Theanine is a characteristic amino acid in tea. It is synthesized in the roots of tea plants under the action of theanine synthase from glutamic acid and ethy-lamine. It is an important substance that forms the taste of tea. It is mainly expressed as fresh and sweet. It is tea. The main ingredient of Chemicalbook's raw body fluid and sweetness. Twenty-six amino acids (6 non-protein amino acids) are identified in tea, which generally account for 1% to 5% of the dry weight of tea, and theanine accounts for more than 50% of the total free amino acids of tea.