Biochemical quality characteristics of CTC black teas of south India and their relation to organoleptic evaluation

A study was conducted over a period of 5 years to quantify the quality characteristics of CTC (crush, tear and curl) black teas produced in Wayanad, Central Travancore, Anamallais, High Range, Nilgiris and Chikmagalur areas of south India and their correlation with organoleptic evaluation. Quality characteristics such as theaflavins (TF), thearubigins (TR), highly polymerised substances (HPS), total liquor colour (TLC), TR/TF ratio and colour index (CI) were estimated. Teas from Karnataka, Nilgiris and Anamallais had the highest theaflavin content and better TR/TF ratio than the teas from Travancore, High Range and Wayanad regions. A significant positive correlation of theaflavin content with the values of thearubigins, total liquor colour, colour index, infused leaf appearance (ILA) and taste (TAS) was observed.     

Comparison of black tea aromas of orthodox and CTC tea and of black teas made from different varieties

Volatile compounds obtained from orthodox black tea and CTC tea were analysed by a g.c.-m.s. method. A difference in the contents of cis-3-hexenol, linalool, linalool oxides, methylsalcylate and geraniol was found between the two types of tea. It was thought that the difference in the contents of volatile compounds might be produced by the individual manufacturing processes. A typical difference in the contents of linalool and geraniol was observed in volatile oils of black teas made from cultivars of v. assamica and hybrids of assamica and sinensis. The difference in the volatile compounds in black teas may be related to the genetic variation.     

CTC红碎茶加工工艺

对从印度引进的CTC红碎茶加工工艺技术作了较详尽的介绍。     

Significant physical attributes affecting quality of Indian black (CTC) tea

In this research work, an attempt was made to discriminate different grades of black crush-tear-curl (CTC) tea based upon their physical attributes such as color of brewed liquor, texture, size and shape of the tea granules obtained by machine vision technique. The principal component analysis (PCA) was applied over two types of data. First, tea samples with seven different quality grades but same mechanical grading and second, samples with same quality grade but nine different mechanical grades (Brokens, Fannings and Dust) were considered for analysis, respectively. The results of PCA showed that best discrimination (100%) in both types of data was given by color attributes only. Correlations among tea samples and physical attributes were determined. Based upon these results it may be concluded that color only attributes are the most significant and sufficient for quantification of tea quality whereas other physical attributes contribute so little to quality estimation that they may be ignored.     

Quality evaluation of black CTC teas based upon seasonal variations

Effects of seasonal variations on the colour and chemical constituents of Indian black tea were investigated. The experimentation involved collection of different black tea samples that were cultivated at the same tea garden but harvested in three different seasons. Measurement of moisture content was done along with theaflavins (TFs), thearubigins (TRs) and colour (CIE La*b* values) of the brewed tea liquor using spectrophotometric approach. The correlation analysis between chemical constituents, that is, TFs and TRs, moisture content, colour and quality grading was done by using principal component analysis (PCA). The results suggest that quality of tea is dependent upon seasonal variations in terms of chemical changes such as TFs, TRs and moisture content, which also correlate well with colour. The efficacy of the colour of brewed tea liquor in explaining the changes in tea quality due to seasonal variations can be beneficial for scientific fixation of prices at tea auction centres.     

Chemical characterisation of CTC black tea of northeast India: correlation of quality parameters with tea tasters' evaluation

BACKGROUND: Consumers have different regional perceptions of tea quality. Objective evaluation based on biochemical data for different regions has been needed for a long time. Biochemical factors regulating this variation would help to remove regional disparities. This study was undertaken on CTC (crust, tear and curl) black tea to generate the biochemical data responsible for quality along with tea tasters' evaluation of three geographical regions of northeast India and to determine the reason for the variation. RESULTS: Brahmaputra valley teas had highest theaflavin (TF), thearubigin (TR), brightness (BR) and total colour (TC) and low crude fibre content (CFC) and total polyphenol (TPP). Brahmaputra valley and Dooars region teas showed high total soluble solid (TSS). Barak valley teas had highest CFC and low TSS, caffeine (CA), TF, TR and TC. Dooars region teas had high CA and TPP and low BR. Dooars region and Barak valley teas contained higher levels of residual catechin than Brahmaputra valley teas. CONCLUSION: Overall quality as evaluated by tea tasters was found to be highest for Brahmaputra valley teas followed by Dooars region and Barak valley teas. This high evaluation can be attributed to higher levels of TF, TR, BR and TSS. Barak valley and Dooars region teas contained high residual catechin, indicating limitation in oxidation during processing. Copyright © 2009 Society of Chemical Industry     

