The fermentation process in tea manufacture

Abstract

The oxidase activity, as detd. by the direct manometric method, did not always completely determine the rate of tea fermentation. Other factors might also play some part. The reliability of the residual uptake method was shown by the fact that when the latter stages of fermentation were carried out in the Warburg apparatus the rate and extent of oxidation were the same no matter how the initial stages were carried out. Thus if factory treated leaf was fermented until half of the tannins were oxidized, and then ground to a paste and suspended in water in Warburg vessels, the O2 uptakes then recorded were precisely the same as those found for the latter half of the fermentation when the process was carried out entirety in the Warburg apparatus. The residual uptake method showed how far the oxidase content controlled the rate of fermentation. The high correlation (r = 0.8663) found between the Qo2 values for fresh green leaf and the rate of fermentation of this leaf under factory conditions showed that it was the oxidase activity which largely detd. the rate of fermentation. In these expts. the wither was a variable and uncontrolled factor, but in no case was the leaf withered to less than 65% moisture so that the effect due to withering was a comparatively small one. The differences in fermentation rates between different jats (Betjan and Kharikatia) were another case where the oxidase activity was the most important factor controlling the process. The increase in rate of fermentation in O2 was also approx. proportional to the increase of Qo2 of the fermenting leaf as detd. manometrically. These however were the only cases where a direct measurement of Qo2 afforded an accurate estimate of the speed of the fermentation process under factory conditions.