Ethylamine content of fresh tea shoots and made tea determined by high performance liquid chromatography

The ethylamine contents of tea shoots and made teas were derived with o-phthalaldehyde and 2-mercaptoethanol, and quantified by high performance liquid chromatography. The coefficient of variation of this method was 1.97% from eight analyses. The levels of ethylamine in tea shoots declined markedly during growth and senescence after plucking; they also declined in the extracts of fresh tea during the incubation at 37°C, but this decrease was completely inhibited by amine oxidase inhibitors. The content of ethylamine in high grade green teas was higher than in low grade teas, but was almost identical in high and low grade black tea. The mean contents of ethylamine in 22 green teas and 17 black teas were 6.76±3.07 μmol g^?1 and 6.40±1.82 μmol g^?1, respectively.     

Effect of shooting period, region of growth and processing method on the Fe and Mn content of tea determined by X-ray fluorescence

X-ray fluorescence (XRF) is an effective technique for qualitative and quantitative analysis of minerals in various agricultural products. Simplicity, high throughput and the possibility of automation make it useful for screening large numbers of samples. Samples of 138 fresh green, black tea and residue of this black tea after brewing were obtained from the Eastern Black Sea region of Turkey and analysed for Fe and Mn content using XRF. Such work appears not to have been reported so far.     

荧光分析法测定粮食鲜样中铅

粮食鲜样经硝解后,其所含铅的形式为Pb2 ,而Pb2 在盐酸介质中形成PbCl2-,在紫外光的照射下发蓝色荧光。利用此原理经荧光分析法可测定大米、小米、小麦样品中的铅含量。该方法的线性范围为0.03mg/L～2.00mg/L,检出限为9.1μg/L,加标回收率为99.90%～100.25%。     

A model for predicting black tea quality from the carotenoid and chlorophyll composition of fresh green tea leaf

The plant pigment (carotenoid and chlorophyll) composition of fresh green leaf of tea for a selection of clones was studied in relation to the quality of black tea produced from processing the same green leaf. The plant pigment composition of the green leaf for nine Kenyan clones was monitored by HPLC at 450 nm. Using discriminant analysis it was shown that clones could be distinguished from one another on the basis of their green leaf plant pigment composition. Using step-wise multiple regression analysis, a linear relationship was established between the levels of six green leaf plant pigments peak 5 (neochrome), peak 17 and 18 (isomers of lutein and/or lutein epoxide), peak 23 (chlorophyll b type compound), peak 26 (aurochrome) and peak 28 (β-carotene)) and the quality of the manufactured black tea for the selected clones as assessed by tea tasters' evaluations. The model had an adjusted R-square value of 0.912 and was significant at P≤ 0.05. The value of the relationship as a means of predicting black tea quality is discussed.     

Ultrafiltration isolation,physicochemical characterization,and antidiabetic activities analysis of polysaccharides from green tea,oolong tea,and black tea

Both fermentation degree and preparation method of polysaccharides could influence the bioactivity of tea polysaccharides. The aim of this study was to compare the physicochemical characterization and biological activities of the polysaccharides isolated by ultrafiltration method from three kinds of tea (green tea, oolong tea, and black tea). The bioactivities of tea polysaccharide fractions were compared from four aspects, including antioxidant activities, antiglycation activities, α-glucosidase inhibitory capability, and hypoglycemic effects on L6 myotubes. Results showed that six polysaccharides (GTPS1, GTPS2, OTPS1, OTPS2, BTPS1, and BTPS2) had different contents of neutral sugar and uronic acid, and they showed different morphologies. Six polysaccharides were composed of the seven monosaccharides with different molar ratios. BTPS1 exhibited the highest DPPH scavenging activity and hydroxyl radical scavenging activity (P < 0.05), and BTPS1 also showed the strongest antiglycation inhibitory effects (P < 0.05). BTPS1 and BTPS2 showed strong inhibitory capacity on α-glucosidase and hypoglycemic effects in L6 skeletal muscle cells. The result suggested that the degree of fermentation of tea could improve their bioactivities (BTPS > OTPS >GTPS), and TPS1 with smaller molecular weight distribution showed higher bioactivities than TPS2. This study can provide a scientific foundation for the application of tea polysaccharides and related functional products.     

