Influence of region of production on clonal black tea chemical characteristics

Production of black tea from the same vegetatively propagated (VP) cultivars, in Kenya and Malawi, shows variations in both chemical composition and quality. Whereas it is possible to produce black teas with similar total theaflavins and individual theaflavins, brightness and total colour levels, black teas from Kenya generally have higher thearubigins, total volatile flavour compounds and flavour index. The black tea fermentation process is much faster in Malawi compared to that in Kenya, as evidenced by faster production of plain black tea chemical parameters, especially theaflavins. Consequently, in Malawi the maximum amount of theaflavins formation takes a shorter fermentation duration than in Kenya. Given ample fermentation duration, fermentation in Kenya produces a similar amount of theaflavins. This makes it necessary to optimise fermentation time, in different geographical regions even when the same cultivar is being processed. The other plain black tea quality parameters (thearubigins, brightness and total colour) were higher in black tea which was processed in Kenya than those processed in Malawi. However, the pattern in the changes in the individual theaflavins or theaflavins digallate equivalent followed that of total (Flavognost) theaflavins, suggesting that the flavan-3-ols patterns in tea leaf might not have been affected by the geographical area of production. The total volatile flavour compounds (VFC), Group I and II VFC and the flavour index were higher in black teas processed in Kenya, further demonstrating the fact that high grown Kenyan teas are more flavoury. In both Kenya and Malawi black teas, aroma quality declined with a long duration of fermentation. Short fermentation time is therefore a method of producing more aromatic black teas. The variations in black tea quality between Malawi and Kenya were possibly due to difference in environmental conditions, leading to different shoot growth rates and biochemical composition in the shoots.     

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.     

Discrimination of teas with different degrees of fermentation by SPME–GC analysis of the characteristic volatile flavour compounds

As tea is traded all over the world, it is necessary for both customs officers and business investigators to develop an easy and reliable method to discriminate teas from each other. A total of 56 kinds of various green, Oolong, and black teas were collected from different countries and markets, and their catechin contents and volatile flavour compounds (VFC) were compared by analyses, using HPLC and solid-phase microextraction–gas chromatograph (SPME–GC). It was found that neither total catechin nor individual catechin contents in green and Oolong teas were significantly different among the samples investigated, but the fermentation processes altered the profiles of tea VFC. Because many of the individual VFC did not change in response to the fermentation levels, several VFC in combination might be more reliable than a single compound to identify broader ranges of teas. A total concentration of five VFC, trans-2-hexenal, benzaldehyde, methyl-5-hepten-2-one, methyl salicylate, and indole, was shown to be able to discriminate clearly unfermented and fermented teas, while that of trans-2-hexenal and methyl salicylate together supplied an index to differentiate semi- and fully-fermented teas. In addition, the SPME–GC analysis was also able to distinguish real jasmine teas from fake jasmine teas based on the disappearance of some grassy/green odorants.     

Variations of the chemical composition of clonal black tea (Camellia sinensis) due to delayed withering

The chemical composition of black teas (Camellia sinensis L) varies when the green leaf from which they are manufactured is withered physically to the same degree but for different periods. Caffeine contents progressively increase with prolonged withering time whereas theaflavins decrease due to prolonged withering. Although the sums of group I and group II volatile flavour compounds (VFC) decrease with prolonged withering time, the flavour index (expressed as group II VFC/group I VFC) increases due to prolonged withering. No significant changes were noted in the thearubigin levels with variation in withering time, but the tasters' evaluations were at a maximum for teas withered for 14 h. Subsequently the evaluation decreased with longer withering times.     

The effects of altitude on the chemical composition of black tea

Changes in quality parameters of crush, tear and curl (CTC) black clonal teas due to variations in altitude within a radius of 10 km were determined. There were significant (P = 0.05) changes in all the quality parameters due to areas of production despite the short sampling radius. The Group I volatile flavour compounds (VFC) increased with decrease in altitude whereas Group II VFC and flavour index (FI), theaflavins (TF), thearubigins (TR) (except in clone TN 14-3) and caffeine increased with increase in altitude. The tasters' evaluation also increased with increase in altitude.     

