The effect of process parameters on seasonal development of flavour in black tea

Analysis by g.l.c. of ether–extractable steam volatile constituents of black tea from a high elevation tea estate in the Western Region (Dimbulla District) of Sri Lanka during seasonal flavour development, indicated the presence of trans-2-hexenal, n-butyraldehyde, cis-3-hexenol, 1-octen-3-ol linalool, methyl salicylate and geraniol as the main flavour constituents. Of these, trans-2-hexenal and linalool showed appreciable seasonal changes in black tea. Leaf quality and manufacturing practices, particularly withering and fermentation, influenced the production of these compounds during black tea manufacture. It is suggested that the relative concentration of these compounds may be partly responsible for the typical flavour quality of Sri Lanka black teas and these may be used as indices of flavour development.     

云南晒青红茶与烘青红茶香气成分对比

采用顶空固相微萃取（headspace solid-phase microextraction,HS-SPME）结合气相色谱-质谱（gaschromatography-mass spectrometry,GC-MS）分析3 种晒青红茶和3 种烘青红茶的香气成分,并利用主成分分析（principal component analysis,PCA）和聚类分析（clustering analysis,CA）找出这2 种不同干燥方式红茶的异同点,以实现对它们的区分。结果表明,2 种红茶中一共鉴定出香气成分76 种,香气成分主要以醇类、酮类和酯类化合物为主,其中醇类化合物相对含量在晒青红茶和烘青红茶中分别占57.43%和60.45%,主要包括芳樟醇、芳樟醇氧化物、香叶醇和橙花叔醇等萜烯醇类物质。通过对比发现,晒青红茶和烘青红茶在香气成分的组成及相对含量上存在较高程度的相似性。但通过使用PCA和CA,晒青红茶和烘青红茶之间能实现较好的区分,说明不同的干燥方式对这2 种红茶的香气成分有一定的影响。因此,通过结合晒青红茶和烘青红茶的香气成分及相对含量,HSSPME-GC-MS结合多元统计学方法能够实现2 种不同干燥方式红茶的区分。     

Effect of the withering process on volatile compound formation during black tea manufacture

The amount and composition of volatile compounds in the volatile oils were compared between non-withered tea and withered tea. Important differences in the aroma constituents were found in the amounts of E-2-hexenal, Z-3-hexanol ester, linalool and its oxides, and methylsalcylate. In withered teas, the amounts of Z-3-hexenol ester, linalool and its oxides, and methylsalcylate were much greater than in non-withered tea, but the E-2-hexenal content was higher in non-withered tea. From the results it was thought that the withering process has an important role in the formation of volatile compounds in tea shoots during black tea fermentation.     

基于品种差异的祁门红茶品质分析

为探究茶树品种对祁门红茶品质的影响,本试验选取种植于祁门产区的‘凫早2号’、‘舒茶早’2个茶树品种鲜叶,采用传统祁门红茶加工方法制成红茶样,并进行感官审评与理化分析。结果表明,2个品种红茶整体都表现出汤色红亮、甜香浓郁的祁门红茶特征品质,但2个品种红茶香气、滋味品质有明显差异。香气化合物分析表明,芳樟醇、顺-己酸-3-己烯酯、香叶醇、水杨酸甲酯、苯乙醇、2-己烯醛等香气化合物在2个红茶样中差异较大,可能是导致2个品种红茶香气品质差异的主要原因。‘舒茶早’红茶酯型儿茶素含量显著低于‘凫早2号’红茶(P<0.05),而咖啡碱及游离氨基酸含量则显著高于‘凫早2号’红茶(P<0.05),使其滋味醇厚度、鲜爽度高于‘凫早2号’红茶。综上,同产区内不同茶树品种加工的红茶,因其次级代谢产物的差异使得红茶风味不同。     

Seasonal and clonal variations in some major glycosidic bound volatiles in Kangra tea (Camellia sinensis (L.) O. Kuntze)

Seasonal and clonal variations in glycosidic bound volatile compounds were studied in tea clones representing the three different varieties viz. sinensis, assamica and cambodiensis grown in Kangra region. Glycosidic bound volatile compounds were characterised by GC–MS and quantification of major volatiles was done by GC. (E)-2-hexenal, benzyl alcohol, phenylethanol, linalool, linalool oxides, geraniol and methyl salicylate were the major glycosidic bound volatiles identified in tea shoot. Clonal variations in the quantity were observed in these bound volatiles. Seasonal variations were also observed in the quantity of bound volatiles in regional Kangra clone during three different growth flushes of tea. These variations in glycosidic precursors of volatile compounds were studied in context with orthodox made tea and its quality. These seasonal and clonal variations in precursors of volatile compounds can be directly correlated to the difference in the quality of tea made from these cultivars.     

