Some Factors Influencing Fermetation Process in Ctc Black Tea Processing:Experiences from Kenya
Tea is an important cash crop for many countries, creating employment in the rural areas where economic opportunities are rare and generating large amounts of foreign exchange.Largely, the price realisation of black tea is dependent on its quality as buyers select what to buy depending on their desired taste.Fermentation process is critical in black tea processing since most of the chemical transformations occur at this stage.Optimising the process ensures that the resultant black tea is of high quality.Black tea theaflavins increase then reach maximum level then declines, but thearubigins increase continuously with fermentation duration.Maximum formation total theaflavin had been thought to imply good black tea quality.The in-line theaflavins analysis earlier developed to optimise fermentation duration has been shown to be less accurate compared to the measurement of the total theaflavins in black made tea.Different tea cultivars ferment at different rates leading to black teas of varying chemical quality parameters composition,particularly the theaflavins, thearubigins and volatile flavour compounds.Fermentation rate also depend on the geographical area of production, oxygen supply, temperatures,degree of wither, and plucking standard.But generally, CTC black tea quality was enhanced by fermenting at cool temperatures below 20℃.Aroma quality of black tea (flavour index (FI)) is estimated as a ratio of Group Ⅱ (responsible for sweet floral smell):Group Ⅰ (responsible for green grassy aroma) volatile flavour compounds (VFC).Short fermentation duration produces black tea with greenish aroma due to high concentration of Group Ⅰ VFC, while medium fermentation duration produces more aromatic black tea resulting from high concentration of the Group Ⅱ VFC thereby improving FI.However,longer fermentation duration reduces quality through reduction of Group Ⅱ VFC and FI.The individual theaflavins form at different rates during fermentation.For production of high quality tea, it is necessary that fermentation conditions are monitored to ensure maintenance of cool temperatures, adequate air supply and maintaining correct fermentation duration to produce black tea of higher values.Also it is necessary to develop cultivar and region specific fermentation parameters to ensure production of high quality CTC black teas.
P.Okinda Owuor
Department of Chemistry, School of Biological and Physical Sciences, Maseno University, P.O.Box 333-4105, Maseno, Kenya
国际会议
International Tea Symposium 2014(ITS 2014)(国际茶叶学术研讨会)
杭州
英文
364-372
2014-09-10（万方平台首次上网日期，不代表论文的发表时间）