3 种名优绿茶的特征滋味成分研究及种类判别

采用高效液相色谱与高分辨质谱相结合的方法对西湖龙井、黄山毛峰和信阳毛尖3 种名优绿茶茶汤中的共有特征滋味成分进行研究,并据此进行种类判别分析。通过研究,确定了以表没食子儿茶素没食子酸酯、咖啡因、表儿茶素没食子酸酯、表没食子儿茶素等为主的15 种共有特征滋味成分,并建立了其相应的特征指纹图谱。利用15 种共有特征成分峰的相对峰面积,建立了多元化典型判别函数,采用逐步判别分析技术对31 个绿茶样品进行了很好的种类判别,判别正确率为100%。     

Epimerisation of tea polyphenols in tea drinks

The present study was carried out to quantify green tea epicatechin (GTE) derivatives and to investigate the origin of epicatechin epimers present in 18 selected canned or bottled tea drinks. The major GTEs present in tea are (?)‐epigallocatechin gallate (EGCG), (?)‐epigallocatechin (EGC), (?)‐epicatechin gallate (ECG) and (?)‐epicatechin (EC). HPLC analysis showed that the content of total GTEs was lower (16.4–268.3 mg l^?1) in the canned and bottled tea drinks than in tea traditionally prepared as a beverage in a cup or teapot (3–5 g l^?1). The major finding was that they contained higher levels of epicatechin epimers, namely (?)‐gallocatechin gallate (GCG), (?)‐gallocatechin (GC), catechin gallate (CG) and (?)‐catechin (C), than of GTEs, ranging from 7.6 to 331.8 mg l^?1. To investigate the origin of these epimers, GTEs were extracted from longjing green tea and autoclaved at various temperatures for 10–60 min. It was found that at least 50% of GTEs were epimerised to their corresponding epimers when autoclaved at 120 °C for 20 min. It is concluded that epicatechin epimers in tea drinks are not originally present in green tea leaf but are instead derived from thermal conversion of GTEs. Copyright © 2003 Society of Chemical Industry     

不同产地扁形绿茶的品质成分差异分析

为了系统和全面地了解扁形绿茶的品质特征,分析来自湖北大悟、浙江磐安、安徽歙县、贵州湄潭、四川峨眉山5个产地扁形绿茶样品的感官品质、色差以及茶多酚、游离氨基酸、水浸出物、咖啡碱、可溶性糖等主要化学成分含量差异。结果表明,龙井茶干茶L1值(亮度值)与b1值(黄蓝色度值)分别达到38.20和19.35,均显著(P<0.05)高于其他4个产地的扁形绿茶,大方茶茶汤L3值最高。大方茶和湄潭翠芽平均水浸出物总量超过48.00%,显著(P<0.05)高于孝感龙剑茶、龙井茶及竹叶青茶。湄潭翠芽的游离氨基酸、咖啡碱、儿茶素、表儿茶素没食子酸酯、儿茶素没食子酸酯含量均最高,表没食子儿茶素没食子酸酯含量以孝感龙剑茶最高。基于各品质成分的相对含量建立的偏最小二乘法判别分析模型成功区分了5个产地的扁形绿茶样品。同时,利用偏最小二乘法判别分析变量重要性因子值筛选到11种关键成分,分别是干茶E1(综合色差值)、干茶a1(红绿色度值)、干茶b1、表儿茶素没食子酸酯、没食子儿茶素没食子酸酯、咖啡碱、游离氨基酸、茶汤a3、茶汤b3、茶汤L3、茶汤E3,可作为区分5个产地扁形绿茶的品质指标。本研究结果将为扁形绿茶加工工艺和品质提升提供一定的科学参考。     

Polyphenolic composition and in vitro antioxidant activities of native‐ and tannase‐treated green tea extracts

The antioxidant activities of native‐ and tannase‐treated green tea extracts along with their major polyphenol components were investigated. The polyphenolic content and composition of the tea before and after tannase treatment were determined by liquid chromatography coupled with mass spectrometry (LC‐MS). Approximately 99% of the (?)‐epigallocatechin gallate (EGCG) and (?)‐epicatechin gallate (ECG) in green tea extract were converted by tannase to (?)‐epigallocatechin (EGC) and (?)‐epicatechin (EC), respectively, after 30 min. Biotransformed green tea exhibited a significantly higher DPPH˙ radical scavenging activities than native green tea (EC₅₀ value of 0.024 ± 0.001 and 0.044 ± 0.001 mg mL^?1, respectively). Kinetic parameters such as scavenging rate and stoichiometry were calculated. The rate of DPPH˙ radical scavenging activities for tannase‐treated green tea extract was shown to be higher than native green tea extract.     

