响应面法优化超声辅助提取油茶叶总酚的工艺研究

目的 采用超声辅助响应面法优化油茶叶总酚的提取工艺。方法 以油茶叶多酚含量为指标, 在单因素实验基础上运用Box-Behnken响应面法设计四因素三水平提取实验。 结果 最佳工艺条件为乙醇浓度50%, 振幅比30%, 超声时间20 min, 料液比1:45(m:V), 在此条件下测得油茶叶多酚含量为(89.506±0.273) mg/g, 与模型预测数值相差较小。结论 在最优条件下, 油茶叶多酚的提取率得到了提高。     

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.     

Optimal extraction conditions for simultaneous determination of catechins and caffeine in green tea leaves

The amount of catechins and caffeine in green tea are considered a standard of quality evaluation for green tea. The objectives of this study were to investigate the optimal conditions for simultaneous extraction of catechins and caffeine and to compare their quantity and composition within the exotic tea varieties. Moreover, 8 tea varieties of exotic origin were tested with the optimal extraction conditions found in this study. Regarding the caffeine and catechins contents, a 2 h room temperature extraction using a 2% phosphoric acid-40% EtOH solution was the most suitable simultaneous extraction method. The total catechins and caffeine contents of the tea leaves ranged 44.25–64.80 and 9.26–13.11 mg/g, respectively. The optimal extraction method of catechins and caffeine in tea leaves may be used for further studies and breeding of high quality tea plants.     

HPLC Analysis of Catechins, Theaflavins, and Alkaloids in Commercial Teas and Green Tea Dietary Supplements: Comparison of Water and 80% Ethanol/Water Extracts

ABSTRACT:  To help meet the needs of consumers, producers of dietary tea supplements, and researchers for information on health-promoting tea compounds, we compared the following conditions for the extraction of tea leaves and green tea-containing dietary supplements: 80% ethanol/water at 60 °C for 15 min and boiled water for 5 min. The following 7 catechins, 4 theaflavins, and 3 alkaloids were separated in a 70-min single HPLC analysis: (−)-epigallocatechin, (−)-catechin, (+)-epicatechin, (−)-epigallocatechin-3-gallate, (−)–gallocatechin-3-gallate, (−)-epicatechin-3-gallate, (−)-catechin-3-gallate, theaflavin, theaflavin-3-gallate, theaflavin-3'-gallate, theaflavin-3,3'-digallate, caffeine, theobromine, and theophylline. The following ranges of concentrations of flavonoids (catechins plus theaflavins) in the tea leaves extracted with 80% ethanol were observed (in mg/g): in 32 black teas, 19.8 to 115.1; in 24 green teas, 12.3 to 136.3; in 14 specialty teas, 4.9 to 118.5; in 7 herbal teas, 0 to 46.0. Total alkaloids in all teas ranged from 0 to 32.6 mg/g. Significantly greater amounts of flavonoids were extracted from the tea leaves with aqueous ethanol than with boiled water. Levels of tea catechins in 10 capsules sold as dietary supplements were about 50 to 75% lower than the amounts listed on the labels. Catechin content of 4 commercial green tea extracts ranged from 96 to 696 mg/g. The results make it possible to maximize the extraction of tea compounds to better relate the flavonoid and alkaloid content of teas and dietary tea supplements to their health-promoting effects.     

Factors affecting the levels of catechins and caffeine in tea beverage: estimated daily intakes and antioxidant activity

Increased public awareness of health benefits of green tea is generally based on the high polyphenol content of tea leaves and the resulting beverage. A number of factors, such as species, season, agronomic condition and age of the leaves, are known to affect the composition of commercial teas. In the present study the effects of factors associated with domestic preparation and analytical methods, such as brewing time, concentration, solvent and type of tea product, on levels of catechins and caffeine, antioxidant activity and estimated daily intakes were investigated. There were large variations in the levels of total catechins: 43 and 117 mg g^?1 dry matter (DM) (brewed for 30 s and 5 min respectively); 72 and 161 mg g^?1 DM (extracted in boiling water and 50% acetonitrile respectively); 72 and 117 mg g^?1 DM (a tea bag and tea leaves respectively). The effects on caffeine content were comparatively smaller. These variations consequently led to considerable variations in estimated daily intakes based on three cups (600 ml), ranging between 538 and 2014 mg g^?1 DM of total catechins and between 103 and 466 mg g^?1 DM of caffeine. The antioxidant activity was highest (26 680 µmol g^?1 DM) for tea leaves brewed for 5 min and lowest (10 110 µmol g^?1 DM) for a tea bag product brewed for 1 min. Copyright © 2005 Society of Chemical Industry     

