Effect of selenium spraying on green tea quality

This research was conducted to determine the effects of different selenium treatments on the sensory and chemical qualities of green tea harvested in the summer tea‐producing season. Green tea was produced from fresh tea leaves sprayed with sodium selenite or organically bound selenium solution. The results showed that the sweetness and aroma of green tea extracts were significantly increased and the astringent taste and bitterness were significantly reduced by selenium spraying during the summer tea‐producing season. Significant differences in astringent taste, bitterness and sweetness of green tea extracts were found between sodium selenite and organically bound selenium treatments. The total amino acid and vitamin C contents of green tea were significantly increased and the ratio of polyphenols and amino acids was significantly decreased by selenium spraying. The vitamin C content of green tea during storage was more stable as a result of selenium treatment. No significant difference was found between sodium selenite and organically bound selenium treatments. These results demonstrate that the sensory and chemical qualities of green tea were significantly improved by selenium spraying. © 2001 Society of Chemical Industry     

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。     

Chemopreventive potential of the tannase-mediated biotransformation of green tea

Green tea (Camellia sinensis) is one of the most widely consumed beverages in the world. The cancer chemopreventive qualities of green tea have been well documented. Epigallocatechin gallate (EGCG) is often described as the most potently chemopreventive green tea catechin; however, the low bioavailability of EGCG is a limiting factor for its biological effect. Thus, the aim of this work was to test the chemopreventive potential of green tea extract and EGCG after tannase-mediated hydrolysis. The results showed that the biotransformed compounds retained most of the beneficial properties of the original compounds, and some beneficial properties were improved in the biotransformed compounds. Biotransformation of EGCG decreased its toxicity without affecting its antiproliferative effects. Furthermore, human cells gene expression profiling showed that the biotransformed compounds modulated the expression of several genes related to carcinogenesis. These results demonstrate the benefits of the biotechnological modification of natural food molecules, allowing the improvement of the nutraceutical potential of a beverage as green tea.     

Comparison of bioactive components in GABA tea and green tea produced in Taiwan

The aim of this study is to investigate the bioactive components of GABA (γ-aminobutyric acid) tea as compared with green tea produced in Taiwan. Using in total 56 tea samples (28 green tea and 28 GABA tea), moisture content, Hunter L, a and b values, phenolic compounds, amino acids including GABA, fatty acids and ascorbic acid were determined. The results showed that moisture, total free amino acids, crude fat, Hunter L value, total nitrogen, free fatty acids and reducing sugar did not differ significantly between GABA tea and green tea. However, GABA tea had higher Hunter a and b values, while green tea had higher total catechin and ascorbic acid contents (p < 0.05). Of major catechins, epicatechin and epigallocatechin gallate were found to be lower in GABA tea than in green tea. For free amino acids, GABA, alanine, ammonia, lysine, leucine and isoleucine were found to be significantly higher in GABA tea, while the glutamic acid, aspartic acid, and phenylalanine were higher in green tea (p < 0.05). Theanine, tryptophan, valine, threonine and methionine were not found to be different between the two kinds of tea.     

EFFECT OF FAR-INFRARED HEATER ON THE PHYSICOCHEMICAL CHARACTERISTICS OF GREEN TEA DURING PROCESSING

ABSTRACT

The green tea leaves (Camellia sinensis var. sinensis) were irradiated by a far‐infrared (FIR) heater during the roasting and drying step, resulting in three different treatments produced. Green tea was extracted by soaking the leaves in water, and the components were analyzed. FIR irradiation, combined with fryer heating during the roasting step and additionally applied after the drying step, increased total phenolic contents of green tea from 116.30 to 171.77 mg/g, and total flavanol contents from 17.54 to 24.76 mg/g, compared with the non‐irradiated control. Ascorbic acid contents also increased from 3.07 to 4.20 mg/g. The amounts of epicatechin gallate and epigallocatechin gallate were significantly increased from 2.41 to 4.59 mg/mL and 20.61 to 28.54 mg/mL, respectively, compared with the non‐irradiated control. FIR irradiation increased Nitrite Scavenging Ability of green tea at pH 3.0 and pH 4.2, while there was no significant difference at pH 6.0. Sweetness, umami and aroma of green tea were enhanced by FIR irradiation, while bitterness and astringency were decreased compared with those of the control. These results show that FIR heating during the green tea process affected the chemical properties of green tea, and the FIR heater can be applied to increase the physicochemical qualities of green tea.

PRACTICAL APPLICATIONS

Green tea, a widely consumed drink, has received much attention because of the beneficial biological effects attributable to its excellent antioxidant activity. In this article, a far‐infrared (FIR)‐heater for industrial application was used during the processing of green tea leaves, and the chemical characteristics and quality of FIR‐treated green tea were determined. FIR irradiation, combined with fryer heating during the roasting step and additionally applied after the drying step, significantly increased phenolic, flavanol, ascorbic acid, epicatechin gallate, epigallocatechin gallate contents and nitrite‐scavenging activity compared with non‐irradiated control. Sensory evaluation also showed a positive effect of FIR irradiation. The results indicated that FIR heater could be easily applied to increase the quality of green tea in the processing line.     

