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.

Impact of UV-C light on safety and quality of fresh-cut melon

“…In addition, after 4 days of storage, melon flavour was perceived as more intense than that of the freshly prepared sample (score 5). As previously reported (Beaulieu, 2007;Lamikanra et al, 2002), the volatile aroma profile in cut Cantaloupe melon can be strongly affected by UV irradiation. Terpenoids, such as geranylacetone, β-cyclocitral, β-ionone among others, can be significantly increased following their synthesis in direct response to UV light stress.…”

“…It can be hypothesised that a low energy UV-light treatment, such as that applied in this paper, could contribute to enhance the overall terpenoid concentration, giving reason to a higher flavour score of the fresh-cut melon in the first days of storage. However, if endogenous terpenoid concentrations become excessively high, offflavour may result (Beaulieu, 2007). To check for alteration of the desirable volatile aroma profile, the judges were asked to indicate the eventual presence of off-flavours in the UV-C treated and control samples stored for increasing time.…”

UV-B-induced changes of volatile metabolites and phenolic compounds in blueberries (Vaccinium corymbosum L.)

“…Moreover, the stimulation of terpene biosynthesis by stress e.g. herbivory attack/wounding or oxidative stress is well known (Arimura, Kost, & Boland, 2005;Beaulieu & Usda, 2007). Due to the fact that UV-B radiation is able to destroy cellular structures it is supposed that this kind of ''wounding'' influences the formation of monoterpenes, too.…”

The molecular and biochemical basis for varietal variation in sesquiterpene content in melon (Cucumis melo L.) rinds

“…Their respective gene products are able to catalyze the conversion of farnesyl diphosphate to (E,E)-a-farnesene and (E)-bcaryophyllene, respectively, when expressed in E. coli, (Mercke et al 2004). Although sesquiterpenes have been found in the flesh of melon fruits (Horvat and Senter 1987;Homatidou et al 1992;Beaulieu and Grimm 2001;Shalit et al 2001;Aubert and Bourger 2004;Beaulieu 2007) little is known about the composition in rinds and the variation within cultivars as well as the factors and biological processes that control their occurrence and accumulation. Here we describe the identification, characterization and molecular regulation of two novel members of the Tps family that are primarily expressed in ripe melon rind tissues: CmTpsNY and CmTpsDul.…”