Changes in the Volatile Composition of Yuzu (<i>Citrus </i><i>junos</i> Tanaka) Cold-Pressed Oil during Storage

Abstract

The changes of 34 components constituting a relative 97.6% of the total volatiles of yuzu (Citrus junos Sieb. ex Tanaka) cold-pressed peel oil and the possible artifacts during storage at −21, 5, and 20 °C were investigated after 1, 3, 6, 9, and 12 months. Major qualitative changes were found after 12 months at 20 °C. Total monoterpene hydrocarbons underwent a large decrease (from 93.3 to 37.7%), with major loses of limonene, γ-terpinene, myrcene, and α-pinene, while notable increases occurred in p-cymene as well as the monoterpene alcohols (from 2.1 to 13.2%). Bicyclogermacrene, the main sesquiterpene hydrocarbon of the fresh oil (1.0%), was virtually depleted. Sesquiterpene alcohols were formed as dominant artifacts (36.1%) and constituted the second most abundant volatile group of the oil after the monoterpene hydrocarbons. (−)-Spathulenol (decahydro-1,1,7-trimethyl-4-methylene-1H-cyclopropylazulen-7-ol) was the main artifact among the 14 identified. The alcohol constituted the second major component of the oil after limonene from the ninth month and accounted for more than 75% of the sesquiterpenic alcohols at 20 °C. The spathulenol was found for the first time to be an artifact in yuzu oil. The compound could be a useful index for monitoring the quality and freshness of yuzu flavor during storage. Keywords: Citrus junos Sieb. ex Tanaka; cold-pressed oil; volatile component; storage time; storage temperature; relative composition; sesquiterpenes; artifact; spathulenol