高效液相色谱-二极管阵列法检测四川绿茶、黄茶、黑茶、红茶和青茶中甲基化儿茶素含量

采用高效液相色谱-二极管阵列检测法(HPLC-DAD)对四川省雅安、成都、乐山、宜宾、绵阳23家企业生产的绿茶、黄茶、黑茶、红茶和青茶中48个茶样的(-)-表没食子儿茶素-3-O(3-O-甲基)没食子酸酯(EGCG3″Me)含量进行了比较研究。结果表明:青茶EGCG3″Me含量最高,在3.14~6.08 mg/g之间,平均值为4.40 mg/g;黑茶EGCG3″Me含量在0~1.72 mg/g,平均值为0.35 mg/g;绿茶和黄茶中EGCG3″Me含量较低;绿茶中含量在0~0.39 mg/g之间,平均值为0.10 mg/g;黄茶中含量在0~0.09 mg/g之间,平均值为0.05 mg/g;红茶中未检出。各茶类间EGCG3″Me含量差异显著,主要原因在于加工所用鲜叶原料(品种、采摘标准等)及加工工艺等不同。建议易过敏人群应适当饮用青茶。     

Determination of flavonols in green and black tea leaves and green tea infusions by high-performance liquid chromatography

Tea flavonols are potent antioxidants and make up 2–3% of the water-soluble solids from tea leaves. In this paper, the conditions necessary for hydrolysing and analysing flavonols in tea leaves and tea infusions are optimised and an isocratic elution system for the determination of the hydrolysed flavonols by high-performance liquid chromotography is presented. Aqueous ethanol was selected as the best solution for hydrolysing flavonoids in tea leaves. The contents of flavonols on a dry weight base in green tea leaves ranged from 0.83–1.59, 1.79–4.05, and 1.56–3.31 g/kg, and in black tea leaves from 0.24–0.52, 1.04–3.03, and 1.72–2.31 g/kg for myricetin, quercetin, and kaempferol, respectively. It was observed that the particle size of ground tea leaves significantly influenced the yield of flavonols. The contents of flavonols in different green tea infusions are given.     

Multielement analysis of Chinese tea (Camellia sinensis) by total-reflection X-ray fluorescence

 Total-reflection X–ray fluorescence (TXRF) was used for the simultaneous determination of 15 elements in tea samples which were produced either by acid digestion or acidified infusion of tea leaves (Camellia sinensis). The accuracy and precision of the method were checked by its application to a certified reference material (GBW 08505 : tea). A variety of 39 tea samples of different kinds and/or qualities produced in different regions of China were analysed. The range and mean of the concentrations of elements in the tea leaves (0.1–30.000 μg g^–1) and their solubility in infusions (0.5–85%) were determined and the influence of the origin, type and quality of the tea samples was studied. In some tea leaves produced in a Se-rich region, the content of Se was found to be very high (up to 7.5 μg g^–1), in contrast to a concentration of only about 0.1 μg g^–1 Se in most of the tea leaves examined. Received: 27 January 1998     

Antioxidant properties and total phenolics content of green and black tea under different brewing conditions

