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...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.展开更多
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 ...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%.展开更多
文摘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.
文摘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%.
