Changes in antioxidant phytochemicals and volatile composition of Camellia sinensis by oxidation during tea fermentation

Monomeric flavonoids (flavan 3-ols or tea catechins) present in Camellia sinensis leaf are transformed to polymeric theaflavin and thearubigin by oxidation occurring during tea fermentation. The distinctive colour, decreased bitterness and astringency, and characteristic flavour are derived from the fermentation process giving fermented teas a marked distinction from non-fermented green tea. Even though teas are available in many different fermentation levels from green to black, the difference in phytochemicals and volatile compounds in teas with different degrees of fermentation has not been fully investigated yet within the same tea leaf. The objective of this study was to observe non-volatile phytochemicals including polyphenolic and volatile compounds changes by oxidation under strict processing control and to evaluate the degree of fermentation for the maximum antioxidant capacity with the same tea material. Harvested tea leaf was immediately processed to different degrees of oxidative fermentation (0%, 20%, 40%, 60%, and 80%). Tea infusions brewed with each processed tea leaf were analysed for polyphenolic profile, total soluble phenolics, antioxidant capacity, and volatile profile using LC–MS, HPLC, Folin–Ciocalteu assay, Oxygen Radical Absorbance Capacity (ORAC), and GC–MS analyses. The flavonoids in non-fermented green tea were significantly lessened during the oxidative fermentation process and the decreased monomeric flavonoids were transformed to polymeric theaflavin and thearubigin as the leaves were more processed. Total soluble phenolics and antioxidant capacity were significantly higher as tea leaves were less processed with a high correlation with individual polyphenolic changes. Volatile compounds present in tea leaf were analysed by GC–MS to observe changes due to processing and were utilised to create a model to differentiate fermentation based on volatile composition. Twenty-four compounds were used to build an initial model which was optimised to 16 compounds with complete separation of the groups using discriminant function analysis. The data suggested that fermentation diminished antioxidant capacity of tea and could result in lowering potential health benefits from flavonoids. This result should be considered for tea manufacturing and the development of functional foods desiring maximum potential health benefits from antioxidant flavonoids in 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.     

电子鼻对不同加工处理工夫红茶香气聚类的 方法评价

目的以电子鼻技术对不同加工工艺的工夫红茶进行香气归类并对各评价方法优劣进行探讨。方法以碧香早为原材料,对工夫红茶传统加工工艺进行研制改进,将萎凋叶进行紫外光照射、做青实验处理,发酵叶添加外源茶汁发酵,对所获得的各实验处理冷冻样及成品茶进行电子鼻分析。结果电子鼻6种传感器中,P40/1、T70/2、PA/2、P30/1等4种传感器对茶叶香气测定的贡献率较大;判别因子分析(DFA)比主成分分析(PCA)更能有效的区分不同工夫红茶样品。结论选用电子鼻不同传感器及相应的统计分析方法,可以对工夫红茶加工不同阶段的香气进行归类,并加以区分。     

Discrimination of teas based on total luminescence spectroscopy and pattern recognition

This paper reports on the application of total luminescence spectroscopy to discriminate between seven different types of tea: four bottled liquid Japanese teas (oolong, green, houji and black teas) and three leaf teas (Kenya, Assam and Ceylon teas). Total luminescence spectra were recorded by measuring the emission spectra in the range 300–700 nm at excitation wavelengths from 250 to 590 nm. Discrimination of teas based on their spectral data was performed by principal component analysis, a common chemometric method used for data reduction and visualisation. The results demonstrate the ability of fluorescence techniques to differentiate between green tea (unfermented), black tea (fermented) and oolong tea (partially fermented). Copyright © 2006 Society of Chemical Industry     

Geographical origin identification and quality control of Chinese chrysanthemum flower teas using gas chromatography–mass spectrometry and olfactometry and electronic nose combined with principal component analysis

Aroma profiles and volatile profiles were established based on volatile and aroma ‐ active components identified by gas chromatography–mass spectrometry and olfactometry (GC–MS–O) and electronic nose (E ‐ nose). The two profiles were used for quality control and origin identification of chrysanthemum flower teas. Results showed that 86 volatile components were identified in five chrysanthemum flower teas, including terpenes, alcohols, ketones, aldehydes, esters and others. Of them, 33 aroma ‐ active components were recognised, including 10 aroma categories. The aroma profiles and volatile profiles were established by 10 aroma categories and E ‐ nose. Chrysanthemum flower teas were divided into five groups on PCA score plots based on their aroma profiles and volatile profiles, and the key volatile (aroma ‐ active) components resulting in the tea sample differences were determined. The quality of chrysanthemum flower teas could be evaluated according to aroma ‐ active components and aroma profiles and origins could be discriminated by PCA combined with GC–MS–O and E ‐ nose.     

