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.     

The impact of mechanization of tea harvesting on the quality of south indian CTC teas

The chemical quality parameters and sensory evaluation of black teas changed with method of plucking. Hand-plucked teas were very rich in their green-leaf biochemical precursors and had higher contents of made-tea quality constituents than shear-plucked teas. The quality deterioration was mainly due to mechanical injury and non-selective plucking with shear-harvesting. However, tea obtained by shear-harvesting from a continuously sheared field over a prolonged period was found to be superior. The use of shears reduced the yield and increased the plucking average with a net decrease in cost of production compared to hand plucking.     

Responses of clonal tea to location of production and plucking intervals

Tea is cultivated in diverse environments causing yield and quality differences in its beverages. To maximise yields and quality, agronomic practices should be optimised. But agronomic recommendations are uniform in different environments in Kenya despite variations in the growth factors responsible for changes in yields and quality. Plucking is labour intensive and a costly agronomic input in tea production. Trials were conducted for ten years in five tea growing regions in Kenya to assess yields and quality responses of clone BBK 35 tea to location of production and harvesting intervals. There were different (P ? 0.05) yields in the various locations, with significant (P ? 0.05) interaction effects between locations and harvesting intervals. Yields declined in three out of five regions but increased in one location with longer plucking intervals. Yields in a geographical area of production can not be used to estimate its expected yields in other tea growing areas. Black tea theaflavins varied significantly (P ? 0.05) with geographical area of production, but other plain tea quality parameters did not vary with location. It is therefore possible to make similar black teas with similar plain tea quality parameters except theaflavins from all tea growing regions of Kenya. Tea quality improved with short plucking rounds. One way to maximise tea quality is through shortening harvesting intervals. It is necessary to establish optimal harvesting rounds in the different tea growing regions in Kenya to maximise yields and quality.     

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.     

Response of some black tea quality parameters to nitrogen fertiliser rates and plucking frequencies

The effects of the rate of application of nitrogenous fertiliser and frequency of plucking (harvesting) on various black tea quality parameters and yields were compared on done 6/8. High rates of nitrogen application and long plucking intervals reduced the theaflavin content and brightness of black tea liquor. The caffeine content of the black tea increased with increasing rates of nitrogen application but decreased with increase in the plucking interval. The Group I volatile flavour compounds increased with nitrogen application rate and long plucking intervals while the Group II volatile flavour compounds and the flavour index decreased. Tasters preferred teas from shorter plucking intervals and low rates of nitrogen application. Yields increased with increasing rates of nitrogen but were lowered by long harvesting intervals. The rate of nitrogen application did not change the distribution of leaf into different standards.     

Influence of withering, including leaf handling, on the manufacturing and quality of black teas - a review

Literature on the influence of withering on maceration, fermentation and drying and on black tea quality is reviewed. The importance of including the handling of the leaf in the field and during transportation as an integral part of withering is stressed. The influence of physical and chemical changes in the green leaf, during withering, on the quality of black teas is discussed. Withering practices vary with climate, producing region, the type of manufacturing process and demands by the markets. Mechanised withering may improve quality by reduced handling of the leaf. The influence of plucking standards on withering and the effect of withering on the storage of tea are discussed.     

Variations in the leaf standard,chemical composition and quality of black tea (Camellia sinensis) due to plucking intervals

Green leaf standard, chemical composition and quality of black tea (Camellia sinensis (L) O Kuntze) change with plucking intervals. Long plucking intervals lead to poor leaf standard with a lot of mature leaves and lower theaflavins, the sum of volatile flavour compounds imparting a sweet flowery aroma (group II volatile flavour compounds), caffeine contents and tasters' evaluations of black tea. The sum of volatile flavour compounds imparting inferior, grassy, green flavour (group I volatile flavour compounds) to tea, however, increases with long plucking intervals.     

