三种茶叶对Cr(Ⅵ)吸附性能比较研究

研究了绿茶、红茶和花茶对Cr(Ⅵ)模拟废水的吸附性能,分别考察了吸附时间、茶叶投加量、Cr(Ⅵ)初始浓度、p H、温度等因素对Cr(Ⅵ)吸附的影响并进行了比较。确定了最佳吸附时间为绿茶90 min,红茶和花茶180 min。三种茶叶对Cr(VI)的吸附效果为绿茶花茶红茶。三种茶叶吸附Cr(Ⅵ)过程为吸热过程,吸附等温方程符合Langmuir和Freundlich方程。     

火焰原子吸收光谱法测定陕西绿茶和黑茶中的微量元素

以陕西茶庄中常见的4种茶叶(3种绿茶和1种黑茶)为研究对象,采用高氯酸-硝酸(1∶4)混酸对样品进行消解,利用火焰原子吸收光谱法测定并比较了陕西绿茶和黑茶中6种微量元素(Ca、Cu、Fe、Mg、Mn、Zn)的含量。结果表明,陕西绿茶和黑茶中均含有丰富的人体必需的微量元素,但不同种类的茶叶中所含微量元素有一定的差异,4种茶叶中微量元素含量大小依次为MgCaMnFeZnCu,各微量元素标准曲线的相关系数在0.992 8～0.999 5之间,相对标准偏差在0.30%～4.65%之间,加标回收率在92.37%～104.95%之间。该方法简单、快捷,具有较高的精密度与准确度,对陕西绿茶和黑茶的科学饮用、茶饮品的合理开发及深度研究提供了重要的实验依据和理论参考。     

美肤的绿茶

看过《绿茶情愫》才恍然绿茶有那么多好处。而最吸引我的是绿茶的美肤作用。绿茶的美肤原理要从茶叶的发醇说起。茶叶按照发酵程度分为发酵茶如红茶,半发酵茶如乌龙茶、普洱茶,不发酵茶如绿茶;按照发酵程度不同,所含的成分也有差异,茶叶的有效成分为丹宁(儿茶素),咖啡因、维生素,矿物质等,但是茶叶中对美肤最有效的维生素 C,却     

石墨炉原子吸收分光光度法测定茶叶中的铅

采用石墨炉原子吸收分光光度法测定了产自福建等地茶叶中的铅含量。方法的线性范围为0~60μg/L,相对标准偏差2.3%~8.7%。茶样检测结果表明,铅合格率为100%;不同种类茶铅含量前三位由高到低依次为绿茶,红茶,黑茶;各类茶铅含量平均值为0.009148mg/kg。     

超声波-氟离子选择电极法测定茶氟含量

使用超声波-氟离子选择电极法测定茶叶中的氟含量。结果表明,采用沸水冲泡茶叶在100℃超声提取,氟溶出效果最好。超声提取20min后,茶叶中氟溶出已基本趋于稳定。对广西本地产7种名茶的测定结果显示砖茶和花茶中氟含量高于绿茶和红茶,但仍低于国家标准和行业标准。属于低氟含量茶。     

饮茶论冲泡

平时生活中,几乎谁都会泡茶,可真正掌握好科学的冲泡方法,还真是门学问。科学实践证明,茶叶的冲泡不外乎三个方面:即茶叶的用量多少、泡茶的水温和冲泡时间长短及冲泡次数。 对茶叶的用量多少,不能一概而论,应酌情而定。一般说来,泡茶时大宗茶叶,如红茶、绿茶、花茶等都习惯用杯泡法。通常,一只普通200至250毫升的茶杯,放     

不同种类茶叶中茶多酚含量的测定

采用离子沉淀法,对不同种类茶叶中的茶多酚含量进行测定。分别考察了不同酸度、浸提温度及浸提时间对测定茶多酚含量的影响,确定以3价铁离子作为沉淀剂时,浸提时间为30 min,料液比低于或等于1∶15,pH为8或9,借助分光光度法测得不同品种茶叶中茶多酚的含量。结果表明:花茶的茶多酚提取率为1.63%,绿茶的茶多酚提取率为5.27%,红茶的茶多酚提取率为1.37%。     

