Volatile evolution, alpha-farnesene catabolism and superficial scald development in delicious apples

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Whiting, Matthew David

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University of Guelph

Abstract

Metabolism in scald-developing and scald-free apple fruits was compared. Fruit volatile analyses by solid-phase microextraction combined with gas chromatography identified approximately 3-fold less evolution of volatile esters and α-farnesene from scald-developing tissues compared to scald-free tissues. High performance liquid chromatography analyses of hexane-extractable components showed that scald-free tissues possess 3-times more α-farnesene compared to scald-developing tissues. α-Farnesene catabolism in vitro was induced by several active oxygen species (O\sb2\sp−, H\sb2O\sb2, and singlet oxygen), and apple membranes. Inhibition of α-farnesene catabolism by antioxidants (ascorbate, α-tocopherol, and diphenylamine) is related to the relative hydrophobicity of the antioxidant. In addition, no α-farnesene catabolites were identified during any experiment. These results suggest that (1) scald-developing tissues might possess reduced lipolytic enzyme activity resulting in generation of fewer volatile precursors (acetyl-CoA), and (2) levels of α-farnesene and its catabolites are unrelated to scald development.

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metabolism, scald-developing, scald-free, apple fruits, volatile esters, catabolism

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