Determination of Residual Catechins, Polyphenolic Contents and Antioxidant Activities of Developed Theaflavin-3,3’-Digallate Rich Black Teas

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.

Quantitative Estimation of γ-Glutamylethylamide in Commercially Available Made Teas [Camellia sinensis (L.) O. Kuntze, Theaceae] in Kenya

A study was carried out to quantitatively estimate the L-theanine content in 19 teas commercially available in the Kenyan market by High Performance Liquid Chromatography (HPLC). The test tea samples analyzed were green (n = 4), black (n = 8) and flavored (n = 7) teas from different origins viz., Kenya (n = 4), Uganda (n = 2), Tanzania (n = 5), Rwanda (n = 4), Cameroon (n = 1) and Sri-Lanka (n = 2) commercially available in the Kenyan market. The estimated Limit of Detection (LOD) of the current method was 0.01% L-theanine. The L-theanine content ranged from below the detection limit (<0.01% L-theanine) to 1.60% L-theanine on a dry weight (d.w) basis. Statistically significant differences (p < 0.05) were observed in the L-theanine contents of black, green and flavoured teas. Rwandan green tea contained the highest L-theanine content with 1.60% d.w. whereas six of the seven flavoured teas had very low theanine levels (<0.01%) that could not be quantified by the current method.

Influence of Geographical Regions on Catechin and Caffeine Levels in Tea (Camellia sinensis)

This study aimed at investigating the influence of different growing conditions in two regions, Timbilil and Kangaita, on the levels of catechins and caffeine. Fresh leaf samples of 60 clones cultivated in both sites were obtained, processed and assayed for levels of caffeine, total and individual catechins using Reverse Phase High Performance Liquid Chromatography (RP-HPLC). The obtained data was subjected to analysis of variance using GENSTAT-C statistical software. Safe for a few clones in the Kangaita site had significantly higher total and individual catechins than those grown in the Timbilil site. A mean epigallocatechin gallate (EGCG) content of 7.9% was observed for Kangaita clones compared to 6.7% in Timbilil. A similar trend was observed for the rest of the individual catechin fractions with a mean epicatechin gallate (ECG) of 3.3% in Kangaita and 2.5% in Timbilil, a mean epigallocatechin (EGC) of 5.2% in Kangaita compared to 5.0% in Timbilil and a mean epicatechin (EC) content of 1.5% in Kangaita compared to 1.4% in Timbilil. Similarly in the total catechins analyses, clones in Kangaita had a mean value of 18.7% compared to 16.2% observed for the Timbilil site clones. However, the Timbilil site clones had significantly high caffeine contents (mean, 4.2%) compared to the Kangaita site clones (mean, 3.9%) although with a few exceptions. Significant interactions (P < 0.05) between clone and region are also observed, suggesting that levels of these biomolecules are bound to differ with the growing region but the extent of variation will vary depending on the clonal genotype. The observed differences in levels of these biologically important biomolecules among the two regions shows the importance of the underlying conditions on the production of tea.

Optimization of Aeration Time in the Development Theaflavin-3,3’-Digallate Rich Black Teas

This study involved the selection of 11 cultivars out of 201 screened cultivars of fresh green and purple coloured tea leaves for use in the manufacture of black teas with optimized antioxidant activities. Individual cultivars containing a combination of high leaf concentrations of the catechin fractions;epicatechin gallate (ECG) and epigallocatechin gallate (EGCG) were used in the processing of theaflavin-3,3’ digallate (TF3) rich black tea. The black tea enrichment with TF3 was carried out through optimization of the processing conditions of each cultivar by varying the aeration times between 0 min and 80 min at an interval of 20 min. The differently processed teas were then assayed for the TF3 contents. The data analysis was carried out using the GENSTAT at p ≤ 0.05. The optimal processing time for Ejulu, TRFK 832/8, TRFK 831/11, TRFK 824/1, SC 31/37, SC 12/28, K-Purple and TRFK 6/8 was found to be 60 min while that of TRFK 301/6, TRFK 301/3 and TRFK 655/1 was 40 min. The optimal TF3 levels were found to range from 0.19% to 0.60%.