Abstract #T25

# T25
Evaluation of inhibition of Listeria monocytogenes by lactic acid bacteria in fresh cheese.
M. R. Lawton*1, S. M. Kozak1, K. G. Jencarelli1, S. D. Alcaine1, 1Department of Food Science, Cornell University, Ithaca, NY.

The growth of Listeria monocytogenes (L. mono) in ready-to-eat (RTE) foods is a large concern in the United States due to its ability to cause morbidity and mortality, especially in immunocompromised individuals. Control of L. mono in food products has previously been evaluated using antimicrobial compounds such as nisin, acids, and other natural compounds such as essential oils. Recently, consumers are moving toward a more natural life style and look for clean label ingredients. Lactic acid bacteria (LAB) have been investigated as protective cultures to control the growth of L. mono in RTE products such as meat. However, contamination of L. mono is a large concern in the dairy industry due to its ability to thrive in fresh style cheeses like queso fresco. Four lactic acid bacteria cultures selected for their performance in inhibiting L. mono growth previously in meat—Lactobacillus curvatus, Lactobacillus sakei, Pediococcus acidilactici, and Leuconostoc carnosum—were evaluated against L. mono in a fresh cheese matrix stored at 6 and 21°C over 21 d. Lab-scale queso fresco cheeses (4 g) containing 5–6 log cfu/g of each LAB culture individually, were surface inoculated with 4 log cfu/g or 2 log cfu/g of a 5 strain cocktail of L. mono. Samples were enumerated for L. mono on d 0, 1, 7, 14, and 21 or d 0, 1, 2, and 4. Overall, none of the treatments showed any significant difference (P > 0.05) from the control when analyzed using the method of least squares and Tukey’s test for pairwise comparisons over time. After 21 d, cheeses reached L. mono concentrations of approximately 7–8 log cfu/g. The results from this study indicate that cultures previously shown to prevent or inhibit the growth of L. mono in meat matrices do not exhibit the same effects in fresh cheese.

Key Words: Listeria, biopreservation, cheese