常见花茶的功能成分与生物活性研究进展

花茶是通过对植物的花或者叶子进行一种更深层次的加工而形成的茶,因其富含多种营养功能成分,对人体的健康有积极地作用。花茶不仅具备养生的功能,同时还有一定的健身功效,因此人们在日常的生活、学习、工作过程中,都喜欢将其作为日常的饮品。近年来,随着经济的快速发展,花茶市场越来越兴盛,花茶种类繁多,有玫瑰花茶、有茉莉花茶、金银花茶、菊花茶、桂花茶和蒲公英等各类花茶百余种。该研究综述了茉莉花茶、玫瑰茶、菊花茶、金银花茶四种常见花茶的营养成分、活性成分及生物活性研究进展。总结发现,上述四种花茶富含蛋白质、维生素、多糖、儿茶素、茶碱类、黄酮类、挥发油类等营养和功能成分,具有抗氧化与延缓衰老、提高免疫力、防治心血管疾病、杀菌抑菌等生物活性。     

Comparison of catechins and volatile compounds among different types of tea using high performance liquid chromatograph and gas chromatograph mass spectrometer

As tea is one of the most popular beverages consumed worldwide, it is important for customers and business investigators to develop an easy and reliable method to discriminate between different types of teas from each other. A total of eighty‐seven types of various white, green, oolong, black and Puer teas were collected from the major tea estates in China, and their catechin contents and volatile compounds were compared by high performance liquid chromatograph and gas chromatograph mass spectrometer. It was found green tea contained the highest concentrations of total catechins, (?)‐epicatechin gallate (ECG) and (?)‐epigallocatechin gallate (EGCG), while oolong teas contained the highest concentrations of (?)‐epigallocatechin (EGC) among these five types of teas. The aroma composition and their quantities in different types of teas varied quite widely. The concentration of ECG, EGCG, pentanal, hexanal, methyl jasmonate, indole, (E,E)‐2,4‐hexadienal and 1,2,3‐trimethoxybenzene was shown to be different and could be used to discriminate white, green, oolong, black and Puer teas. The result showed that different types of teas could be partially classified by cluster analysis using index of individual catechins and volatile components.     

Changes in volatile compounds upon aging and drying in oolong tea production

BACKGROUND: Long‐term storage (aging) with periodic drying of fresh oolong tea gives rise to so‐called old oolong tea. Alteration of aroma compounds is expected when a fresh oolong tea is converted into an old one, as the two teas smell drastically different. The aim of this study was to compare the volatile compounds in fresh and old oolong teas. RESULTS: Significant differences were observed between the volatile compounds in fresh and old oolong teas. This observation suggested that long straight chains of alcohols and acids were putatively decomposed while shorter‐chain acids, their amide derivatives and many nitrogen‐containing compounds were generated during the tea conversion processes. The overall patterns of volatile compounds observed in five different preparations of old oolong tea were fundamentally identical. This consensus pattern was different from that observed in oolong tea either stored for more than 10 years without drying or prepared at relatively low temperatures and short baking time. CONCLUSION: Characteristic aroma nitrogen‐containing compounds, including N‐ethylsuccinimide, 2‐acetylpyrrole, 2‐formylpyrrole and 3‐pyridinol, were consistently found in the examined old oolong teas. These compounds might be regarded as typical constituents at least for a certain kind of old oolong tea. Copyright © 2010 Society of Chemical Industry     

栗香型绿茶研究进展

栗香是优质绿茶的特征香型之一,不仅是绿茶评价等级的标准,而且是消费者选择的重要依据。对栗香型茶树品种、栗香型绿茶的加工工艺、关键香气成分及其判别方法进行综述和展望,以期为栗香型绿茶的定向加工提供参考。     

