雪菊中抗氧化活性物质的提取工艺研究

通过单因素实验和正交试验,考察不同因素如提取剂浓度、提取温度、提取时间、料液比等对雪菊中抗氧化成分提取效果的影响,确定最佳提取工艺条件。结果表明:在超声提取工艺下,影响提取效果的主次因素为料液比提取温度提取溶剂提取时间,最佳提取工艺条件为料液比1∶8、提取温度65℃、提取溶剂70%乙醇、提取时间3.5h。     

茼蒿精油提取工艺的研究

以茼蒿为原料,对茼蒿精油的提取方法进行了研究。通过不同溶剂提取效率的比较,确定乙醇为最佳提取溶剂,并对乙醇提取茼蒿精油的溶剂浓度、温度、时间和料液比进行单因素实验与正交设计实验,确定最佳提取工艺条件为:乙醇浓度85%,提取温度45℃,提取时间6.5h,料液比1∶15。     

杏仁脂肪油的提取工艺与精炼

用石油醚(60-90℃)做为溶剂,通过料液比、进料温度、超声波提取时间对杏仁脂肪油提取率的影响,在单因素实验的基础上,做正交实验,并对所提取出的杏仁油进行精炼和理化指标检查。结果表明,各因素对超声波提取杏仁油的影响次序为:料液比>提取时间>进料温度,工艺参数为:料液比为1:7,提取时间为30min,进料温度为60℃,杏仁油的提取率为46.50%,超声波提取所用的时间少。     

葡萄籽中原花青素提取条件研究

采用乙醇溶剂提取的方法提取葡萄籽中原花青素,考察提取温度、提取时间、乙醇浓度及料液比等因素对原花青素提取的影响,并用正交实验的方法对实验结果进一步优化,确定最佳提取条件为:乙醇浓度为70%,提取温度为50℃,提取时间80 min,料液比为1:6.     

超声法提取猴头菇多糖工艺优化研究

目的:考察超声法提取猴头菇多糖的影响因素,并优化提取工艺。方法:以猴头菇多糖提取率为评价指标,用苯酚-硫酸法测定多糖含量,在单因素实验基础上,以超声提取时间、超声提取温度和料液比为实验因素,通过正交实验筛选最佳提取工艺条件。结果:影响猴头菇多糖提取率的因素依次为提取温度提取时间料液比;最佳工艺条件为提取时间20min,提取温度60℃,料液比1∶15 (g/mL),在此条件下猴头菇多糖得率为6.16%。结论:该工艺方便可行。     

响应面法优化超声辅助提取黄秋葵花总黄酮的工艺研究

目的采用响应面法对超声辅助提取黄秋葵花总黄酮的工艺进行优化。方法在提取剂浓度、液料比例、提取温度、水浴提取时间、超声波提取时间试验结果的基础上,采用Box-Behnken design试验设计原理,设计4因素3水平试验,以响应面分析法优化液料比例、乙醇浓度、提取温度、水浴提取时间4个因素对黄秋葵花总黄酮提取率的影响。结果黄秋葵花总黄酮提取率的最佳工艺条件为:液料比例160:1(mL:g)、乙醇浓度42%、提取温度80℃、水浴提取时间16 min和超声提取时间30 min。在此条件下,黄秋葵花总黄酮的提取率为(2.487±0.05)%,真实值与模型预测值相对误差为1.23%。结论该提取工艺提高了黄秋葵花总黄酮的提取率,为其开发利用提供理论支持。     

马兰总黄酮提取工艺优化及不同部位含量测定

以马兰全株为材料运用超声波辅助法进行黄酮类化合物的提取,采用正交试验法分析比较乙醇体积分数、料液比例、水浴温度和提取时间对总黄酮提取量的影响。结果表明:各因素的影响大小依次为:提取温度>乙醇体积分数>提取时间>料液比例;马兰中总黄酮提取的最佳工艺为,乙醇体积分数75%,料液比例(g∶mL)1∶30,水浴温度70℃,提取时间90min,在该工艺下测得马兰总黄酮含量为16.452%;从3月～7月,马兰同一部位总黄酮含量存在显著差异性(P<0.05),7月份达最高值,叶为37.076%;茎次之,为8.501%;根最少,为4.314%。同时,同一月份中马兰不同部位总黄酮含量也存在显著差异性(P<0.05),其中叶中总黄酮含量最高。     

米渣残油的提取及其脂肪酸组成分析

以米渣为原料,研究利用石油醚提取米渣残油的工艺条件,通过单因素实验和正交实验,探讨了提取温度、料液比、提取时间对米渣残油提取率的影响,并对制备的油脂进行了脂肪酸组成分析.结果表明,最佳工艺条件为:温度20℃,料液比为1:7,浸出时间2h,在此条件下,米渣残油的提取率为8.85%;米渣残油主要由8种脂肪酸组成,其中饱和脂肪酸含量25.5%,不饱和脂肪酸为73%,米渣残油中油酸与亚油酸的比例为1:1.04,符合国际卫生组织推荐的油酸和亚油酸比例为1:1的最佳比例.     

