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

摘要

Control of Listeria monocytogenes in queso frescoand other fresh cheeses continues to be a challenge inthe United States. These cheese types are particularlychallenging due to their high moisture and high pH,which provide favorable conditions for the growth of L.monocytogenes. Protective cultures (i.e., viable strainsof lactic acid bacteria that inhibit other microorganisms)have been investigated in foods such as meat asan alternative, clean-label control strategy for L. monocytogenes.However, the efficacy of protective culturescan vary by food matrix. In this study, we were interestedin whether protective cultures used to control L.monocytogenes in meats could be applied to control thepathogen in queso fresco. We selected 4 commerciallyavailable bacterial cultures used for the control of L.monocytogenes in meat: Lactobacillus curvatus, Lactobacillussakei, Pediococcus acidilactici, and Leuconostoccarnosum. We incorporated these cultures into batchesof queso fresco during manufacturing and evaluatedthem for their ability to inhibit the growth of surfaceappliedL. monocytogenes at levels of 1 × 10~2 and 1 ×10~4 cfu/g. We stored the queso fresco at 6 and 21°C forup 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 bacterialcultures did not significantly inhibit the growth ofL. monocytogenes in queso fresco. The results from thisstudy highlight the complexity of antagonistic bacterialinteractions and their potential variability across foodmatrices. Protective cultures represent an important,clean-label tool for the control of L. monocytogenes infoods, but each strain must be evaluated in the foodenvironment it is intended for to ensure its efficacy.