Biochemical changes during fermentation process of black tea manufacture

The quality of black tea is mainly depends on the standard of plucking the green leaf. The most attractiveness of tea as beverage for the main part due to the presence of Polyphenol and caffeine. Young tea shoots are extremely rich in Polyphenol and caffeine which constitute up to 30 percent and 4 percent. Although many of the biochemical transformations occur during the withering phase of tea manufacture, but the most noticeable changes occur during fermentation. Fermentation is an oxidation process by which the Polyphenol in leaf gets oxidized with the help of endogenous enzyme namely Polyphenol oxidase. Before rolling, Polyphenol and Polyphenol oxidase are located in different compartments in the cell wall. When the green leaf gets crushed during rolling, the Polyphenol and the enzyme mixed in the presence of oxygen and the bio-chemical changes takes place. This involves the oxidation of catechins to theaflavins and thearubigins in the presence of polyphenol oxidase, and unsaturated fatty acids and amino acids to volatile flavour compounds, is thought to be the most critical stage in tea manufacture. TF and TR are basically pigments. The end product of fermentation is TF and TR which are responsible for briskness, brightness and color of the tea liquor. Chemically optimum fermentation may be assessed by monitoring the profile of TF content and taking the time required for the production of maximum TF, proper balance between TF and TR is also essential for a good cup of tea. In this study the colorimetric estimation of substances (polyphenols) and the remaining products such as TF, were carried out to determine the OFT. Fermented dhool 60 to 75 minutes showed that the highest tea liquor color, TF, TR, HPS and caffeine were identified.