湖北麦冬块根多糖提取工艺的优化

以湖北麦冬块根为原料,采用蒽酮—硫酸法测定多糖含量。通过单因素实验和正交实验考察了提取温度、提取时间、料液比和提取次数对湖北麦冬多糖提取率的影响,确定了湖北麦冬多糖的最佳提取工艺条件为:提取温度80℃,提取时间90min,料液比1:40,提取次数1次。     

超声波提取山楂籽油的技术研究

以山楂籽油的提取率为考察指标,在单因素实验基础上,研究提取时间、料液比、浸提温度以及超声功率4个因素对山楂籽油提取率的影响,并通过正交实验得出最佳提取条件。实验结果表明:影响山楂籽油提取率的四个因素的主次顺序为:超声功率>浸提温度>料液比>提取时间,最佳提取条件为提取时间30 min,料液比1∶10,浸提温度45℃,超声功率200 W。在此条件下通过验证实验得到山楂籽油的提取率为10.61%。     

Tea extraction methods in relation to control of epimerization of tea catechins

Effect of water temperature and ethanol concentration on epimerization and extractability of tea catechins was investigated. The results showed that epigallocatechin gallate (EGCG) and epicatechin gallate (ECG) were partially epimerized into gallocatechin gallate (GCG) and catechin gallate (CG), respectively, when tea catechins extract was heated in water solution at 100 °C for 2 h or dry tea was extracted in water at 100 °C. The epimerization of the catechins was inhibited if the tea catechins extract was heated as solid powder and the dry tea was extracted in 50% (v/v) ethanol or in water at 80 °C or below. When the dry tea was extracted in water, the extractability of catechins increased with the increase of extraction temperature up to 100 °C, but there was no statistically significant difference in total catechins between 80 °C and 100 °C. When teas were extracted using ethanol solutions, the highest extractability of total catechins was obtained in 50% (v/v) ethanol for dry tea and in 75% (v/v) ethanol for fresh tea leaf. In order to reveal the real profiles of tea catechins in teas to be tested, dry tea should be extracted in 50% (v/v) ethanol for 10 min, while fresh tea leaf should be extracted in 75% (v/v) ethanol for 10 min. For commercial extraction, temperature should be controlled at 80 °C if water is used as the solvent. Copyright © 2007 Society of Chemical Industry     

Effect of pH on cream particle formation and solids extraction yield of black tea

Effect of pH on tea solids extraction yield was significant in increasing instant tea yield. Solids extraction yield was doubled when tea was extracted at pH 1.2 compared with that extracted in boiling distilled water with pH 6.8. H⁺ encouraged black tea cream particle formation by either releasing more solids into the infusion or stimulating polyphenols to interact with polysaccharides and nucleophilic groups on protein in tea infusions. HPLC results revealed that theaflavins and tea catechins were leading substances affecting the formation of cream particles and infusion colour. Theaflavins and some tea catechins, such as EGCG, ECG and EGC, were dissociated or degraded under alkaline conditions and thus tea cream particles tended to dissolve and tea infusion became dark in colour. Feasibility of stepwise extraction of instant teas used for iced tea and normal drinking tea, by controlling temperature and pH, is also considered in the present paper.     

普洱熟茶不同溶剂萃取层中儿茶素及黄酮醇类化合物差异的研究

目的 探索普洱熟茶在不同溶剂(乙酸乙酯和正丁醇)萃取中儿茶素和黄酮醇类化合物的组成及含量的差异,构建一种有效提取普洱熟茶中儿茶素及黄酮醇类物质的方法.方法 以普洱熟茶(2008年生产)的水提物为研究对象,分别用乙酸乙酯和正丁醇溶剂萃取的萃取层为分析供试样,采用高效液相色谱法(high performance liqui...     

Decaffeination of fresh green tea leaf (Camellia sinensis) by hot water treatment

Hot water treatment was used to decaffeinate fresh tea leaf in the present study. Water temperature, extraction time and ratio of leaf to water had a statistically significant effect on the decaffeination. When fresh tea leaf was decaffeinated with a ratio of tea leaf to water of 1:20 (w/v) at 100 °C for 3 min, caffeine concentration was decreased from 23.7 to 4.0 mg g⁻¹, while total tea catechins decreased from 134.5 to 127.6 mg g⁻¹; 83% of caffeine was removed and 95% of total catechins was retained in the decaffeinated leaf. It is considered that the hot water treatment is a safe and inexpensive method for decaffeinating green tea. However, a large percentage of tea catechins was lost if rolled leaf and dry tea were decaffeinated by the hot water treatment and so the process is not suitable for processing black tea.     

Microwave-assisted extraction of phenolic compounds from tea residues under autohydrolytic conditions

Phenolic compounds were extracted from three kinds of tea residues (green, oolong and black tea residues) by microwave-assisted extraction in water under autohydrolytic conditions without using any catalyst or organic solvent. Productions of phenolic compounds were enhanced by microwave heating at 230 °C. The main phenolic constituent in the extract from green tea residue was pyrogallol (24.6%) which was estimated to be originated from degradations of catechins. Derivatives of guaiacyl units of lignin such as dihydroconiferyl alcohol (10.3%) and vanillin (8.1%) were, however, the main constituents in oolong tea residue. In the case of black tea residue, derivatives of both catechins and lignin were comparably extracted. These phenolic compounds are interesting as a bio-based chemical feedstock such as phenolic precursors and antioxidants.     

