Appearance Color Measurement of Green Tea and its Application to Evaluation of Green Tea Grade

Abstract

In order to establish the evaluation method of the appearance color of green tea, the correlation between the Hunter's color difference meter values and the sensory scores by expert panels were investigated using commercially packed green teas with three grades, high, medium and low.
The best correlation was obtained between the Hunter's a/b ratio value and sensory scores. The correlation coefficient between both values were about -0.9 or higher for each grade teas.
Furthermore, high and low grade teas were discriminated by the quality control diagrams made from two variables, Hunter's a/b ratio value and nitrogen content, which relates the appearance and flavor of tea, respectively.
From these results, it was concluded that the Hunter's color difference measurement method is usefull to grade green tea by the appearance color.