Abstract

Two lactic acid bacterial isolates, C-1-92 (Lactococcus lactissubsp. Lactis) and #152 (Enterococcusdurans) with excellent inhibitory activity against L. monocytogenes at 4-37oCin various conditions were evaluated.A cocktail of three L. monocytogenes strains were used to inoculate green peppers and apples at 21±1oC at a concentration of 3log CFU/cm².After 48h post-inoculation, green peppers and apples were individually treated with 0.1% peptone, 5log CFU/ml C-1-92 or #152.These two lactic acid bacteria were further evaluated in hot and green pepper plants by similar methods.After 14 days the population of L. monocytogenes on green pepper treated with control, #152, and C-1-92 studies was 3.4, 2.3, and 1.3log CFU/cm², respectively.The application of C-1-92 treatment reduced the L. monocytogenes population by 2.1log CFU/cm² (P<0.05) when compared to the control.For apple studies, L. monocytogenes population treated with C-1-92 or #152 were below detection level (0.69CFU/cm², P<0.05) and 50% samples were detected by selective enrichment only at day 14; whereas, L. monocytogenesin control group was 2.6CFU/cm².Pepper plants studies indicated that the treatment significantly reduced listeria count 5 days following treatment. The average count of listeria in C-1-92 or #152 treated hot peppers was 0.7 and 0.96log CFU/cm², respectively, whereas the average count in hot peppers of control group was 2.5log CFU/cm².Listeria reduction from green pepper plants were similar with results obtained from hot pepper plants study. The intervention by Lactococcus lactis subsp. Lactis (C-1-92) can substantially reduce the existence of L. monocytogeneson the surface of fresh produce.

Keywords: Lactic acid bacteria; Listeria monocytogenes; Produce.