陕西省不同产地绿茶中6种活性成分含量的比较

目的：采用高效液相色谱法HPLC,对陕西不同产区(安康、汉中和商洛)绿茶中茶氨酸(theanine)、没食子酸(gallic acid,GA)、咖啡碱(caffeine,CAF)、表没食子儿茶素(epicatechin gallate,EGC)、表儿茶素没食子酸(epicatechin gallate,ECG)及表没食子儿茶素没食子酸酯(epigallocatechin gallate,EGCG)的含量进行分析比较。方法：绿茶经热水提取后采用HPLC测定上述6种活性成分的含量,色谱柱(250mm×4.6mm,5μm),流动相为0.05%三氟乙酸溶液(A)、乙腈(B)梯度洗脱,流速为1mL/min,柱温25℃,检测波长：190nm和280nm。结果：3个产区中6种组分的含量在0.325～47.061mg/g之间,产区间各组分含量存在显著性差异(P＜0.05),其中汉中绿茶中GA的平均含量最高,安康绿茶中茶氨酸、CAF、ECG、EGC、EGCG的平均含量最高。     

Quantitative and Qualitative Portrait of Green Tea Catechins (Gtc) Through Hplc

Green tea (Camellia sinensis) is a prosperous source of polyphenols, especially catechins. In the current research, an effort was made to optimize the extraction conditions for maximum yield of catechins from the local green tea Qi-Men. For the purpose, three different solvents were used, i.e., aqueous ethanol (50%), aqueous methanol (50%), and water at different time intervals (20, 40, and 60 min). Green tea catechins were quantified through HPLC using a C18 column and UV detector. The antioxidant activity of green tea catechins was measured through in vitro tests including DPPH radical scavenging ability and antioxidant activity. Results showed that extraction through aqueous ethanol resulted in maximum yield of green tea catechins (17400 ± 0.19 mg/100 g green tea leaves. Moreover, epigallocatechin, epigallocatechin gallate, epicatechin gallate, and epicatechin ranged from 4.26 ± 0.09 to 6.4 ± 0.2, 12.1 ± 0.123 to 17.7 ± 0.3, 1.32 ± 0.03 to 1.81 ± 0.02, 5.48 ± 0.099 to 8.6 ± 0.2 g/100 g of dry-extract, respectively. Furthermore, highest antiradical (80.65 ± 3.69%) and antioxidant activity (67.12 ± 3.08%) were observed in catechins extracted through aqueous ethanol.     

A simple and rapid turbidimetric method for determining catechins in beverages

We have developed a simple and rapid turbidimetric method to determine catechins based on the fact that many polyphenols produce hydrogen peroxide in an alkaline environment and that hydrogen peroxide oxidises cerium to generate cerium oxide precipitates. Four catechins (epicatechin, epigallocatechin, epicatechin gallate, epigallocatechin gallate) aggregated with these precipitates to form massive precipitates with increased turbidity. The catechins solution (0.18 mL) was mixed with 0.02 mL of 1% CeCl₃ solution, and absorbance (650 nm) was measured immediately after agitation for 3 min using a spectrophotometer. Absorbance was strongly correlated (0.99) with the concentration of each catechin compound. For commercially bottled green tea, the estimated catechin content determined using this turbidimetric method showed better correlation with the content determined by high‐performance liquid chromatography than that determined using ferrous tartrate method, which is the official Japanese method for determining the tannin content of green tea.     

