TEA 251 



(d) Body of liquor, measured principally by the total 

 soluble matter, of which a large part is tannin both fermented 

 and unfermented. 



It was found that the fermentation is the result of enzyme 

 action ; the presence of bacteria during the fermentation pro- 

 cess is distinctly injurious, rendering the tea sour and unfit 

 for consumption. In order to prevent deleterious changes of 

 this sort, it is necessary that the fermentation should be carried 

 on under aseptic conditions, that is, scrupulous cleanliness 

 must be maintained throughout the process. The use of anti- 

 septics is injurious to the enzyme as well as to the micro- 

 organisms. If the temperature also is kept at about 80 F. 

 the change is found to be mainly enzymic. The chemical 

 change which takes place during fermentation consists essen- 

 tially in an oxidation of the tannin. It has been found indeed 

 that there are two enzymes present; one of these colours 

 guiachum resin blue at once, the other does so only in presence 

 of hydrogen peroxide. The main ferment is an oxidase, causing 

 the darkening of tea juice and also of pyrogallol and hydro- 

 quinone. It has been found that the flavour improves in pro- 

 portion to the amount of enzyme in the leaf. It would appear 

 that in the tea leaf the tannin is combined with sugar ; during 

 fermentation this compound is split up and the tannin is 

 oxidised to brown products. This oxidised tannin combines 

 with other substances in the leaf-forming compounds, some of 

 which are insoluble in water ; there is, therefore, a decrease in 

 soluble tannin. It is possible for this to go too far and the 

 pungency of the tea to be injuriously affected. 



The enzyme increases during the withering of the leaf, and 

 one of the most important results of Dr. Mann's investigations 

 is the possibility of the exact control of the withering process. 

 The object of withering is twofold to soften the leaf in pre- 

 paration for rolling, and to produce the greatest amount of 

 enzyme. Under normal conditions these two changes are 

 practically simultaneous, but in very dry weather the leaf 



