Changes in the volatile composition of yuzu (Citrus junos Tanaka) cold-pressed oil during storage

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 degrees C were investigated after 1, 3, 6, 9, and 12 months. Major qualitative changes were found after 12 months at 20 degrees C. Total monoterpene hydrocarbons underwent a large decrease (from 93.3 to 37.7%), with major loses of limonene, gamma-terpinene, myrcene, and alpha-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 degrees 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.