“紫娟”茶中的EGCG3"Me成分研究

"紫娟"是云南大叶群体种中的一种稀有茶树品种,因富含花青素成分其新鲜嫩梢的芽、叶、茎均呈现紫色,从而具有很高的科研价值和经济开发潜力,当今其功能化学成分的研究已成为了茶学研究热点之一。本文采用HPLC以及LC-MS技术首次报道分析了茶树特异品种"紫娟"中的表没食子儿茶素-3-O-(3-O-甲基)没食子酸酯(EGCG3"Me)成分及高EGCG3"Me含量"紫娟"茶的加工工艺。结果表明,茶树特异品种"紫娟"鲜叶中含有EGCG3"Me成分(含量为1.05%);在一芽五叶新梢不同嫩度的鲜叶中,第三叶的EGCG3"Me含量最高(含量为1.24%);采用蒸青绿茶或者晒青绿茶的加工工艺可以使成茶有效保留鲜叶中的EGCG3"Me成分。此外,还分析比较了普通炒青绿茶与"紫娟"绿茶中主要儿茶素成分的含量差异,发现较高的ECG和EC含量而较低的EGCG含量是茶树特异品种"紫娟"绿茶中儿茶素组成的主要特点。     

In vitro human skin permeation and cutaneous metabolism of catechins from green tea extract and green tea extract-loaded chitosan microparticles

Catechins are major antioxidants in green tea (Camellia sinensis or Camellia assamica), but because they do not permeate the skin well, the application of green tea in cosmetic products has so far been limited. This study aims to evaluate the cutaneous absorption of catechins from an extract of green tea and from a green tea extract-loaded chitosan microparticle. The catechin skin metabolism was also examined. The results suggest that chitosan microparticles significantly improve the ability of catechins to permeate skin. The cutaneous metabolism of the catechins significantly affected their permeation profiles. Epicatechin (EC) and epigallocatechin (EGC) penetrated the skin more than epigallocatechin gallate (EGCG) and epicatechin gallate (ECG). The galloyl groups in EGCG and ECG were enzymatically hydrolysed to EGC and EC, respectively. Dehydroxylation of catechins was also observed. Chitosan microparticles effectively prevented enzymatic changes of the catechins; therefore, chitosan microparticles are here found to be the promising carriers for enhancing the skin permeation.     

Determination of catechins in green tea infusions by reduced flow micellar electrokinetic chromatography

A sulfated-β-cyclodextrin (s-β-CD) modified reduced flow micellar electrokinetic chromatography (RF-MEKC) method was developed and validated for the determination of catechins in green tea. The optimal electrolyte consisted of 0.2% triethylamine, 50 mmol/L SDS and 0.8% s-β-CD (pH = 2.9), allowing baseline separation of five catechins in 4 min. The samples and standards were injected at 0.6 psi for 5 s under constant voltage of −30 kV. Sample preparation simply involved extraction of 2 g of tea with 200 mL water at 95 °C under constant stirring for 5 min. The method demonstrated excellent performance, with limits of detection (LOD) and quantification (LOQ) of 0.02–0.1 and 0.1–0.5 μg/mL, respectively, and recovery percentages of 94–101%. The method was applied to six samples of Brazilian green tea infusions. Epigallocatechin gallate (23.4–112.4 μg/mL) was the major component, followed by epigallocatechin (18.4–78.9 μg/mL), epicatechin gallate (5.6–29.6 μg/mL), epicatechin (4.6–14.5 μg/mL) and catechin (3.2–8.2 μg/mL).     

The effect of ascorbic acid,citric acid and low pH on the extraction of green tea: How to get most out of it

Green tea seems to have a positive impact on health due to the therein-found flavanols. The amounts of these substances depend on tea preparation. In this paper, the influence of steeping time (3–7 min) and temperature (70–100 °C) on the content of the main flavanols in green tea (epicatechin EC, epicatechin gallate ECg, epigallocatechin EGC, and epigallocatechin gallate EGCg) is presented. Furthermore, additives (phosphate buffers, ascorbic acid in different amounts, and citric acid) are used to investigate the influence of pH, antioxidative, and chelating agents, simulating the addition of lemon juice or pure vitamin C.     

SEPARATION OF INDIVIDUAL CATECHINS FROM GREEN TEA USING SILICA GEL COLUMN CHROMATOGRAPHY AND HPLC

Crude catechin mixtures from green tea were separated into six fractions using a silica gel column chromatography and a chloroform-methanol-water (65:35:10, v/v/v, lower phase) solvent system. Fraction I was free of catechins, fraction II contained epicatechin (EC), fraction III had epicatechin and epigallocatechin (EGC), fraction IV possessed EGC, fraction V contained EGC, epicatechin gallate (ECG) and epigallocatechin gallate (EGCG), and fraction VI had EGCG. EC and EGC were separated from fractions II, III and IV using HPLC with a RP-18 semipreparative column and a water-dimethylformamide-methanol-acetic acid (157:40:2:1, v/v/v/v) solvent system. For isolation of EGC, ECG and EGCG from fractions V and VI a water-acetonitrile-methanol-acetic acid (159:36:4:1, v/v/v/v) solvent system was employed. Chemical structures of purified catechins were further confirmed by ESI-MS.     

