绿茶新鲜度的风味感官表征及化学基础研究

Green tea is susceptible to light, oxygen, temperature and other factors during the storage process, and gradually lost its primary bright color and fresh flavor, which results in the loss of the unique sensory qualities. Based on the sensory evaluation system of the freshness of green tea and the statistical analysis technologies, this project want to reveal the main changes of the green tea flavor compounds during storage by comparing the NIST and Wiley databases and calculating the aroma index with helps of modern intelligent sensory evaluation system, such as electronic nose and GC-MS-O. By comparing the threshold and activity of the key flavor compounds, the key factors closely related to the freshness of green tea were selected, and the quantitative description system of green tea freshness marked with references was established with those factors. Then, the discriminant model of freshness of green tea was established by using the system to train E-nose, which can test the freshness of green tea objectively by E-nose. This work aims to reveal the relationship of freshness of green tea and flavor chemistry compounds and evaluation it by an objective method in order to standardization of green tea market.

绿茶在储存过程中极易受到光照、氧气、温度等影响，逐渐失去原先鲜亮的色泽和清新的风味，从而失去了绿茶特有的品质特征。本项目从建立绿茶新鲜度的感官评价体系入手，结合电子鼻、GC-MS-O等现代智能感官审评系统，采用关键风味化合物的组学分析手段，通过比对NIST和Wiley数据库、计算香气指数以及GC-O嗅闻感受，以揭示绿茶风味变化的主要化学基础；通过比较关键风味物质的阈值和活力值，筛选出与绿茶新鲜度密切相关的标记物；通过拟合标记物和人工感官审评的结果，建立有参比标记物的绿茶新鲜度定量描述体系；进而用该体系训练电子鼻，建立绿茶新鲜度的判别模型，以实现绿茶新鲜度的客观判定，对科学评价绿茶新鲜度、推荐绿茶的最佳品饮期，规范绿茶市场有着重要的参考价值。

绿茶在储存过程中极易受到光照、氧气、温度等影响，逐渐失去原先鲜亮的色泽和清新的风味，从而失去了绿茶特有的品质特征，香气更是由新鲜的绿茶香转变成陈气。该项目首先建立了科学评价绿茶新鲜度的方法和评判模型：项目采用加速货架期实验法（ASLT）获得不同加速陈化温度下的失鲜茶样，再从绿茶新鲜度的感官评价体系入手，结合传统感官审评技术和图像技术、茶叶内含物的变化规律，确定了储存期绿茶品质差异程度表，并基于Q10法、威布尔危害法和双边方向性检测，理论推算和感官验证均发现，存于20℃、30℃、40℃下茶样将分别储藏至67天、55天、45天时品质劣变至失鲜状态。预测存于4℃和-20℃温度下的茶样在93天和150天时品质失鲜。.项目基于GC-MS-O嗅闻技术，采用DB-5MS和DB-WAX两种极性的色谱柱双柱定性，使用了SPE法和SPME法香气的萃取方式，富集绿茶的香气物质以揭示绿茶陈气产生的物质基础。引入了 AMDIS 软件，通过 Agilent MSD Chemstation与AMDIS结合，更准确的从复杂基质中解析到目标化合物，提高了茶叶中挥发性化合物定性的准确性。并结合PCA、OPLS-DA统计方法和化合物OAV值评判，筛选出了绿茶重要香气活性化合物，对所筛选出新陈茶的重要活性化合物进行集合运算、绘制韦恩图等，最终得出绿茶陈气化合物主要为3,5-辛二烯-2-酮，苯乙醇，β-紫罗酮和亚麻酸、水杨酸甲酯、氨茴酸甲酯等。本项目对科学评价绿茶新鲜度、了解绿茶陈化的机理、推荐绿茶的最佳品饮期，规范引导绿茶消费有着重要的意义。.