Determination of Conversion of Chlorophyll to Pheophytin in Green Tea

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  • クロロフィルのフェオフィチンへの変化の測定法
  • Application of Dietrich's Method to Discoloration of Green Tea during Storage
  • Dietrich法の茶への応用

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In order to study the discoloration of green tea during storage, we investigated the application of Dietrich's method, in which the conversion of chlorophyll to pheophytin was determined.<BR>The formula described by Dietrich was as follows:<BR>percent conversion= RX-R0/R100-R0×100<BR>where, R0: ratio of optical density (OD) readings 534 mμ/556 mμ for zero conversion<BR>R100: ratio of OD readings 534 mμ/556 mμ for 100% conversion<BR>RX: ratio of OD readings 534 mμ/556 mμ for the unknown<BR>Using green tea, the following equation was obtained.<BR>percent conversion= Rx-0.96/1.29 × 100<BR>Yet, as this equation may vary slightly with some conditions of analysis used, it seems to have need for each analyst to set up his own equation with each instrument.<BR>The procedure and calculation by this method in green tea are; add 40 ml. of 90% acetone to 0.3g. of powdered green tea in a 50ml. flask and extract pigments allowing to stand for 3 to 5 hours. Then, read the OD at 534 mμ and 556 mμ of the supernatant of the acetone extract and calculate percentage conversion by the above equation.<BR>Then, it was recognized that the percentage conversion in this method agreed approximately with that calculated from pigment contents which were estimated in the method of TAN et al.

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