Survival of Penicillium expansum and patulin production on stored apples after wash treatments

Penicillium expansum is a widespread fungus found on apples that causes fruit decay and may lead to production of a toxic secondary metabolite, patulin. This study was undertaken to evaluate the effectiveness of several chemical sanitizers against P expansum NRRL 2304 and to establish sanitizing wash treatments that would inhibit P expansum growth and subsequent patulin production on Empire apples destined for cider. Wash treatments included 200 ppm NaOCl, 1% StorOx(R), 0.5% potassium sorbate, 300 PPM SO2, and 0% to 5% acetic acid. Spores of P expansum or inoculated apple slices were dipped in sanitizing wash solution for 5 min, and mold growth and patulin production was monitored on subsequent storage. It was found that 0.5% potassium sorbate and 300 ppm SO2 did not affect mold survival or patulin production; 1% StorOx(R) was effective against mold spores in solution (4 log Most Probable Number destruction of spores), but there was no significant reduction in spore count when the same solution was used to sanitize mold-inoculated apple discs. Washing with 200 ppm NaOCl delayed growth of P expansum on inoculated apple discs but failed to completely inhibit patulin production. Acetic acid solution (2% to 5%) was the most efficient chemical against R expansum. A wash treatment with greater than or equal to2% acetic acid for more than 1 min is recommended to completely inhibit growth of P expansum and subsequent patulin production on apples destined for cider.