The effect of withering on fermentation of tea leaf and development of liquor characters of black teas

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Abstract
Depression in polyphenol oxidase (PPO) activity during the withering of tea leaf (Camellia sinensis) in black tea manufacture affected the oxidative‐condensation of tea flavanols in forming theaflavins (TF) and thearubigins (TR), which are associated with brightness, briskness and ‘body’ of tea liquors. In contrast to conventionally manufactured CTC teas, unwithered fresh leaf CTC produces a higher proportion of TF and lower TR, resulting in bright, brisk and thin liquors. Hardness of wither was accompanied by a further depression in PPO activity, and formation of TF also declined with a concomitant loss in brightness and briskness. The TR content increased up to a certain degree of wither and thereby improved the ‘body’ of the liquor. Very hard wither, accompanied by a large reduction in moisture content, restricts PPO activity. It appears that in the fresh leaf, high moisture levels together with dissolved oxygen accelerate the enzymic oxidation and produce large amounts of TF. Senescence of the leaf seems to facilitate the production of TR.

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