2022 年 227 巻 3 号 p. 230-241
We have developed a new method for cultivation of green tea that contains highly functional theanine in high concentration, has excellent flavor, and reduces thermal energy costs. By applying organic fertilizer containing fish meal and shading with cheesecloth with a shading rate of 85-90%, it has become possible to cultivate green tea comparable to high-grade matcha (powdered green tea) with a theanine concentration of 2% or more. Using this method, freshly picked tea leaves were steamed, twisted, and dried using a primary drying tea roller in an air-heating furnace with a main shaft with press and stir arms. The tea leaves were then directly transferred to a tea dryer without transferring to a four-step rolling process typically used in the conventional crude tea making process in Japan. This unrefined tea was then preserved at 5°C and 15°C under nitrogen gas to carry out aging for seven months. In parallel, a part of this unrefined tea was refined and powdered with a crusher. This powdered green tea is also subjected to aging in the same manner. As a result, although we were not able to scientifically elucidate the aging effectiveness, we were able to develop a powdered green tea with a high theanine content that was as tasty as intermediate-grade matcha in sensory evaluation, at a low cost comparable to the production cost of commercially available high-grade sencha.