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2.G i G.1

2.2 i G.1

2.2 i G.1

Note: ND = not detected by plating.

a Values are means ± standard deviation of three experiments with duplicate determinations per experiment.

b Treatments applied for 3 min.

c Cocktail of Salmonella spp. containing S. Stanley H0558, S. Poona RM2350, and S. Saphra 97A3312. (Data from Ukuku and Fett [74].)

d Cocktail of L. monocytogenes containing strains Scott A., ATCC 15313, LM-4, and H7778. (Data from Ukuku and Fett [8].) e Data from Ukuku et al. [41].

Note: ND = not detected by plating.

a Values are means ± standard deviation of three experiments with duplicate determinations per experiment.

b Treatments applied for 3 min.

c Cocktail of Salmonella spp. containing S. Stanley H0558, S. Poona RM2350, and S. Saphra 97A3312. (Data from Ukuku and Fett [74].)

d Cocktail of L. monocytogenes containing strains Scott A., ATCC 15313, LM-4, and H7778. (Data from Ukuku and Fett [8].) e Data from Ukuku et al. [41].

Sapers et al. [38] reported reductions in the aerobic plate count on cantaloupe surface of less than 1 log when rind plugs were washed by immersion in 1000 ppm chlorine, 1% APL KLEEN 246 (an acidic detergent formulation supplied by Cerexagri; www.cerexagri.com), or 4% trisodium phosphate. Immersion of whole cantaloupes freshly inoculated with Salmonella spp. in 1000 ppm chlorine solution for 5 minutes resulted in population reductions of 3 logs for salmonella [39,40]; however, the reduction was only 2 logs when the treatment was applied 5 days after inoculation (Table 10.2). With a nonpathogenic E. coli (ATCC 25922), the reduction was greater than 4 logs with freshly inoculated melons but less than 1.5 logs when the treatment was applied 72 hours after inoculation [41]. However, with L. monocytogenes, the time interval between inoculation and treatment had no effect on treatment efficacy [8].

Barak et al. [42] obtained a 1 log reduction in the population of Pantoea agglomerans (a surrogate for S. Poona) on inoculated cantaloupe by immersion in 150 ppm sodium hypochlorite for 20 seconds, followed by a 2-minute cold water rinse. In studies with cantaloupes inoculated with E. coli O157:H7, Materon [37] reported reductions generally exceeding 5 logs from washing by immersing the melons for 1 or 10 minutes in solutions containing 200 ppm chlorine, 1.5% lactic acid, or 1.5% lactic acid + 1.5% hydrogen peroxide at 25 or 35°C. In view of the efficacy data obtained by other investigators, these extraordinary results are difficult to explain. It is possible that the recovery of attached bacteria from the melon surface by rubbing with a sponge was substantially less efficient than predicted by the investigator's validation procedure. Alternatively, the presence of residual lactic acid or hydrogen peroxide in the lowest dilutions plated may have been inhibitory to E. coli O157:H7 on Petrifilm™

The FDA advises consumers to wash melons with cool tap water with scrubbing but without use of soap or detergents immediately before eating. Consumers are also advised to wash cutting boards, utensils, and counter tops often using hot soapy water followed by diluted bleach as a sanitizer. Avoidance of cross contamination with meat, poultry, or fish is essential (www.fda.gov/bbs/topics/ANSWERS/2002/ANS01167.html/). Fresh-cut processing studies conducted by one of the authors clearly demonstrated the need to develop and rigorously adhere to a strict protocol for sanitizing knives, cutting boards, and other food contact surfaces and equipment to avoid cross contamination and achieve an acceptable product shelf life. Attention to detail was found to be critical [38].

While the literature on efficacy of washing melons is limited and contradictory, the overall trend suggests that microbial populations attached to melon surfaces can be reduced by several logs if sanitizers are applied by immersion of melons in the solution with scrubbing and/or agitation. Treatment efficacy may be reduced if the time interval between contamination and washing is greater than one day, a likely situation with preharvest contamination. Since human pathogens transferred from the rind to the flesh are capable of growth on the flesh surface, the presence of even small numbers of survivors following a sanitizing wash represents a significant risk to consumers. Consequently, there is a great need for better methods of disinfecting melons so that this risk is minimized.

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