Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/18/2005
Publication Date: 9/1/2005
Citation: Rudell Jr, D.R., Mattheis, J.P., Fellman, J.K. 2005. Relationship of superficial scald development and a-farnesene oxidation to reactions of diphenylamine and diphenylamine derivatives in 'Granny Smith' apple peel. Journal of Agricultural and Food Chemistry. Interpretive Summary: Superficial scald is a peel disorder of apples that can render the fruit unmarketable. Pre-storage treatment of apples with the antioxidant diphenylamine is a common practice for controlling scald. The present study evaluates the scald control mechanism of diphenylamine using treatment of apples with diphenylamine and diphenylamine derivatives and subsequent analysis of their metabolism as well as that of a peel component, a-farnesene, that plays a role in development of the disorder. Scald was ameliorated only by derivatives substituted with certain functional groups and only in specific positions. a-Farnesene oxidation correlated with decreasing scald efficiency of the treatment. This evidence indicates that scald control provided by diphenylamine depends on the availability of specific positions on the molecule to allow for donation of hydrogen to "trap" reactive compounds thought to provoke scald.
Technical Abstract: 'Granny Smith' apple fruit, treated at harvest with aqueous emulsions containing diphenylamine (DPA) and DPA derivatives, were evaluated for superficial scald after 6 months of cold storage plus 0 or 7 days at 20 deg C. Metabolism of these derivatives and a-farnesene oxidation were also evaluated after 6 months. Derivatives substituted in the para position controlled scald unlike those substituted in the amino, ortho, or meta positions. The extent of scald control was also dependent on the chemical nature of the functional group used to derivatize DPA. Hydroxylation of DPA and DPA derivatives during storage was not associated with scald control. Methoxylated DPA derivatives produced during storage resulted from O-methylation of C-hydroxylated derivatives rather than C-methoxylation of DPA. N-nitorsodiphenylamine provided partial scald control possibly resulting from its degradation to DPA indicating the amino hydrogen of DPA may be crucial for scald control. This is supported by the fact that increased a-farnesene oxidation accompanied increased scald incidence. Results suggest that functional group position and chemical properties both contribute to the efficacy of DPA derivatives for scald control.