Role of Ethylene in Aroma Formation in Cantaloupe Charentais Melon

Abstract

The headspace of ACC oxidase antisense hybrid Cantaloupe Charentais melon has been sampled, analysed by GC-MS and compared to that of the corresponding nontransformed hybrid fruit. The main volatiles extracted in non-transformed hybrids fruit were esters, with an overwhelming contribution by acetates. In antisense hybrid fruit the total volatiles were 60% to 85% lower than those of the non-transformed hybrids. Odour values of major esters were calculated. The most potent odorants were ethyl butanoate and branched-chain esters such as ethyl 2-methylpropanoate and ethyl 2-methylbutanoate. In transformed melons, potent odorant levels were less than 5% those of non-transformed hybrids. By contrast, volatiles with low odour values such as 2-methylpropyl acetate and 2-methylbutyl acetate were a half to a fifth those of nontransformed hybrids. Analysis of the biosynthetic pathways of the branched-chain esters that have valine and isoleucine as precursors demonstrates that ethylene specifically controls the production of the most potent odorants.