Effect of Degree of Fermentation on Phenolic Profiles and Quality of Black Tea

Abstract

Tea is one of the most popular beverages in the world next to water and consumed by over two-thirds of the world's population. The quality of tea is mainly affected by the fermentation process where the chemical changes occur during manufacturing of black tea. Even though, Ceylon tea is considered as the world's number one brand, there is no clear evidence of the best fermentation time for the best phenolic profile of Ceylon black tea. Therefore, the objective of the present study was to determine the best phenolic profile, sensory attributes and final quality of manufactured black tea as affected by the fermentation time. Black tea was manufactured using six tea cultivars including high quality (TRI 777 and DT 1), moderate quality (TRI 2 0 2 4 and TRI 2025) and low quality (TRI 2023 and K145). The manufacturing process was carried out in the Environmentally Controlled Manufacturing (ECM) Unit controlling their fermentation time as 0.5 ,1 ,1 .5 ,2 ,2 .5 and 3 h. The form of refrigerated flush was freeze dried with the use of a freeze drier system before the chemical analysis was carried out. Then the freeze dried flush and manufactured black tea were chemically analyzed for total polyphenols (TPP) using the spectrophotometer and individual catechins (TCA) using High Performance Liquid Chromatography (HPLC). The theaflavin (TF), thearubugins (TR), total colour and total brightness of black teas were determined using Roberts and Smith method. The tea tasting was evaluated by professional tea tasters in term s of tea liquor colour, taste, aroma, strength and infusion of manufactured black on a five-point hedonic scale. The results of the present study revealed that the TPP values ranged from 16.39 to 22.53% and TCA values ranged from 8.96 to 16.36% and the values were at the optimum levels for high, moderate and low quality tea cultivars. The most favourable fermentation time for selected cultivars of Camellia sinensis were around one hour for high quality cultivars, around one and a half hours for moderate quality cultivars and around two hours for low quality cultivars. It can be concluded that fermentation time has a significant effect on the phenolic profile and final quality of the made black produced from high, moderate and low quality tea cultivars.