Dynamics of Catechins Degradation and Theaflavins Formation during Fermentation in Clonal Black Tea

Abstract

Catechins and theaflavins (TFs) contribute to quality and health benefits of tea beverages. Catechins are converted mainly to TFs and thearubigins during fermentation. TFs form in quadratic manner reaching maximum levels then decline. It is not documented if the decline is due to depletion of some catechins. Catechins have been implicated to have beneficial pharmacological activities. Although TFs have similar activities, there have been claims that green teas have higher beneficial pharmacological activities. This is despite the fact that green teas are generally processed from Camellia sinensis var. sinensis with lower total catechin content, unlike black teas, which are generally processed from Camellia sinensis var. assamica, which generally have higher catechins contents. It is not documented levels of residual catechins at optimal fermentation durations are similar to the levels in green teas. This trial was conducted to determine if some individual catechins get depleted in the course of fermentation to cause levels of TFs reaching maximum then declining using a fats and a slow fermenting clones over an extended fermentation duration.  It was also conducted to determine if the levels of residual catechins in black tea are similar to those in green teas.  The experimental designs were randomised complete block and correlational designs clone (6/8 (fast fermenter) and S15/10 (slow fermenter)) with fermentation durations (0, 30, 60, 90. 120, 150, 180 minutes) as treatments, replicated six times. Leaf was miniature CTC manufactured. Individual catechins declined (p\(\le\) 0.05) with fermentation durations following exponential and/or power functions (p\(\le\) 0.01), the decline being faster in clone 6/8 than S15/10. Individual TFs increased (p\(\le\) 0.05) with fermentation duration in quadratic patterns (p\(\le\) 0.01) reaching maximum after different durations in different clonal patterns. Depletion rates of catechins varied with clones and individual catechins. Large quantities of residual catechins remained in black teas after 70–120 minutes fermentation, normally considered optimal fermentation duration in Kenya, thereby contributing to quality and human health benefits. Thus, in addition to the beneficial pharmacological activities conferred by TFs, the optimally fermented black teas have substantial pharmacological activities due to the residual catechins. Individual TFs reached maximum levels at different times. No catechin was exhausted even after long fermentation duration in both clones. This demonstrates that total and theaflavins reaching a maximum after then declining during fermentation duration is not due to exhausting of individual catechins, but due transformation of the TFs to thearubigins and other highly polymerised phenolic compounds.