 The antioxidant activity and the total phenolics content of various tea extracts were analysed. Green and black tea were brewed from 0.5 min up to 10 min under different brewing conditions (stirring the extract, chopping the tea leaves before brewing). For measuring the antioxidant activity, the Trolox equivalent antioxidant capacity (TEAC) test and the low density lipoprotein (LDL) oxidation test were used. In all cases the antioxidant activity as well as the content of the phenolics increased with the brewing time. In black tea (brewed without stirring or chopping), the total phenolics increased from 33.8 mg/100 ml after 0.5 min up to 68.4 mg/100 ml after 10 min brewing time. Stirring during brewing led to higher phenolic yields in the extract. Thus, phenolics in stirred black tea ranged from 44.5 mg/100 ml (0.5 min) to 96.7 mg/100 ml (10 min). Chopping the tea leaves resulted in the highest content of phenolics. Antioxidant activity was well correlated with the corresponding total phenolics content. The results of the LDL oxidation test varied more than those of the TEAC test. Received: 27 May 1998 / Revised version: 15 July 1998     

Antioxidant properties and total phenolics content of green and black tea under different brewing conditions

 The antioxidant activity and the total phenolics content of various tea extracts were analysed. Green and black tea were brewed from 0.5 min up to 10 min under different brewing conditions (stirring the extract, chopping the tea leaves before brewing). For measuring the antioxidant activity, the Trolox equivalent antioxidant capacity (TEAC) test and the low density lipoprotein (LDL) oxidation test were used. In all cases the antioxidant activity as well as the content of the phenolics increased with the brewing time. In black tea (brewed without stirring or chopping), the total phenolics increased from 33.8 mg/100 ml after 0.5 min up to 68.4 mg/100 ml after 10 min brewing time. Stirring during brewing led to higher phenolic yields in the extract. Thus, phenolics in stirred black tea ranged from 44.5 mg/100 ml (0.5 min) to 96.7 mg/100 ml (10 min). Chopping the tea leaves resulted in the highest content of phenolics. Antioxidant activity was well correlated with the corresponding total phenolics content. The results of the LDL oxidation test varied more than those of the TEAC test.     

Characterisation of white tea – Comparison to green and black tea

An overview is given on the manufacture of the different types of tea along with the most important phenolics present in tea and methods of analysis. Compositional data are presented for green, white and black teas. A differentiation of green and black tea by using the ratio between total phenolics and sum of the major catechins seems to be feasible. For white tea there is no general accepted definition. Possible approaches are geographic origin, the botanical variety and the manufacture or the appearance. The differentiation between green and white teas by the ratio mentioned above is not possible.     

不同工艺古丈毛尖红茶与绿茶的香气成分分析

目的比较分析古丈毛尖不同工艺红茶与绿茶的香气成分。方法采用减压蒸馏萃取法(vacuum distillation extraction, VDE)提取5种不同制作工艺的古丈毛尖红茶与绿茶中香气成分,用气相色谱-质谱法(gas chromatography-mass spectrometry, GC/MS)定性,面积归一法定量。结果茶样中共检测出香气成分90种,其中共有成分8种。红茶香气主要成分(含量占比超过3%)包括香叶醇、苯乙醇、苯甲醇、呋喃氧化芳樟醇、苯乙醛。红茶1及红茶2以呋喃氧化芳樟醇、苯乙醇、香叶醇为主(含量占比超过10%);红茶3以苯乙醇、苯甲醇、香叶醇为主;红茶4以苯乙醇、香叶醇为主;红茶5以呋喃氧化芳樟醇、苯乙醇、苯甲醇、香叶醇为主。绿茶香气主要成分(含量占比超过3%)包括二甘醇二丙酸酯、苯甲醇、3, 4, 4-三甲基-3-戊醇、3-(1, 3-二甲基丁氧基)-2-丁醇、2-叔丁基-4-甲基-5-氧代-[1, 3]二氧戊环-4-甲酸、香叶醇。结论古丈毛尖在香气成分上,红茶主要以醇类和醛类为主,绿茶以醇类和酯类为主,在制茶工艺上,日光萎凋1～2h,室内萎凋至含水量60%左右的制茶工艺较优。     