超声波-氟离子选择性电极法测两种茶叶中的氟含量

利用超声波-氟离子选择性电极法对红茶、绿茶两种茶叶中氟含量进行测定,并对影响测定结果的一些因素进行了研究。结果红茶、绿茶中氟含量分别为120.70、106.57 mg/kg,该测定方法的加标回收率为93.50%~109.60%。结果表明超声波-氟离子选择性电极法操作简单,回收率高,能满足对茶叶样品的测定。     

茶叶中微量元素的溶出规律

沸水浸泡茶叶,应用原子吸收光谱法测定了绿茶和红茶的茶叶干样、茶水和茶渣中8种微量元素含量,计算茶叶中微量元素的溶出率和残留率,探讨茶叶中微量元素的溶出规律。结果表明,绿茶和红茶的茶叶干样、茶水和茶渣中8种微量元素含量及溶出率、残留率各有差异。     

茶叶中稀土研究进展

稀土是近年来我国茶叶质量安全问题中的热点,关于茶叶稀土元素限量标准引起各界争论。茶树对轻稀土(La,Ce,Y和Nd等)具有较强的生物富集作用,其中茶树叶片中的稀土含量与生长期呈显著的正相关。本文简要概述了稀土元素的类别、毒理学研究进展和茶叶中稀土含量现状及溶出规律,并对茶叶中稀土元素的来源进行初步的分析。探讨了限量标准,为今后科学制定茶叶中稀土的限量标准,加强对茶叶监管提供参考。     

The green tea, a good choice for cardiovascular disease prevention?

Tea (Camellia sinensis) has been used for centuries as a medical drink. Around two-thirds of the world's population drink tea. It is originated from southern China and entensive cultivated in Asia and in central African countries. Tea can be grouped into three main types, black, oolong, and green tea. Green tea is not fermented and is a major beverage consumed in Asian countries. Green tea is produced from freshly harvest leaves of the tea plant and they contain water, proteins, carbohydrates, minerals, vitamins and polyphenols of the flavonoid type. The major flavonoids in green tea are catechins which constitute about one third of its total dry weight. The major catechin present is epigallocatechin gallate (>50%). New data have increased the interest in green tea or its catechins and its role in treatment of cardiovascular disease (CHD) risk factors. The aim of the present paper is to review some studies that have found a relationship between green tea and CHD risk factors. From some of them it can be summarized that of green tea and its catechins consumptions (i) decrease body weight by interfering within the sympathoadrenal system and fatty acid synthesis, (ii) decrease cholesterol absorption and plasma levels, (iii) have strong free radical-scavenging activity inhibiting LDL oxidation, (iv) reduce the adhesion molecule expression, (v) have antitrombotic activities by inhibiting platelet aggregation and (vi) decrease systolic and diastolic blood pressures. The positive effects found suggest that a daily intake of 7 cups of green tea (3.5 g catechins) is a good choose for CHD prevention; however, it is still necessary more studies to check the action of the green tea and its catechins in humans in order to recommended its use in the general population or only in target subjects.     

Furan fatty acid concentrations in tea infusions prepared from green,black, and herbal teas

Furan fatty acids (FuFAs) are valuable antioxidants with highly effective radical scavenging properties which are widely distributed at low levels in food. Previous research indicated that tea is a valuable source of FuFAs. However, tea is only consumed in form of infusions. To fill this gap, we prepared infusions from different herbal, green, and black teas. Initial measurements with GC-MSMS of tea verified previous findings that 11-(3,4-dimethyl-5-penylfuran-2-yl)-undecanoic acid (11D5) was the prevalent FuFA in tea matrix. Therefore, 11D5 was quantified in tea infusions by means of UHPLC-MSMS equipment after mild alkaline hydrolysis. While herbal tea infusions were low or free of FuFAs, 11D5 was detectable in all samples of green and black tea infusions. Amounts of 11D5 were higher in green tea than in black tea. Moreover, Darjeeling tea infusions were by ~30% richer in 11D5 than black and green teas from other regions. Each cup of green and black tea infusion may provide 20–60 μg 11D5, which is about 5% of the amounts found in tea samples. Spread over the day, regular tea consumption may contribute to the intake of valuable FuFAs.     

