Characteristic Pattern of Aroma Ester Formation from Banana, Melon, and Strawberry with Reference to the Substrate Specificity of Ester Synthetase and Alcohol Contents in Pulp.

Abstract

Volatile esters produced from banana, melon and straw berry fruits were investigated by analyzing head-space gas. In the case of banana, ethyl and butyl esters were found to be main esters and isobutyl and isoamyl esters followed. In melon, ethyl esters were predominant, and in strawberry methyl esters were mainly observed. In all cases of these fruits, acetate and butyrate were the main esters. Alcohol acyl CoA transferase (ester synthetase) was extracted from these fruits. A high reactivity of the enzyme was observed when propyl, isobutyl, butyl and isoamyl alcohols were used as the substrates, whereas a low reactivity was observed when methyl, ethyl and amyl alcohols were used. The enzyme from banana and melon reacted well with acetyl CoA, propionyl CoA and butyryl CoA, while the enzyme from strawberry reacted well with valeryl CoA besides the above three acyl CoAs. Branched chain acyl CoAs (isobutyryl and isovaleryl) were poor substrates for the enzyme. Ethyl alcohol was predominant among alcohols observed in pulp of banana and melon fruits, whereas methyl alcohol was predominant in strawberry. From these observations, it may be concluded that esters produced from fruits have alcohol moieties reflected alcohol contents in the pulps and have acid moieties reflected acyl CoA specificity of the ester synthetase.