茶汤回甘滋味效应形成机制研究

Tea is one of the most important agricultural products in China. “Sweet aftertaste”, which significantly influences the taste quality of tea leaves, is one of the important evaluation indexes for tea quality. In our former study, non-gallated catechins and gallic acid were found as the main contributors for sweet aftertaste of tea infusion. However, the production way of the sweet aftertaste and the taste interactions between different taste substances are not clear. It is difficult to regulate and control the sweet aftertaste of tea infusion without explicit formation mechanism. This project will use the technologies from sensory science, analytical chemistry and molecular biology to analyze the taste structure-activity relationship of sweet-aftertaste compounds, the change of the chemical structure during the processing in the mouth, and the relation between sweetness receptors and sweet aftertaste compounds, to construct the model of sweetness receptors recognition and confirm the way of production for sweet aftertaste. Then the taste interactions between the sweet-aftertaste compounds and the other taste factors (other taste compounds and environmental effect factors) will be focused to study. After that, the taste effects of the sweet-aftertaste compounds in tea infusions will be analyzed. From above, we will reveal the formation mechanism of sweet aftertaste from tea infusion. Beginning from a new aspect, this study tried to offer a new explanation of the formation mechanism of sweet aftertaste from tea infusion with the analyzing method of molecular biology. The results will improve the taste theory of tea infusion, and help to regulate the sweet aftertaste of tea infusion. The results also provide theory base to improve the flavor quality of low-and-medium grade tea and its efficient utilization.

茶叶是我国重要农产品。“回甘效应”是影响茶汤滋味品质极为重要的正面感官性质和评判指标，但是回甘滋味效应相关研究报道极少。我们前期研究发现非酯型儿茶素和没食子酸具有显著回甘效应，但其产生途径不明确，缺乏系统的形成机制，无法实现精准调控，限制了中低档茶资源的有效利用。本项目采用感官科学、分析化学及分子生物学等手段，研究茶汤关键回甘滋味化合物呈味构效关系，分析回甘滋味化合物在模拟口腔加工过程中的化学结构（或构型）衍变，明确口腔加工衍生物与甜味受体的识别关系，构建甜味受体识别模型，阐明回甘滋味效应的产生途径，进一步研究回甘滋味化合物与其他味感因子的滋味互作效应，揭示茶汤回甘滋味效应形成机制。本课题结合分子生物学分析手段，从一个全新的角度来阐述茶汤回甘滋味效应形成机制；研究结果不仅可以完善茶叶滋味化学理论，而且可以为茶饮料滋味品质调控和中低档茶资源利用等提供理论指导。

本项目研究了回甘滋味化合物（SAC）的呈味特性与以SAC为核心的呈味互作效应，并基于生产实践提出了改善夏秋滋味品质的可行性建议，最后还通过构建人味觉受体体外功能表达与人体口腔加工体系重点研究了茶汤回甘滋味的形成机制。研究结果对丰富茶叶滋味科学理论体系和提升茶饮料加工技术都具有相当意义。项目主要在以下六个方面取得进展：（1）研究明确了没食子酸（GA）与没食子酸钠（SG）是继非酯型儿茶素之外绿茶中具有回甘滋味特征的化合物；（2）系统明确了4种SAC的呈味特性及以其为核心的多层次呈味互作效应；（3）提供了单宁酶水解改善夏秋茶滋味品质的可行性方案；（4）初步明确了4种SAC的两种回甘滋味形成机制，其中EC/EGC通过分别激活人苦味与甜味受体产生回甘，而GA/SG作为人甜味受体拮抗剂而产生回甘；（5）发表学术论文7篇，均为食品领域前25%SCI论文；（6）申请发明专利3项，培养硕士生1名、博士生1名。现已完成了计划研究内容，实现了项目预期目标。