Abstract:

The composition of free amino acids and color in raw Pu-erh teas of different origins were comparatively
investigated. The contents of eighteen free amino acids (Asp, Thr, Ser, Glu, Gly, Ala, Cys, Val, Met, Ile, Leu, Tyr, Phe, Lys,
His, Arg, Pro, and Thean) in Pu-erh raw teas and tea infusion color (brightness L*, and chromaticity values Δa* and Δb*)
from Xishuangbanna Prefecture and Lincang City, Yunnan province, China, respectively, were analyzed by automatic amino
acid analyzer, HPLC and color difference meter. Variation analysis and principal component analysis (PCA) were used for
data analysis. The results showed that the free amino acids had distinct geographical features. The contents of main flavor
amino acids such as Thean, Asp, Glu and Arg were higher in samples from Xishuangbanna than in those from Lincang.
Use of PCA provided a clear distinction of the samples from the two regions. The contents of total amino acids, Asp, Glu,
Thean and His were higher in tableland tea than in old plant tea, but the content of His was lower. Furthermore, there were
significant differences in the contents of total amino acids, Glu, His, and Arg between tableland tea and old plant tea, as well
as differences in main flavor amino acids, L*, a*and b* also displayed significant difference between the two geographic
origins. L* and b* were higher but a* was lower in samples from Xishuangbanna. No significant difference in the color of
tea infusion existed between tableland tea and old plant tea.

Key words: Pu-erh tea, raw tea, free amino acid, color differences