The effect of harvest date on aroma compound production from ‘Golden Delicious’ apple fruit and relationship to respiration and ethylene production

Abstract

The maturity of apple fruit at harvest was examined as a factor affecting later flavour development. Respiration, ethylene production and aroma compound emanation at 20 °C from ripening ‘Golden Delicious’ apple fruit harvested at different stages of maturity and their changes during ripening were studied. Volatile compound production was highly maturity-dependent and closely related to the changes in the respiratory rate and ethylene production. Earlier-harvested fruit (4 weeks ahead of the climacteric rise) had reduced respiration, and ethylene production, with lower and later total aroma synthesis than that for optimal-harvested fruit. Among the 36 aroma compounds identified by GC-MS, four flavour and character impact compounds were examined in detail. The onset of production and rates of synthesis of butylacetate, hexylacetate, 2-methylbutylacetate and ethyl-2-methylbutanoate during maturation and ripening were determined. The production trends of straight-chain (butylacetate and hexylacetate) and branched-chain (2-methylbutylacetate and ethyl-2-methylbutanoate) volatile compounds were similar to that of total aromas, except for a later increase in ethyl-2-methylbutanoate. As fruit development approached optimal harvest date for fruit quality, respiration, ethylene- and aroma production occurred with less of a delay reaching greater maximum levels. It is suggested that fundamental physiological processes such as respiration and ethylene production may be limiting factors for volatile production in earlier-harvested fruit.