电子鼻和GC-MS结合化学计量学应用于高香红茶与传统工夫红茶香气特征的研究

为探究高香红茶与传统工夫红茶香气差异,采用电子鼻和GC-MS技术研究了高香红茶与传统工夫红茶香气品质差异的关键因素。结果表明:高香红茶以花香为主,传统工夫红茶香气呈现甜香。GC-MS在两种红茶中检测出78种挥发性物质,其中氧化芳樟醇、芳樟醇、水杨酸甲酯、正戊醇、2-环丙基乙醇、香芹醇、β-环柠檬醛、2-乙基呋喃、对薄荷-1,3,8-三烯和1,4-戊二烯等是区分不同风味红茶的重要香气成分。传统工夫红茶的电子鼻检测响应值总和明显高于高香红茶,通过多元统计分析可选出S6、S10电极信号用于鉴别不同风味红茶,并预测1,4-戊二烯是鉴别不同风味红茶的重要挥发性物质。研究结果明确了高香红茶的香气组成特征及其与传统工夫红茶香气特征的区分,为不同风味红茶的进一步分类提供理论依据。     

不同品种青砖茶化学成分与抗氧化活性的比较分析

本研究第一次分析比较了赤壁群体种、中茶108、槠叶齐和丹桂品种所制青砖茶在感官品质、化学成分及抗氧化活性方面的差异。采用顶空固相微萃取-气相色谱-质谱仪联用技术,对4个品种青砖茶样品挥发性成分进行了分析鉴定。结果表明,不同品种青砖茶的化学成分含量有明显差异;总抗氧化能力、抑制羟自由基能力和DPPH自由基清除能力以中茶108、槠叶齐和丹桂所制青砖茶较高;相关性分析表明青砖茶茶汤的抗氧化活性主要与茶多酚、儿茶素类化合物总量以及咖啡碱总量具有较大的相关性,其中与表没食子儿茶素没食子酸酯(EGCG)和苹果酸的相关性最强;可溶性糖、反-2-癸烯醛、壬醛与感官评分呈极显著正相关,而没食子酸、3-甲基呋喃、苯乙酮、异佛尔酮等与感官评分呈极显著负相关;不同品种青砖茶的醛类、酮类和醇类化合物具有明显的差异,其中丹桂品种所制青砖茶的品种香明显,与其芳香醛和酮类物质含量较高相关;感官审评结果显示,4个品种所制青砖茶的品质无显著差异。通过对不同品种青砖茶的主要品质化学成分含量、抗氧化活性以及感官品质等分析,为青砖茶品种选育及其应用提供参考依据。     

Screening of the antioxidant properties and polyphenol composition of aromatised green tea infusions

BACKGROUND: Aromatised green teas are widely sold and popular owing to their fragrance. In this study the antioxidant activity of six commercial green tea infusions was assessed by three complementary assays. RESULTS: In order to evaluate the tea infusions as antioxidant sources, their phenolic content (Folin‐Ciocalteu assay), cupric ion‐reducing antioxidant capacity (CUPRAC) and 2,2‐diphenyl‐1‐picryhydrazyl (DPPH) radical‐scavenging ability were determined. Their content of polyphenols was also determined by high‐performance liquid chromatography/mass spectrometry (HPLC/MS) in negative electrospray ionisation mode. Some teas with citrus aroma, besides having a relatively high content of catechins, also contain other phenolic compounds such as naringin and hesperidin. The three assays used to evaluate the antioxidant capacity of the tea infusions gave different rank orders. Therefore an antioxidant index was calculated for better correlation of the results, and its highest value was obtained for Clear Green Mint tea infusion. CONCLUSION: The studied teas, besides having a relatively high content of catechins, also contain naringin and hesperidin, which are not present in ‘pure’ green tea. It is important to run multiple assays to get a better estimate of the antioxidant capacity of a given sample. Copyright © 2012 Society of Chemical Industry     

