粉砕方法および粒度の異なる抹茶の流動性

Abstract

抹茶の流動性試験の結果をまとめると以下のようになる．（1） 石臼抹茶，ボールミル抹茶，微粉抹茶の流動開始振動加速度はほぼ同じであった．粗粉抹茶は，流動を開始するのに強い外力を要した．（2） ボールミル抹茶は，流動開始振動加速度と終了加速度が近接しており，非常に流動性が良かった．（3） 石臼抹茶は，帯電しやすく流動性は低かった．帯電は湿度と関連しており，抹茶を取り扱うときはある程度の湿度を保つ方ことで流動性が良くなる．（4） 抹茶は帯電制御によって流動性が向上するので，抹茶を扱うプロセスには除電設備を備えるのが望ましい．（5） Carr流動性指数では，粉砕方法の異なる抹茶の差は小さかったが，本粉粒体流動性試験装置を用いることによって，抹茶の流動性の違いを明確に評価できた．; Matcha, powdered green tea, is difficult to handle in the factory or manufacturing facilities due to its small particle size and low density. In the present study, the powder flowability properties of various matcha samples were investigated using a dynamic powder flow tester with high detection sensitivity to facilitate machine handling during matcha manufacturing. The sample powders were prepared from tea leaves picked during different seasons (i.e. the first, second, third, and fourth crops) using a stone mill or ball mill. Matcha ground with the electrostatically charged stone mill showed poor flowability, whereas that ground with the ball mill showed fairly good flowability. The fine and coarse powders classified after ball-milling had different characteristics. Furthermore, it was found that the electrostatic discharge of matcha can improve flowability, depending on humidity.