Abstract
This study was carried out to characterize total residual catechins and their fractions, polyphenolic contents and antioxidant activities of black teas enriched with high levels of theaflavin-3,3’-digallate. The made teas were processed from eleven selected cultivars. A comparative study was carried out between the processed teas and those from commercially grown Kenyan cultivars in relation to the above chemical parameters. A correlation matrix analysis was also conducted to find out whether a relationship existed between the antioxidant activities and the said chemical parameters. The total residual catechins were found to range between 3.10% and 8.08%. The total polyphenol levels varied between 19.00% and 28.90%, while the antioxidant activities of the teas ranged from 82.70% to 91.70%. There was a significant p < 0.001 correlation between the antioxidant activity and total polyphenols (r = 0.8948). There was also a high correlation p < 0.001 between the antioxidant activity and total catechins (r = 0.8878). Out of the four catechin fractions, the antioxidant activity correlated most with EGCG (r = 0.8774). The total polyphenolic contents and antioxidant activities for most of the cultivars were comparable to those of the green tea reference standard. From the figures obtained, it can be concluded that the most of the newly developed black teas of the selected cultivars have higher quality and enhanced antioxidant activities and that they can be recommended for commercial production.
Highlights
Black tea is one of the most widely consumed beverages in the world owing to its refreshing taste and health benefits attributed to the antioxidants [1]
Black tea is processed through weathering of fresh tea leaves and subjecting them to aeration process
The comparability of the green tea reference standard with most of the cultivars with regards to their antioxidant activity shows that there may be no significant difference in antioxidant activity between green teas and the TF3 enriched black teas
Summary
Black tea is one of the most widely consumed beverages in the world owing to its refreshing taste and health benefits attributed to the antioxidants [1]. Mainly the theaflavins (TFs), Thearubigens (TRs) and unoxidized catechins all of which contribute to the overall antioxidative property of the tea [2]. The aeration process produces the brown coloured compounds (TFs and TRs) found in black tea [3]. Fresh tea leaves contain catechins, which comprise the reactants used in the formation of black tea TFs and TRs [4]. Consumers are increasingly becoming aware of the health benefits of black tea the beverage’s price will be determined by their level of bioactivity. This research work sought to characterize the various bioactive compounds in those manufactured black teas
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