Title: Inactivation of Salmonella on whole cantaloupe by application of an antimicrobial coating containing chitosan and allyl isothiocyanate Authors
Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 10, 2012
Publication Date: April 1, 2012
Citation: Chen, W., Jin, Z.T., Gurtler, J., Geveke, D.J., Fan, X. 2012. Inactivation of Salmonella on whole cantaloupe by application of an antimicrobial coating containing chitosan and allyl isothiocyanate. International Journal of Food Microbiology. 155:165-170. Interpretive Summary: Recently recalls due to cantaloupe contamination with Salmonella and Listeria have heightened public concern as to the microbiological safety of this fruit. An antimicrobial coating method was developed to decontaminate cantaloupes. The coating solutions with chitosan and allyl isothiocyanate killed more than 99.999 percent of Salmonella on the surface of cantaloupes and prevented them from recontamination. These results indicate that the application of an antimicrobial coating may be an effective method for decontamination of cantaloupes.
Technical Abstract: This study investigated the antimicrobial effect of a chitosan coating + allyl isothiocyanate (AIT) and nisin against Salmonella on whole fresh cantaloupes. Cantaloupes were inoculated with a cocktail of three Salmonella strains and treated with chitosan, chitosan + AIT, chitosan + nisin, and chitosan + AIT + nisin coatings. With AIT concentrations increasing from 10 to 60 ppm, the antibacterial effects of coating treatments against Salmonella increased. Chitosan coatings with 60 ppm AIT (chitosan+60AIT) reduced more than 5 log CFU/cm2 of Salmonella. The addition of nisin to the chitosan-AIT coating synergistically increased the antibacterial effect; coatings with nisin (25 mg/ml or 25000 IU/ml) + 30 ppm AIT resulted in a 4.8 log reduction of Salmonella. The chitosan + 60AIT coating significantly (p is less than 0.05) reduced populations of native bacteria on cantaloupes to ca. 2 log CFU/cm2 during the first 6 days and the populations remained the same through day 14 at 10C. The same coating treatment completely inactivated mold and yeast on cantaloupe at day 1 and no regrowth occurred up even after 14 days of storage. Scanning electron microscopy revealed that cell membrane damage and leakage of intercellular components occurred as a result of the chitosan-AIT coating treatments. No changes in overall appearance and color of cantaloupe rind and flesh due to coating treatments were observed during storage by visual evaluation. These results indicate that the application of an antimicrobial coating may be an effective method for decontamination of cantaloupes.