HS-SPME-GC-MS对传统红碎茶和CTC红碎茶挥发性化合物分析和比较

选取中国和斯里兰卡7?个地区的14?个不同商业品牌的红碎茶,包括传统加工（orthodox,OTD）红碎茶和压碎撕裂卷曲（crush, tear and curl,CTC）红碎茶,采用顶空固相微萃取-气相色谱-质谱联用法对其挥发性风味化合物比较分析。结果鉴定出59?种挥发性化合物,其中萜烯类化合物占10.38%～60.34%,酮类物质占1.1%～22.09%,酯类物质占3.18%～41.83%,为最丰富的3?类挥发性化合物。结果表明,CTC红碎茶中挥发性成分数量较低,其中醛类化合物和醇类化合物含量较低,但酯类化合物含量高于OTD红碎茶。萜烯指数可被用作区分茶叶产地的一种手段,但还缺乏精准性,需结合其他参数鉴定茶叶产品产地。     

Relationship between process of withering and aroma characteristics of black tea

Volatile flavour components (VFC), caffeine, crude fibre, ash and total water soluble solids (TSS) were analysed in orthodox and CTC black teas manufactured from normal and hard withered leaves. With the increase of wither, VFC, TSS and caffeine were found to increase but not crude fibre. The withering process in black tea manufacture appears to control the development of terpenoids, improving flavour quality in brewed tea.     

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.     

Variation in catechin contents in relation to quality of ‘Huang Zhi Xiang’ Oolong tea (Camellia sinensis) at various growing altitudes and seasons

The variations in the contents of catechins and phenolic compounds in relation to the quality scores (QS) and taste scores (TS) in the ‘Huang Zhi Xiang’ Oolong tea grown in different seasons and at different altitudes were determined. The study demonstrated that the contents of (−)-epigallocatechin gallate (EGCG), catechin gallate (CG), and total catechins (TC) in the Oolong teas grown at a high altitude were significantly higher than those grown at a low altitude. Furthermore, the contents of EGCG, CG, and TC in the autumn tea were significantly higher than those from the spring tea grown at a low altitude. However, no significant differences in the contents of EGCG, CG, and TC were observed between the spring and autumn teas grown at a high altitude. In addition, the contents of (−)-epigallocatechin (EGC), (+)-catechin (C), (−)-gallocatechin (GC), and simple catechins (SC) in the spring tea leaves were significantly higher than those in the autumn tea leaves grown at a low altitude, but they were not significantly different from those in the autumn tea leaves grown at a high altitude. The contents of EGCG, CG, and TC in the Oolong teas were positively and significantly correlated to the taste score (TS) and quality score (QS) of the Oolong tea. Thus, the contents of EGCG, CG, and TC could be the important quality parameters of the ‘Huang Zhi Xiang’ Oolong tea. This work suggested that the production of the ‘Huang Zhi Xiang’ Oolong tea grown at low altitudes should utilize the autumn tea leaves while the production of Oolong tea grown at high altitudes can use both the spring and autumn tea leaves.     

Antimicrobial activity of tea as affected by the degree of fermentation and manufacturing season.

Bacillus subtilis, Escherichia coli, Proteus vulgaris, Pseudomonas fluorescens, Salmonella sp. and Staphylococcus aureus were used to test the antimicrobial activity of tea flush extract and extracts of various tea products. Among the six test organisms, P. fluorescens was the most sensitive to the extracts, while B. subtilis was the least sensitive. In general, antimicrobial activity decreased when the extents of tea fermentation increased. The antimicrobial activities of tea flush extract and extracts of tea products with different extents of fermentation varied with test organisms. Tea flush and Green tea, the unfermented tea, exerted the strongest antimicrobial activity followed by the partially fermented tea products such as Longjing, Tieh-Kuan-Ying, Paochung, and Oolong teas. On the other hand, Black tea, the completely fermented tea, showed the least antimicrobial activity. It was also noted that extracts of Oolong tea prepared in summer exhibited the strongest antimicrobial activity, followed by those prepared in spring, winter and fall.     

Pyrrolizidine and tropane alkaloids in teas and the herbal teas peppermint,rooibos and chamomile in the Israeli market

Dehydro pyrrolizidine alkaloids (dehydro PAs) are carcinogenic phytotoxins prevalent in the Boraginaceae, Asteraceae and Fabaceae families. Dehydro PAs enter the food and feed chain by co-harvesting of crops intended for human and animal consumption as well as by carry-over into animal-based products such as milk, eggs and honey. Recently the occurrence of dehydro PAs in teas and herbal teas has gained increasing attention from the EU, due to the high levels of dehydro PAs found in commercially available teas and herbal teas in Germany and Switzerland. Furthermore, several tropane alkaloids (TAs, e.g. scopolamine and hyoscyamine) intoxications due to the consumption of contaminated herbal teas were reported in the literature. The aim of the present study was to determine the dehydro PAs and TAs levels in 70 pre-packed teabags of herbal and non-herbal tea types sold in supermarkets in Israel. Chamomile, peppermint and rooibos teas contained high dehydro PAs levels in almost all samples analysed. Lower amounts were detected in black and green teas, while no dehydro PAs were found in fennel and melissa herbal teas. Total dehydro PAs concentrations in chamomile, peppermint and rooibos teas ranged from 20 to 1729 μg/kg. Except for black tea containing only mono-ester retrorsine-type dehydro PAs, all other teas and herbal teas showed mixed patterns of dehydro PA ester types, indicating a contamination by various weed species during harvesting and/or production. The TA levels per teabag were below the recommended acute reference dose; however, the positive findings of TAs in all peppermint tea samples warrant a more extensive survey. The partially high levels of dehydro PAs found in teas and herbal teas present an urgent warning letter to the regulatory authorities to perform routine quality control analysis and implement maximum residual levels for dehydro PAs.     

