Se^4＋沉淀法提取茶多酚及制备工艺比较

用水、乙醇、丙酮作提取剂，用Ca^2 、Ar^3 、Zn^2 等金属离子作沉淀剂，分别提取绿茶中的茶多酚，对其得率进行比较，结果表明以Se^4 作沉淀剂，茶多酚的提取率达29．5％，茶多酚硒盐在强酸中最佳转溶条件为料酸比为1：10(v／v)，反应时间30min，条件易于控制，且得率高。     

浸提-沉淀法提取茶叶脚料中的茶多酚

采用浸提-沉淀联合方法提取茶中多酚类物质,考察浸提时间、沉淀剂的选择、pH值、溶剂用量等参数对茶多酚提取率的影响.研究表明提取茶多酚的最优工艺条件为浸提温度60℃,乙醇浓度65％,浸提时间30 min,浸提次数2次,选择氯化锌作为沉淀剂,m(氯化锌)∶m(茶粉)=0.2,转溶pH值6～6.5,转溶时间小于10 min.在此工艺条件下茶多酚产品提取率大于10％,纯度大于95％.最后,确立了以茶末等茶叶生产脚料为原料提取茶多酚的综合工艺流程,为工业化流程提供了理论依据.     

超声-微波辅助联合提取茶多酚和茶多糖工艺研究

以常熟"沙家浜"粗绿茶为原料,水为提取溶剂,研究提取时间、料液比和微波功率对茶多酚和茶多糖得率的影响,通过正交试验优化茶多酚和茶多糖的超声-微波辅助联合提取工艺.确定茶多酚和茶多糖的超声-微波辅助联合提取工艺为:提取时间40 min,液料比1:30(g/mL),微波功率80 W,固定超声功率50 W,在最佳工艺条件下,茶多酚得率为10.57%,茶多糖得率为3.25%.     

甘南沙棘叶中茶多酚两种提取方法的对比

以甘南沙棘叶为原料,利用正交法优化了乙醇提取茶多酚的工艺,并在此基础上进一步优化了微波提取茶多酚的工艺.结果表明,乙醇提取沙棘叶茶多酚的最佳条件为:时间3h,乙醇浓度70%,温度60℃,料液比1∶50(g/mL),茶多酚的提取率为11.3%;微波提取沙棘叶茶多酚的最佳工艺参数为:时间300s,料液比1∶30(g/mL),乙醇浓度50%,微波辐射为中高火,茶多酚的平均得率为16.9%,相对标准偏差RSD为0.4225%.比较两种方法可以看出,微波法提高了沙棘叶中茶多酚的得率,且明显缩短提取时间.     

超滤膜分离技术提取茶多酚的研究

以福建安溪铁观音茶叶的茶梗为原料,联合采用超滤法和沉淀法,水浸提其中活性成分茶多酚的最佳浸提条件为:温度(80±3)℃,料液比1∶20,浸提时间40 min.使用10万分子量的超滤膜,在25℃的温度下,驱动压力0.15 MPa,料液比1∶80下进行超滤,使茶叶中的活性成分得到保留的情况下有效地澄清了茶汁,改善了茶饮料的感官品质.进一步探讨了金属离子沉淀法自超滤后茶汁中提取茶多酚的条件,结果表明,最佳沉淀提取条件:Zn2+为沉淀剂,Na2CO3溶液调节pH=6.00,茶多酚的沉淀率为91.7%,纯度97.1%.     

一种提取茶多酚的新方法

分别以无水乙醇、纯水以及乙醇与水的混合溶剂作提取剂,采用微波加热的方式,对茶叶中的茶多酚进行提取。实验结果表明,在同等操作条件下,以乙醇与水的混合溶剂作提取剂时提取率最高,以无水乙醇作提取剂时提取率最低;采用乙醇与水的混合溶剂进行提取时,以（NH4）2SO4作析相盐,使之形成双水相体系,此时提取率比未使用析相盐时明显提高。     

热浸提法提取茶叶中茶多酚的方法优化

为探究热浸提法提取立顿绿茶中茶多酚的最佳工艺条件,以乙醇为溶剂,选取液固比、溶剂浓度、浸提时间和提取温度4个指标为影响因素,以茶多酚的提取率为考察指标,采用正交试验设计表L16(45)设计试验条件,对提取工艺进行了优化.结果表明,各因素对茶多酚提取率的影响大小依次为液固比>溶剂浓度>浸提温度>提取时间,最佳的提取工艺条件为:液固比120∶1、提取温度80℃、浸提时间30 min、乙醇浓度75%,在该条件下茶多酚的提取率可达茶叶质量的17.23%.     

不同工艺对茶多酚提取效率和质量的影响研究

本文比较分析了目前从茶叶中提取茶多酚的四种工艺的主要特点和不足,并比较了工艺条件对茶多酚的提取效率和质量的影响.结果表明,提取率较好,茶多酚含量较高是金属离子盐沉淀和树脂吸附茶多酚提取工艺.     

从茶叶中提取天然抗氧化剂——茶多酚方法研究

本文研究了Ca~(2 )、Fe~(3 )、Zn~(2 )等离子提取茶多酚(Tea Polyphenols,TP)的条件,确定了最佳工艺和参数。采用最佳工艺提取TP,提取率可达10.4％,纯度>98％。     

茶叶中咖啡因与茶多酚综合提取实验的改进

使用纯水、乙醇水溶液及乙酸乙酯为溶剂,对茶叶中的咖啡因及茶多酚进行综合提取,避免了常规方法中有毒试剂氯仿的使用。系统考察了溶剂浸渍次数、加入量及萃取时间对咖啡因和茶多酚提取率的影响,筛选出了综合提取咖啡因和茶多酚的最佳条件。     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help?     

只要努力,不要后悔

There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love.     

浅谈移民问题

Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject.     

Sister Carrie, an Adherent of Desires

Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities.     

Improvement of one-cycle controller by use of proportional integral differential controller

1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec…     

库克斯顿城堡

城堡, 是欧洲典型的建筑之一, 每个城堡都有一个美丽的传说或是一段历史。从本期开始, 我们将推出“城堡之旅”, 带各位读者去浏览、观赏欧洲各地的城堡, 开始一段文化与历史的旅途!     

The Reader Response Approach to Teaching of English Literature

During interview with English majors, it was found that a majority of students expressed disappointment with their experience of English literature classes. Students' dislike of learning English literature appears to be the major problem of teaching English literature in China. Reader response approach is a good way to solve this problem. In this paper, I explain the rationale behind the reader response approach, such as its origin, definition, features, assumptions, and strategies. Then I illustrate how reader response approach works as a teaching strategy by presenting several teaching models. At last I evaluate its usefuiness for teachers and present the advantages of reader response approach in Chinese context.