42 EXPERIMENT STATION RECORD. 



J 07). — Au extensive table showing the various tea districts in the world and the 

 kinds of teas produced in each. 



The fermentation of tea, 1, H. H. Mann {Indian Tea Assoc. [Pajiiphlct], 

 1906, pp. 22). — Three former reports have been issued by the author on this 

 subject (E. S. R., 17, p. 254), in which it has been shown that the oxidizing 

 enzym developed during withering is the principal and probably the only 

 active agent in bringing about the changes of color and flavor which take place 

 during fermentation. In the present report the changes which take place in 

 some of the constituents of the tea itself, more specirtcally the t:innin, are 

 considered. 



The marketable value of tea is closely connected with the quantity of tannin 

 which may be easily extracted from the tea by boiling water. Caffein, which 

 is the principal stimulating material of tea, does not bear a close relationship 

 to market value. In good teas it appears to be present in quantities varying 

 from 3 to 5 per cent, and in the lowest grades it may go down to 2 or 3 per 

 cent. Analyses are given of several samples of tea to show that the market 

 value is closely related to the total soluble matter and tannin content. Tannin 

 is the chief source of pungency in teas, and is caused in greatest measure by 

 the unfermented tannin. The color of the liquor, on the other hand, is caused 

 chiefly by the fermented taimin. The body of the liquor is measured princi- 

 pally by the total soluble matter, of which a large part is tannin, fermented 

 and unfermented. 



The tannin in the leaf appears to be combined with sugar. During fer- 

 mentation the enzym of the tea causes slight oxidation of the tannin, as a 

 result of which the sugar is separated and the tannin undergoes a loss of 

 water and the colorless tannin of the tea leaf is transformed into brown products. 



In investigations on the withering of tea it was found that "(1) The soluble 

 matter and the soluble tannin in the leaf increase during the withering process, 

 so long as the leaf does not dry up. (2) This increase in the important con- 

 stituents of the leaf continues right through the process, so long as no drying 

 takes place. ... (3) So soon as the drying of the leaf takes place, a large 

 reduction in the amount of soluble matter and soluble tannin is noticed." 



Data are given which show that during fermentation a considerable reduc- 

 tion in the amount of soluble matter and soluble tannin in the leaf takes place, 

 and this is increased with heavy rolling. In the absence of fermentation 

 organisms it was found that normal fermentation of the leaf is complete in 

 •about 5.5 hours at most, including the rolling, where the temperature is main- 

 tained at 80° F. In fact, very little change takes place after 4 hours have 

 passed. At a temperature above 85° F, a darker brown oxidation product of 

 tannin is produced which is completely insoluble in water, the formation of 

 which rapidly reduces the pungency, color, and body of the liquor and there- 

 fore greatly injures the quality of the tea. Among the practical conclusions 

 reached is, that in order to make the best tea the temperature of the fermenting 

 room must be kept down to 82° F. Suggestions are given on the consti'uction 

 of fermenting houses whereby this temperature may be maintained. This 

 temperature, with a saturated atmosphere, and the absence of injurious organ- 

 isms are believed necessary conditions to the manufacture of the best tea. 



Some observations were made to determine the effect of light on fermenta- 

 tion, as some planters use yellow, some red, and some blue light in this process. 

 The rapidity of fermentation was pi-actically the same under white, red, and 

 yellow light, but was less rapid under a blue light. No difference was noticed 

 in the percentage of tannin, but only in the total soluble matter. The ultimate 

 result was the same whatever the lighting used, providing direct sunlight and 