Ethylamine content of fresh tea shoots and made tea determined by high performance liquid chromatography

The ethylamine contents of tea shoots and made teas were derived with o-phthalaldehyde and 2-mercaptoethanol, and quantified by high performance liquid chromatography. The coefficient of variation of this method was 1.97% from eight analyses. The levels of ethylamine in tea shoots declined markedly during growth and senescence after plucking; they also declined in the extracts of fresh tea during the incubation at 37°C, but this decrease was completely inhibited by amine oxidase inhibitors. The content of ethylamine in high grade green teas was higher than in low grade teas, but was almost identical in high and low grade black tea. The mean contents of ethylamine in 22 green teas and 17 black teas were 6.76±3.07 μmol g^?1 and 6.40±1.82 μmol g^?1, respectively.     

Determination of alkaloids and phenolic compounds in black tea processed by two different methods in different plucking seasons

The effects of two different rolling methods and three tea plucking seasons on alkaloids and phenolics, mainly flavan‐3‐ols and theaflavins, in black tea were studied using an improved high‐performance liquid chromatographic method. Better separation of all tea compounds analyzed—the most important factor for their identification and quantitation—was achieved only with long elution gradients, which overcame the limitations of previously reported methods. Precision of the assay method was very high since intra‐day and inter‐day variations were within 0.76% and 1.66%, respectively. All analytes exhibited good linearity over the range evaluated with a correlation coefficient of 0.9987–1.000. Among the four solvents evaluated, 80% methanol was the most solvent for extracting individual tea compounds. The extraction method applied exhibited good repeatability (CV: 0.39–3.29%). The content of tea compounds analyzed varied with processing method and plucking season. Teas processed using the Cay‐Kur method contained higher levels of identified phenolic compounds than orthodox teas, but their alkaloid content was similar to each other. The most abundant alkaloid in teas was caffeine, ranging from 17.84 mg g^?1 dry weight in September plucking to 23.79 mg g^?1 dry weight in May plucking. With respect to phenolic compounds, theaflavins were at the highest level, 14.27 mg g^?1 dry weight, in Cay‐Kur tea processed in May. Copyright © 2007 Society of Chemical Industry     

The changes in black tea quality due to variations of plucking standard and fermentation time

Catechin levels in green leaf, total theaflavins, brightness, thearubigins, colour, flavour index and sensory evaluation decrease with coarse plucking standard in clone 6/8. The sum of Group I volatile flavour compounds and C₆ aldehydes and alcohols, in particular, increases with coarse plucking standard. The sum of Group II did not follow a particular pattern, but flavour index decreased with coarse plucking standards. The decrease in total theaflavin levels was due to the decrease in all the individual theaflavins. Although all the individual theaflavin levels decreased with coarse plucking standards, the decrease was greater in galloylated theaflavins, especially in theaflavin digallate, compared with simple theaflavin. Short fermentation times produced black teas with higher brightness and flavour index, but lower theaflavins, thearubigins and colour, irrespective of plucking standard. Total theaflavins reached a maximum after 90 min of fermentation, irrespective of the plucking standard, whereas ungalloylated theaflavin levels decreased with extended fermentation duration at all plucking standards, theaflavin-3-gallate and theaflavin-3, 3’-digallate levels increased, resulting in the increase in theaflavin digallate equivalent. Brightness and flavour index decreased while thearubigins, colour, and Groups I and II volatile flavour compound levels increased with long fermentation.     

