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Owuor O.P.,Maseno University | Kamau D.M.,Tea Research Foundation of Kenya | Jondiko E.O.,Maseno University
Journal of Food, Agriculture and Environment | Year: 2010

Variations in requirements for tea production in Kenya and factors controlling growth and production of secondary metabolites responsible for the quality parameters are indicative of the need for non-uniform recommendations. Nitrogen is the main nutrient for which tea shows easily demonstrable yield and quality responses. Fertilizer applications at rates between 100 and 250 kg N/ha/year of NPKS 25:5:5:5 are currently recommended in tea production. Although yield and black tea quality variations with nitrogen rates had been observed in the past, the studies were at single geographical locations. Where comparisons were done at different locations, the genotypes were different making it impossible to isolate environmental and genotypic effects. The response of single genotype to varying rates of nitrogen in the major tea growing areas has not been reported. Consequently, it is not known if the recommended nitrogen rates are optimal in all tea growing areas for production of high yields and good quality black teas. Trials were conducted in five major tea growing regions of Kenya to quantify the yields and illustrate plain tea quality parameters responses of cultivar BBK 35 to varying rates of NPKS 25:5:5:5 fertiliser applied at 0, 75, 150, 225 and 300 kg N/ha/year. Yields were recorded for a period of ten years (1998 to 2007). Pluckable shoots from the plots were processed into black tea and analyses for quality carried out in 2007. Yields significantly (P ≤ 0.05) increased while quality declined with increasing rates of nitrogen. The mean yield varied in the following order: Sotik Highlands ≥ Changoi > Karirana > Kipkebe ≥ Timbilil. Also plain black tea quality as measured by theaflavins, thearubigins, total colour, brightness and sensory evaluations varied with geographical area of production. The theaflavins declined in the order: Changoi ≥ Karirana > Timbilil ≥ Kipkebe > Sotik Highlands. There was significant (P ≤ 0.05) interaction between geographical area of production and nitrogen fertilizer rates in yields demonstrating that yield response of BBK 35 to nitrogen varies with localities. The actual optimal nitrogen for the individual locations, however, will also be affected by quality, cost of production including cost of fertilisers and realised tea prices. Location specific recommendations need to be developed to promote high yields and production of high quality black teas in the different tea growing regions.

Muoki R.C.,Institute of Himalayan Bioresource Technology | Muoki R.C.,Tea Research Foundation of Kenya | Paul A.,Institute of Himalayan Bioresource Technology | Kumar S.,Institute of Himalayan Bioresource Technology
Functional and Integrative Genomics | Year: 2012

Abstract Drought poses a significant threat to tree plants including tea [Camellia sinensis (L.) O. Kuntze] that yields a popular beverage "tea." Consequence of drought is heat and salt stress, for which data on molecular response in tree species are not available. The present work analyzed drought-responsive subtracted cDNA libraries of tea to identify drought-responsive genes. Temporal and spatial gene expression suggested the involvement of chaperones as one of the major mechanisms to protect the plant against drought-related damages. A common response of thaumatin like protein, chitinase, and late embryogenesis abundant protein3 across four stresses suggests these to be useful targets to generate "drought stress proof" tea. ©Springer-Verlag 2012.

Kerio L.C.,Tea Research Foundation of Kenya | Wachira F.N.,Association for Strengthening Agricultural Research in East and Central Africa ASARECA | Wanyoko J.K.,Tea Research Foundation of Kenya | Rotich M.K.,Egerton University
Food Chemistry | Year: 2013