Selected Tea and Tea Pomace Extracts Inhibit Intestinal α-Glucosidase Activity in Vitro and Postprandial Hyperglycemia in Vivo

Type 2 diabetes mellitus (T2DM) is a metabolic disorder characterized by postprandial hyperglycemia, which is an early defect of T2DM and thus a primary target for anti-diabetic drugs. A therapeutic approach is to inhibit intestinal α-glucosidase, the key enzyme for dietary carbohydrate digestion, resulting in delayed rate of glucose absorption. Although tea extracts have been reported to have anti-diabetic effects, the potential bioactivity of tea pomace, the main bio waste of tea beverage processing, is largely unknown. We evaluated the anti-diabetic effects of three selected tea water extracts (TWE) and tea pomace extracts (TPE) by determining the relative potency of extracts on rat intestinal α-glucosidase activity in vitro as well as hypoglycemic effects in vivo. Green, oolong, and black tea bags were extracted in hot water and the remaining tea pomace were dried and further extracted in 70% ethanol. The extracts were determined for intestinal rat α-glucosidases activity, radical scavenging activity, and total phenolic content. The postprandial glucose-lowering effects of TWE and TPE of green and black tea were assessed in male Sprague-Dawley (SD) rats and compared to acarbose, a known pharmacological α-glucosidase inhibitor. The IC₅₀ values of all three tea extracts against mammalian α-glucosidase were lower or similar in TPE groups than those of TWE groups. TWE and TPE of green tea exhibited the highest inhibitory effects against α-glucosidase activity with the IC₅₀ of 2.04 ± 0.31 and 1.95 ± 0.37 mg/mL respectively. Among the specific enzymes tested, the IC₅₀ values for TWE (0.16 ± 0.01 mg/mL) and TPE (0.13 ± 0.01 mg/mL) of green tea against sucrase activity were the lowest compared to those on maltase and glucoamylase activities. In the animal study, the blood glucose level at 30 min after oral intake (0.5 g/kg body wt) of TPE and TWE of both green and black tea was significantly reduced compared to the control in sucrose-loaded SD rats. The TPE of all three teas had significantly higher phenolic content than those of the TWE groups, which correlated strongly with the DPPH radical scavenging activity. This is the first report of tea pomace extract significantly inhibits intestinal α-glucosidase, resulting in delayed glucose absorption and thereby suppressed postprandial hyperglycemia. Our data suggest that tea pomace-derived bioactives may have great potential for further development as nutraceutical products and the reuse of otherwise biowaste as valuable bioresources for the industry.     

Immobilization of β-glucosidase and its aroma-increasing effect on tea beverage

β-Glucosidase was effectively immobilized on alginate by the method of crosslinking–entrapment–crosslinking. After optimization of the immobilized conditions, the activity recovery of immobilized β-glucosidase achieved to 46.0%. The properties of immobilized β-glucosidase were investigated. Its optimum temperature was determined to be 45 °C, decreasing 10 °C compared with that of free enzyme, whereas the optimum pH did not change. The thermal and pH stabilities of immobilized β-glucosidase increased to some degree. The K_m value for immobilized β-glucosidase was estimated to be 1.97 × 10^?3 mol/L. The immobilized β-glucosidase was also applied to treat the tea beverage to investigate its aroma-increasing effect. The results showed that after treated with immobilized β-glucosidase, the total amount of essential oil in green tea, oolong tea and black tea increased by 20.69%, 10.30% and 6.79%, respectively. The storage stability and reusability of the immobilized β-glucosidase were improved significantly, with 73.3% activity retention after stored for 42 days and 93.6% residual activity after repeatedly used for 50 times.     

Antioxidative effect of ethanol tea extracts on oxidation of canola oil

There is an increasing interest in the biological effects of natural antioxidants present in teas on formation ofin vivo free radicals, carcinogenesis, and atherogenesis. Teas are traditionally classified into six major groups, namely, green, yellow, white, black, dark-green, and oolong teas. The present study examined the antioxidative activity of ethanol extracts from these six major groups of teas against oxidation of heated canola oil. The oxidation was conducted at 100°C by monitoring oxygen consumption and changes in linoleic and linolenic acids in canola oil. The ethanol extracts of green, yellow, and white teas strongly inhibited oxidation of canola oil compared to butylated hydroxytoluene, probably due to the presence of natural polyphenols. In contrast, oolong teas examined exhibited only moderate antioxidative activity because of the partial destruction of natural polyphenols by semifermentation. The ethanol extracts of black, dark-green, and ginseng teas studied showed little or no protection to canola oil from lipid oxidation, probably due to the complete destruction of natural polyphenols by fermentation during manufacturing processes.     