Effects of cosolvents on the decaffeination of green tea by supercritical carbon dioxide

Due to the adverse effects of the caffeine in a variety of plant products, many methods have been explored for decaffeination, in efforts to remove or reduce the caffeine contained in plant materials. In this study, in order to remove caffeine from green tea (Camellia sinensis) leaves, we have employed supercritical carbon dioxide (SC–CO₂), which is known to be an ideal solvent, coupled with a cosolvent, such as ethanol or water. By varying the extraction conditions, changes not only in the amount of caffeine, but also in the quantities of the principal bioactive components of green tea, including catechins, such as epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG) and epicatechin (EC), were determined. The extraction conditions, including temperature, pressure and the cosolvent used, were determined to affect the efficacy of caffeine and catechin extraction. In particular, the type and concentration of a cosolvent used constituted critical factors for the caffeine removal, combined with minimal loss of catechins, especially EGCG. When the dry green tea leaves were extracted with SC–CO₂ modified with 95% (v/v) ethanol at 7.0 g per 100 g of CO₂ at 300 bar and 70 °C for 120 min, the caffeine content in the decaffeinated green tea leaves was reduced to 2.6% of the initial content. However, after the SC–CO₂ extraction, a substantial loss of EGCG, as much as 37.8% of original content, proved unavoidable.     

Optimization of green extraction methods for cinnamic acid and cinnamaldehyde from Cinnamon (<Emphasis Type="Italic">Cinnamomum cassia</Emphasis>) by response surface methodology

The major compounds of cinnamon are cinnamic acid and cinnamaldehyde, for which the conditions of microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), and reflux extraction (RE) were optimized using response surface methodology for comparing their efficiencies in terms of extraction yield, consumption of time and energy, and CO₂ emission. The results indicated MAE superiority to UAE and RE owing to the highest yield of target compounds (total yield: 0.89%, cinnamic acid: 6.48 mg/100 mL, and cinnamaldehyde: 244.45 mg/100 mL) at optimum MAE conditions: 59% ethanol, 147.5 W microwave power and 3.4 min of extraction time. RE resulted in comparable yields with the highest consumption of time, energy, and solvent, and least CO₂ emission. Therefore, it is concluded that MAE is the most efficient method for green extraction of cinnamic acid and cinnamaldehyde from cinnamon powder compared to UAE and RE.     

Simultaneous purification of tea polyphenols and caffeine from discarded green tea by macroporous adsorption resins

To separate and purify tea polyphenols and caffeine from discarded green tea crude extract with macroporous adsorption resins (MARs), the adsorption properties of twenty kinds of MARs are systematically evaluated. The results show that GS-18 has higher separation efficiency than other MARs, and the experimental data fit best to the pseudo-second-order kinetic model. And adsorption isotherms and thermodynamics of tea polyphenols and caffeine on GS-18 are investigated. The separation parameters of tea polyphenols and caffeine from discarded green tea crude extract are optimized according to dynamic adsorption/desorption experiments with the column packed with GS-18. Through only one cycle treatment, the content of tea polyphenols increases 3.0-fold from 20 to 60 % with a recovery yield of 91 % and that of caffeine increases 3.1-fold from 7 to 22 % with a recovery yield of 98 %. The results demonstrate that the method of MARs will provide useful help for the development of large-scale separation of tea polyphenols and caffeine from discarded green tea in industry.     