Predication of Japanese green tea (Sen-cha) ranking by volatile profiling using gas chromatography mass spectrometry and multivariate analysis

The sensory quality ranking of Japanese green tea (Sen-cha) was evaluated and predicted using volatile profiling and multivariate data analyses. The volatile constituents were extracted from tea infusion using vacuum hydrodistillation and analyzed using GC/MS. A quality of green tea could be discriminated to a high or low grade regarding the volatile profile by partial least squares discriminant analysis (PLS–DA). A quality ranking predictive model was developed from the relationship between subjective attributes (sensory quality ranking) and objective attributes (volatile profile) using partial least squares projections to latent structures together with the preprocessing filtering technique, orthogonal signal correction (OSC). Several volatile compounds highly contributed to model prediction were identified as various odor-active compounds, including geraniol, indole, linalool, cis-jasmone, dihydroactinidiolide, 6-chloroindole, methyl jasmonate, coumarin, trans-geranylacetone, linalool oxides, 5,6-epoxy-β-ionone, phytol, and phenylethyl alcohol. The whole fingerprints of these volatile compounds could be possible markers for the overall quality evaluation of green tea beverage.     

Fingerprint of volatile flavour constituents and antioxidant activities of teas from Thailand

The volatile flavour components of different teas growing in Thailand were extracted using the simultaneous distillation and extraction (SDE) technique. These volatiles were investigated by GC–MS. At least 54 components representing 76.51–83.32% of all samples were identified. Hotrienol, geraniol and linalool were found to be the major components in Green Oolong tea. Green Assam tea contained linalool, geraniol and α-terpineol as the key flavour constituents. Chin Shin Oolong tea was dominated by linalool, indole and cis-jasmone whilst the major flavour volatiles of Chin Hsuan Oolong tea were trans-nerolidol, cis-jasmone and geraniol. Indole, geraniol and cis-jasmone were detected as the main constituents in Four Season tea. Change of quality and quantity of volatile flavour components was related to fermentation methods that increased volatiles were illustrated by the semi-fermented tea processing method. Green Assam tea infusion extract was evaluated to have the strongest antioxidant activities with the highest amount of phenol content followed by Four Season tea, Chin Shin Oolong tea, Chin Hsuan Oolong tea and Green Oolong tea, respectively.     

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.     

Comparison of gas chromatographic volatile profiling methods for assessing the flavour quality of kenyan black teas

A comparison is made of the various ratios used to quantify black tea aroma such as: ratio of sum of gas chromatographic peak areas of compounds eluting before linalool (3,7-dimethyl-1,6-Octadien-3-ol) to those eluting after linalool (Wickremasinghe-Yamanishi ratio); gas chromatographic peak areas of compounds imparting sweet flowery aroma (Group II volatile flavour compounds) to those imparting green grassy aroma (Group I volatile flavour compounds), Owuor's flavour index; ratio of the sum of gas chromatographic peak area of the terpenoids to non-terpenoids, i.e. Mahanta ratio; and gas chromatographic peak area of linalool to E-2-hexena1, i.e. Yamanishi-Botheju ratio. The Wickremasinghe-Yamanishi ratio and Owuor's flavour index showed a significant relationship, the Mahanta ratio showed a significant but poor relationship, and the Yamanishi-Botheju ratio had no relationship with the tasters evaluation of Kenyan clonal CTC black teas. Similar results were obtained from orthodox black teas manufactured from different varieties.     

Analysis of chemical components in oolong tea in relation to perceived quality

Properties of leaf and infusion colours, chemical components and volatile flavour compounds of oolong teas and their correlation with perceived quality score given by tea‐tasting panel were analysed. The scores for appearance and infused leaf correlated strongly with concentrations of chlorophyll a (chl a), chlorophyll (chl b) and chlorophyll (chl) (r = 0.355–0.433, P < 0.05) and the total quality score (TQS) positively correlated with concentrations of chl a, chl b and chl (r = 0.517–0.533, P < 0.01). The perceived taste score and TQS positively correlated with the concentration of total free amino acid (r = 0.514, 0.694, P < 0.01) and theanine (r = 0.500, 0.684, P < 0.01). The volatile composition and their quantities varied widely among oolong tea samples. Nerolidol, indole, benzeneacetaldehyde, linalool, linalool oxide I, hexanal, benzyl nitrile, geraniol and 1‐penten‐3‐ol were prevailing volatile compounds detected in most of oolong tea samples. Principal component analysis screened ten principal components with the first three (glutamic acid, total catechins and benzeneacetaldehyde) explaining 27.86%, 20.00% and 14.46% of the total variance, respectively. Regression analysis upon the ten principal components formulated a prediction model on the total quality score with 78.5% probability. The result showed that oolong teas could be partially classified by cluster analysis based on principal components.     

