Reduction of microbial populations on prunes by vapor-phase hydrogen peroxide

Vapor-phase hydrogen peroxide (VPHP) was used to disinfect prunes. Concentrated hydrogen peroxide solution (35%, wt/wt) was volatilized into a stream of dried air to approximately 3.1 mg/l (wt/vol) of hydrogen peroxide. Dried prunes obtained from commercial dehydrators were treated with VPHP and compared to untreated prunes. Microbial populations were determined for treatment comparisons. Untreated dried prune microbial populations were 155, 107, and 111 CFU/g of prunes on aerobic plate count agar, potato dextrose agar, and dichloran rose bengal agar, respectively. In contrast, VPHP-treated prune microbial populations were reduced to near zero on all media after 10 minutes of VPHP exposure. The color of prunes exposed for 20 min or longer, however, showed oxidation damage. No hydrogen peroxide residues were detected 90 days after treatment.