the growth of L. monocytogenes. Cheese (soft and hard cheeses) exposed to the plant environment during further processing (e.g., packaging) are at risk of cross-contamination with L. monocytogenes that may be present on food contact surfaces. Finding long-term solutions for improving the safety of these foods requires innovative approaches. We hypothesize that a lactic acid bacteria (LAB) intervention will be effective in controlling L, monocytogenes in cheese products. LAB is safe for consumption and are generally recognized as safe by the Food and Drug Administration. Some LAB strains have been shown to produce a variety of antimicrobial compounds that can inhibit L. monocytogenes such as: organic acids, hydrogen peroxide and anti-microbial protein (bacteriocins). Novel interventions such as biological control systems using competitive exclusion could potentially be used to reduce or eliminate L. monocytogenes in cheese products. Our preliminary data indicates that dipping cheese contaminated with L. monocytogenes in a LAB solution reduced Listeria by 90% after a 4 h dwell period. Furthermore, a greater reduction may be achieved over the course of more time and research is needed to further evaluate the potential reduction over a 60 d period. To meet the overall objective, we will investigate novel, newly isolated lactic acid bacteria (LAB) strain that exhibited antimicrobial activity and identify additional LAB strains that are most effective against L. monocytogenes. The final objective of this study is to evaluate the bacteriocins produced by these LAB strains.