Antilisterial activity of freeze-dried bacteriocin-containing powders produced by lactic acid bacteria against Listeria innocua NRRL B-33016 on cantaloupe (Cucumis melo) surface

Abstract

Bacteriocins produced by lactic acid bacteria may reduce pathogenic loads on cantaloupe surfaces. The efficacy of these bacteriocins on reducing the pathogenic loads of Listeria was evaluated. Non-pathogenic bacteria, Listeria innocua NRRL B-33016 was used as a surrogate for L. monocytogenes. Two bacteriocins, (1) nisin and (2) pediocin, were produced from Lactococcus lactis subsp. lactis ATCC 11454 and Pediococcus acidilactici RS2, respectively. L. innocua NRRL B-33016 was inoculated on the cantaloupes surface at a concentration of 4.69 ± 0.37 log CFU/cm2, and then the melons were stored for 16 days at 4 °C. The antimicrobial activity on L. innocua of the powders was 3.34 × 107 and 1.01 × 108 international units (IU)/g, respectively. Application of nisin freeze-dried bacteriocin-containing powder (NBP), pediocin freeze-dried bacteriocin-containing powder (PBP), or the combination of pediocin-nisin freeze-dried bacteriocin-containing powder (PNBP) significantly reduced L. innocua on the cantaloupes by approximately 1.29, 1.09, and 1.68 log CFU/cm2, respectively. Compared to the controls, bacteriocin applications significantly reduced APC, yeast, and mold counts regardless of bacteriocin type. This study demonstrated that bacteriocins could reduce Listeria, aerobic bacteria, yeast, and mold counts on the cantaloupes surface; and that PNBP was more effective in reducing Listeria than NBP or PBP alone.