A 12-day shelf life study was conducted at 7°C to determine whether Escherichia coli O157:H7 on spinach can be controlled effectively by selected strains of lactic acid bacteria (LAB) alone or in combination with chlorine as a multihurdle intervention. The multihurdle intervention
consisted of both LAB and chlorine and was applied to spinach as a rinse and evaluated in comparison to LAB alone and chlorine and water rinses. Reductions achieved by all treatments also were compared with those observed for an inoculated control. The spinach was inoculated by submersion
in a solution containing an E. coli O157:H7 cocktail at 1.0 × 106 CFU/ml. LAB were applied postharvest at a concentration of 2.0 × 108 CFU/ml, and 200 ppm of chlorine was used for the chlorine rinse. All spinach samples were packaged in commercial packaging,
held in a retail display case, and tested for E. coli O157:H7 on days 0, 1, 3, 6, 9, and 12 using the Neo-Grid filtration system and CHROMagar. Survival of LAB throughout the shelf life also was determined. Significant reductions in pathogen populations were achieved by water (P
= 0.0008), LAB (P < 0.0001), chlorine (P < 0.0001), and multihurdle (P < 0.0001) treatments when compared with controls. The multihurdle treatment produced the greatest reduction from control populations, a reduction of 1.91 log CFU/ml. This reduction was significantly
greater than that achieved with water (P < 0.0001), LAB (P = 0.0025), and chlorine (P < 0.0001) alone, indicating that the application of chlorine and LAB is most effective as a combination treatment. The results obtained from this study indicate that the industry
standard chlorine wash may be more effective when applied in combination with LAB.
Document Type: Research Article
Department of Animal and Food Sciences, Texas Tech University, Box 42141, Lubbock, Texas 79409-2141, USA
Publication date: February 1, 2010
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