The application of an effective antibacterial agent to the surface of whole melons may be desirable. There are several reports that nisin, used in combination with a chelating agent, exhibits a bactericidal effect towards both Gram-positive and Gram-negative bacteria [49-53]. Treatment of whole and fresh-cut cantaloupe and honeydew melon with nisin-EDTA significantly reduced the natural microflora and extended the shelf life [17]. We also found that sodium lactate was inhibitory to the native microflora on melons [19]. The antimicrobial activity of lactic acid is due both to a lowering of pH and to disruption of the outer membrane of Gram-negative bacteria [54]. Application of lactic acid (2%) as an antimicrobial spray applied to animal carcasses to reduce surface populations of E. coli O157:H7 and salmonella has been reported [55]. Sorbic acid (pKa of 4.76) and its potassium salt are widely used in foods at a concentration of 0.02 to 0.3% to inhibit yeasts and molds, but they also have antibacterial activity [56]. However, washing inoculated whole melons with sodium lactate (2%), potassium sorbate (0.02%), EDTA (0.2 M), or nisin (50 ^g/ml), when tested individually, did not cause significant (p > 0.05) reductions in salmonella populations. Treatment of whole cantaloupe with nisin-EDTA may lead to both increased shelf life and a reduced risk of foodborne illness due to contamination with salmonella or other pathogens [17].

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