Short communication: Evaluation of commercial meat cultures to inhibit Listeria monocytogenes in a fresh cheese laboratory model

Abstract

Control of Listeria monocytogenes in queso fresco and other fresh cheeses continues to be a challenge in the United States. These cheese types are particularly challenging due to their high moisture and high pH, which provide favorable conditions for the growth of L. monocytogenes. Protective cultures (i.e., viable strains of lactic acid bacteria that inhibit other microorganisms) have been investigated in foods such as meat as an alternative, clean-label control strategy for L. monocytogenes. However, the efficacy of protective cultures can vary by food matrix. In this study, we were interested in whether protective cultures used to control L. monocytogenes in meats could be applied to control the pathogen in queso fresco. We selected 4 commercially available bacterial cultures used for the control of L. monocytogenes in meat: Lactobacillus curvatus, Lactobacillus sakei, Pediococcus acidilactici, and Leuconostoc carnosum. We incorporated these cultures into batches of queso fresco during manufacturing and evaluated them for their ability to inhibit the growth of surfaceapplied L. monocytogenes at levels of 1 × 10 2 and 1 × 10 4 cfu/g. We stored the queso fresco at 6 and 21°C for up to 21 d. After 14 d, Listeria was able to grow to 1 × 10 7 cfu/g on the cheese. Our data show that the bacterial cultures did not significantly inhibit the growth of L. monocytogenes in queso fresco. The results from this study highlight the complexity of antagonistic bacterial interactions and their potential variability across food matrices. Protective cultures represent an important, clean-label tool for the control of L. monocytogenes in foods, but each strain must be evaluated in the food environment it is intended for to ensure its efficacy.

Comparative Genomics of Leuconostoc carnosum

“…Contamination of meat products with L. carnosum may restrict the growth of spoiling and pathogenic bacteria (Jacobsen et al, 2003;Lawton et al, 2020). As a matter of fact, the capability of L. carnosum to deteriorate meat products seems to be a strainspecific feature.…”

Lactic Acid Bacteria Adjunct Cultures Exert a Mitigation Effect against Spoilage Microbiota in Fresh Cheese

“…Latilactobacillus sakei is more frequently used as a protective agent in meat and meat products to control Listeria monocytogenes and other pathogenic bacteria [ 53 , 54 ] thanks to its ability to grow in cold storage conditions and driving, at the same time, the fermentation process. When this species is forced to grow in a different food environment, such as cheese, it can sometimes vary its own efficacy [ 55 ].…”

Evaluation of Lactose Oxidase as an Enzyme-Based Antimicrobial for Control of L. monocytogenes in Fresh Cheese

“…Laboratory-scale queso fresco was produced following previous methods with modifications dependent on the goal of each experiment that will be discussed as follows with modifications from a previously established method [ 12 ]. Pasteurized, homogenized milk was collected from the Cornell Dairy.…”

“…However, this method is currently not cost-effective, significant wheying-off was observed, and the queso fresco was found to have different textural and rheological properties when compared to a control at 20 °C [ 10 ]. The efficacy of antimicrobial combinations of nisin, lauric arginate, and ɛ-polylysine [ 11 ], protective cultures [ 12 ], and phage endolysin PlyP100 [ 13 ] have all been explored to inhibit L. monocytogenes in queso fresco, demonstrating that finding an effective control method for this pathogen is a priority for the dairy industry. Consumers are currently moving toward a trend of desiring products with “clean labels” [ 14 ].…”