Free and glycosidically bound monoterpene alcohols in Qimen black tea

An extraction and analysis method to determine the free and bound monoterpene alcohols in Qimen black tea was developed, and the varietal and seasonal changes in both free and bound monoterpene alcohols were investigated. The contents of the flavour components released from the bound forms increased greatly after addition of the crude enzyme, which was extracted from fresh tea leaves, and incubated at 37 °C for 10 h. Most of the b/f values of monoterpene alcohols, the ratios of bound to free forms, were greater than 1, indicating that the bound forms were in higher concentrations than the corresponding aglycones in fresh tea leaves. Geraniol was the highest among the monoterpene alcohols both in the amount released from the bound form and the b/f value. This indicated that the crude enzyme used in this experiment was very effective for the release of geraniol. The sequence of the contents of both bound and free flavours in different seasons was, generally: spring > summer≥autumn. Both forms of monoterpene alcohols exhibited a marked decrease in concentration in summer and autumn compared with those in spring.