云南凤庆“大山茶”的生化成分测定

"大山茶"是近年来在云南凤庆地区发展较快的一个地方栽培材料,但对其缺乏种质评价。本文以"大山茶"和云抗-10#等茶树一芽二叶鲜叶为材料,日光干燥,测定比较生化成分。应用高效液相色谱法、分光光度法测定发现"大山茶"的水浸出物、茶多酚、游离氨基酸和茶多糖含量分别为48.77%±0.26%、36.01%±0.92%、1.66%±0.09%和7.76%±0.99%,儿茶素总量为(154.49±31.54) mg/g,咖啡碱为(17.42±1.44) mg/g。应用液质联用技术从"大山茶"晒青茶甲醇提取物中鉴定了44种化合物。HPLC测定儿茶素时发现"大山茶"3个峰的峰面积大于相同质量的云抗-10#样品对应峰面积,其中2个峰初步鉴定为3-没食子酰基奎宁酸(3-Galloylquinic acid)和柯里拉京(Corilagin)。本研究初步揭示了"大山茶"内含物质组成,为进一步评价该种质资源提供了实验依据。     

超声波辅助提取与电渗析脱盐耦合技术对绿茶茶汤理化性质的影响

本文对比不同功率超声辅助热水提取与传统热水提取的绿茶茶汤理化性质差异,并对其进行电渗析处理,探究电渗析对绿茶茶汤的理化性质及冷却后浊度及沉淀率的影响。结果表明,超声辅助热水提取的绿茶茶汤中可溶性固形物、茶多酚含量、咖啡碱含量均高于传统热水提取,且随超声功率增大先升高后降低,超声功率增加至390 W时,绿茶茶汤中茶多酚及咖啡碱含量达最大值,分别为5903.14、1091.87 mg/kg。电渗析处理能显著降低绿茶茶汤中金属离子含量及电导率,热水提取、130 W超声提取及520 W超声提取的茶汤中钾的脱除率分别为67.46%、80.20%、89.59%,锰的脱除率分别为64.92%、77.35%、88.56%;电渗析处理可显著降低绿茶茶汤的浊度,并对茶汤的“冷后浑”具有抑制效果,且对超声辅助提取的茶汤“冷后浑”的抑制效果较热水提取效果更好。     

Microwave-assisted extraction of chlorogenic acids from green coffee beans

Microwave-assisted extraction (MAE) has been considered as a potential alternative to conventional solvent extraction for the isolation of phenolic compounds from plants. Aqueous and alcoholic extracts of green coffee bean obtained by MAE were quantitatively analysed for total yield of extracts, chlorogenic acids, caffeine and total polyphenol content. The extracts were also evaluated for radical-scavenging activity, using 1,1-diphenyl-β-picrylhydrazyl radical. Under optimum conditions of time (5 min), temperature (50 °C) and wattage (800 W), the maximum chlorogenic acids and caffeine could be extracted with water as solvent. The extracts contained chlorogenic acids and caffeine in the ranges of 31–62% and 22–40%, respectively. The yields of MAE under optimum conditions were higher than those from the conventional solvent extraction at 5 min and 50 °C and the extracts showed radical-scavenging activity of >75%, even at the concentration of 25 ppm. The MAE process can thus be predicted and controlled for industrial application.     

Vesicle-enhanced liquid-phase pulsed discharge extraction of polyphenols from green tea leaves

A vesicle-enhanced liquid-phase pulsed discharge (V-LPD) was proposed to extract polyphenols from green tea leaves. The optimal extraction conditions obtained by the process optimization were 3% (w/v) dodecyl trimethy lammonium bromide (DTAB)/sodium dodecyl sulfate (SDS) vesicle, 10% (v/v) ethanol/vesicle, 66 mL/g liquid-to-solid ratio, 5 kV discharge voltage, and 2.5 min extraction time. Under these optimal conditions, the polyphenols yield was 124.650 ± 1.197 mg/g, which was observably higher than that by heat reflux extraction (HRE) (108.156 ± 1.437 mg/g) for 45 min and that by ethanol-enhanced LPD (116.123 ± 1.164 mg/g) for 4 min. The energy consumptions of V-LDP and ethanol-enhanced LPD were far lower than that by HRE. Similar chemical constituents were observed by HPLC analysis in three extraction methods, and the extracts obtained by V-LPD had the highest antioxidant capacity. Therefore, the V-LPD is a time-saving and energy-saving method for the extraction of polyphenols.Industrial relevanceGreen tea is considered to be an important source of polyphenols. The potential of V-LPD has been demonstrated as a time-saving and energy-saving alternative using vesicle solvents for the simultaneous cell disruption and strengthening diffusion of polyphenols from green tea leaves. The polyphenols obtained with V-LPD process can be used in an array of pharmaceutical, cosmetic and food applications.     