湖北优良茶树品系绿茶香气成分分析

采用感官审评法和顶空固相微萃取法结合气相色谱-质谱联用技术,对6 个茶树品系所制绿茶的香气成分进行系统鉴定分析。结果表明,6 个茶树品系所制绿茶均具有鲜、清、高等典型的绿茶香气特征,其中01-4-7、20-2-1和03-7-1带有花香;共检出55 个香气成分,以醛类、醇类、酯类化合物为主,芳樟醇、壬醛、(Z)-己酸-3-己烯酯和香叶醇含量较高,其次是(E)-己-3-烯基丁酸酯、二甲硫、水杨酸甲酯、庚醛、癸醛等;不同茶树品系所制绿茶在香气物质含量上存在较大差异,部分样品存在一些含量较高的特异性香气成分;共得到9 个气味活度值相对较高的香气成分,依次为芳樟醇、癸醛、二甲硫、β-紫罗兰酮、香叶醇、壬醛、庚醛、(E)-2-壬烯醛、(Z)-己酸-3-己烯酯,对所测样品的香气形成贡献较大。多重分析表明：在香气成分上,6 个茶树品系与福鼎大白茶（对照）存在较大差异,其中茶树品系03-7-4、01-4-7、07-7-68和03-7-1所制绿茶的香气成分较为相似,20-2-1含有较高含量的酯类化合物且香气总量高,07-7-64有高含量的醛类化合物;关键变量分析表明有19 个香气成分是所测样品间的关键差异香气成分。     

斯里兰卡红碎茶与滇红碎茶主要香气成分比较分析

目的 比较分析斯里兰卡红碎茶与滇红碎茶香气成分及含量的差异性,探明区分两地红碎茶差异的主要香气成分。方法 采用GC-MS法测定斯里兰卡红碎茶及滇红碎茶样品的香气成分,通过主成分分析法比较斯里兰卡红碎茶与滇红碎茶香气成分特征差异性,根据第一主成分贡献值大小,筛选出决定区分两地红碎茶差异的主要香气成分。结果 两地红碎茶样品共分析到香气化合物40种,以醛类、酮类、酯类、醇类为主,香气成分及含量相近,但略有差异。其中反-2-己烯醛、苯乙醇、香叶醇、壬醛香气成分滇红碎茶明显高于斯里兰卡红碎茶（高出80%以上）,分别高出110.00%、108.73%、93.64%、84.91%,二氢猕猴桃内酯、吲哚香气成分滇红碎茶明显低于斯里兰卡红碎茶（50%以上）,分别低至56.19%、52.38%。其中烯类香气成分滇红碎茶比斯里兰卡红碎茶高出最为明显,高出53.53%,吲哚类香气成分滇红碎茶比斯里兰卡红碎茶低出最为明显,低出52.48%。两类红碎茶中,水杨酸甲酯占比最高,在斯里兰卡红碎茶中最高可达26.60%,在滇红碎茶中最高可达29.79%。斯里兰卡红碎茶和滇红碎茶中,酯类和醇类含量最高,酯类在斯里兰卡红碎茶中最高可达34.38%,在滇红碎茶中最高可达35.69%,醇类在斯里兰卡红碎茶中最高可达32.48%,在滇红碎茶中最高可达34.84%。各香气成分中二氢猕猴桃内酯（C15）、反-戊酸-2-己烯酯（C29）最能代表斯里兰卡红碎茶香气特征,a-萜品醇（C30）、橙花醇（C40）最能代表滇红碎茶香气成分特征。结论 对香气成分进行分析,可明显区分斯里兰卡红碎茶与滇红碎茶特征。     

