苦丁茶の遊離アミノ酸組成，ミネラル含量，総ポリフェノール含量と官能評価

Abstract

Ku-ding cha, a tea consumed in China′s southern region, is manufactured from the leaves of the family of Oleaceace, Aquifoliaceae, etc. “Ku” means bitter ; Ku-ding cha tastes much more bitter than green tea. In order to clarify the components, we have determined the contents of the free amino acids, minerals and total polyphenols in 14 kinds of Ku-ding cha, a green tea and mate. Twenty-two free types of protein amino acids and eleven non-protein amino acids in each leaf were analyzed using an amino acid analyzer. Theanine, a characteristic amino acid in green tea, was not found in Ku-ding cha. The free amino acid contents were quite different between the Ku-ding cha and green tea. As a result of the atomic absorption spectrometry and inductively coupled plasma-mass spectrometry analyses, most of the mineral contents in the Ku-ding cha leaves and infusion were similar to those of the green tea and mate. The total polyphenol content was analyzed using the Folin-Ciocalteu assay. Some Ku-ding cha was higher than the green tea regarding the total polyphenol content, while others were less than half that of the green tea. As a result of a sensory analysis using a scoring method, Ku-ding cha was evaluated to be bitter. Ku-ding cha contains a low concentration of bitter free amino acids such as valine and leucine, and bitter mineral such as magnesium. These results suggest that the bitterness of Ku-ding cha is derived not from the free amino acids or minerals, but from the polyphenols.