Chen Lin, Wang Huajie, Ye Yang, Wang Yuefei, Xu Ping
Institute of Tea Science, Zhejiang University, Hangzhou 310058, China.
Tea Research Institute, Chinese Academy of Agricultural Sciences, Hangzhou 310008, China.
Food Chem X. 2023 Feb 26;17:100615. doi: 10.1016/j.fochx.2023.100615. eCollection 2023 Mar 30.
Polyphenol oxidation during fermentation plays a critical role in the formation of flavor and function of black tea. However, how the specific structures of tea polyphenols affect their oxidation kinetics during black tea fermentation is still unknown. Here, we found that the oxidations of tea polyphenols, including 7 catechins, 4 phenolic acids and 11 flavonoid glycosides followed pseudo-first-order kinetics during fermentation. Molecular structure and oxygen concentration collaboratively regulated the oxidation rate of different polyphenols. Pyrogallol structure was more easily to be oxidized than catechol and monophenol structure in B-ring, the gallic group in C-ring could inhibit oxidation of catechins, while the role of sugar moiety of flavonoid glycosides was differentiating. In addition, oxygen was found to be the key factor limiting the oxidation rate of polyphenols in regular black tea fermentation, and the oxidation rate constants of tea polyphenols were linearly and positively correlated with oxygen concentration.
发酵过程中的多酚氧化在红茶风味和功能形成中起关键作用。然而，茶多酚的具体结构如何影响其在红茶发酵过程中的氧化动力学仍不清楚。在此，我们发现包括7种儿茶素、4种酚酸和11种黄酮苷在内的茶多酚在发酵过程中遵循准一级动力学。分子结构和氧气浓度共同调节不同多酚的氧化速率。在B环中，连苯三酚结构比儿茶酚和单酚结构更容易被氧化，C环中的没食子酰基可抑制儿茶素的氧化，而黄酮苷糖基部分的作用则具有差异性。此外，发现氧气是常规红茶发酵中限制多酚氧化速率的关键因素，茶多酚的氧化速率常数与氧气浓度呈线性正相关。