A novel technique for chitosan microparticle preparation using a water/silicone emulsion: green tea model

Many effective methods such as spray drying, coacervation, ionic gelation, solvent evaporation and sieving have been suggested for entrapping bioactive compounds into micro‐ or nanoparticles. However, those methods still have some limitations owing to high temperature requirement, difficulty in particle harvesting or low entrapment for uncharged molecules. In this study, a novel chitosan microparticle preparation method was developed using water‐in‐silicone emulsion technique with green tea extract as a model active compound. Chitosan microparticles of diameter <5 μm were obtained from 2% chitosan solution with tripolyphosphate (TPP) solution as the hardening agent. The size and properties of the particles appeared to depend on several parameters such as TPP, emulsifier concentrations and pH. High concentration of emulsifier led to low encapsulation and particle aggregation. Entrapment efficiency of chitosan microparticles was improved with lower pH of the tripolyphosphate solution [59.94 ± 3.97 of epigallocatechin gallate (EGCG)] while slowing release of catechins. Epigallocatechin and epicatechin were released almost completely within 2 h under acidic condition whereas EGCG and epicatechin gallate were slowly released. In neutral condition, release of catechins depended on their molecular stabilities. The stabilities of catechins loaded in chitosan microparticles were varied under various temperatures. The degradation of tea catechins increased with temperature. However, the degradation of tea catechins loaded in chitosan microparticles was less than that of free catechins. Thus, the new technique for preparing chitosan microparticles containing heat‐sensitive water soluble green tea extract was successfully developed. The technique is suitable for micro‐encapsulation of hydrophilic compounds into chitosan microparticles with the ease of harvesting technique.     

醇香酶解绿茶浓缩液工艺研究

随着制茶工艺学的发展和各门科学技术的相互渗透,酶技术在茶叶加工尤其是深加工中的应用愈来愈多。以绿茶为原料,采用固定化单宁酶、纤维素酶、风味蛋白酶和β-葡萄糖苷酶进行复合酶解浸提制备绿茶浓缩液,利用HPLC、GC-MS和氨基酸自动分析仪对茶浓缩液中的有效成分和香气成分进行测定,并与常规水浸提法制得的茶浓缩液进行比较,结果显示:此工艺条件浸提所得绿茶浓缩液中茶多酚、氨基酸含量都高于常规绿茶浓缩液,其中儿茶素组成发生了很大变化,酯型儿茶素EGCG、ECG的含量比常规绿茶浓缩液低,而非酯型儿茶素EGC、EC以及没食子酸(GA)的含量则明显提高,且浓缩液开汤后味道浓醇、鲜爽;用SDE法提取香气成分,酶解茶浓缩液的香气物质含量显著高于常规绿茶浓缩液,并且比常规绿茶浓缩液多了1-戊烯-3-醇、4-萜烯醇、1-辛烯-3-醇等多种特有香气成分。     

Analysis of tea catechins in vegetable oils by high‐performance liquid chromatography combined with liquid–liquid extraction

In this study, a method was developed for the determination of various tea catechins in vegetable oils. Firstly, vegetable oils including tea seed oil, sunflower seed oil and soya bean oil were extracted by methanol/water (40:60, v/v), and then, a high‐performance liquid chromatography (HPLC) method was developed for the simultaneous determination of GA, caffeine, EGC, EGCG, EC, ECG, GC, GCG, C and CG. For the compounds detected in tested vegetable oils, LODs were in the range of 0.05–1.65 ng, both intraday and interday relative standard deviations (RSDs) were <5.0%, and the recovery rates were in the range of 96.2–100.5% with RSD <3.7%. The results showed in vegetable oils which declared to had added tea catechins in, the concentrations of tea catechins were less than that showed in package label, and the content of EGCG was the highest in all samples. Therefore, the advancement made in our study will facilitate studies of tea catechins in oil industry.     

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.     

Effect of tannase treatment on protein-tannin aggregation and sensory attributes of green tea infusion

Effect of tannase enzymatic treatment on protein-tannin aggregation and sensory attributes of green tea infusion was investigated. Green tea leaves were extracted with hot water at 85 °C for 20 min, the tea infusion was then treated with tannase. Results showed that both EGCG and ECG of the tea catechins were hydrolyzed by tannase into EGC and EC, respectively, accompanied by production of gallic acid. The tannase-treated tea infusion had a relatively lower binding ability with protein. Changes in the content of tea catechins, formation of tea cream, and turbidity of tea infusion with or without tannase treatment were measured after 4 weeks. Content of catechins in the tannase-modified tea remained almost unchanged, while those without tannase treated (control) decreased significantly (p < 0.05). Meanwhile, better color appearance and less tea cream formation were observed for the tannase-treated green tea, and tea cream formed for the control after storage. Results of the sensory evaluation showed that mouth feeling, taste and the overall acceptance of the tannase-treated green tea infusion were all better than those of the control.