Submitted to: Journal of Food Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 4, 2003
Publication Date: June 1, 2004
Citation: Ukuku, D.O., Fett, W.F. 2004. Method of applying sanitizers and sample preparation affects recovery of native microflora and salmonella on whole cantaloupe surfaces. Journal of Food Protection. 67:999-1004. Interpretive Summary: There are no standardized methods for applying wash treatments to cantaloupes and for recovering surviving native microflora or Salmonella, a bacterial human pathogen, on melons after washing. Therefore, the microbial safety of fresh-cut melons prepared in the supermarket, at home or by the fresh-cut industry is a concern. Accordingly, we compared four washing methods (dipping, dipping with rotation, dipping with agitation, and dipping with rubbing) using chlorine or hydrogen peroxide, two recovery methods (stomaching and blending of rind plugs) and five selective recovery media for Salmonella. We found that washing with chlorine or hydrogen peroxide with agitation or by rubbing for 2 min can reduce the native microflora populations and Salmonella by 99.99%. This information will assist the industry to ensure microbiological safety of cantaloupes, and thereby, reducing the incidence of food poisoning outbreaks associated with cantaloupes.
Technical Abstract: Standardized methods for applying wash treatments to cantaloupes and for recovering surviving native microflora or Salmonella on inoculated melons after washing are lacking. Accordingly, the objectives of this study were to compare four washing methods (dipping, dipping with rotation, dipping with agitation, and dipping with rubbing) using 200 ppm chlorine or 5% H2O2, two recovery methods (stomaching and blending of rind plugs) and five selective recovery media for Salmonella. Whole cantaloupes were submerged in a cocktail of five strains of Salmonella (each at ~ 2 × 108 CFU/ml) for 10 min and allowed to dry for 1 h inside a biosafety cabinet and stored at 20oC for ~23 h prior to washing. The recovery of Salmonella from whole cantaloupe without washing averaged 5.09 log10 cfu/cm2 by blending and 4.30 log10 cfu/cm2 by stomaching for the five selective agar media. Microbial populations (Salmonella or the indigenous aerobic mesophilic bacteria, gram-negative bacteria, lactic acid bacteria, Pseudomonas spp., and yeast and mold) were not significantly (p>0.05) reduced by washing with water regardless of the treatment method employed. Washing with chlorine or H2O2 by dipping, with or without rotation for 2 min, also did not reduce microbial populations. However, populations of all classes of native microflora as well as Salmonella were significantly (p<0.05) reduced by sanitizer treatments (2 min) applied with agitation or by rubbing. In general, sanitizer treatments applied by rubbing resulted in greater log10 reductions (by up to 1.7 log10 unit) than for treatments applied with agitation. Populations of native microflora and Salmonella recovered from melon samples were higher (by up to 1.8 log10 unit) by blending compared to stomaching. In most instances, selective media used did not differ significantly (p>0.05) for recovery of Salmonella after washing treatments. Blending melon rind rather than stomaching should be used to estimate microbial populations attached on whole cantaloupe surfaces.