Effect of UV Irradiation on Cut Cantaloupe: Terpenoids and Esters

Abstract

Recent studies demonstrated that ultraviolet (UV) radiation enhanced terpenoids and decreased esters in thin-sliced cantaloupe. In preliminary studies treating fresh juices with UV, terpenoid compounds that normally were not isolated, or found in minute quantities, were elevated and only low molecular weight alcohols, ketones, and aldehydes decreased. Subsequently terpenoid induction/oxidation in UV-treated cut cantaloupe was reinvestigated. UV exposure increased the concentrations of terpenoids in cantaloupe tissue. However, UV exposure alone was not the sole factor responsible for enhanced terpenoids. UV-enhanced terpenoid production appears to be both cultivar- and maturity-dependent. Concomitant decreases in the ester content of UV-treated samples occurred using a previously published system. Yet, we established that almost identical ester losses occurred in thinly sliced laminar tissue receiving 60 min UV or air exposure in an open system. Tissue samples that were exposed to UV in a closed system often did not suffer correspondingly equal ester loss. Marked tissue warming (4.3 +/- 0.5 degrees C in 60 min) occurred during UV treatments in thin-sliced tissue. Ester loss from cantaloupe tissue was caused by the experimental procedure, but not by UV treatment per se. These findings are supported by the observation that UV is not responsible for chemical transformations to ester bonds, esterase, and lipase decrease in stored cut cantaloupe, and no lipid oxidation volatiles were observed in thin-sliced control tissue, while oxidized terpenoids were recovered. Information gathered indicates that improper cutting, handling, sanitation treatment, and storage can radically alter the desirable volatile aroma profile in cut cantaloupe, and potentially lead to decreased consumer acceptance.