Application of Lactic Acid Bacteria for Preand Post-Harvest Treatment to Control Listeria Monocytogeneson the Surface of Produce

Two lactic acid bacterial isolates, C-1-92 (Lactococcus lactis subsp. Lactis) and #152 (Enterococcus durans) with excellent inhibitory activity against L. monocytogenes at 4-37 oC in various conditions were evaluated. A cocktail of three L. monocytogenes strains were used to inoculate green peppers and apples at 21±1 oC 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. monocytogenes in 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. monocytogenes on the surface of fresh produce