(25) Characterization of Volatile Biosynthesis in `Jonagold' Apples (Malus ×domestica Borkh.) during the Ripening Process

Abstract

The objective of the experiment was to determine developmental changes in major aroma profiles in `Jonagold' apple (Malus ×domestica Borkh.) and analyze climacteric fruit characteristics. Changes in internal ethylene production, respiration, skin color, texture, and aroma concentration were measured during maturation and ripening of `Jonagold' apple fruit. Patterns for skin color, starch, and internal ethylene content were typical for the variety. Volatile compounds and CO2 increased after a rapid increase in ethylene production. Total ester emission peak coincided with fruit softening. Hexyl acetate, 2-methylbutyl acetate, butyl acetate, and hexyl 2-methylbutanoate were found to be the major volatile compounds detected by GC/MS. Long chain esters, such as hexyl acetate and butyl acetate, contributed during the early stages of ripening and short chain esters such as n-propyl acetate and butyl propanoate increased later. Esters are formed by combining alcohol moiety with CoA derivative of fatty acid moiety by the action of alcohol acyl transferase (AAT). The alcohols butanol, 2-methylbutanol, propanol, and hexanol increased at an earlier developmental stage than the esters for which they acted as substrates.