Oxidation of Added Alcohol to Acid in Banana Pulp, and Specificity of Acid in its Esterification

Studies on Biosynthesis of Esters in Fruit Volatiles. Part 4

Abstract

When disks of banana pulp were incubated with vapor of alcohol (propyl-, iso-butyl-, butyl-, iso-amyl-, and amyl alcohol), they produced not only acetate ester of the alcohol, but also other ester with acids which were converted from added alcohols (propyl propionate, iso-butyl isobutyrate, butyl butyrate, iso-amyl iso-valerate, and amyl valerate). These indirect esterification of added alcohols occrred strongly with strait-chain alcohols and weakly with branched alcohols. When straight-chain acids were added to the disks of banana pulp, conversion rate to esters was also higher than the rate of branched acids. Since both butyryl CoA and iso-butyryl CoA showed similar extent of esterification, the difficulty of conversion of branched-chain acids to ester may be found in the step of acyl CoA formation. Above these results show one of the good explanations that banana volatile esters consist mainly of acetate and butyrate for acid moiety, iso-butyl alcohol and iso-amyl alcohol for alcohol moiety.