导　　师： 梁月荣

学科专业： 090203

授予学位： 博士

作　　者： ;

机构地区： 浙江大学

摘　　要： 茶叶原料影响茶饮料品质，好的原料可以简化生产工艺，降低生产成本，提高产品的品质和保质期。但是关于不同茶树品种原料的绿茶饮料适制性问题的研究还十分有限。本研究根据当前绿茶饮料生产需要，在研究绿茶鲜汁饮料的基础上，提出了不同品种适制性的成因，如不同茶树品种的热加工特性以及贮藏过程中品质变化特点。结果表明： 1．绿茶鲜汁的最适提取温度为50℃；茶水比为1：60时，提取率可达到27.91％；浸提10min相对较好。不同采摘嫩度的茶叶原料，固形物浸提率随着嫩度的降低而相应增加；茶多酚提取率随嫩度的增加而增加，咖啡碱除1芽1叶提取率较大外，其余不显著；不同嫩度对氨基酸提取率影响不显著。1芽3叶，1芽4叶感官品质和耐贮特性都明显优于嫩度大1芽1叶和1芽2叶，但前二者之间差异不显著。从生产实际考虑绿茶鲜汁饮料可以选用1芽4叶较好。 2．不同茶树品种的浸提特性比较结果表明：浙农139、水古品种固形物提取率较高，菊花春和碧云品种虽比上述二者提取率略低，也远高于其它品种。如果要从生化成分浸出效果来看的话，茶多酚、氨基酸和咖啡碱三者浸出效果较好的为浙农139、水古、碧云三个品种。 3．不同品种茶饮料经高温灭菌，茶多酚和咖啡碱略微增加，氨基酸的含量相对增加幅度较大。灭菌过程中表型儿茶素类分别向对应的异构体转变。叶绿素在灭菌过程中降解幅度从16％至40％，如果能够在灭菌过程中有效地防止叶绿素的降解，则对于保护绿茶汤色有利。表型儿茶素类含量较大的品种如菊花春、浙农139、浙农23汤色变化较小，可见，表型儿茶素类对绿茶饮料的稳定性具有很大的作用。在茶饮料生产选择原料时，选取表型儿茶素类含量高的品种，有利于延长茶饮料的货架期。 4．感官审评结果表明，在整个贮藏过程中，汤色较为稳定的品种有浙农139、浙农138、鸠坑；而滋味品质始终能够保持较好品种有浙农139、浙农138、鸠坑；而香气品质保持较好的有浙农139、浙农23、菊花春。综合品质表现较好的有：浙农139、浙农138、菊花春三个品种。 5．绿茶饮料冷后浑的主要成分为儿茶素类，约占浑浊量的21.4％-37.9％，其中EGCG和EGC分别占39.37％-55.09％和20.74％-37.09％，两种儿茶素合计可占冷 后浑总量的70/%以上。随着儿茶素类氧化程度的增加，儿茶素类参与冷后浑的能 力也增强，因为在茶饮料贮藏过程中形成的冷后浑中非表型儿茶素类比例增加， 而表儿茶素的增加不明显，说明了非表型儿茶素类更易参与到冷后浑的形成。 绿茶鲜汁饮料冷后浑中占较大比例的是可溶性多糖，约占5，1/%~16.2/%，咖啡 碱约占5.4/%一8.7/%，蛋白质约占1.4/%一2.6/%。还有少量的叶绿素参与了冷后浑的 形成，但由于叶绿素在冷后浑中所占的比例非常小，在选取绿茶原料时选用叶绿 素含量高的品种对绿茶饮料的汤色有利。 6.不同茶树品种浑浊活性蛋白含量的不同造成了不同品种冷后浑特性的差 异。本研究表明，参与冷后浑形成的主要是18.4KD及小于18.4KD、25KD、3OKD 左右小分子量蛋白质，不同品种参与到浑浊中的小分子量蛋白质所占比例相似; 大分子量蛋白质的含量可能与不同茶树的遗传背景有关。 7.本研究还首次发现，绿茶饮料适制性好的茶树品种生化成分方面具有以下 3个特征:①儿茶素类总量和表型儿茶素类总量含量较高;②简单儿茶素类在总 儿茶素类中所占比例较大/(大于30/%/);③蛋白质///(EGCG+EGC/)的百分比较低/(约110rk 左右/)。这3个特征可作为绿茶饮料生产原料选择时的理论指标。 综合本研究的结果，浙农139、浙农23和菊花春3个品种具有较好的绿茶饮 料适制性，它们不但感观品质得分较高，而且在茶饮料加工和贮藏过程中品质也 较为稳定，是加工绿茶饮料的最好原料品种。 Green tea is one of the most widely consumed non-alcoholic beverages in the world. It is generally believed that catechins derivatives are active components responsible for beneficial effects associated with drinking tea. Also, green tea is receiving much attention for specific health claims and because of the presence functional constituents, such as EGCG. In recently years, canned and bottled tea drinks are getting popular worldwide. A suitable product of green tea extract is presumed to have a better taste. And the color of green tea extract, clear greenish-yellow, without any trace of red-brown color have been judged to be very appealing. But it is difficult for the bottled green tea beverages to keep their infusion color and sensory quality during processing and storage. Presently, almost all green tea beverages are derived from dried green tea, which is manufactured by a long-term drying by heating. Such a production process will lead to loss different functional components of green tea fresh leaf, so the liquor color from the dried green tea leaves turns yellow because of adverse heat from processing. In fact, the raw material from different varieties can play an important character in keeping good infusion color, and taste quality. But the research in this field is little, especially, on processing and storage. So the goal of the present study was to examine thermal stability under heat processing condition and long-term stability of quality of different beverages during their storage, and to know some mechanism and characters about different varieties on their manufacture. 