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     

高效液相色谱法测定速溶滇红茶制品中茶黄素含量

目的 建立高效液相色谱法测定速溶滇红茶制品中茶黄素含量。方法 样品提取后, 采用Agilent ZORBAX SB-C18色谱柱分离, 以0.1%甲酸乙腈-0.1%甲酸水溶液为流动相进行梯度洗脱, 流速为1 mL/min, 柱温30℃, 检测波长为280 nm, 外标法定量。结果 4种茶黄素单体在各自浓度范围内线性关系良好, 相关系数均大于0.9995, 检出限和定量限分别为1.1~1.6 μg/g和3.7~5.5 μg/g, 加标回收率为95.08%~104.50%, 相对标准偏差均小于2.01%。结论 本检测方法具有较好的重复性、精密度及稳定性, 适用于检测速溶滇红茶制品中茶黄素的含量。     

Correlation of theaflavins content and valuations of kenyan black teas

Correlation between theaflavins content and tasters' valuations of Kenyan black teas generally give positive but statistically non-significant correlation coefficients. In 105 correlations using 12 samples each, only eight analyses gave statistically significant (P?0.05) correlations. Theaflavins contributed positively towards valuations but Kenyan black plain teas have high and possibly above optimum theaflavins content. Consequently other factors appear to play major roles in tea pricing, for example the generally higher prices realised by Kenyan black plain teas compared to Malawi black plain teas can only be partly attributed to the higher theaflavins content of the Kenyan teas.     

闪式提取红茶中茶黄素的工艺研究

探讨了闪式提取红茶中茶黄素的工艺。以茶黄素得率为指标,在单因素实验基础上,选取乙醇浓度、提取时间、料液比、提取次数为影响因素,利用正交试验对提取工艺进行优化。结果表明,闪式提取茶黄素的最佳工艺条件为:乙醇浓度60%,提取时间80s,料液比1:20(g/mL),提取次数2次。在此条件下,茶黄素得率为(4.98±0.05)mg/g。与传统加热回流法相比,闪式提取法得率提高7.56%,乙醇用量减少31.43%,提取时间大大缩短。闪式提取是一种快速有效提取红茶中茶黄素的方法。     

基于单宁酶处理原料制备的高茶黄素速溶红茶品质分析

目的 研究基于单宁酶发酵加工的红茶原料,制备高茶黄素含量的速溶红茶。方法 以速溶红茶中的茶黄素含量为主要评价指标,对红茶原料进行两种提取溶剂处理和不同茶叶状态,即茶叶和茶叶磨碎样处理,同时分析其感官品质及其它化学成分含量。结果 本研究发现用60%乙醇提取工艺制备的速溶红茶中,茶黄素含量显著高于水提取工艺,茶叶状态则是茶粉原料浸提效果显著高于茶叶原料浸提效果,且速溶红茶中茶黄素含量达到2.3%,是传统红茶原料中茶黄素的3倍,速溶红茶得率达到了38%。结论 以高茶黄素茶叶为原料,并将其磨成粉,用60%乙醇提取作为提取剂制备速溶红茶,其制备的速溶红茶富含茶黄素,为速溶茶的生产加工提供了一定的理论依据,也可以为夏秋茶资源的开发利用提供新方法。     

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.     

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.     

小叶种红茶发酵外观色差及其主要品质成分相关性

目的依据形成红茶优良品质的理化变化原理,借助现代科学仪器无损检测手段判断小叶种红茶发酵程度。方法在小叶种红茶发酵过程中,对发酵叶色差及不同发酵程度茶样的儿茶素、茶黄素等成分进行跟踪检测。结果发酵叶色差"L,a,b"值逐步上升或下降,其值在180~240 min均有"稳态"的存在,结合不同发酵程度茶样感官审评结果,得出"稳态"即是小叶种红茶发酵的最佳品质状态,尤以210 min最佳。儿茶素含量呈现逐渐下降趋势,茶黄素含量呈现的先增长再下降的变化趋势,茶红素与茶黄素比值的变化情况,均与发酵叶色外观差值存在显著性相关。结论采用统计方法分析色差值与审评结果之间的相关性,探讨小叶种红茶发酵适度的判别指标,提出适度发酵相关判别式ΔL≤0.10,Δa≤0.16,Δb≤0.16和品质的线性回归方程。     

In-vitro studies on the effect of polyphenol oxidase and peroxidase on the formation of polyphenolic black tea constituents

Flavanols (catechins and gallocatechins) isolated from green tea leaves (Camellia sinensis) (L) O Kuntze) were treated in vitro with polyphenol oxidase, peroxidase and a combination of both. The flavanol levels and those of the products formed were monitored by reversed-phase high-performance liquid chromatography (HPLC using spectrophotometric detection at 280 and 380 nm. Flavanols and theaflavins were quantified, whilst integrated peak areas are given for the remaining compounds. After fermentation in the presence of polyphenol oxidase higher levels of theaflavins and resolved thearubigins were obtained, whilst peroxidase produced higher amounts of chromatographically unresolved thearubigins of higher molecular weight, observed as a rise in the HPLC baseline, in the presence of peroxidase a significant decrease in the levels of all flavonol glycosides was observed, whilst in the presence of polyphenol oxidase only myricetin glycoside levels decreased.     

