Is the bitterness of the two-step fermentation tea "Goishi tea" caused by cyclic dipeptide?

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K05864
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 38050:Food sciences-related
• Research Institution: Kochi University
• Principal Investigator: Ukeda Hiroyuki 高知大学, その他部局等, 理事・副学長 (60184991)
• Co-Investigator(Kenkyū-buntansha): 島村 智子 高知大学, 教育研究部総合科学系生命環境医学部門, 教授 (50350179)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: 後発酵茶 / 碁石茶 / 環状ジペプチド / 二次機能 / 苦味 / カテキン

Outline of Final Research Achievements

This research was conducted to elucidate the bitter taste factor and other substances involved in the taste of Goishi tea, a traditional two-step fermented tea produced in Otoyo-cho, Nagaoka-gun, Kochi. During this research period, it was elucidated that the formation mechanism of cyclic dipeptides in fermented foods such as Goishi tea, developed a simultaneous determination method for proline-containing cyclic dipeptides abundant in fermented foods, and elucidated taste-related substances using taste sensors. Finally, we conclude that the mechanism for the development of bitterness in Goishi tea differs from that of green tea and involves proanthocyanidins, a catechin polymer, in addition to amino acids, cyclic dipeptides, and peptides.

Free Research Field

食品化学

Academic Significance and Societal Importance of the Research Achievements

碁石茶は世界的に見ても珍しい二段階発酵茶であり歴史的価値も高い伝統食品である。近年、その生体調節機能に関する研究は多く実施されてきたが、食品の根幹ともいえる風味に関する学術研究は乏しい状況にあった。本研究は、碁石茶独特の風味を化学的な成分分析と味覚センサーを用いた客観的官能評価を組み合わせて紐解いたものであり、伝統食品に新たな科学的根拠を付与したと言える