Biochemical analysis for identification of quality in black tea (Camellia sinensis)

Abstract

In this study we investigated methods to increase tea quality by developing quality markers for the breeder, as well as methods to improve quality during the manufacturing process. The compounds investigated for identifying quality markers were the major green leaf flavan-3-ols, caffeine and the major theaflavins. To be able to analyze the theaflavins in the manufactured black tea, we developed a non-aqueous capillary electrophoresis method. This non-aqueous capillary electrophoresis method can also be used to improve tea quality by optimizing the black tea manufacturing procedure. We also investigated the ability of improving the tea quality by the addition of tannase to alter the contents of the individual theaflavins in the black tea. To identify flavan-3-ols and theaflavins related to tea quality, twenty good and twenty poor quality tea clones were selected from the breeding programme at the Tea Research Foundation of Central Africa. The contents of the individual flavan-3-ols of fresh tea leaves and the contents of the individual theaflavins were analyzed with capillary electrophoresis. Total theaflavin and individual theaflavin content was determined in the black tea manufactured from the same leaves for each clone. The above parameters were correlated with total scores and valuation from two tea tasters with regression analysis. The significance of the differences between the good and poor quality clones was determined with the Student’s t-test and the distribution free Kruskal-Wallis test. Our results suggest that (-)-epicatechin and (-)-epicatechin gallate contents of the fresh leaf can be used to predict the quality potential of new clones early in the breeding programme. The suitability of quality improvement during the manufacturing stage was also investigated by the addition of tannase. The added tannase resulted in statistical significant increase in free theaflavins. With the use of a low dose of tannase, a significant increase in the tea quality was observed by one tea taster.