Quantification of α-Farnesene and Its Conjugated Trienol Oxidation Products from Apple Peel by C₁₈-HPLC with UV Detection

Abstract

Conjugated triene oxidation products of the sesquiterpene α-farnesene are thought to induce development of the storage disorder superficial scald. A C18-HPLC method was devised which allows simultaneous quantification of α-farnesene and its major oxidation product, a conjugated trienol, in hexane extracts of apple peel using UV detection at 232 and 269 nm. Identification of the compounds was confirmed by UV spectrometry, HPLC with diode array detection, and GC−MS. Apples of high (Granny Smith, GS), moderate (Red Delicious, RD), and low (Gala) susceptibility to scald were stored for up to 6 months at 0 °C under 1.5, 3, or 100% oxygen or in air. Peel samples were analyzed for α-farnesene and conjugated trienol content, which correlated well with scald susceptibility and occurrence. Levels of both sesquiterpenoids were ≥20-fold higher in GS than in Gala. Storage under low (1.5 or 3%) oxygen decreased farnesene and trienol levels in each cultivar. Two lots of RD fruit harvested 1 week apart differed markedly in farnesene and trienol production; fruit from the earlier harvest had higher levels of both and developed scald, whereas fruit from the later harvest did not scald. These results support the proposal that scald susceptibility of apple cultivars is a function of farnesene production and its oxidation to conjugated trienols. Keywords: α-Farnesene; conjugated triene; C18-HPLC; apple; storage; scald