杀青方法对紫色芽叶加工绿茶品质的影响

目的：探讨紫芽绿茶的最佳杀青方法。方法：以自选紫芽品系9803的一芽二、三叶为原料,分别用微波、锅炒、蒸汽、热风4种杀青方法对鲜叶进行杀青处理制备绿茶,并选取具有代表性绿茶样进行感官审评、滋味品质和香气品质分析。结果：4种杀青方法中,微波绿茶样感官审评的综合得分最高（89.65）,且微波绿茶样的主要理化成分——水浸出物、茶多酚、花青素、氨基酸和咖啡碱保留量显著高于其他3种绿茶（P＜0.05）;且酚氨比值、酯型儿茶素与总儿茶素的比值均为最低,分别为12.18和0.72。结论：4种杀青方法中以微波杀青工艺制备的紫芽绿茶品质最优。     

Extraction behaviors of caffeine and chlorophylls in supercritical decaffeination of green tea leaves

The decaffeination of green tea using supercritical carbon dioxide (SC-CO₂) was optimized by response surface methodology (RSM) for the maximal removal of caffeine, and the coextration of chlorophylls was also monitored during decaffeination. The experimental conditions for the SC-CO₂ extraction of caffeine were set up according to the Box-Behnken design of RSM. The relationships between the extraction yield of caffeine and various parameters used for the SC-CO₂ extraction such as pressure, temperature and concentration of ethanol were studied at a fixed CO₂ flow rate. The extraction yields of caffeine and total chlorophyll were significantly influenced by extraction pressure, temperature and concentration of cosolvent, and their extraction yields behaved almost in parallel at different extraction conditions that were obtained by varying pressure, temperature and ethanol cosolvent concentration. At the optimal decaffeination conditions such as 3.0 g of 95% (v/v) ethanol cosolvent per 100 g of CO₂, 23 MPa, 63 °C and an extraction duration of 120 min for 10 g of green tea leaves, the extraction yields for caffeine and catechins were 96.60% (w/w) and 40.61% (w/w), respectively, and the substantial coextraction of total chlorophyll (43.09% of the total amount) was also observed during the decaffeination process.     

Extraction and Removal of Caffeine from Green Tea by Ultrasonic-Enhanced Supercritical Fluid

ABSTRACT: Low-caffeine or caffeine-removed tea and its products are widely welcomed on market in recent years. In the present study, we adopt ultrasonic-enhanced supercritical fluid extraction process to remove caffeine from green tea. An orthogonal experiment (L16 (4⁵)) was applied to optimize the best removal conditions. Extraction pressure, extraction time, power of ultrasound, moisture content, and temperature were the main factors to influence the removal rate of caffeine from green tea. The 5 factors chosen for the present investigation were based on the results of a single-factor test. The optimum removal conditions were determined as follows: extraction pressure of 30 MPa, temperature at 55 °C, time of 4 h, 30% moisture content, and ultrasound power of 100 W. Chromatogram and ultraviolet analysis of raw material and decaffeinates suggests that under optimized conditions, the caffeine of green tea was effectively removed and minished without damaging the structure of active ingredients in green tea.     

响应面优化维吾尔调和茶提取工艺及抗氧化活性

利用印度豆蔻、红花、玫瑰花、丁香、薄荷、小茴香、甘草、干姜、姜黄、茯砖茶配制了维吾尔调和茶,并以其为研究对象,在单因素的基础上,考察提取时间、提取温度、料液比对维吾尔调和茶总酚提取量的影响;进一步采用Box-Behnken法优化维吾尔调和茶浸提工艺,并考察了维吾尔调和茶的抗氧化活性。结果表明,最优工艺条件为提取时间24 min、提取温度85.5 ℃、料液比1:54 (g/g)。在此条件下获得的实际总酚提取量为(46.86±0.814) mg/g,p=0.1723与预测值无显著性差异。维吾尔调和茶具有较好的还原能力,ABTS+、DPPH自由基清除作用的IC₅₀分别为:30.837、13.399 mg/mL,说明维吾尔调和茶具有较好的抗氧化活性。     

