冷冻对红茶品质影响的研究

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摘 要
红茶是以茶树的芽叶为原料，经过萎凋、揉捻（切）、发酵、干燥等典型工艺过 程精制而成。由于茶叶有特定的采摘季节，明显限制了传统红茶的生产。近年来，关 于改进红茶加工工艺的研究虽多，也只是在提高品质方面，少有涉及鲜叶的保存与运 输、茶叶生产的季节性限制。红茶的制茶工艺并不复杂，但在加工过程中各种成分的 变化却是十分复杂，在红茶加工过程中，鲜叶中的化学成份变化较大，茶多酚大量减 少，产生了茶黄素、茶红素等新的成份。香气物质从鲜叶中的 50 多种，增至 300 多 种。一部分咖啡碱、儿茶素和茶黄素络合成滋味鲜爽的络合物。本文基于红茶传统的 加工工艺中添加一项工艺——冷冻，首先将茶鲜叶在冷冻状态下保存一段时间，然后 再根据传统做法制成红茶，并探究冷冻对传统工艺红茶品质的影响。 冷冻处理后的鲜叶，经分析其细胞破损率，结果表明：鲜叶的细胞损伤率可达到 85.7%，说明冷冻方式可较有效损伤叶细胞。 应用传统红茶、鲜叶冷冻不同处理制法，探讨鲜叶冷冻制作红茶方式。结果表 明：加工工艺的改变，红茶主要内含成分的含量也发生了不同程度的变化；鲜叶 冷冻制作的红茶茶多酚、氨基酸的含量明显高于传统红茶，咖啡碱和可溶性糖的 含量则低于传统红茶。感官品质亦表明：鲜叶冷冻制作的红茶滋味、汤色和叶底 均优于传统红茶品质，而其香气则稍逊于传统红茶，说明鲜叶冷冻应用于红茶是 可行的。 对鲜叶冷冻时间和温度与发酵时间和温度，采用正交设计 L9(3 4)，分别以茶 多酚、氨基酸、可溶性糖、咖啡碱、TFs、TRs、TBs 及感官品质为目标，探讨冷冻处 理制作工夫红茶的较佳工艺。茶多酚正交试验结果分析表明：处理样 A3B1C3D2 (发 酵时间 170min、发酵温度 22℃、冷冻时间 9d、冷冻温度 -40℃ )试验设定条件最有 利于茶多酚的积累，而感官品质结果显示，适当降低茶多酚的含量有利于红茶品质的 提高。氨基酸正交试验结果分析表明：处理样 A1B1C1D1(发酵时间 110min、发酵温 度 22℃、冷冻时间 3d、冷冻温度 -20℃ )对氨基酸的累积条件亦最佳。可溶性糖正 交试验结果分析表明：处理样 A3B3C2D1(发酵时间 170min 、发酵温度 32℃、冷冻时 间 6d、冷冻温度 -20℃ )对可溶性糖的保留量条件最佳，且感官品质结果显示该处理 样滋味甜醇，综合品质最佳。咖啡碱正交试验结果分析表明：处理样 A2B3C1D2(发酵 时间 140min、发酵温度 32℃、冷冻时间 3d、冷冻温度 -40℃ )对咖啡碱的保留量条 件最佳，但咖啡碱的含量与红茶品质无明显的相关性，对红茶品质并非最佳，只可作 为一项参考指标。 茶黄素正交试验结果分析表明： 处理样 A2B1C2D3(发酵时间 140min 、 发酵温度 22℃、冷冻时间 6d、冷冻温度 -70℃ )对茶黄素含量愈高，愈有利于红茶品质的提高，所以 在加工过程中应尽量保留茶黄素的含量。 茶红素正交试验结果分析表明： A1B2C2D2(发 酵时间 110min、发酵温度 27℃、冷冻时间 9d、冷冻温度 -40℃ )对茶红素的保留量 条件最佳，但茶红素的含量太高会使茶汤深暗、鲜爽度低，故茶红素的含量应适量。 茶褐素正交试验结果分析表明： 处理样 A1B1C1D1(发酵时间 110min、 发酵温度 22℃、 冷冻时间 3d、冷冻温度 -20℃ )的茶褐素含量最低。 综合上述较优的结果，处理样 A1B1C1D1、A3B3C2D1、A2B1C2D3 的加工工艺条件 不论是在增加有效生化成分，还是感官品质都有利于红茶品质的提高；香气方面： A1B1C1D1 香精油总量虽然较低，但芳香物质数量偏高，A3B3C2D1、A2B1C2D3 的香精 油总量和芳香物质数量在所有处理样中均处于中等，符合一般红茶标准。较高红茶品 质主要内含成分一般要求茶多酚、咖啡碱、TRs 适量，氨基酸、可溶性糖、TFs 偏高， TBs 尽可能少。故结合感官品质和实际生产成本，A1B1C1D1 工艺条件，即发酵时间 110min、发酵温度 22℃、冷冻时间 3d、冷冻温度 -20℃有利于红茶品质提高，且 生产成本较低，更易实现实际生产。 关键词 ：红茶，冷冻，发酵，成分，品质
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Abstract
Black tea in the shoots of tea as raw material is refined by withering, rolling (cut), fermentation, drying and other typical process. As the tea has specific picking season, significantly limiting the production of traditional black tea. In recent years, research on improving the processing of black tea are numerous, it was only to improve of the quality, few involved in the preservation and transportation of fresh leaves and the restriction. Production process of black tea is not complicated, but the changes between the various components in the process are very complex. The chemical composition of fresh leaves is changed dramatically in process of black tea. Tea polyphenols reduced by more than 90%, transformed into other substances such as theaflavins, thearubigins etc. Aroma substances have increased from 50 kinds of fresh leaves to more than 300 kinds. Part of the caffeine, catechins and theaflavins convert to complexes with fresh and brisk taste. Based on the tea the traditional process, we add a procedure - frozen to explore the effect of freezing on traditional black tea quality. First keeping the fresh leaves stored in the frozen state for some time, and then makes them of black tea according to traditional practices. Analyze the cell breakage rate of frozen fresh leaves, the results showed that: The damage rate of fresh leaves cell can reach 85.7%, which illustrate frozen can more effective injury the cells of leaves. Using different processes as traditional black tea and freezing fresh leaves. Explore the way of making black tea by freezing the fresh leaves. The results showed that: If the processing is changed, the main contents of the tea-containing component will also vary with different degrees. Polyphenols and amino acid content were significantly higher than the traditional black tea; the contents of caffeine and soluble sugar were decreased. Sensory review also showed that: The sensory quality score in aspects of taste、 liquor color and infused leaves of black tea adding frozen processes were higher than the traditional black tea except aroma. In order to further obtain the best combination of freezing time、temperature freezing and fermentation time 、 fermentation temperature, the author use L9 (34) orthogonal experimental design, and take polyphenols, amino acids, soluble sugar, caffeine, TFs, TRs, TBs and sensory quality as the goal. The results of tea polyphenols orthogonal test analysis showed that: The condition of A3B1C3D2(Fermentation time 170min, fermentation temperature 22° C, the freezing time 9d, freezing temperature -40° C) is most conducive to