Quality response of clonal black tea to nitrogen fertiliser,plucking interval and plucking standard

Variations in the black tea quality of high‐yielding clone S15/10 in response to rates of NPKS 25:5:5:5 fertiliser of 200 and 400 kg N ha⁻¹ year⁻¹, plucking intervals of 7, 14 and 21 days and a selective plucking standard of up to two leaves and a bud or an unselective plucking standard were studied. Generally, quality declined with longer plucking intervals and unselective plucking. Although there was a general decline in quality with increasing nitrogen rate, only the black tea total colour declined significantly on increasing the nitrogen rate from 200 to 400 kg N ha⁻¹ year⁻¹. For each nitrogen rate and each plucking interval, unselective plucking reduced the black tea quality. No significant interactions between any two of the three (nitrogen rate, plucking interval and plucking standard) or all three factors were noted, indicating that the patterns of response were similar. The results demonstrate that black tea quality changes due to the factors studied occur in the same pattern with variations in treatments. Poor black tea quality due to any of the factors studied cannot therefore be corrected by varying the other factors. © 2000 Society of Chemical Industry     

Changes in enzyme activities (polyphenol oxidase and phenylalanine ammonia lyase) with type of tea leaf and during black tea manufacture and the effect of enzyme supplementation of dhool on black tea quality

Variation in polyphenol oxidase (PPO) and phenylalanine ammonia lyase (PAL) activities with respect to different cultural and manufacturing processes and their effects on black tea quality were studied. There was a wide variation between enzyme activities of different clones, as well as variation due to seasonal changes and shoot maturity. Field practices such as plucking rounds and pruning had a great impact on enzyme activities. The enzyme activities positively correlated with tasters' scores. The extent of change in enzyme activities at different stages of manufacture differed widely. The loss of activity during withering could be restored by rehydration. Residual activity was observed in made tea. Supplementation of enzymes enhanced the black tea quality markedly in terms of cuppage and creaming properties.     

不同花色福鼎白茶中挥发性萜类化合物的对映异构体分布

采用顶空固相微萃取法结合手性气相色谱-质谱联用技术对不同花色福鼎白茶的香气成分进行分析,得出白毫银针、白牡丹及寿眉样品中14 种挥发性萜类化合物的对映异构体分布情况。相对定量分析结果表明,S-芳樟醇、S-Z-橙花叔醇及(2S,5R)-芳樟醇氧化物B在大部分白茶样品中具有较高的相对含量,而茶螺烷的4 个对映异构体的相对含量普遍较低。对映异构体比例（enantiomeric ratio,ER）分析结果表明,S-柠檬烯、(2S,5S)-芳樟醇氧化物A、(2S,5R)-芳樟醇氧化物B、S-芳樟醇、(2R,5R)-茶螺烷A、(2R,5S)-茶螺烷B、R-4-萜品醇、S-α-松油醇、S-香茅醇、S-α-紫罗兰酮、S-Z-橙花叔醇、S-E-橙花叔醇、(1R,2R)-茉莉酸甲酯及(1R,2S)-茉莉酸甲酯是大部分福鼎白茶中相应萜类化合物的主导立体构型,其中芳樟醇、茶螺烷B、4-萜品醇、香茅醇、α-紫罗兰酮、芳樟醇氧化物A及Z-橙花叔醇的ER值与福鼎白茶的采摘嫩度呈现一定的相关性。多元统计分析结果表明,12 个萜类化合物对映异构体的含量在不同花色福鼎白茶中存在显著差异,其中R-芳樟醇、(2R,5S)-茶螺烷B、S-α-松油醇、R-E-橙花叔醇、R-Z-橙花叔醇、S-柠檬烯及S-E-橙花叔醇在白毫银针样本中含量最高,(2R,5R)-芳樟醇氧化物A及(2S,5R)-茶螺烷B含量与白毫银针样本呈负相关;S-Z-橙花叔醇及(1S,2S)-茉莉酸甲酯在白牡丹样本中含量普遍较高;而R-α-紫罗兰酮在寿眉样本中有较高的含量分布。本研究为后续白茶香气品质形成机理研究、白茶花色等级判别及指纹图谱构建等提供理论依据。     

