Species and production area discrimination of semi-fermented tea in Taiwan

• Main Author: 馮佳慶
• Other Authors: 翁義銘
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/04691740058130184348

碩士 === 國立嘉義大學 === 食品科學系研究所 === 103 === Tea is not only one of the most popular drinks all over the world, but also an important agricultural commodity of Taiwan. In recent years, due to the continuously rising economy and the continuously expanding domestic market in Taiwan, tea has become the most important drink in daily life. It is believed that the Taiwan’s semi-fermented tea possesses the best quality worldwide. After joined the World Trade Organization (WTO), low-priced tea imported from foreign countries into Taiwan has ruined the reputation of Taiwan’s tea and caused the economic loss. Traditionally, characterization and originality of tea are conducted by so-called tea experts. However, this type of discrimination has several disadvantages, including subjective inconsistency and loss of inaccuracy resulted from olfactory fatigue. Therefore, scientific methods to rank and distinguish tea are worth developed. In the present study, the discrimination among various tea species (CSOolong, TTES#12, and SJChue) and originality of cultivation area (Ali-shan, Nan-tou, and Ping-lin) was determined by the physicochemical properties. Tea samples were analyzed by HPLC and the chromatographs were used to establish the chemical fingerprint of tea samples. Furthermore, principal component analysis (PCA) and discriminant analysis were conducted to classify and pre-distinct the cultivation areas and species of tea samples. The results revealed that the main differences among tea species were the content of polyphenolic compositions. Among them, content of epicatechin gallate was significantly different and thus it was considered to be the target compound to distinguish three different tea species. Differences among tea samples in various areas were pH, color, and component of free amino acids. Among them, tea samples in Ali-shan and Nantou could be significantly distinguished from total free amino acids. Moreover, mainly difference in amino acid components was the content of glutamine which was significantly higher in Ali-shan tea than that in Nan-tou. Original HPLC spectrum combined with the results of PCA and discriminant analysis could effectively distinguish tea samples. Spectrums of polyphenols and alkaloids were more effective than free amino acid spectrum. As for identifying tea species, free amino acid spectrum exhibited a success rate of 81% that means it is a good index to identify different species. However, the success rate was 100% when identifying different tea species by spectrums of polyphenols and alkaloids. The results of identifying production areas revealed that 78.6% and 85.7% success rate by free amino acid spectrum and polyphenols-alkaloids spectrum, respectively. Unsuccessful discrimination was found between Ali-shan and Ping-lin because of no significant differences was detected in the tea samples. If the tea samples of Ping-lin area were deleted, tea samples from Ali-shan and Nantou area could be fully discriminated by polyphenols-alkaloids spectrum. Collectively, chemical fingerprint spectrum could be used to discriminate tea species and originality of cultivation area.