The Use of Vinegar Vapor to Reduce Postharvest Decay of Harvested Fruit

Abstract

Vapors of several common vinegars containing 4.2% to 6.0% (= 2.5 to 3.6 mol·L -1 ) acetic acid effectively prevented conidia of brown rot [ Monilinia fructicola (G. Wint.) Honey], gray mold ( Botrytis cinerea Pers.:Fr.) , and blue mold ( Penicillium expansum Link) from germinating and causing decay of stone fruit ( Prunus sp.), strawberries ( Fragaria × ananassa Duchesne), and apples ( Malus × domestica Borkh.), respectively. Fruit were fumigated in 12.7-L sealed containers in which vinegar was dripped on to filter paper wicks or vaporized by heating from an aluminum receptacle. Vapor from 1.0 mL of red wine vinegar (6.0% acetic acid) reduced decay by M. fructicola on `Sundrop' apricots ( Prunus armeniaca L.) from 100% to 0%. Similarly, vapor from 1.0 mL of white vinegar (5.0% acetic acid) reduced decay in strawberries by B. cinerea from 50% to 1.4%. Eight different vinegars, ranging from 4.2% to 6.0% acetic acid, of which 0.5 mL of each vinegar was heat-vaporized, reduced decay by P. expansum to 1% or less in `Jonagold' apples. The volume of heat-vaporized white vinegar (5.0% acetic acid) necessary to reduce decay by P. expansum on `Jonagold' apples to zero was 36.6 μL·L -1 of air. Increasing the number of conidia on the apple surface reduced the effectiveness of vinegar vapor. The number of lesions caused by P. expansum on `McIntosh' apple decreased exponentially with increasing time of fumigation, approaching zero after about 6 hours. These results suggest that vinegar vapor could be an effective alternative to liquid biocides such as sodium hypochlorite for sterilization of surfaces contaminated by conidia of fungal pathogens.