微波辅助萃取(MAE)绿茶的浸提动态过程研究

以绿茶作为材料,采用微波辅助萃取(MAE)技术,变化微波功率、浸提时间、浸提溶剂量、浸提溶剂4个变量因子,对浸提过程中茶汤的有效成分——茶多酚、氨基酸和咖啡碱等动态变化进行研究。比较绿茶中不同有效成分在不同条件下进行MAE过程的萃取效率,并利用SPSS软件把动态过程归结为各种模型,得到的模型分别是:Y=-10.877 0.40055×X-0.00196×X2 3.324×10-6×X3(360W);Y=-2.472 0.27910×X-0.001167×X2 1.4345×10-6×X3(540W);Y=-16.492 0.72497×X-0.00463×X2 9.061×10-6×X3(720W)。     

Extraction of active ingredients from green tea (Camellia sinensis): Extraction efficiency of major catechins and caffeine

The effect of different extraction set-ups that influence the extraction efficiency of catechins and caffeine from green tea leaves (variety Fanning Belas, China) were studied using different aqueous and pure solvents (acetone, ethanol, methanol, acetonitrile, water), different temperatures (60, 80, 95 and 100 °C) and times (5–240 min). Raw extracts were analysed for contents of major catechins (EC, EGC, ECG, EGCG), caffeine, proanthocyanidins and flavonols (myricetin, caempherol, quercetin). Starting material was found to contain 191 g major catechins/kg material, 36 g caffeine/kg material and 5.2 g flavonols/kg material on a dry mass basis. The content of major catechins in green tea extracts varied from approximately 280–580 g/kg dry extract, with extraction efficiencies of major catechins varying from 61% to almost 100%. Content of caffeine in extract was in the range of 75 g/kg, where its extraction efficiency varied from 62% to 76%. Average extraction yield was 30% with exceptions when using pure acetone and acetonitrile, where extraction yield was about 3%. Contents of flavonols and proanthocyanidins were in the ranges 6–20 and 12–19 g/kg, respectively. Different extraction procedures with water were also investigated and optimal conditions determined: maximum achieved extraction efficiency of catechins with water was obtained at 80 °C after 20 min (97%) and at 95 °C after 10 min of extraction (90%). Degradation of catechins was observed at higher extraction temperatures and with prolonged extraction times. Using a lower ratio of solvent to material, extraction efficiencies were increased by applying a multi-step extraction procedure. Optimal extraction procedure was then performed using decaffeinated green tea leaves, which were obtained by high-pressure extraction with CO₂, when 98% of caffeine was selectively isolated without significant impact on valuable catechins.     

Optimising the extraction of tea polyphenols, (−)‐epigallocatechin gallate and theanine from summer green tea by using response surface methodology

In this study, response surface methodology was applied to determine the optimal conditions for the extraction of tea polyphenols, EGCG and theanine from summer green tea. As results, the optimal extraction conditions were determined to be temperature 96 °C, time 40 min and ratio of water to raw material 16 mL g^?1. Under these optimal conditions, the experimental values for tea polyphenols, EGCG, theanine and IC₅₀ for DPPH free radical scavenging activity were 133.41 ± 3.12 mg gallic acid g^?1, 30.23 ± 1.22, 3.99 ± 1.13 mg g^?1 and 724.95 ± 15.12 μg mL^?1, respectively. There was no statistical difference at significant level of 0.05 between the experimental and predicted values. The results suggested that the regression models were accurate and adequate for the bioactives extraction from summer green tea.     

原料对茶绿色素提取率的影响

分别以鲜茶、杀青叶、干茶为试材,采用四因素四水平正交试验设计对茶绿色素浸提工艺参数进行了系统的研究。试验结果表明,杀青叶是提取茶绿色素最好的原料;采用100%的乙醇,4.5mL∶1g的醇茶比,75℃水浴浸提25min,浸提效果最佳,提取率为31.50%。茶绿色素含有丰富的茶多酚、咖啡碱、氨基酸等有效成分,是一种优良的天然食用色素。