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Simultaneous determination of free amino acids in Pu-erh tea and their changes during fermentation
Yuchen Zhu1, Yinghua Luo2, Pengpu Wang1
1College of Food Science & Nutritional Engineering, National Engineering Research Centre for Fruits and Vegetables Processing, Key Laboratory of Fruits and Vegetables Processing, Ministry of Agriculture, Engineering Research Centre for Fruits and Vegetables Processing, Ministry of Education, China Agricultural University, Beijing 100083, China.
Abstract:
Pu-erh ripened tea is produced through a unique microbial fermentation process from the sun-dried leaves of large-leaf tea species (Camellia sinensis (Linn.) var. assamica (Masters) Kitamura) in Yunnan province of China. In this study, the changes of amino acid profiles during fermentation of Pu-erh tea were investigated, based on the improved HPLC-UV method with PITC pre-column derivatization for the simultaneous determination of twenty free amino acids. Results showed that aspartic acid, glutamic acid, arginine, alanine, theanine and tyrosine were the major amino acids in tea samples. Fermentation significantly influenced on the amino acid profiles. The total free amino acid contents significantly decreased during fermentation (p<0.05). Meanwhile, low amount of acrylamide were detected. Its concentration increased after 7-days' fermentation and then decreased gradually. The results provided the useful information for the manipulation of fermentation process according to the changes of amino acids and acrylamide contents in Pu-erh ripened tea.
