Submitted to: Journal of Food Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/11/2005
Publication Date: 5/4/2005
Citation: Sapers, G.M., Annous, B.A., Jones, D.M., Burke, A.M. 2005. Improved recovery procedure for evaluation of sanitizer efficacy in disinfecting contaminated cantaloupes. Journal of Food Science. 70(4): M242-M247. Interpretive Summary: Numerous outbreaks of foodborne illness associated with Salmonella contamination of cantaloupes and detection of Salmonella in surveys of imported and domestic cantaloupes have focused the attention of regulatory agencies and researchers on the problem of melon decontamination. To conduct research in this area, it is necessary to artificially contaminate cantaloupes with a target organism in a manner which simulates natural contamination, and to use sampling and recovery methods that permit accurate enumeration of the target bacteria. Our objective was to develop improved recovery methodology for use in research on the efficacy of disinfection treatments for contaminated cantaloupes. The effects of inoculation method, melon post-inoculation storage, and sampling method on recovery of Salmonella Poona and E. coli NRRL B-766 (a surrogate for S. Poona) from inoculated melons were determined. Less than 1% of the cells applied to each spot could be recovered. The population of Salmonella on cantaloupe surface increased about one hundred-fold during post-inoculation storage at 20 C, while E. coli showed no growth. Improved methodology for sampling the entire rind of contaminated cantaloupes with an electric peeler rather than using numerous small plugs of rind was validated with both organisms. Estimates of the attached microbial populations obtained with the new sampling methodology were not significantly different from those obtained by blending rind plugs taken from multiple sites on the melon surface, the procedure used in previous studies, but the new procedure was simpler and substantially less time consuming. Use of the new procedure would enable investigators to design melon experiments with more treatment conditions or greater numbers of samples to improve the value and reliability of the experimental results.
Technical Abstract: Fresh and fresh-cut cantaloupes have been associated with numerous outbreaks of salmonellosis. Sampling of potentially contaminated melons is complicated by the inefficiency of recovering attached bacteria by rinsing procedures and the difficulty in sampling and homogenizing the large mass of most melons. Improved methodology for recovering microbial contaminants from cantaloupe surfaces is needed. Recovery of bacteria from the entire rind of cantaloupes, obtained with a mechanical peeler, and use of a new method for calculating melon surface area were investigated using melons spot or dip inoculated with suspensions of Salmonella Poona or E. coli NRL B-766 containing 9-10 log CFU/mL. Attached population levels of 5-6 log CFU/spot were recovered, representing less than 1% of the cells applied to each spot. About 2 logs of growth of Salmonella, but not E. coli, was found during post-inoculation storage at 20 C. Estimates of the attached microbial populations obtained with the new sampling methodology were not significantly different (p<0.05) from those obtained by blending replicate rind plugs taken from multiple sites on the melon surface, the procedure used in previous studies, but the new procedure was simpler and substantially less tedious. Recovery was the same by both procedures for dip- and spot-inoculated samples and for post-inoculation holding times up to 72 h. Use of the new procedure will enable investigators to design melon experiments with more treatments or greater replication.