ANTIOXIDANT PROPERTIES OF POLYPHENOLS EXTRACTED FROM GREEN AND BLACK TEAS

The catechins, including epicatechin gallate (ECG), epigallocatechin (EGC), and epigallocatechin gallate (EGCG), and the theaflavins, including theaflavin (TF), theaflavin monogallate (TF-1), and theaflavin digallate (TF-2), were extracted from green tea and black tea, respectively. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging ability, superoxide-scavenging efficiency, and lipid oxidation-inhibition ability of the pure compounds listed above as well as epicatechin (EC), carnosol, carnosic acid, and butylated hydroxytoluene (BHT) were investigated.
The DPPH radical-scavenging ability of the catechins was EGCG > ECG > EGC > EC and of the theaflavins was TF-2 > TF-1 > TF. EGCG, ECG, EGC, TF-2, TF-1, and TF showed higher DPPH radical- and superoxide-scavenging abilities than carnosol, carnosic acid, and BHT. EGCG, ECG, EGC, carnosol, and carnosic acid showed higher lipid oxidation-inhibition activity, as measured by the Rancimat method, than BHT and theaflavins.     

Impact of heating on chemical compositions of green tea liquor

Heating pasteurization changed flavour of green tea liquor and it was a technical barrier in ready-to-drink tea production. The effect of heating on chemical compositions of green tea liquor was investigated by high performance liquid chromatography and gas chromatography–mass spectrometry. With increase of heating temperature from 85 °C to 120 °C, the green tea liquor became darker and less green, but deeper yellow in colour. During the heating, epigallocatechin gallate, epigallocatechin, epicatechin and epicatechin gallate partially epimerized, and concentration of total catechins decreased. Twenty volatiles were identified and concentrations of pentanol, cis-3-hexenol, linalool oxide I, linalool oxide II and β-ionone were decreased while phenylacetaldehyde, linalool, linalool oxide III, α-terpineol and indole increased. The decline of volatiles with pleasant odours and increase of some volatiles with unpleasant odours, such as indole (animal-like) and α-terpineol (faint ammoniacal), was considered to be responsible for the change in flavour of green tea liquor. Treatment at 85 °C caused fewer changes in liquor colour and concentrations of catechins and volatiles and it is recommended that extraction and pasteurization of canned ready-to-drink green tea should be carried out at 85 °C or less.     

利用活性真菌转化简单儿茶素为酯型儿茶素

研究从茶树的鲜叶、茎部和茶树土壤中分离出活性真菌,通过利用天然微生物的转化能力,使简单儿茶素转化为功能性较强的复杂型酯型儿茶素。实验结果表明:筛选出了具有转化能力的活性菌种,能有效地将简单儿茶素转化为酯型儿茶素,而且其转化能力良好。并对此种活性真菌进行形态学和生理生化的初步检测,判断其属于丝状真菌藻状菌纲,毛霉目,内囊霉科,内囊霉属。     

Taste characterisation of green tea catechins

There has been interest in biological activities of green tea catechins. However, little is known about the taste characteristics of catechins. To assess the taste characteristics of catechins ((?)–epicatechin (EC), (?)–epicatechin gallate (ECg), (?)–epigallocatechin (EGC) and (?)–epigallocatechin gallate (EGCg)), sensory evaluations were performed. The taste intensity increased with increased catechins concentration. Among them, ECg showed the strongest taste. Catechins had tastes that consisted primarily of astringency and bitterness. Therefore, taste palatability decreased with increasing catechin concentrations. In line with taste intensity, taste palatability of ECg was the lowest. Taste sensor analysis and mouse behavioural assays showed same results. EC and ECg were more stable in Ringer’s solution than EGC and EGCg. Furthermore, taste cell responses to ECg that had the strong taste and better stability among catechins used were recorded. Some taste cells responded to ECg. This result suggests that ECg might be recognised by taste cells.     

