Department of Agricultural Resources and Economics

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Subject: search.filters.subject.Catechins

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    Optimization of manufacturing conditions of the new purple leafed Kenyan teas (TRFK 306) – maceration style and withering duration
    (2018) Kilel, E.C.; Wanyoko, J.K.; Faraj, A.K.; Ngoda, P.
    Purple tea in Kenya, TRFK 306, has received great attention due to its perceived health benefits though how it should be optimally manufactured has not been researched on exhaustively. The current study investigated on the two possible methods of manufacture – Cut Tear and Curl (CTC) and orthodox manufacture - with varying withering time of 0, 5, 10, 15 and 20 hours. Catechins, gallic acid, caffeine, total polyphenols and antioxidant activity were assayed as quality indicators. If gallic acid and caffeine are the main chemicals targeted, then orthodox type with longer withering, 15 – 20 hours, is usually recommended. When targeting catechins especially epigallocatechin gallate and high total polyphenols, orthodox type of manufacture whichever the withering time is proposed. CTC with withering hours of 15-20 produces teas with high antioxidant activity. It was concluded that TRFK 306 is best processed by orthodox or CTC but with longer withering time.
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    The polyphenolic composition and radical scavenging properties of Kenyan tea cultivars
    (2015) Karori, S.M; Wachira, F.N; Ngure, R.M; Mireji, P.O.; Koech, R.K
    Interest in medicinal and health enhancing properties of functional components in foods continues to arouse a lot of interest. Polyphenolic fractions in tea are potent bioactive molecules. In this study, the polyphenolic composition of 25 different types of Kenyan tea cultivars was determined using the HPLC and the Folins Ciocalteus spectrophotometric methods. Total polyphenols, total catechins, individual catechins and antioxidant activity were significantly (P < 0.05) different among tea varieties, with green tea having the highest levels of total polyphenols ranging from 19.70% to 26.12%, TC (8.51% to 17.60%), individual catechins, and AA (86.65% to 94.50%). In vitro bioassay carried out using 2, 2'-diphenyl picryl hydrazyl radical showed epigallocatechin gallate was the most potent catechin and the most potent in antioxidant activity (r = 0.968***). Epigallocatechin (r = 0.659***, P < 0.001), epicatechigallate (r = 0.454*, P < 0.001), and epicatechin (EC) (r = 0.780***, P < 0.001), showed significant (P < 0.05) antioxidant activity. Black tea contained high levels of theaflavins and thearubigins (2.072% to 17.12%), respectively which accounted for its antioxidant activity (r = 0.803*** and r = 0.859***, respectively). Gallic acid also showed significant (r = 0.530*) contribution to the antioxidant activity in black tea. Data obtained from this study reveals that different Kenyan tea cultivars have different polyphenolic composition which imparts on their unique biochemical qualities. Cultivar type is therefore a critical factor in determining the antioxidant potency of tea product and that black tea processed from suitable cultivars could be potent in antioxidant activity when compared to green tea. Green and white tea products are rich in catechins, black tea products are rich in TFs and TRs while purple tea is rich in anthocyanins.
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