Quality standards of CTC black teas as influenced by sources of potassium fertiliser

The quality aspects of CTC (crush, tear and curl) black teas were examined against different sources of potassium fertiliser. Potassium supplied as muriate of potash (MOP) improved the liquor components such as theaflavin (TF), thearubigin (TR) and TF/TR ratio at higher levels. The same effect was noticed at lower level itself when the source of K was changed to sulfate of potash (SOP). Termination of K application reduced the TF/TR ratio drastically. The entity responsible for strength, body and colour of tea brew, namely highly polymerised substances, attained its optimum proportion at an NK ratio of 1:0.21 using SOP. Generally, there was a good response from SOP‐treated blocks to caffeine. The flavour index was a maximum at a 1:0.42 NK ratio, using SOP. A slight peak and trough were observed in the case of crude fibre content and water extract over control and MOP‐treated blocks. The leaf K content was negatively correlated with CFC content of made tea. An antagonism was observed between leaf K and Mg. Copyright © 2005 Society of Chemical Industry     

2014茶园机械化技术发展研究进展

本文分析了2014我国茶园机械化发展情况,总结了该年度的论文、专利等科研成果。由分析结果可知,2014年我国茶园机械研究取得了较多成果。例如,首台智能采茶机器人、空气动力驱动型悬浮式采茶机研制成功;以机器视觉为核心的智能采茶技术研究增多;高地隙茶园管理机入选国家农机推广补贴目录等。然而,存在的问题也比较突出。例如,研究偏向采茶、植保等使用比较频繁的机械,其他茶园作业机械研究成果较少;针对丘陵山区茶园的适用机械研究很少,可用设备匮乏,区域发展仍不平衡;现有机械设备水平参差不齐,采茶类机械自动化程度较高,但其他类机械还比较笨重;研发力量单薄,投入力度不够。这些现象均表明,我国茶园机械化发展中的问题依然很多,还有很多工作要做。     

Biological and chemical factors affecting the valuations of north-east indian plains teas: II.—Statistical evaluation of the biochemical constituents and their effects on briskness,quality and cash valuations of black teas

An attempt has been made to determine, by using the multiple regression technique, the most importank biochemical constituents affecting ‘briskness’, ‘quality’ and ‘cash valuation’ and also their effects on these liquor characteristics and on the cash valuation of North-East Indian plains black teas. The multiple regression analyses showed that regardless of tasters, for crushing, tearing and curling (C.T.C.) manufactured teas, five biochemical constituents—total oxygen uptake and theogallin (TG) of unprocessed tea shoots, and theoflavin (TF), epicatechin gallate (ECG) and TG of black tea—together accounted for the major part of the total variations in each of briskness, quality and cash valuation. For orthodox manufactured teas, seven constituents—enzyme activity, total oxygen uptake and ECG of unprocessed tea shoots, and TF, ECG, TG and water-soluble solids (other than ash, TF, thearubigin, epigallocatechin, epigallocatechin gallate (EGCG),ECG, TG, caffeine nitrogen and amino acid nitrogen) of black tea—together accounted for the major part of the total variations in briskness, quality and cash valuation. Further, regardless of tasters and methods of manufacture, four biochemical constituents—total oxygen uptake of unprocessed tea shoots, and TF, ECG and TG of black tea—were the main guiding constituents of a desirable North-East Indian plains tea because these four constituents together accounted for about 50% of the total variations in each of briskness, quality and cash valuation, both of C.T.C. and orthodox teas. The effects of total oxygen uptake and TF on each of briskness, quality and cash valuation, both of C.T.C. and orthodox teas, were generally found to be beneficial, whereas the effects of ECG and TG of black tea were generally beneficial only beyond certain concentrations.     