Flavanol Composition and Caffeine Content of Green Leaf as Quality Potential Indicators of Kenyan Black Teas

The flavanol composition and caffeine content of green tea leaf, black tea quality parameters of theaflavins, thearubigins, liquor brightness and total colour varied more among clones than with time of the year. In green leaf, either (-)epicatechin gallate or (-)epigallocatechin gallate was the dominant flavanol present. Regression analysis of tasters' preferences for black teas against green leaf chemical components showed positive and significant correlations for (-)epicatechin gallate (r = 0·498, P ⩽ 0·05 for taster A; r = 0·665, P ⩽ 0·01 for taster B, and r = 0·678, P ⩽ 0·01 for both tasters' overall ranking), (-)epigallocatechin gallate (r = 0·513, P ⩽ 0·05 for taster B; r = 0·532, P ⩽ 0·05 for both tasters' overall ranking and caffeine (r = 0·523, P ⩽ 0·05 for taster A; r = 0·657, P ⩽ 0·01 for taster B; and r = 0·686, P ⩽ 0·01 for both tasters' overall ranking). Similar regressions against black tea theaflavins, thearubigin content, liquor brightness and total colour were not significant. The results suggest that the green leaf chemical components, (-)epicatechin gallate, (-)epigallocatechin gallate and caffeine could be used as quality potential indicators during clonal selection and propagation. © 1997 SCI.     

EFFECT OF FAR-INFRARED HEATER ON THE PHYSICOCHEMICAL CHARACTERISTICS OF GREEN TEA DURING PROCESSING

ABSTRACT

The green tea leaves (Camellia sinensis var. sinensis) were irradiated by a far‐infrared (FIR) heater during the roasting and drying step, resulting in three different treatments produced. Green tea was extracted by soaking the leaves in water, and the components were analyzed. FIR irradiation, combined with fryer heating during the roasting step and additionally applied after the drying step, increased total phenolic contents of green tea from 116.30 to 171.77 mg/g, and total flavanol contents from 17.54 to 24.76 mg/g, compared with the non‐irradiated control. Ascorbic acid contents also increased from 3.07 to 4.20 mg/g. The amounts of epicatechin gallate and epigallocatechin gallate were significantly increased from 2.41 to 4.59 mg/mL and 20.61 to 28.54 mg/mL, respectively, compared with the non‐irradiated control. FIR irradiation increased Nitrite Scavenging Ability of green tea at pH 3.0 and pH 4.2, while there was no significant difference at pH 6.0. Sweetness, umami and aroma of green tea were enhanced by FIR irradiation, while bitterness and astringency were decreased compared with those of the control. These results show that FIR heating during the green tea process affected the chemical properties of green tea, and the FIR heater can be applied to increase the physicochemical qualities of green tea.

PRACTICAL APPLICATIONS

Green tea, a widely consumed drink, has received much attention because of the beneficial biological effects attributable to its excellent antioxidant activity. In this article, a far‐infrared (FIR)‐heater for industrial application was used during the processing of green tea leaves, and the chemical characteristics and quality of FIR‐treated green tea were determined. FIR irradiation, combined with fryer heating during the roasting step and additionally applied after the drying step, significantly increased phenolic, flavanol, ascorbic acid, epicatechin gallate, epigallocatechin gallate contents and nitrite‐scavenging activity compared with non‐irradiated control. Sensory evaluation also showed a positive effect of FIR irradiation. The results indicated that FIR heater could be easily applied to increase the quality of green tea in the processing line.     

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.     

GREEN TEA CATECHINS AS INHIBITORS OF OXIDATION OF MEAT LIPIDS

Antioxidant activity of green tea catechins, namely, epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG) and epigallocatechin gallate (EGCG) was evaluated in a meat model system. The inhibitory effect on 2-thiobarbituric acid (TBA) values of catechins was concentration dependent, being highest at 200 mg/kg. At 200 mg/kg, the antioxidant activity of catechins as evaluated by TBA values was EGCG ≈ ECG > EGC > EC. The hexanal and pentanal contents in the headspace volatiles of meats treated with catechins at 200 mg/kg was also evaluated. These results indicated that EGCG was most active followed by ECG and EGC; EC was least effective. In comparison with α-tocopherol, catechins were generally more effective in controlling oxidation of meat lipids. Based on TBA results, butylated hydroxytoluene (BHT) was less effective, but exerted a better effect than catechins in prevention of oxidation as evidenced by the hexanal/pentanal data.