HEXANAL VAPOR ACTS AS RESIDUELESS ANTIFUNGAL AGENT THAT ENHANCES AROMA BIOSYNTHESIS IN APPLE FRUIT

Abstract

Hexanal vapor inhibited hyphal growth of Penicillium expansum Link, and Botrytis cinerea Pers, on PDA media and on apple slices. After 48 hours exposure to 100 μl.liter -1 (ppm) hexanal, the hyphal growth of both fungi was approximately 50% that of untreated controls. At a concentration of 250 μl.liter -1 (ppm), neither fungus grew during the treatment period; however, some growth of both fungi occurred 120 hours after treatment. At concentrations of hexanal vapor of 450 μl.liter -1 (ppm) or more, the growth of both fungi ceased and the organisms were apparently killed, neither showing regrowth when moved to air. When fungi were allowed to germinate and grow for 48 hours in hexanal-free air, a subsequent 48-hour exposure to 250 μl.liter -1 (ppm) hexanal slowed colony growth relative to controls for several days and a 48-hour exposure to 450 μl.liter -1 (ppm) stopped growth completely. Concentrations of hexanal that inhibited fungal growth on PDA also retarded decay lesion development on 'Golden Delicious' and on 'Jonagold' apple slices. Hexanal treatment stimulated aroma volatile production in 'Jonagold' and 'Golden Delicious' apple slices with hexanol and hexylacetate production strongly enhanced after 20-30 hrs of treatment. A small amount of butylhexanoate and hexylhexanoate production was also noted.