School of Agriculture and Biotechnology
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Item 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.Item Prospects for organic tea farming in Kenya: Two case studies(2015) Kamau, D.M.; Kekana, V.; Sitienei, K.; Wanyoko, J.K.; Nyabundi, K.Organic tea farming entails non-use of pesticides and inorganic fertilizers, including the processing and packaging of the tea. This implies that documents must be filed which prove all requirements are met throughout the growing, processing, packaging, and which can be traced by the organic certification organization. Today, almost all kinds of tea grown in Kenya are non-organic. This is despite the fact that only NPK fertilizers are used in tea farms. It is difficult just to make an organic tea farm because of the many non-organic tea farms around it. Dispersals of chemical fertilizers or herbicides and other chemical agents interfused through the soil from surrounding farms can enter the organic farm. Therefore, it is necessary to make a buffer zone or shelterbelt between an organic tea farm and nonorganic tea farm or to embrace organic tea cultivation together with the neighbouring farmers. However, the starting point is to establish that organic tea can indeed be grown economically. Two long term studies comparing different sources of organic manures in Kericho and Kangaita were assessed for yield, some soil properties and tea quality chemical parameters. The results reveal that although the organic manures do not give as high yields as the enriched manure treatments from inorganic sources, rates of 120-150 kgN/ha would suffice to replenish the lost nutrients thus maintaining tea bush health and also optimal yields. The soil pH, available K and Ca results also demonstrated that the organic manures can maintain the acidity levels of the soils thus addressing the often controversial land sustainability problem arising from use of external inputs in tea agroecosystems. Organic manures and enriched manures increased the TF and TR content while caffeine increased with increase in nitrogen rates. This was more pronounced when using inorganic fertilizers and enriched manures. The study suggests that development and promotion of organic and low carbon in the Tea Industry is key to the attainment of ecological health and environment protection by both the tea producers and consumers. Tea growers have to be compensated by benefiting from premium organic tea prices due to the loss in yields as seen by the higher yields arising from the enriched manures.Item Antioxidant, antimicrobial and synergistic activities of tea polyphenols(2015) Koech, K.R.; Wachira, F.N.; Ngure, R.M.; Wanyoko, J.K.; Bii, C.C.; Karori, S.M.; Kerio, L.C.Microbial resistance to conventional antibiotics has become an increasing global problem and there is a need to find out novel, potent antimicrobial agents with alternative modes of action as accessories to antibiotic therapy. This study investigated the antioxidant, antimicrobial and synergistic properties of tea polyphenols. The tea germplasm from Kenya, China and Japan that are grown in Kenya were characterised for their biochemical profiles. The total phenolic content, theaflavins and thearubigins content of different tea products used in this study were determined spectrophotometrically according to Folin-Ciocalteus and flavognost methods respectively. The individual catechin contents were characterised by high performance liquid chromatography (HPLC) and identified according to their HPLC retention times, elution order and comparison with authentic standards. The antioxidant activity of tea polyphenols was determined using UV-Vis spectrophotometer on its ability to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical. The Agar Disc Diffusion method was used to screen for antimicrobial and synergistic activities of the tea liquors. Black, green, purple coloured leaf and white (silvery tips) tea products characterised for their biochemical profiles differed significantly in the levels of total polyphenols, total catechins, catechins fractions, theaflavins and thearubigins (P ≤ 0.05). Green, purple coloured leaf (aerated) and black tea from terminal buds and white tea products analysed in this study exhibited slightly higher antioxidant activity compared to black tea. The different types of tea products assayed in this study exhibited significant influence on the inhibition zone diameters against bacteria and fungi exposed to the tea extracts. Methicillin and penicillinase resistant S. aureus ATCC 25923, C. albicans ATCC 90028 and a clinical isolate of C. neoformans were more susceptible to all tea extracts than E. coli and S. typhi. There was synergism between most tea extracts and penicillin G against methicillin and penicillinase resistant S. aureus ATTC 25923.Item Assessing the effect of grading on the in vitro availability of Fe, Zn, Cu, Pb and Cd from CTC black tea(2015) Moseti, K.O.; Kinyanjui, T.; Wanyoko, J.K.; Wachira, F.N.In vitro analyses of trace element content in biological systems play an increasingly important role in assessing the environmental impact on health. A quantitative study of five trace elements namely Fe, Zn, Cu, Pb and Cd in cut, tear and curl (CTC) black Tea of different grades randomly sampled from four tea growing countries in East Africa, viz., Kenya, Uganda, Rwanda and Tanzania was carried out. The total element content as well as the water extractable content of the tea samples was done by Atomic Absorption Spectroscopy (AAS). Data obtained was analyzed using Graph-pad Prism statistical software for Windows, version 5.0 and P < 0.05 considered to be statistically significant. The significance of the difference between means for black tea and tea infusions was determined by one way ANOVA and the least significant difference test was used for mean separation where significant differences were recorded among group means. It was observed that tea contains the studied elements and only a very small portion of the total element content lixiviates into tea liquor during tea making process. The general extractability pattern of the elements studied was in the order Fe > Zn > Cu > Pb > Cd, indicating that tea is an important dietary source of Fe, Zn and Cu. Taking into account the high tea to water ratio used in preparing the analysed tea extracts, these data is best regarded as the extractability potential of the tea liquor and does not reflect the actual concentrations contained in the tea liquor that we actually consumed. However, the need to enact safety guidelines with regard to the liquor element composition is imperative.Item The anti-inflammatory properties of Kenyan tea(2015) Karori, S.M .; Ngure, R.M.; Wanyoko, J.K.; Wachira, F.N.An in vivo study was carried out to determine the effect of different types of Kenyan tea extracts on male Swiss albino mice infected with Trypanosoma brucei brucei isolate KETRI 2710. The isolate produced a similar clinical picture after a pre-patent period of five days post-infection (DPI). Parasitemia levels in the untreated mice and those given different tea developed exponentially at similar rates reaching the peak of parasitemia 8 DPI. Between 9 and 13 DPI parasitemia decreased more rapidly in tea treated compared to the untreated mice which indicated that tea lowered parasitemia. Anaemia indicated by a fall in erythrocyte packed cell volume (PCV) occurred within 4 DPI and remained below the normal levels until the terminal stages of the disease. A significant difference (P < 0.05) was observed 11 DPI between the tea treated and the untreated mice indicating that tea enhanced resistance to erythrocyte destruction. Mice treated with tea exhibited significantly (P < 0.01) reduced parasite induced hypoalbuminemia as compared to the untreated demonstrating that tea ameliorated inflammation induced by T. brucei brucei. Black tea, which is the principle tea product from Kenya, displayed remarkable properties some even comparable to those of green tea. Tea was more efficacious than dexamethasone, an established anti-inflammatory drug, demonstrating its therapeutic potential.