On the Rcle of Oxydase in the Preparation of 

 Commercial Tea. 



BY 



K. Aso. 



It is well known that fresh tea-leaves if steamed after being 

 collected, will preserve their green color, while if exposed to a 

 partial drying in the sun, they will turn gradually brown. The 

 former is the first operation in the preparation of the green tea 

 and the latter that of the black tea of commerce. 



About ten years ago, Prof. Kozai 1 found that the tea- 

 leaves if once sufficiently steamed do not undergo further 

 change or the so-called fermentation, but that in the further 

 preparation of black tea, the sacks of rolled and pressed 

 tea-leaves showed a gradual rise of temperature to 34°5 C at an 

 air-temperature of 24 0 C. 2 He further observed that black tea 

 contains considerably less tannin than green tea : 



\galloiannic acid/ 



The development of the black color seemed to me to be due 

 to the action of an oxydizing enzyme upon the tannin of the 

 tea-leaves, and this has led me to the following tests. 



The tea leaves were collected in the middle of September, 

 taking only the five uppermost leaves of each branch. They 

 were pulverised and extracted at the ordinary temperature with 



* Kozai, Bull. College of Agric., Tokyo. Vol. I. No. 7. 1890. 

 3 1 he process of " fermenting " Consists in pressing the rolled leaves into sacks, 

 arranging them, side by side, under a white cloth and placing them in a sunny plice. 



In 100 parts of the dry matter, 



Original Green Blick 



leaves. tea. tea. 



Tannin. 