SBSE-GC-MS分析不同等级宁红茶的差异香气成分

宁红茶是我国最早的工夫红茶之一。为探究宁红茶的香气品质成分特征，本研究收集了不同等级（贡品、特级、一级）的宁红茶，采用国标法进行感官评价；再利用搅拌棒吸附萃取（SBSE）结合气相色谱-质谱联用仪（GC-MS）进行香气成分检测，统计分析筛选出差异香气成分；最后利用偏最小二乘法回归分析（PLS-RA）明确对不同等级宁红茶香气品质具有重要影响的差异香气成分。感官结果表明，宁红茶等级越高，整体品质更好。三个等级宁红茶中共鉴定出142种香气成分，分为9个类别，其中酯类（41.29%）和醇类（30.03%）的相对含量较高；水杨酸甲酯（217.44‰）、芳樟醇（88.52‰）、香叶醇（65.54‰）、β-紫罗兰酮（56.07‰）、叶绿醇（52.72‰）和苯乙醛（41.04‰）等是相对含量较高的单个香气成分。Tukey s-b(K)方差分析得到69个极显著差异挥发性成分（P<0.01），其中α-荜澄茄油烯、芳樟醇、芳樟醇氧化物Ⅳ、月桂烯、橙花醇、橙花醛和反-β-罗勒烯等香气成分在贡品中相对含量较高，β-环柠檬醛、茶香螺烷、己酸苄酯和己酸香叶酯等在特级茶中相对含量较高，而叶绿醇、水杨酸苄酯、己酸反...     

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.     

Comparison of the effects of black and green tea on in vitro lipoprotein oxidation in human serum

Lipoprotein oxidation is a process thought to be involved in atherogenesis. Dietary antioxidants that prevent or inhibit oxidative damage to lipoproteins may help to prevent atherosclerosis. Both black and green teas can be major dietary sources of flavonoids and other phenolics with antioxidant activity. Results of previous studies suggest that green tea may have a greater antioxidant potential than black tea. The aim of this study was to assess and compare the effects of black and green tea on in vitro lipoprotein oxidation. The tea extracts were prepared using a method similar to that used to prepare infusions of tea for drinking. Antioxidant activities of seven black teas and four green teas were assessed using an in vitro assay that measures Cu²⁺ ‐induced oxidation of lipoproteins in human serum. All tea extracts inhibited in vitro lipoprotein oxidation in human serum to a similar extent. No significant difference in antioxidant activity was found between black and green tea. Caffeine prepared to a comparable concentration to that found in tea had no effect on lipoprotein oxidation. Further studies are required to determine the importance of these findings in relation to possible protective effects of black and green tea consumption against atherogenesis and cardiovascular disease. © 1999 Society of Chemical Industry     

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.     

Simultaneous determination of theanine,gallic acid,purine alkaloids,catechins, and theaflavins in black tea using HPLC

In the present study, we employed high performance liquid chromatography with an amide‐C₁₆ column to determine the eighteen major active ingredients in black tea, including theanine, gallic acid, four purine alkaloids, eight catechins and four theaflavins. The method was successfully used to analyse two new kinds of black teas from the leaves of Camellia ptilophylla and Camellia kucha in China and several other world‐ famous black teas. Forty percentage ethanol was chosen as the extraction solvent for preparing tea extracts. All of the eighteen compounds could be separated within 86 min with a gradient elution system. Excellent linearity was observed for all the standard calibration curves, and correlation coefficients were above 0.9991. The developed method is accurate and sensitive enough for the determination of active components in black tea.     

A study on chemical estimation of pu‐erh tea quality

Chemical compositions and infusion colour differences of seven pu‐erh tea samples and their correlation to sensory quality were investigated. The results showed that the pu‐erh tea contained 37.1 mg g^?1 caffeine, 15.7 mg g^?1 amino acids, 67.0 mg g^?1 polyphenols and 8.41 mg g^?1 total catechins, on average. Among the 17 tested volatile compounds, n‐valeraldehyde was not detected. The most abundant volatile was β‐ionone and the next was linalool oxide II. Infusion colour analysis showed that the pu‐erh tea had deep hue with ΔE ranging from 66.8 to 79.2. Spearman's linear correlation analysis showed that total quality score (TQS) of the pu‐erh tea was significantly correlated to concentration of amino acids, linalool oxide II and infusion colour indicator ΔE. Five components were extracted from the 34 tested indicators by principal component analysis and were regressed on the TQS to produce six Pearson's linear regression equations for estimating sensory quality of pu‐erh tea, among which two were statistically significant, ie TQS = 57.47 ? 0.18geraniol + 0.33polyphenols ? 1.14n‐caproaldehyde ? 1.38linalool oxide I + 0.21caffeine (p < 0.01) and TQS = 57.42‐0.03Citral + 0.33polyphenols ? 1.14n ? caproaldehyde ? 1.40linalool oxide I + 0.20caffeine (p < 0.01). Copyright © 2004 Society of Chemical Industry     

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。