Flavour volatiles of Assam CTC black teas manufactured from different plucking standards and orthodox teas manufactured from different altitudes of Darjeeling

Biochemical correlations between volatile flavour constituents (VFC) of CTC bluck teas manufactured from fine and coarse plucking of Assam tea and orthodox teas fiom three different altitudes were carried out by GC-MS. In general, fine plucking produced more monoterpenoids and less nonterpenoids than coarse plucking. The volatile flavour compounds were similar in all types of tea except that geranoic acid was detected in Darjeeling teas. The different ecosystems of Assam and Darjeeling have been found to have a pronounced impact upon aroma concentration. However, major diferences between the volatiles of teas from the different altitudes at Darjeeliny appear to be not so significant.     

中国名优茶机械的开发利用与发展

回顾了名优茶机械开发的历史背景及对我国名优茶生产与发展所起的重要作用,认为名优茶机械的发展不但有利于名优茶产量和品质的提高,也是实施品牌战略和发展有机名优茶的必要手段和基础,对名优茶机械的设计与发展提出了建议。     

不同等级CTC红碎茶生化成分分析

以不同等级CTC红碎茶为研究对象,通过对感官审评、生化成分和挥发性成分比较分析,探明不同等级CTC红碎茶的品质特点,为CTC红茶加工工艺的改进和品质提升提供借鉴。结果表明,不同等级CTC红碎茶中游离氨基酸和可溶性糖含量没有显著差别(p<0.05),咖啡碱含量增加显著(p<0.05),茶多酚则显著降低(p<0.05)。儿茶素组分含量整体下降,茶黄素、茶红素和茶褐素总量增加,茶红素和茶褐素比值变化与汤色色泽变化一致。不同等级CTC红碎茶中以法尼基焦磷酸/牻牛儿基焦磷酸前体物形成的挥发性成分为主。因此,茶多酚、咖啡碱和茶红素含量是调节不同等级CTC红碎茶品质的主要原因。不同等级CTC红碎茶主体挥发性成分并没有改变。     

Chlorophylls and degradation products in orthodox and CTC black teas and their influence on shade of colour and sensory quality in relation to thearubigins

Chlorophylls and concomitant pigments along with catechins were analysed in shoots from various Tocklai released clones with pronounced genetic variation and in the corresponding orthodox black teas. Comparison of these values with tasters' score showed that the shade of colour of an orthodox black tea is influenced mostly by pheophytin and thearubigins. The degradation of chlorophyll into pheophytin and pheophorbide was also studied in orthodox and crush - tear - curl (CTC) teas. The observations indicated that both pheophytin and pheophorbide are always higher in orthodox than in CTC teas made from the same leaf source.     

Changes in the quality parameters of seedling tea due to height and frequency of mechanical harvesting

Quality parameters of black tea change due to the use of a mechanical harvester, varying plucking round lengths and plucking heights. Compared with hand plucking, mechanically harvested teas have inferior quality as measured by volatile flavour compounds, theaflavins and caffeine. Similarly, longer plucking rounds produced inferior teas compared with shorter rounds. Raising mechanical plucking height by 2 cm from the previous plucking height caused less quality deterioration than increasing the height by 1 cm irrespective of plucking rounds.     

The impact of processing techniques on tea volatiles

The impact of various cultural and manufacturing techniques on volatile flavour composition was studied in order to optimize the conditions for production and retention of aroma in relation to tea quality. The Flavour Index was in the order: clonal variation—Assam > > Cambod > China Shoot maturity—Bud + 1st leaf > > > 2nd leaf > > 3rd leaf; plucking interval 7 day > 14 day; processing—green leaf > withered leaf—fermented dhool < dried tea < < tea brew; withering—soft < normal < hard. VFC Group I was in general dominated by trans-2-hexenal and Group II by linalool, phenylacetaldehyde and geraniol. Fresh green leaf had a high content of hexanol, hexanal, hexenol, hexenal and methyl salicylate. Upon withering, a sharp increase in Group I was noticed, the most remarkable being in hexenol. Group II also increased, but the extent was less except for linalool. During fermentation, Group I alcohols showed a sharp reduction with concomitant increases in aldehydes, especially trans-2-hexenal. In Group II, all compounds increased except methyl salicylate and the ionones. In the firing stage, high losses of Group I and Group II were registered. All the Group I compounds showed a decline with the progress of withering, but the opposite applied to Group II compounds, except for the alcohols. Mechanical injury during handling of leaf before cutting increased the Group I content enormously. The addition of exogenous fatty acids, mainly linoleic acid, produced substantial amounts of Group I compounds, dominated by trans-2-hexenal and hexanal. The inhibition of lipoxygenase totally reduced the formation of Group I volatiles.     