1. An orthogonal experiment was applied to study the effect of extracting temperature, duration and ratio of tea to water on the quality of fresh green tea juice. The results showed that with the rising temperature and extending extracting duration, the extracted solids yield increased, the color of infusion turned yellow and lightness of infusion decreased, and tea cream increased. The optimum condition of extraction was as fallows: the raio of tea to water 1:60, temperature 50#,and extraction duration 10min. Considering the plucking standard, we found that a bud with three leaves or a bud with four leaves can give a good taste quality, and can keep a good color and sensory quality during heat processing and storage. 2. Solids extracting ratio of the Zhenongl39 and Shuigu cultivars are obviously higher than the others under the same extracting conditions. On the other hand, the extracting ratio of caffeine, amino acid and tea polyphonels of Zhenongl39, Shuigu and Biyun were higher than the others tested. Chemical composition is important for taste sensory; according to our results, Zhenongl39, Shuigu and Biyun would be good raw material for green tea beverage. 3. The lightness and greenness of beverage decreased during heat processing, whereas yellowness of the liquor increased.The differences of different cultivars are not so obvious. The concentration of tea polyphenols and caffeine did not change corresponding to the change of the color, but the concentration of amino acids in beverage increased during heat processing and protein content decreased. The concentration of chlorophyll decreased during heat processing. Because chlorophyll plays an important role in beverage before heat processing, it is important for green tea beverages to sterilize with the low temperature. 4. In the course of storage, changes in color of Zhenongl39, Zhenong23 and Jiukeng are relatively slight; and the yellowness of Shuigu, Longjing 43 and yingshuang are stronger than the others. The chlorophyll would be degraded gradually in the course of storing, but because of the lower content after sterilization, at large, the degradation is not so seriouly. The sensory quality of green tea beverage would become more sweet, less bitter and astringent with increasing time of storage. There are some differences in change of color and sensory quality. For example, the infusion colors of Jiukeng, Zhenongl39 and Zhenongl38 were comparatively stea

关 键 词： 不同品种 绿茶饮料 适制性 热加工 贮藏处理 色差 冷后浑 感官品质

分 类 号： [TS275]

领　　域： [轻工技术与工程] [轻工技术与工程]