Tannins as hydrogen carriers in biological oxidation

Chemical Changes in the Harvested Tobacco Leaf: Part II. Chemical and Enzymic Conversions during Fermentation and Aging

“…The oxidation of the "polyphenols" is a significant effect not only per se, but also in view of the possibility that these compounds may act as oxygen-transferring agents, and as mediators for the oxidation of other leaf components which, without such mediation, would remain unchanged. Roberts (179)(180)(181)(182) expresses the opinion that the phenolic compounds may introduce, via a dynamic change between their hydroquinone and quinone forms, the direct oxidation of hydroxy acids and carbohydrates. Thus, the actions of the autoxidizable compounds are possibly of great importance for the entire fermentation process.…”

The fermentation process in tea manufacture. 12. The origin of carbon dioxide

“…At this stage some polyphenol oxidation is still progressing, so that the data indicate at least 90 % inactivation of respiratory activity as a result of the fine mince. The low rate of oxygen uptake in leaf minces, obtained from species low in polyphenols, affords similar evidence, although Sreerangachar (1949) has queried these data and pointed out that the initial rate of oxygen uptake in a mince of Tropaeolum maju8 leaf (Roberts & Sarma, 1940) is of the same order as that recorded by Jensen (1923) for the intact tissue. We consider the initial rate represents a brief phase of irreversible oxidation of carriers and emphasize that after this short initial rapid uptake, lasting not longer than 15 min., the rate of oxygen uptake falls to less than 10 % of this level.…”

“…to corn records oxygen uptakes a] for systems consisting of enzyme and green leaf enzyme and a tea catech ficant difference in the R. the two latter systems a] factors necessary to ena substances such as glucos Table 7 table also shows a low carbon dioxide output for an ,nd carbon dioxide outputs infusion of Hibiscus rosa-sinensis leaf. This was (1) minced leaf, (2) washed shown by Roberts & Sarma (1940)…”

Studies on the fermentation of Ceylon tea. 8. Further observations on the relationship of tea fermentation to normal respiration

“…It can be shown, however, that even under these conditions of grinding there exists an appreciable amount of normal respiration in the finely minced tissues. Roberts & Sarma (1940) have given Qo2 and R.Q.…”