Imo‐shochu is a Japanese traditional spirit made from sweet potatoes. Characteristic volatile compounds in imo‐shochu are mainly derived from the sweet potato and its flavour significantly depends on the quality and cultivar of sweet potato used. Thus, the effects of the cultivation period of sweet potatoes on sensory characteristics and composition of volatile compounds of imo‐shochu were investigated. Sweet potatoes (cv. Koganesengan) used in this study were harvested at 120, 150 or 180 days after planting, and each sample was used to prepare imo‐shochu. The imo‐shochu samples were evaluated by eight panellists in a blind study, who ranked them on the basis of various odour and taste attributes. Rank sums were calculated and data were analysed using the Friedman test. The compositions of the volatile compounds in the imo‐shochu samples were analysed using gas chromatography–mass spectrometry (GC‐MS). Sensory evaluations showed that a longer cultivation period of the sweet potatoes enhanced the floral aroma and characteristic taste of imo‐shochu. In addition, imo‐shochu prepared with the sample cultivated for 150 days was evaluated to have a sweeter taste than that prepared with the other samples. The GC‐MS analysis showed that imo‐shochu prepared with the sample cultivated for 180 days contained a lower concentration of monoterpene alcohols, but higher concentrations of β‐damascenone, rose oxide, and fatty acid esters than the imo‐shochu prepared with the sample cultivated for 120 days. These differences in the composition of the volatile compounds affected the sensory qualities of the imo‐shochu. Copyright © 2016 The Institute of Brewing & Distilling

The study investigated the distribution of monoterpene glycoside in a sweet potato tuber. The steamed tuber was divided into 11 parts and powdered after being freeze-dried. Monoterpene glycosiderich fractions were extracted from the freeze-dried samples using methanol. This fraction was subjected to GC-MS analyses to quantitative liberated monoterpene alcohol before and after enzyme treatment. Nerol and geraniol were liberated efficiently by β-glucosidase while linalool and α-terpineol were done so by β -primeverosidase. However, citronelool was not liberated by either enzyme treatment. These results showed that the monoterpene alcohols except for citronelool existed as glycosides in sweet potato tuber. Consequently, nerol, geraniol, linalool, and α-terpineol contents were compared between different parts of the tuber. The greatest amount of nerol was liberated from the center part of tuber, comprising 38% of the total nerol content. Meanwhile, geraniol, linalool, and α-terpineol were mainly distributed to the skin part, respectively comprising 37% , 66% and 60% . Our results further showed that the center part of the tuber had relatively small amounts of linalool and α-terpineol; in particular, linalool was not found in the center part. These results showed that the distribution of monoterpene glycoside differed among the tuber tissues. Key words：

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