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Background

Green tea has been an important part of food culture in Japan as shown in “Japanse tea ceremony”, which is a Japanese cultural activity to demonstrate the elegancy of preparing powered green tea. Currently, there are various type of tea in the world, but green tea is still the most common and popular tea in Japan.

Green tea is recognized as medicine as well as beverage. From ancient times, it is known that green tea has health benefits to humans. With the increasing interest in the health benefits of green tea, the characteristics of components have been well studied.

One of the beneficial components of green tea is L-theanine. Theanine, or γ-glutamylethlamide is a non-protein derived amino acid found solely in tea plant (Camellia sinensis). L-theanine is the most abundant amino acid in teas, and green tea contains more amount of amino acids than fermented ones [1].

It has been reported that theanine can reach to the brains and cause calming effect by promoting alpha brain waves [2]. It has also been reported in a rat test that theanine can act as a neurotransmitter and decrease blood pressure significantly in hypertensive rats[2]

In addition to that, theanine gives distinctive flavor and savory taste to green tea, which is responsible for its umami taste in green tea. For these reasons described above, green tea containing more theanine is considered to have the higher quality. Theanine content can be one of the powerful indicator for tea promoter to prove their Japanese tea quality.

Currently, theanine content in green tea is measured by instrumental analysis, but it costs too much for easy test[3]. To solve this problem, we proposed a biosensor to evaluate the theanine content in green tea.

Reference

[1] Wang, Lin, et al. "Analysis of free amino acids in Chinese teas and flower of tea plant by high performance liquid chromatography combined with solid-phase extraction." Food Chemistry 123.4 (2010): 1259-1266.
[2]Juneja, Lekh Raj, et al. "L-theanine—a unique amino acid of green tea and its relaxation effect in humans." Trends in Food Science & Technology 10.6 (1999): 199-204.
[3] すぐに上げます。