How manufacturing processes affect the level of pesticide residues in tea

Tea (both green and black) is consumed throughout the world, both for pleasure and therapeutic purposes. Most people will be unaware of their involuntary exposure to residues of pesticides lingering in processed tea and so possibly transferring into infusions of tea. The purpose of this work was to study the effect of green tea and orthodox black tea manufacturing processes on the fate of pesticides sprayed onto tea bushes (Camellia sinensis). The fates of residues of dimethoate, quinalphos, dicofol and deltamethrin in these two different types of tea manufacturing processes were compared. For black tea, the manufacturing process involves leaf harvesting, withering, rolling, fermentation and drying; and for green tea, leaf harvesting, microwave heating, rolling and drying. The two processes resulted in the same concentration factor of plant material into the dried commodity, while the decreases in residue levels were different for different pesticides. Initial microwave heating and dehydration in the green tea manufacturing process resulted in greater loss of pesticide residues than did withering and dehydration in black tea; no significant reduction in residue level resulted from the rolling and fermentation steps in black tea. Residue levels in both green and black teas were reduced during final drying. Copyright © 2004 Society of Chemical Industry     

基于电子鼻和HS-SPME-GC-MS技术解析乌牛早茶的挥发性风味物质

为探究乌牛早的嫩叶和老叶在不同温度下挥发性物质成分,本文利用电子鼻测试不同温度下乌牛早茶叶的气味差异,并结合固相微萃取和气质联用(HS-SPME-GC-MS)技术对挥发性风味物质进行分析。结果表明:电子鼻能灵敏地检测到不同温度处理条件下嫩叶和老叶的气味变化,主成分分析(PCA)显示各个样品间差异明显。通过GC-MS分析在常温和处理温度40、60、80、100℃的乌牛早嫩叶中分别检测出15、20、14、17、17种挥发性物质,其主体风味成分主要有花果香味的芳樟醇、橙花醇等醇类物质。同时,在相同温度处理条件下的老叶中分别检测出21、21、19、18、27种挥发性物质,其主体风味成分主要有清新叶草香味的水杨酸甲酯等酯类物质。     

南茶高纬度北引对茶叶品质的影响

目的研究南茶高纬度北引后对茶类适制性及绿茶品质产生的影响。方法通过理化方法,分析同一品种茶树在高纬度北引后对其叶片厚度、鲜叶成分、不同茶类感官品质、绿茶成分及感官品质所产生的变化。结果随着纬度的增加,绿茶品质较好,而红茶品质较差;随着南茶高纬度北引,叶片厚度、氨基酸、水溶性糖、水浸出物和芳香物质(精油)总量等含量随纬度增大而增加;茶多酚含量则相反;对精油中各成分分析显示,北方茶烃类成分较多,醇类成分较少。结论本研究明确了南茶高纬度北引后茶叶品质特点及化学成分基础。     

牛奶对茶汤纳米聚集体茶多酚分布特性的影响

茶汤纳米聚集体是茶多酚和蛋白质等自组装而成的纳米胶粒,是各组分介于游离分子与沉淀颗粒的中间状态。为探究牛奶对茶汤茶多酚分布特性的影响,本研究以云南大叶种蒸青绿茶、红茶为原料,以1:50茶水比浸提茶汤,按不同比例添加全脂、半脱脂和脱脂牛奶,利用超滤离心技术分离茶汤纳米聚集体,采用动态光散射技术分析各组茶汤纳米聚集体的总光强和平均直径,采用福林酚法分析其茶多酚浓度和分布率,比较研究牛奶添加比例、脂肪含量和茶类等因素对纳米聚集体物理化学特性和茶多酚分布特性的影响。结果表明:添加不同脂肪含量的牛奶均会促使部分牛奶纳米胶粒与茶汤纳米聚集体结合,导致茶汤超过90%的茶多酚富集于纳米聚集体,使绿茶和红茶的游离茶多酚比例分别降低78%和67%。初步证实:添加牛奶会促进绿茶、红茶的茶多酚参与分子聚集,使游离茶多酚比例大幅降低。     

Green tea from purple leaf coloured tea clones in Kenya- their quality characteristics

