Fumigation with acetic acid vapor to control decay of stored apples

Abstract

Introduction. Apples are potentially subject to blue mold decay caused by Penicil- lium expansum if stored at 1 °C for three or more months or if wounded during handling. Results from trials with apples contaminated with conidia of P. expansum and fumigated in small cham- bers with acetic acid (AA) vapor indicated that fruit could be sterilized to reduce decay without effect on fruit quality. The objective of this study was to determine if larger quantities of apples treated with AA vapor would have less decay after storage and/or wounding. It was also impor- tant to determine if fumigation would affect apple quality and aroma. Materials and methods. Apple cultivars were harvested at commercial maturity for use in AA fumigation trials. Apples arti- ficially or naturally contaminated with conidia of P. expansum were fumigated with AA vapor in a 1 m3 gas tight chamber at 10 °C for 1 h to 24 h or dipped in 450 μg thiabendazole 〈 L -1 solu- tion. Fruit fumigated in standard wooden or plastic apple boxes, or small wooden bins were either wounded and evaluated for decay after a week at 20 °C or stored at 1 °C for three or more months and evaluated for decay. Then apple quality was assessed. Results. Apples naturally contaminated with Penicillium spp. that had been stored at 1 °C in air storage and treated with AA vapour had 50% less decay than the control fruit. In another experiment, AA fumigation was as effective as thiabendazole in reducing decay. AA fumigation reduced decay of fruit coming out of storage for apples stored for 3 months, and a second AA fumigation reduced infection of wounds on these same apples. AA fumigation before storage did not affect apple quality or vinegar aroma. Discussion. AA fumigation showed great potential for reducing decay in stored apples. It could be used as an organic alternative to synthetic fungicides for control of blue mold decay.