HPLC法测定红茶和绿茶葵瓜子中的食用合成色素

建立HPLC法测定红茶、绿茶葵瓜子中食用合成色素的方法。样品溶液经聚酰胺吸附,用氨∶乙醇∶水溶液解吸附,中和后用水浴浓缩,定量,过滤。采用Agilent C18柱,以0.02 mol/L醋酸铵溶液-甲醇为流动相,梯度洗脱,流速为1.0 mL/min,柱温35℃,检测波长254 nm。进样体积为10μL。在选定的色谱条件下,柠檬黄、日落黄、苋菜红、胭脂红、亮蓝、诱惑红、赤藓红7种色素均可得到良好分离;7种色素在10.0~50.0μg/mL范围内均呈较好的线性关系;平均回收率(n=9)瓜子壳的为88.8%~97.3%,瓜子仁的为83.0%~92.6%。该方法准确可靠,可用于瓜子中合成色素测定。     

Chemopreventive effects of tea in prostate cancer: green tea versus black tea

The polyphenol compositions of green tea (GT) and black tea (BT) are very different due to post-harvest processing. GT contains higher concentrations of monomeric polyphenols, which affect numerous intracellular signaling pathways involved in prostate cancer (CaP) development. BT polymers, on the other hand, are poorly absorbed and are converted to phenolic acids by the colonic microflora. Therefore, after consumption of GT, higher concentrations of polyphenols are found in the circulation, whereas after BT consumption the phenolic acid levels in the circulation are higher. The majority of in vitro cell culture, in vivo animal, and clinical intervention studies examine the effects of extracts of GT or purified (-)-epigallocatechin-3-gallate (EGCG) on prostate carcinogenesis. These studies provide strong evidence supporting a chemopreventive effect of GT, but results from epidemiological studies of GT consumption are mixed. While the evidence for a chemopreventive effect of BT is much weaker than the body of evidence with regard to GT, there are several animal BT intervention studies demonstrating inhibition of CaP growth. This article will review in detail the available epidemiological and human clinical studies, as well as animal and basic mechanistic studies on GT and BT supporting a chemopreventive role in CaP.     

绿茶、乌龙茶、红茶贮藏过程中品质劣变机理及保鲜技术研究进展

茶叶的生产具有较强的时效性和季节性,且茶叶疏松多孔,长期贮藏过程中极易受环境影响而变质。作为广受消费者青睐的世界三大饮料之一,保持其贮藏品质对提高茶叶商品价值,推进我国茶产业的发展具有重要意义。近年来针对茶叶贮藏过程中的品质变化原因兴起了各种保鲜技术。该文通过讨论茶多酚、氨基酸、维生素C、叶绿素、脂质等物质的氧化降解,总结了绿茶、乌龙茶、红茶等的陈化劣变机理,同时概述了水分、温度、氧气、光照等影响茶叶贮藏品质的4大因素,并详细阐述了运用干燥、冷藏、脱氧、生物保鲜剂等方法进行茶叶贮藏的相关技术,最后展望了茶叶保鲜的深入研究方向,以期为相关茶叶保鲜新技术的研究提供科学理论指导。     

Effects of tea leaf waste of green tea,oolong tea,and black tea addition on sudangrass silage quality and in vitro gas production

This study evaluated the fermentation characteristics and in vitro gas production of sudangrass (Sorghum sudanese) silage with tea leaf waste of green tea, oolong tea and black tea added. All types of tea leaf waste contain large amounts of nitrogen (N) and tannins, and a small amount of low‐water‐soluble carbohydrates. Sudangrass was preserved without (control) and with green tea waste (GTW), oolong tea waste (OTW) or black tea waste (BTW) at rates of 50, 100 and 200 g kg^?1 fresh matter in laboratory silos. The pH and butyric acid levels were significantly lower in GTW at all rates and in OTW at the 200 g kg^?1 rate, whereas those levels were high in the control and BTW‐treated silage. Lactic acid level was appreciably higher in GTW‐ and OTW‐treated silage than the control and BTW‐treated silage. The addition of all types of tea waste increased the total N and tannins of the silage, whereas the acid detergent insoluble N was increased in the OTW‐ and BTW‐treated silage. GTW treatment increased gas production within a 96‐h period compared with the control, whereas OTW and BTW additions at 200 g kg^?1 rates caused lower gas production. It is concluded that the fermentation characteristics and feed value of the silage incorporating with tea leaf wastes are different for these types of tea leaf. Among the three kinds of tea waste, GTW is the most valuable material as a silage additive. Copyright © 2004 Society of Chemical Industry     