The Kenyan tea industry wishes to diversify its tea products, and in line with this, anthocyanin – rich teas were developed at the Tea Research Foundation of Kenya. These teas have purple-coloured leaves and the green colour is masked. In total, 12 accessions of the purple leaf coloured teas and 2 standard tea varieties were studied. Clones Hanlu and Yabukita are Chinese and Japanese tea varieties, respectively, known for good green tea, and they were used as reference standards. Little if any research had been done to characterize the quality of these purple leaf coloured teas and this study investigated their total polyphenols (TPP), catechins, caffeine, gallic acid and theanine. These are the major green tea quality parameters. Results showed that the new Kenyan tea clones had higher total polyphenols than had the reference standard tea varieties, which had 17.2% and 19.7% while the lowest among the Kenyan clones was 20.8%. On catechin quality index, K-purple and TRFK 91/1 showed high index values of 15.9 and 13.3, respectively, while clones TRFK 83/1 and 73/5 showed low index values of 0.74 and 1.0, respectively. Hanlu had the highest caffeine level with 2.42% while clones TRFK KS 3, TRFK KS 2 and TRFK 83/1 had relatively high caffeine levels among the purple leaf coloured teas, with 2.33%, 2.22% and 2.21%, respectively. Clone TRFK 73/5 had the lowest caffeine content, with 1.16%. Theanine analysis showed that most purple leaf coloured teas had more theanine than had the reference standard clones, except TRFK 83/1 and K-purple, which were lower than the reference standard clones. The implication of the green tea chemical quality parameters is also discussed. It is concluded that all the studied clones/varieties have above the minimum 14% of total polyphenols. Clones K-purple and TRFK 91/1 showed high green tea quality indices with the latter doubling with high levels of theanine; hence its highly recommended for green tea manufacture.     

闷黄对槠叶齐品种黄小茶品质的影响

通过设置不同湿闷时间（2、4、6 h）和不同干闷时间（12、24、36、48、60、72 h）组合,结合感官审评与理化分析,探究闷黄工序对槠叶齐品种加工黄小茶品质的影响。结果表明:鲜叶适当摊放后杀青,在温度45 ℃、空气湿度70%的条件下闷4～6 h再揉捻成条,初干至八成干,再闷黄48～60 h后足干,该闷黄组合工艺加工的黄小茶品质最好。此条件下茶叶水浸出物、游离氨基酸、可溶性糖总量均增加,儿茶素和黄酮苷等多酚类化合物含量降低,其中酯型儿茶素含量降低,简单儿茶素变化差异不显著,咖啡碱含量变化小。对该工艺下的4个黄茶样及绿茶对照样进行香气检测分析,共检测出110种香气组分,其中57种香气组分只在黄茶中检测出。4个黄茶中共有香气组分有22种,在各黄茶中的组成及比例相似,均以碳氢化合物、醇类、酮类和酯类为主,其中具有愉快香气的芳樟醇氧化物、香叶醇、β-紫罗兰酮氧化物、二氢猕猴桃内酯和β-柠檬醛等化合物促进了黄茶良好香气品质的形成。     

不同规格CTC红碎茶理化与香气成分比较

从感官审评、理化成分、香气成分等方面对4个规格的CTC红碎茶进行分析。结果表明,所有红碎茶干茶色泽以棕褐、茶汤以红亮为主,滋味以浓、强、鲜为突出特点,香气类型为甜香,碎茶3号感官品质评分最高。各类理化成分含量在不同规格红碎茶中有显著差异,水浸出物、茶碱和儿茶素总量随颗粒减小而降低;碎茶3号茶多酚（25.68 mg/g）、咖啡碱（43.67 mg/g）和儿茶素总量（96.93 mg/g）含量最高,碎茶5号黄酮总量（20.30 mg/g）最高。GC-MS从4个规格红碎茶中检测到醇类（44.11%~51.84%）、酯类（15.31%~18.96%）、醛类（5.99%~11.56%）等9类共100种香气物质,共有香气成分21种;碎茶3号香气成分与其他规格差异最大,香气物质种类最为丰富;碎茶2号和末茶香气成分最接近,碎茶5号香气物质种类最少。通过分析,不同规格CTC红碎茶在感官审评、化学成分和香气成分方面各有差别,初步探明不同规格CTC红碎茶的品质差异。