茶黄素药理作用及其作用机制研究进展

茶黄素最早是于红茶的发酵过程中发现的,一类由多酚类物质经氧化聚合反应而形成的具有苯并卓酚酮结构的色素。它能够显著改善茶汤的色泽以及茶汤滋味的强度和鲜爽度,是评价红茶质量的重要指标。同时,茶黄素还具有高效的抗氧化、抑菌、抗病毒、抗炎、抗肿瘤、抗心血管疾病等药理作用。本文综合国内外最新研究进展,对茶黄素的药理活性和作用机制进行了综述。      

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     

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.     

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.     

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.     

Analysis of the theaflavin composition in black tea (Camellia sinensis) for predicting the quality of tea produced in Central and Southern Africa

A parameter of black tea that correlates with quality is highly desired. Twenty good and 20 poor quality tea clones were selected from the breeding programme at the Tea Research Foundation (Central Africa) (TRF(CA)). The theaflavin (TF) composition of the black tea manufactured from each clone was analysed by capillary electrophoresis and correlated with total scores and valuation from two tea tasters with regression analysis. The significance of the differences between the 20 good and 20 poor quality tea clones was determined with the Student t‐test and the distribution‐free Kruskal–Wallis test. The sum of the TFs of the black tea correlated well (r = 0.785, P = 0.0002) with the value of the tea. Of the individual TFs determined in the black tea, the highest correlation was obtained with TF‐3′‐monogallate (TF‐B) (r = 0.788, P = 0.0016), TF‐3‐monogallate (TF‐A) (r = 0.741, P = 0.0004) and free TF (TF‐f) (r = 0.705, P = 0.0002). TF‐B (m = 24.90) followed by TF‐A (m = 12.48) showed the steepest slopes against value, making them good indicators for value. The TF‐digallate (TF‐dg) content did not show significant correlation with value (r = 0.316, P = 0.358). The individual TF content thus can be used for optimising the black tea manufacturing process in Central and Southern Africa. © 2002 Society of Chemical Industry     

Impact of shoot maturity on chlorophyll content,composition of volatile flavour compounds and plain black tea chemical quality parameters of clonal leaf

Chlorophyll content in black teas increased with a rise in shoot maturity, while the theaflavin content, brightness, total colour and tasters' evaluation declined. The increase in chlorophyll content in black teas of clone S15/10 was in a parallel with the greenness of the black tea infusions as described by tea tasters. These relationships were less pronounced in clone 6/8. The thearubigins content and the individual volatile flavour compounds composition in black tea remained the same or declined with increased shoot maturity, respectively. The results suggest that the impact of chlorophyll content on black tea quality is clonal dependent and becomes more significant as tea shoots mature and when the other plain black tea chemical quality parameters are low.     

Aflatoxins in black tea in Iran

Aflatoxins (AFs) are highly toxic, and carcinogenic secondary fungal metabolites and have been detected in various food commodities. In this regard, 40 black tea samples including domestic and imported black tea were analysed for aflatoxin contamination by high-performance liquid chromatography using a post-column derivatisation procedure (Kobra cell) with fluorescence detection. Samples were randomly collected in 2010 from Tehran markets. The results revealed that 30 among 40 samples were contaminated with aflatoxins (27.5% of the total). Mean AFB1 content was 10.0 ng/g and mean of aflatoxin total was 12.07 ng/g for the 11 contaminated samples.     

Changes in the quality parameters of clonal black tea due to fermentation time

Flavour index and Group II volatile flavour compounds of clonal black tea progressively decreased while Group I compounds increased during fermentation process. However, theaflavins in made black tea and tasters' evaluation of such tea changed in a quadratic manner with fermentation time. The rate of production of the individual theaflavins varied within a clone and between different clones as fermentation progressed. The results explain the errors obtained when only one quality parameter is used to estimate optimum fermentation time in black tea manufacture.     

Black tea thearubigins—their HPLC separation and preparation during in-vitro oxidation

A reverse phase, gradient elution HPLC method has been developed to separate black tea thearubigin compounds. Using diode array spectroscopy, spectral data are provided for the major pigment peaks. The analytical method has been used to monitor the formation of the thearubigin compounds during black tea fermentation. In-vitro model fermentation systems using partially purified tea polyphenol oxidase and mixtures of six pure catechins have also been analysed. Data are presented to relate many of the thearubigins in black tea liquors to their catechin precursors. Manipulation of the in-vitro model system conditions will be used to prepare various thearubigins for further structural studies.