The fermentation process in tea manufacture

Abstract

(5). The oxidase in tea leaf is compared with ascorbic acid, catechol and cytochrome oxidases, and its properties found to agree best with those of the latter. The tea oxidase system has little substrate specificity, is attached firmly to the tissue, and is readily inactivated by alcohol at 30[degree]C. Oxidase activity increases with O2 tension. Ascorbic acid is not oxidized directly in fermenting tea leaf but by the primary oxidation product of tea tannin. Onslow''s classification of plants into oxidase and peroxidase types may need revision; the true distinction may be between plants with catechol and cytochrome oxidases as the enzymes primarily important in respiration. A revised scheme for tea-fermentation is proposed.[long dash](6). With suspensions of finely divided tea leaf in water, the rate of O2 uptake per unit quantity of tissue increases with dilution. At the same time the rate and extent of carbohydrate oxidation decreases. These observations are in accordance with the theory that the fermentation (i.e., tannin oxidation) in tea leaf, which follows extensive damage, is due to dispersion of the coenzymes throughout the tissue. Other effects of damage to tissue on cellular respiration are shown to be inoperative in the case of tea fermentation.