Seasonal variations in theaflavins,thearubigins, total colour and brightness of Kangra orthodox tea (Camellia sinensis (L) O Kuntze) in Himachal Pradesh

Variations in theaflavins, thearubigins, total colour and brightness of orthodox black tea were studied for four consecutive years (1993–1996) with a view to evaluating the effects of changing weather conditions on the quality of Kangra tea. A degree of withering of 600–650 mg g⁻¹ during the first, second and fourth seasons was optimal for the development of significantly higher brightness and total colour characteristics. The quality of rainy season teas suffered owing to high chlorophyll content and low degree of withering. Hot air circulation through the withering troughs to assist evaporation of leaf moisture increased the brightness and total colour of rainy season teas. High atmospheric demand during the dry season assisted loss of green leaf moisture, but withering and brightness exhibited significant negative correlations with high relative humidity and rainfall. Summer season teas were superior in their total colour and brightness. © 2000 Society of Chemical Industry     

不同采制季节信阳白茶品质成分的比较分析

该研究采用高效液相色谱法（HPLC）等方法对春季、夏季和秋季茶树鲜叶加工而成的18款信阳白茶茶样中的8种儿茶素、6种黄酮类、2种酚酸、3种嘌呤碱等品质成分进行测定,对不同采制季节的信阳白茶进行品质成分进行对比分析。主成分分析（PCA）和聚类分析（HCA）技术均能将信阳白茶茶样按照采制季节不同进行归类,分为春季、夏季和秋季白茶。通过独立样本t-检验和单因素方差分析,探究了不同采制季节信阳白茶中儿茶素、黄酮类、嘌呤碱等品质成分差异。结果显示：不同采制季节信阳白茶中的品质成分均存在显著性（p<0.01）或极显著性（p<0.001）差异;春季白茶中(-)-表没食子酸儿茶素（EGC）、(-)-表没食子儿茶素没食子酸酯（EGCG）和鞣花酸含量极显著性（p<0.001）高于夏季或秋季白茶,含量分别为33.26、59.30、2.81 mg/g左右;夏季白茶中(-)-儿茶素没食子酸酯（CG）、(-)-没食子儿茶素没食子酸酯（GCG）、花旗松素、芦丁、杨梅素、山奈酚、槲皮素、木犀草素含量极显著性（p<0.001）高于秋季白茶,含量分别高达0.72、4.40、0.84、2.40、0.97、0.21、0.25、0.11 mg/g;秋季白茶中(+)-儿茶素（C）、(-)-表儿茶素（EC）、(-)-表儿茶素没食子酸酯（ECG）、没食子酸、咖啡碱和可可碱极显著性（p<0.001）高于夏季或春季白茶,含量分别为4.98、14.35、27.02、10.10、36.85、1.53 mg/g。该研究揭示了信阳白茶的品质特征和不同采制季节信阳白茶品质成分差异,为白茶等茶叶采制季节的识别提供了科学依据。     

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。     

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     

Comparative studies on the qualities of green teas in Karst and non-Karst areas of Yichang,Hubei Province,PR China

Green teas (Camellia sinensis) from the non-Karst and the Karst areas of Yichang, Hubei Province, PR China, have been compared as regards l-proline content of the green tea and the quality, as well as the soil properties. The results showed that some qualities of green tea from the Karst region, such as a higher content of l-proline and a lower contents of aluminum and fluoride were beneficial. Other qualities of green tea from the Karst region, for example, the lower content of tea polyphenols, were not beneficial. The differences in amino acids and caffeine contents were not statistically significant.     