Black (aerated) and green (unaerated) tea products, processed from 10 green and 18 purple leaf coloured cultivars of Kenyan origin, and two tea products, from the Japanese cultivars, Yabukita and Yutakamidori, were assayed for total polyphenols (TP) content, individual catechin profiles and in vitro antioxidant capacity (AA). In addition, the phenolic content of the tea products was determined using the Folin-Ciocalteu phenol reagent. Catechin fractions were identified using reverse phase high performance liquid chromatography (HPLC) with a binary gradient elution system. The AA% of the tea products was determined using a 2,2′-diphenyl picrylhydrazyl (DPPH) radical assay method. The results showed that TPs, catechin profiles and antioxidant activities were significantly (p ≤ 0.05) higher in unaerated than in aerated teas. Tea products from the purple leaf coloured tea cultivars had levels of TPs, total catechin (TC) and antioxidant activities similar to those from the green leaf coloured cultivars, except for teas from the Japanese cultivars that were very low in the assayed parameters. Caffeine content was significantly (p ≤ 0.05) lower in products from the purple leaf coloured cultivars than in those from the green leaf coloured tea cultivars. Antioxidant activity (%) was higher in tea products from the Kenyan germplasm than in those from the Japanese cultivars. Antioxidant potency of tea products was significantly (r = 0.789, p ≤ 0.01) influenced by the total anthocyanin content of the purple leaf coloured cultivars. Cyanidin-3-O-glucoside was the anthocyanin most highly correlated with AA% (r = 0.843, p ≤ 0.01 in unaerated tea). Total catechins in the unaerated products from the green leaf coloured tea cultivars were also significantly correlated with antioxidant capacity (r = 0.818 p ≤ 0.01). Results from this study suggest that the antioxidant potency of teas is dependent on the predominant flavonoid compound, the type of tea cultivar and the processing method. © 2012 Elsevier Ltd. All rights reserved.

Azapagic A.,University of Manchester | Bore J.,Tea Research Foundation of Kenya | Cheserek B.,Tea Research Foundation of Kenya | Kamunya S.,Tea Research Foundation of Kenya | Elbehri A.,Food and Agricultural Organization of the United Nations
Journal of Cleaner Production | Year: 2015

Kenya is the third largest producer of tea in the world, the majority of which is exported, contributing 20% to the total national income from exports. Yet, its environmental impacts are currently unknown. This study considers for the first time one of the impacts - the global warming potential - of production and consumption of Kenyan black tea. The system boundary is from 'cradle to grave'. Both small- and large-scale production of tea is considered. The functional unit is defined as 1kg of dry tea and the tea is assumed to be consumed in the UK. The results suggest that the total impact of tea is equal to 12.45kg CO2 eq./kg of dry tea for the large-scale and 12.08kg CO2 eq./kg for the small-scale production, indicating that the scale of production does not influence the impact. The main contributor is tea consumption which is responsible for 85% of the impact because of the electricity used to boil water. Tea cultivation and processing contribute around 10% to the total. The contribution of transport is relatively small (4%). The global warming potential from waste management is negative because of the credits for recycling of post-consumer tea packaging. The results are most sensitive to consumer behaviour, with the impact almost doubling with doubling the amount of water boiled for each cup of tea. Drinking tea with milk has even greater impact, increasing the total impact by up to three times. Appropriate consumer engagement programmes are needed to encourage behavioural change. © 2015 Elsevier Ltd.

Korir M.W.,Egerton University | Wachira F.N.,Association for Strengthening Agricultural Research in East and Central Africa ASARECA | Wanyoko J.K.,Tea Research Foundation of Kenya | Ngure R.M.,Egerton University | Khalid R.,Tea Research Foundation of Kenya
Food Chemistry | Year: 2014

Several studies have demonstrated that tea flavonoids protect cells and tissues against free radicals which have been implicated in the etiology of oxidative stress-related disease disorders. However, black tea is commonly consumed with additives that could otherwise affect the bioavailability of the active tea molecules. In this study, the biochemical parameters of Kenyan teas were determined and the effect of added milk and sweeteners on the antioxidant activity of Kenyan teas was investigated. The effect of tea antioxidants on glutathione (GSH) was also evaluated in vivo in a time series study using Swiss mice. Green teas had the highest levels of total polyphenols, total and individual catechins, while black teas had high levels of total thearubigins, total theaflavins and theaflavin fractions. The antioxidant activity was high in green teas though some of the black teas were as efficacious as the green teas. The addition of milk, sugar and honey significantly (p < 0.05) decreased the antioxidant activity of tea in a concentration-dependent manner. Addition of the sweetener, stevia (Stevia rebaudiana Bertoni), showed no significant (p > 0.05) influence on the antioxidant activity of tea and therefore can be recommended as a preferred sweetener for tea. Significantly (p < 0.001) higher levels of GSH were observed in plasma than in other tissues. GSH levels were generally highest 2 h after tea consumption, which indicates the need to repeatedly take tea every 2 h to maximise its potential health benefits. © 2013 Elsevier Ltd. All rights reserved.

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