The effects of blending clonal leaf on black tea quality

Although most clones are selected for quality and yields, there are clones in production with superior yields but producing inferior black tea quality and vice versa. Some of these clones with superior yield give very poor black tea quality characteristics. Such clones are normally not progressed in selection programmes. Blending the clonal leaf prior to maceration results in the production of black teas with average quality relative to the amount of the clonal leaf in the mixture. There is no evidence of clonal incompatibility. Slow fermenting clones with superior yields may therefore be selected and planted, provided they are not planted in single stands. ©     

名优绿茶仿生采摘指研制

提出了一种能够模仿人工"提手采"动作的仿生采摘指结构,并完成了采摘指的结构设计。为了提高采摘指的灵巧性和结构紧凑性,对采摘指进行了运动学和静力学分析,通过遗传算法对结构几何参数进行了优化,使得驱动力的传递效率提高了26.6%。在此基础上制作了采摘指原理样机,并完成了气力驱动与控制系统的设计,室内初步试验结果表明:采摘成功率近70%,能够实现预期动作。     

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     

Rapid and selective quantification of L-theanine in ready-to-drink teas from Chinese market using SPE and UPLC-UV

An ultra performance liquid chromatography (UPLC) method combined with solid phase extraction (SPE) sample pre-treatment was developed and validated for the rapid quantification of L-theanine in ready-to-drink (RTD) teas. UPLC analysis of twenty-seven RTD teas from the Chinese market revealed that the L-theanine levels in various types of RTD teas were significantly different. RTD green teas were found to contain highest mean L-theanine level (37.85±20.54 mg/L), followed by jasmine teas (36.60±12.08 mg/L), Tieguanying teas (18.54±3.46 mg/L) black teas (16.89±6.56), Pu-erh teas (11.31±0.90 mg/L) and oolong teas (3.85±2.27 mg/L). The ratio of total polyphenols content to L-theanine content could be used as a featured parameter for differentiating RTD teas. L-theanine in RTD teas could be a reliable quality parameter that is complementary to total polyphenols.     

红紫芽品种的茶类适制性研究

以不同季节红叶1号、红叶2号、丹妃三个红紫芽品种（系）为供试原料制成绿茶、白茶和红茶,通过茶叶品质分析及感官审评方法综合评价了红紫芽茶树品种（系）的茶类适制性。结果表明,同一品种（系）制成的绿茶和白茶理化成分含量高于对应的红茶。绿茶中各理化成分含量最高,可溶性糖含量三季平均为4.24%~4.69%,而红茶则为3.54%~3.96%。氨基酸含量在白茶中高于绿茶和红茶,白茶中含量达3.40%以上,而红茶和绿茶中含量在3%左右。红紫芽绿茶中花青素含量夏季>秋季>春季,夏季含量为0.086%~0.115%;除了春季白茶检出痕量的花青素外,其余不同季节的白茶和红茶均未检出花青素。感官审评结果表明,白茶普遍具有优雅、浓郁的花香或果香,滋味甜醇鲜爽的特点;红茶普遍具有甜香浓郁、滋味甜醇鲜爽的特点;绿茶品质成分丰富,汤色呈红紫色。研究认为,红紫芽茶更适合制作红茶和白茶,而制成的绿茶则可以作为一种新型特异茶饮进行推广。本研究为红紫芽茶的深入利用提供了理论基础和实践依据。     

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.     

Compositional changes in chlorophylls and carotenoids during the four flushes of tea in North East India

The quantitative changes of two pigments, chlorophylls a and b, and four major carotenoids, β-carotene, lutein, violaxanthine and neoxanthine, were investigated during four flushes of North East Indian plain teas from a deep skiffed area between April and October 1982. The tea flushes with different genetic properties were taken fromn from various Tocklai-released clones: TV-1 (Camellia sinensis (L.) O. Kuntze), TV-2 (C. assamica (Masters) Wight), TV-9 (C. assamica ‘Cambod’) and TV-17 (C. sinensis, hybrid). They showed marked changes in these pigment constituents throughout the plucking period, which affected the organoleptic property of the black tea produced.