Vermicompost extracts influence growth,mineral nutrients,phytonutrients and antioxidant activity in pak choi (Brassica rapa cv. Bonsai,Chinensis group) grown under vermicompost and chemical fertiliser

BACKGROUND: Multiple studies have been reported on the effect of compost tea on suppression of certain plant diseases. However, relatively little work has been done to investigate the effect of vermicompost tea on yield and nutritional quality of vegetable crops. In this study, experiments were conducted to determine the effect of extraction method on vermicompost tea quality and subsequent effects on growth, mineral nutrients, phytonutrients and antioxidant activity of pak choi plants grown under organic (vermicompost) and synthetic (Osmocote) fertilisation. Three vermicompost teas obtained by different extraction methods, namely non‐aerated vermicompost tea (NCT), aerated vermicompost tea (ACT) and aerated vermicompost tea augmented with microbial enhancer (ACTME), were applied to the plants. Aerated water served as control. RESULTS: Mineral nutrients were significantly higher in ACTME compared with other teas, but total microbial population and activity did not differ with extraction method. All vermicompost teas similarly enhanced plant production, mineral nutrients and total carotenoids, and this effect was most prominent under organic fertilisation. Antioxidant activity and total phenolics were higher under organic compared with synthetic fertilisation. Vermicompost teas generally decreased phenolics under organic fertilisation and increased them under synthetic fertilisation compared with the control. CONCLUSION: The effect of vermicompost tea on crop growth is largely attributable to mineral nutrient, particularly N, uptake by plants. Non‐significant differences among extraction methods on plant response within fertiliser regimes suggest that aeration and additives are not necessary for growth promotion and nutrient quality under the conditions reported here. Copyright © 2009 Society of Chemical Industry     

Analysis of mineral composition of some Assam and Darjeeling black teas

Black teas manufactured in Darjeeling and Assam were analysed for various macrominerals such as P, K, Ca, Mg and microminerals such as Mn, Fe and Cu. A considerable amount of minerals, eg K (40-46 mg), Mg (2.7-3.0 mg), Ca (0.48-0.66 mg) and traces of Mn (0.28-0.40 mg), Fe (0.16-0.20 mg), P (29-41 μg) and Cu (12-22 μg) were found in a cup of black tea brew. Black teas manufactured from the leaf coming from a pruned section and fine portion usually showed higher mineral content than tea manufactured from unpruned sections and coarse grade teas of Darjeeling. Assam CTC tea was found to be richer in mineral content compared to Darjeeling orthodox tea.     

四川主栽茶树品种红茶香气成分的SPME-GC-MS分析

采用固相微萃取结合气相色谱-质谱联用法对采自名山白毫131、福鼎大白茶、福选9号、早白尖和四川中小叶群体种5 个主栽品种制作的工夫红茶香气成分进行分析。在5 个品种红茶中共分离鉴定出148 种香气化合物,其中包含醇类、醛类、酯类、酮类、烃类、酸类等。主要的香气贡献成分是醇类化合物,相对含量在45.97%～63.78%之间,其中主体香气成分有香叶醇、芳樟醇及其氧化物、苯乙醇、3,7-二甲基-1,5,7-辛三烯-3-醇、苯甲醇、橙花叔醇、水杨酸甲酯、癸酸乙酯、顺-3-己烯醇己酸酯、苯乙醛、柠檬醛等,这些成分是决定四川工夫红茶甜花香和果香的重要组分。四川主栽品种红茶香气类型属于中间型,富含芳樟醇和香叶醇,其中名山白毫131、四川中小叶群体种和福鼎大白茶红茶萜烯指数较低,分别为0.57、0.60和0.65,表明这3 个品种红茶香气高锐,属于高香型红茶,这与感官审评结果一致。因此,高香或花香型四川工夫红茶宜选用名山白毫131、四川中小叶群体种或福鼎大白茶鲜叶制作。     

12种单丛茶香气成分研究

选取银花香、茉莉香、雪片、柚花香、黄枝香、杏仁香、芝兰香、蜜兰香、鸭屎香、锯朵仔、白叶单丛、肉桂香12种单丛茶叶,采用顶空固相微萃取-气相色谱质谱联用技术(HS-SPME-GC-MS)和感官评价法,研究不同香型单丛茶的主要呈香物质及香气物质的差异。结果显示,12种单丛茶样中鉴定出包括醇类、酮类、醛类、酯类、含氮化合物等47种香气化合物,其中醇类相对含量最高,其次是含氮类。浓花型单丛茶主要香气组分以芳樟醇及其氧化物、橙花叔醇、吲哚、苯乙腈、己醛、顺-茉莉酮为主;花蜜协调型以芳樟醇及其氧化物、1-乙基-2-甲酰基吡咯、柠檬烯、1-乙基吡咯、苯乙腈为主;浓蜜型以芳樟醇及其氧化物、柠檬烯、1-乙基-2-甲酰基吡咯、1-乙基吡咯、6-甲基-5-庚烯-2-酮、水杨酸甲酯为主。芳樟醇及其氧化物是所有茶样的主要香气成分,相对含量为22.14%~68.42%。随着蜜香增强,具有花香青香的橙花叔醇、己醛、吲哚和苯乙腈相对含量降低,吡咯类、柠檬烯的相对含量增加。同一类型茶样中主要成分相对含量的差异,形成各自特征香气。感官审评的结果与香气物质的分析结果一致。