Lactose monolaurate (LML) was previously found to be an antimicrobial against Listeria monocytogenes in culture medium at concentrations between 3 and 5 mg ml(-1) . In this study, the microbial inhibitory activity of LML in dairy products inoculated with a 5-strain cocktail of clinical isolates of L. monocytogenes was investigated. Addition of LML at a concentration of 5 mg ml(-1) resulted in 4.4, 4.0 and 4.2 log reductions in 0.5% fat, 1% fat and 3.25% fat milks, respectively; 4.1, 4.4, and 3.5 log reductions in nonfat, 1% fat, and 1.5% fat yogurts, respectively; and 4.0 log reductions in both nonfat and 2% fat cottage cheese. The inhibitory effect of LML was only observed at 37°C and not 5°C. Experiments suggest that both the lauric acid and the esterified lactose moiety of LML play roles in the growth inhibition.
Significance and impact of the study: A novel sugar ester, lactose monolaurate, inhibited the growth of a five-strain cocktail of Listeria monocytogenes in milk, yogurt and cottage cheese. This is the first report of the use of a sugar ester to inhibit the growth of Listeria in food systems.
Keywords: Listeria monocytogenes; cottage cheese; growth inhibition; lactose monolaurate; milk; sugar esters; yogurt.
© 2013 The Society for Applied Microbiology.