A reliable technique to identify superior quality clones from tea germplasm

Abstract

Variations in the substrate level and enzyme activity of prominent south Indian tea germplasm were studied. The content of polyphenols, catechins (substrates) and polyphenol oxidase (PPO) showed variation, which influenced the final black tea quality. The enzyme PPO occurs in tea shoots and catalyzes the reactions between catechins to form theaflavins in the presence of oxygen. The catechins mainly epicatechin (EC), epigallo catechin gallate (EGCG), epicatechin gallate (ECG) and epigallo catechin (EGC) get mixed with PPO during the oxidation process to form quality constituents like theaflavins (TF), thearubigins (TR) and high polymerized substances (HPS). Theaflavins and their fractions such as simple theaflavin, theaflavin monogallate, (TFMG), theaflavin digallate (TFDG) in black tea are the essential quality constituents that are responsible for the liquor characteristics where as TR and high polymerized substances impart colour to the liquor. As oxidation of macerated leaves proceed through different stages of tea manufacture, a decline in PPO activity, polyphenol and catechin contents were observed. Data revealed that the oxidation reaction was faster during the initial stages of oxidation. During the period, oxygen consumption was higher and declined thereafter. Ratio between the enzyme (PPO) and its substrate (catechins) were used to characterize the quality potential of tea clones. An attempt has also been made to categorize prominent tea clones as high, moderate and average quality clones based on their enzyme substrate ratio. Theaflavin content (oxidation product) of different tea clones suggests that the ratio between PPO and catechins forms an important criterion which determines black tea quality. Results obtained were compared with standard clones of known high quality (CR-6017) and moderate quality (SA-6). The study reveals that the enzyme substrate ratio can be used to identify superior quality clones from the existing tea germplasm.