Ester biosynthesis in relation to harvest maturity and controlled-atmosphere storage of apples
1995
Fellman, J.K. | Mattheis, J.P.
Volatile esters from acids and alcohols are important components of flavor and odor perception in apples. The relationship between alcohol acetyl CoA transferase (AAT) acetate ester-forming activity, non-ethylene volatile emission, and flesh volatile content of apples during the maturation period and after removal from controlled-atmosphere (CA) storage was investigated. At the appropriate times, apples were sampled for volatile compounds in the headspace and flesh using solid sorbent along with purge-and-trap capillary gas chromatography. Development of a spectrophotometric assay for AAT activity using 5,5'-dithiobis-(2-nitrobenzoic acid) to react with free CoA liberated in the esterification reaction is reported. Subsequently, acetate ester forming activity was assayed on partially-purified extracts of cortical tissue. Ester forming activity is apparently sensitive to oxygen atmospheres as well as stage of harvest maturity. Upon removal from low-oxygen atmospheres, AAT activity is initially depressed but recovers to levels approaching that of air-stored controls. Flesh concentrations of acetate esters, major contributors to apple flavor, are related to levels of enzymatic activity in the tissue. It is important to identify preclimacteric harvest windows that include information concerning the biosynthesis of odor and flavor volatile components in order to ensure maximum quality attributes in apples stored for long periods of time.
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