不同茶类寡肽含量的测定和分析

Determination and analysis of contents of different tea oligopeptides

  • 摘要: 【目的】构建适于普通理化实验室操作的茶叶寡肽定量方法,为茶叶寡肽研究提供技术支持。【方法】以六大茶类的30份样品为试材,考察溶剂浓度、提取温度和提取时间对茶叶中寡肽含量的影响;利用三氯乙酸沉淀提取液中的大分子量蛋白质后,采用甲醛滴定法和凯氏定氮法分别测定提取液中游离氨基酸含量及游离氨基酸和寡肽总量,计算二者差值即为寡肽含量;同时利用建立的寡肽定量方法,分析不同茶类寡肽含量的差异。【结果】提取溶剂对茶叶寡肽含量有显著影响(P<0.05),提取温度影响较小,提取时间无显著影响(P>0.05)。优化的提取条件为:使用50%乙醇,80℃下加热回流提取30 min;该方法的稳定性较好(重复试验相对标准偏差<5.00%),可用于六大茶类30份茶叶样品的寡肽含量实际测定。测定结果显示,六大茶类寡肽含量均值排序为:黄茶>白茶>黑茶>绿茶>红茶>乌龙茶,其中,黄茶和白茶的含量为3.88%~6.00%,黑茶和绿茶的含量为2.45%~6.53%,红茶的含量为1.90%~4.84%,乌龙茶的含量为0.70%~3.93%。【结论】通过优化提取方法,并将凯氏定氮法与甲醛滴定法结合,较好地实现茶叶寡肽的定量测定;同时发现茶类的加工工艺及原料嫩度可能对茶叶寡肽含量有影响。

     

    Abstract: 【Objective】 To construct a quantitative method for tea oligopeptides suitable for general physical and chemical laboratory operations, and to provide methodological support for tea oligopeptide research.【Method】 With 30 samples of six major tea types taken as test materials, effects of solvent concentration, extraction temperature and extraction time on oligopeptide content in tea were investigated. After precipitating the large molecular weight proteins in the extract by trichloroacetic acid, the free amino acid content and the total amount of free amino acids and oligopeptides in the extract were determined by formaldehyde titration and Kjeldahl method, respectively, and the difference between the two was calculated as the oligopeptide content. At the same time, the established oligopeptide quantitative analysis method was used to analyze the difference of oligopeptide content of different teas.【Result】 Extraction solvent significantly influenced the content of tea oligopeptides(P<0.05), the effect of extraction temperature was small, but the extraction time did not have a significant effect(P>0.05). The optimized extraction conditions were as follows:50% ethanol, heating at 80℃ and reflux extraction for 30 min;this method showed a good stability(relative standard deviation of repeated test < 5.00%), and it could be used for the actual determination of oligopeptide content in 30 tea samples of six teas. The determination results showed that the order of mean oligopeptide content of the six major teas was as follows:yellow tea>white tea>dark tea>green tea>black tea>oolong tea, among which, oligopeptide content in yellow tea and white tea was 3.88%-6.00%, in dark tea and green tea was 2.45%-6.53%, in black tea was 1.90%-4.84%, and in oolong tea was 0.70%-3.93%.【Conclusion】 Through optimized extraction method combining Kjeldahl nitrogen determination method with formaldehyde titration method, the quantitative determination of tea oligopeptide can be well operated;at the same time, the processing technology and tenderness of tea raw materials may influence the content of oligopeptides in teas.

     

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