绿茶、红茶加工工艺对茶鲜叶中多酚类物质的影响

采用槠叶种一芽二、三叶鲜叶,按照传统的加工工艺分别制成绿茶和红茶。以鲜叶为对照,应用分光光度法和RP—HPLC法对绿茶、红茶的多酚类物质进行了分析,结果表明:与鲜叶相比,(1)绿茶中多酚类物质总量保持不变,而红茶中多酚类物质总量下降了43.8%;(2)绿茶中儿茶素总量几乎不变,而红茶下降了80.6%;(3)红茶中茶黄素和茶红素分别上升了565.5%和74.5%。     

Biological and chemical factors affecting the valuations of north-east indian plains teas: I.—Statistical association of liquor characteristics with cash valuations of black teas

An attempt has been made, by using the multiple regression technique, to determine whether the term ‘quality’ of the North-East Indian plains black teas has its own single characteristic as recognisable by tea- tasters or if it is the integration of some of the other important liquor characteristics, viz., colour, strength, brightness and briskness, and to determine the influence of those liquor characteristics including quality on the ‘cash valuations’ of black teas. The multiple regression analyses showed that in general, regardless of tasters and methods of manufacture, quality of North-East Indian plains black tea was found to depend mainly on briskness, quality being increased with an increase in briskness. Cash valuations, both of crushing, tearing and curling (C.T.C.) and orthodox manufactured teas, in general, depended mainly on quality and/or briskness, cash valuation being increased with increase in quality and/or briskness.     

滚筒式干燥机转速对茶叶感官品质影响的研究

通过对茶叶在干燥机滚筒内的运动轨迹的分析,研究干燥机滚筒的转速对茶叶感官品质的影响.结果表明,在滚筒转速为35～40 r/min时,绿茶感官品质明显提高.     

The effect of withering on fermentation of tea leaf and development of liquor characters of black teas

Depression in polyphenol oxidase (PPO) activity during the withering of tea leaf (Camellia sinensis) in black tea manufacture affected the oxidative-condensation of tea flavanols in forming theaflavins (TF) and thearubigins (TR), which are associated with brightness, briskness and ‘body’ of tea liquors. In contrast to conventionally manufactured CTC teas, unwithered fresh leaf CTC produces a higher proportion of TF and lower TR, resulting in bright, brisk and thin liquors. Hardness of wither was accompanied by a further depression in PPO activity, and formation of TF also declined with a concomitant loss in brightness and briskness. The TR content increased up to a certain degree of wither and thereby improved the ‘body’ of the liquor. Very hard wither, accompanied by a large reduction in moisture content, restricts PPO activity. It appears that in the fresh leaf, high moisture levels together with dissolved oxygen accelerate the enzymic oxidation and produce large amounts of TF. Senescence of the leaf seems to facilitate the production of TR.     

The response of quality and yield of black tea of twocamellia sinensis varieties to methods and intervals of harvesting

The sensory evaluation and chemical quality parameters of black teas changed with variety, plucking round length and method of plucking. Hand plucked teas had higher theaflavins (TF), caffeine, brightness, flavour index. Group II volatile flavour compounds (VFC) and sensory evaluations, but lower Group I VFC than shear plucked teas irrespective of variety. Black teas plucked from short plucking rounds were superior to those from long plucking rounds as assessed by TF, caffeine, brightness, the chemical aroma quality parameters and sensory evaluation. Long plucking intervals and shear plucking reduced tea yields and produced coarser leaf than short plucking intervals and hand plucking respectively.