基于傅里叶变换红外光谱的不同茶山古树普洱茶鉴别研究

Discrimination study of Pu-erh tea made from ancient trees from different tea mountains based on Fourier transform infrared spectroscopy

中文关键词:  古树普洱茶  傅里叶变换红外光谱法  茶山  鉴别  咖啡因

英文关键词:Pu-erh tea made from ancient trees  Fourier transform infrared spectroscopy  tea mountain  discrimination  caffeine

中文摘要:

      目的 基于混合物红外光谱原理及方法, 对不同茶山普洱茶组成差异进行整体分析与评价, 探讨普洱茶“一山一味”说法的科学性。方法 选取易武、景迈等云南12座茶山的古树晒青茶, 采用透射法傅里叶变换红外光谱(Fourier transform infrared spectroscopy, FT-IR)采集其超微茶粉、水提取物及茶渣的红外光谱图, 并处理为标准化红外光谱和二阶导数红外光谱(second derivative infrared spectroscopy, SD-IR), 进一步通过相似度评价、光谱差异分析及特征峰相对强度比较, 对不同茶样的物质组成差异进行识别与评价。结果 12种茶叶FT-IR谱间相关系数(R)高于0.98, 均具有3354、2925、1649、1517、1451、1239、1147、1039、764、611 cm-1等共有峰, 但SD-IR谱的1649、1577、1568、1540、1532、1147、486 cm?1峰具有不同的强度或形状。景谷、易武、贺开茶粉486 cm?1处峰强度相对较低, 其中景谷的最低, 约为攸乐茶的75%。12种茶叶的化学组成整体相似度很高, 景谷、易武、贺开茶样中咖啡因含量相对较低, 但与其他茶样的光谱差异亦不到2%, 但据SD-IR谱486 cm?1处峰相对强度可快速比较不同茶样中咖啡因相对含量, 不同茶山茶样间可利用SD-IR谱差异进行鉴别。结论 不同茶山茶叶间或多或少的组成差异均可在红外光谱上体现, 红外光谱法适用于普洱茶组成差异整体识别与评价, 普洱茶“一山一味”说法具有一定的科学性。

英文摘要:

      Objective To analyze and evaluate the overall composition differences of tea samples from different ancient tea mountains based on the principle and method of mixture infrared spectroscopy, and explore the scientific nature of the statement "one mountain, one flavor" of Pu-erh tea. Methods The infrared spectra of the ultra-fine tea powders, water extracts and extraction residues from the sun-dried raw tea of ancient trees from 12 tea mountains in Yunnan province, such as Yiwu and Jingmai were collected, and the infrared spectra were processed into standardized infrared spectra and second derivative infrared spectroscopy (SD-IR), furthermore, the similarity evaluation, spectral difference analysis and characteristic peak intensity analysis based on those spectra were carried out for the discrimination and evaluation of the substance composition differences among different tea samples. Results All spectral correlation coefficients (R) were over 0.98 and all 12 kinds of tea samples had common FT-IR peaks at 3354, 2925, 1649, 1517, 1451, 1239, 1147, 1039, 764, 611 cm?1 and so on, even so, SD-IR peaks including 1649, 1577, 1568, 1540, 1532, 1147 and 486 cm?1 had different absorption intensities or peak shapes. Tea samples from Jinggu, Yiwu and Hekai had relative low peak intensities at 486 cm?1, that from Jinggu was the lowest, which was only about 75% to the tea from Youle. The overall chemical compositions of the 12 kinds of tea samples were very similar, the caffeine content in Jinggu, Yiwu and Hekai tea samples was relative lower than that of others, but the spectral differences with other tea samples were only less than 2%, but the relative content of caffeine in different tea samples could be conveniently compared based on the SD-IR peak intensity at 486 cm?1, Tea samples from different tea mountains could be thoroughly discriminated according to SD-IR spectral differences. Conclusion More or less compositional differences among tea samples from different tea mountain can be appeared in their FT-IR spectra, FT-IR analytical method is suitable for the overall identification and evaluation of the composition differences of Pu-erh tea samples, to some extent, the statement of "one mountain, one flavor" about Pu-erh tea has a certain scientific nature.