Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2005
Publication Date: 7/15/2005
Citation: Bari, M.L., Kawasaki, T., Inatsu, Y., Ukuku, D.O., Isshiki, K., Kawamoto, S. 2005. Combined action of nisin and pediocin with sodium lactate, citric acid, phytic acid and potassium sorbate and edta in reducing listeria monocytogenes population of inoculated fresh-cut produce. Journal of Food Protection. 68(7):1381-1387.
Interpretive Summary: There are many reports of disease due to consumption of fresh-cut produce that were contaminated with bacterial human pathogens. The inability of chlorine to completely inactivate human bacterial pathogens on whole and fresh-cut produce and the possible formation of carcinogenic chlorinated byproducts suggest the need for other antimicrobial washing treatments. In order to improve the microbial quality of cabbage and broccoli as well as mung bean sprouts, the use of a combination of nisin or pediocin (natural bacterial products) with citric acid, phytic acid, sodium lactate, potassium sorbate and EDTA which facilitates entry of nisin or pediocin into bacteria for reducing native microflora of cabbage, broccoli and mung bean sprouts and the inoculated population of L. monocytogenes was investigated. Cabbage, broccoli and mung bean sprouts inoculated with L. monocytogenes were washed with nisin or pediocin plus all the acids listed above. Microbial quality of the fresh-cut vegetables was evaluated. Both natural bacterial products individually or in combination with the acids substantially reduced the populations of L. monocytogenes on fresh-cut vegetables. All treatment combinations were not effective in reducing Listeria populations on mung bean sprouts. The results of this study indicate that treatments with nisin or pediocin plus phytic acid after fresh-cut processing would improve the microbial quality of fresh-cut cabbage and broccoli.
Technical Abstract: Nisin (50 µg/ml) or pediocin (100 AU/ml) individually or in combination with sodium lactate (NaL) (2%), potassium sorbate (KS) (0.02%), phytic acid (0.02%), and citric acid (10 mM) were tested as sanitizer treatments for reducing L. monocytogenes on cabbage, broccoli and mung bean sprouts. Cabbage, broccoli and mung bean sprouts were inoculated with a five strain cocktail of L. monocytogenes to give 4.61 log10 CFU/g, 4.34 log10 CFU/g and 4.67 log10 CFU/g, respectively. Inoculated produce were left at room temperature (25°C) for up to 4 h before antimicrobial treatment. Washing treatments were applied to inoculated produce for 3 min and surviving bacterial populations were determined. The effect of the washing treatments on L. monocytogenes population on the produce was determined. When tested alone all compounds resulted in 2.20 to 4.35 log10 reductions of L. monocytogenes on mung bean, cabbage and broccoli respectively. The combination treatments nisin- phytic acid and nisin-pediocin- phytic acid, gave significant (p < 0.05) reductions of L. monocytogenes on cabbage and broccoli but not on mung bean sprouts. Pediocin treatment alone or in combination with any of the organic acid tested was more effective in reducing L. monocytogenes population than the nisin treatment. Although none of the combination treatments completely eliminated the pathogen on the produce yet the results suggest that such treatments can be used to ensure the microbial quality of fresh-cut cabbage, brococoli and mung bean sprouts.