氢氧化钙处理鲜马铃薯渣干燥动力学研究

目的 探讨氢氧化钙[Ca(OH)2]处理鲜马铃薯渣的干燥效率及其干燥动力学。方法 研究干燥温度(30、40、50、60℃)、相对湿度(13%、33%、54%、75%)和载物量(10、30、50、70 g)对Ca(OH)₂处理鲜马铃薯渣的干燥曲线、干燥速率曲线、水分有效扩散系数以及干燥活化能的影响,并建立干燥动力学模型,将干燥特性曲线进行非线性拟合。结果 Ca(OH)₂处理鲜马铃薯渣主要为降速干燥,干燥温度越高,相对湿度越低,载物量越少,鲜马铃薯渣的干燥速率越快,水分有效扩散系数为2.48554×10^-11～13.15592×10^-11 m²/s,干燥活化能为12.06kJ/mol。Logarithmic为Ca(OH)₂处理鲜马铃薯渣拟合程度最好的干燥动力学模型。结论 经Ca(OH)₂处理的鲜马铃薯渣较容易干燥,Logarithmic模型可以较好描述其水分变化规律,为描述和预测Ca(OH)₂处理鲜马铃薯渣干燥过程中...     

夏季茶鲜叶加工花香型绿茶工艺技术研究

以茶树品种碧香早的夏季一芽一叶茶鲜叶为原料,在传统绿茶加工工艺基础上,将"做青(晒青、晾青、摇青、静置)"工艺技术融入其摊放工序中,通过感官审评及滋味、香气品质成分分析,优化夏季茶鲜叶加工花香型绿茶的"做青"工艺技术。结果表明,采用晒青5 min、晾青0.5h、晒青5min,晾青0.5h,10r/min摇青10转,静置1h,15r/min摇青60转为最佳"做青"工艺,加工出的夏季绿茶花香显露,滋味醇正,苦涩味降低,水浸出物、氨基酸、可溶性糖含量分别比传统工艺绿茶增加了1.29%,11.08%,10.50%,而茶多酚、儿茶素含量、酚氨比、酯型儿茶素/简单儿茶素则分别降低了6.05%,2.35%,15.38%,19.15%;同时新增了苯甲醇、柏木醇、α-合欢烯、柠檬醛等花香成分,且香草醇、橙花醇的相对含量高于传统工艺绿茶;说明在传统绿茶加工的摊放工序中融入"做青"工艺技术,可加工出具有花香品质的夏季绿茶。     

Effect of consecutive steeping on antioxidant potential of green,oolong and black tea

After water, tea is considered to be one of the most consumed drinks worldwide. To get the maximum benefit from the whole‐leaf teas, the manufacturers provide instruction that these teas can be steeped 2–3 times over 6–8 h. In this study, the effect of consecutive steeping on radical‐scavenging ability of whole leaf green tea (unfermented), oolong tea (partially fermented) and black tea (fully fermented) was determined. Green tea showed the highest level of antioxidant activity, total phenolic and flavonoid content followed by oolong tea and black tea irrespective of the number of steeping done. The result also demonstrated that re‐steeping reduced the antioxidant potential of teas. Moreover, it was revealed that green tea is the best candidate for re‐steeping followed by oolong and then black tea.     

近红外定量分析青烟叶中K、Ca、Mg含量的研究

本文利用近红外光谱仪(NIR)结合偏最小二乘法,用漫反射方法测定了青烟叶中K、Ca、Mg三种化学成分,试验证明,NIR可以用于测试青烟叶中这三种化学成分的含量。