红茶、绿茶提取物联合应用的护肤功效研究

以红茶提取物、绿茶提取物为考察对象,考察了红茶提取物和绿茶提取物的单独及联合应用的防晒、保湿、抗氧化、美白、抗衰老等功能,测试了二者在以上功能联合应用是否具有协同增效作用。结果表明,红茶、绿茶提取物在保湿、抗氧化、美白、抗衰老等功能上,联合应用比二者单独应用效果更强,其中2 g/L红、绿茶提取物混合物在抑制酪氨酸酶、弹性蛋白酶方面的联合指数CI仅为0.29和0.054,协同增效效果显著。     

柚子皮茶挥发性成分HS-GC-MS检测法评价与条件优化

采用顶空法提取柚子皮茶中的挥发性物质,再用气质联用仪进行分析测定。以月桂烯为评价指标,实施线性试验和重现性试验,结果表明：在0.1～0.9 g范围内,峰面积与样品量间存在良好的线性关系,相关系数R达到0.9832;重现性试验数据间的标准偏差（RSD）值为2.7%,说明精密度良好,应用HS-GC-MS检测柚子皮茶挥发性物...     

Antioxidant activity of various teas against free radicals and LDL oxidation

Tea is a widely consumed beverage throughout the world. We assessed the antioxidant activity of six teas, including the aqueous extracts of green tea and oolong tea (Camellia sinensis), tochu (Eucommia ulmoides), Gymnema sylvestre, Japanese mugwort (Artemisia princeps), and barley (Hordeum vulgare), against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and LDL oxidation, and examined the association of LDL oxidizability with the plasma catechin levels in 10 healthy volunteers with a single dose of 5 g green tea powder. In vitro, the inhibitory effects of DPPH radicals and LDL oxidation were found to be strongest in the extract of green tea and weakest in that of barley. After the ingestion of green tea powder, the lag time increased from basal 52.2±4.1 to 60.3±4.2 min at 1 h and 59.5±4.1 min at 2 h, and then returned to the baseline lag time (51.9±1.4 at 4 h and 52.1±4.7 min at 6 h). Regarding the plasma catechin levels, epigallocatechingallate and epicatechingallate significantly increased from basal 3.7±1.3 and 0.8±0.8 ng/mL to 65.7±11.6 and 54.6±12.6 ng/mL at 1 h, and 74.4±18.6 and 49.4±7.1 ng/mL at 2 h, respectively. Green tea therefore showed the strongest antioxidant activity among the six different teas, and the inhibitory effects of green tea on LDL oxidation depended on the plasma catechin levels.     

Antioxidant activity of tea extracts in lipids and correlation with polyphenol content

The present study examined the antioxidative activity of water and ethanol extracts of green and black tea leaves against the oxidation of heated sunflower oil and lard. Oxidation was conducted at 110 °C in the Rancimat test. Total polyphenols and catechin contents in tea extracts were measured. The research showed that the total polyphenol content in green and black tea leaves was 205.2 and 148.7 mg/g, respectively. In tea leaves extracts, it ranged between 245.9 mg/g and 837.7 mg/g and depended on the extraction solvent and the kind of tea used (p <0.001). The highest polyphenol content was observed in samples extracted with 95% ethanol, lower contents were found with the use of water. Results showed that the highest antioxidant activity, measured as an induction period, with 1000 ppm green tea ethanol extract, was comparable to á‐tocopherol activity in sunflower oil. In lard, the longest induction period was measured with 500 and 1000 ppm of green tea ethanol extract. Other tea extract concentrations were significantly less active. Statistical analysis of the tea extract antioxidant activity in lipids in the Rancimat test showed an essential influence of the catechin contents. Further statistical analysis also showed an influence of (?)‐epicatechin gallate (ECG), (?)‐epicatechin (EC), and (+)‐catechin (C) contents in the tea extracts on the antioxidant activity in lipids. It was stated that the antioxidant activity was higher in tea extracts containing high levels of ECG, EC, and C.