Lactic Acid Bacteria Synergy: Electrostatic Spraying, Dipping, and Formulation Applications of Lactobacillus salivarius L28 and Enterococcus faecium J19 to Enhance Cheese Safety Against Listeria monocytogenes

Abstract

Recent outbreaks of listeriosis linked to cheese and recalls of cheese contaminated with Listeria monocytogenes have emerged as a significant public health concern due to the ability of this pathogen to grow during refrigerated storage. We hypothesized that a lactic acid bacteria (LAB) intervention applied onto the surface of cheese by electrostatic spray, dipping or formulation of the product with LAB would be effective in controlling L monocytogenes growth during refrigerated storage. The purpose of this study was to utilize two LAB strains, including J19 Enterococcus faecium and L28 Lactobacillus salivarius individually and in combination, to reduce L. monocytogenes on the surface of cheese during a 60 d of refrigerated storage period. We inoculated various cheeses with a five-strain cocktail of L. monocytogenes. After inoculation, the surface of cheeses had a L. monocytogenes concentration of approximately 10⁶ CFU/cm² on day 0 and the cheeses were subjected to a LAB electrostatic spray or dipping treatment. Electrostatic spray treatments were as follows, (1) L28 at a concentration of 10⁸, (2) J19 at a concentration of 10⁸ and (3) a combination of L28 and J19 at a concentration of 10⁸ at a 1:1 ratio. Resultant L. monocytogenes populations were enumerated on days 0, 1, 3, 7, 14, 30, 45, and 60. Results indicated that J19 inhibited L. monocytogenes, while the L28 and the combination resulted in little inhibition. When utilizing J19 as an intervention, there was always an immediate reduction of L. monocytogenes on all cheese types on day zero of approximately 1 log10. The use of J19 as a biological intervention in cheese could improve the safety of cheeses that may become contaminated with L. monocytogenes.