4种乌龙茶树鲜叶适制绿茶、黄茶、白茶、红茶可行性研究

选用‘毛蟹’、‘丹桂’、‘九龙袍’、‘矮脚乌龙’4个乌龙茶树品种新梢为原料,分别蒸青固样并加工成绿茶、黄茶、白茶、红茶。所制茶样通过感官审评和生化成分分析,分析其茶类适制性。结果表明:用‘毛蟹’试制的绿茶,其氨基酸含量在4个品种中最高,为2.02%,酯型儿茶素含量为10.27%,仅低于九龙袍;用‘毛蟹’试制的黄茶,其水浸出物含量、氨基酸含量和咖啡碱含量分别为40.91%、2.13%、3.96%,均高于其它3个品种;用‘毛蟹’试制的白茶,其水浸出物含量在4个品种中最高,为44.32%,茶多酚含量为24.28%,仅低于矮脚乌龙;用‘矮脚乌龙’试制的红茶,其水浸出物含量、茶多酚含量、儿茶素总量和茶黄素含量均为4个品种中最高,分别为40.17%、23.34%、3.18%、0.42%。感官审评结果表明,‘毛蟹’制绿茶、黄茶和白茶品质均优,‘矮脚乌龙’制红茶品质优,‘丹桂’制白茶品质较优。综上,‘毛蟹’品种茶类适制性强,适制绿茶、黄茶和白茶,‘矮脚乌龙’适制红茶,‘丹桂’适制白茶。     

“紫娟”茶中的EGCG3"Me成分研究

"紫娟"是云南大叶群体种中的一种稀有茶树品种,因富含花青素成分其新鲜嫩梢的芽、叶、茎均呈现紫色,从而具有很高的科研价值和经济开发潜力,当今其功能化学成分的研究已成为了茶学研究热点之一。本文采用HPLC以及LC-MS技术首次报道分析了茶树特异品种"紫娟"中的表没食子儿茶素-3-O-(3-O-甲基)没食子酸酯(EGCG3"Me)成分及高EGCG3"Me含量"紫娟"茶的加工工艺。结果表明,茶树特异品种"紫娟"鲜叶中含有EGCG3"Me成分(含量为1.05%);在一芽五叶新梢不同嫩度的鲜叶中,第三叶的EGCG3"Me含量最高(含量为1.24%);采用蒸青绿茶或者晒青绿茶的加工工艺可以使成茶有效保留鲜叶中的EGCG3"Me成分。此外,还分析比较了普通炒青绿茶与"紫娟"绿茶中主要儿茶素成分的含量差异,发现较高的ECG和EC含量而较低的EGCG含量是茶树特异品种"紫娟"绿茶中儿茶素组成的主要特点。     

LC/MS characterization of phenolic constituents of mate (Ilex paraguariensis,St. Hil.) and its antioxidant activity compared to commonly consumed beverages

Mate is a tea-like beverage widely consumed in South America, prepared from the dried leaves of Ilex paraguariensis, St Hil. The total polyphenols (PP) and antioxidant activity of mate infusions and acid–methanol/acetone extracts were determined in three commercial brands, and compared to commonly consumed beverages like green and black teas, red, rosé and white wines, and orange juice. Mate had a PP content comparable to tea and orange juice, and, when normalized for the PP content of beverages, mate had an antioxidant activity slightly higher than wines, orange juice and black tea, but lower than green tea. LC/MS analysis of mate extracts showed that caffeoylquinic and dicaffeoylquinic acid isomers were the major components of the phenolic fraction of mate. Mixed mono-, di- and tri-esters of quinic acid and other hydroxycinnamates were also detected. Several quercetin and kaempferol glycosides were identified. Consumption of mate infusions would significantly contribute to the overall antioxidant intake, providing high amounts of caffeoylquinic acid derivatives, with biological effects potentially beneficial for human health.     

树莓叶茶和嫩尖茶抗氧化活性成分研究

目的 研究树莓叶茶和嫩尖茶的抗氧化活性成分。方法 对树莓叶茶和嫩尖茶的鞣花酸、黄酮和多酚含量进行了测定, 并与绿茶炒青进行了比较, 在此基础上考察了不同种类茶叶对DPPH和ABTS自由基的清除能力。结果 树莓叶茶和嫩尖茶的鞣花酸含量较为丰富, 最高达26.75 mg/g, 是特级炒青6.8倍, 黄酮含量也较绿茶炒青高, 达18~22 mg/g; 树莓嫩尖茶的多酚含量同炒青接近, 均超过180 mg/g, 两者的抗氧化活性均较强, 而树莓叶茶的总多酚含量较低, 仅为绿茶和树莓嫩尖茶36%~39%, 抗氧化活性较弱。相关性分析发现茶叶样品的抗氧化活性与多酚含量呈极显著正相关。结论 树莓叶茶抗氧化性较弱, 而嫩尖茶具有较强的抗氧化活性, 可以加以推广。     

野化白云黄茶闷黄过程中的品质成分变化及其菌种分离鉴定

为了掌握野化白云茶树鲜叶加工成黄茶加工过程的影响因素,该研究对比分析了野化白云茶加工的黄茶、烘青绿茶、半烘半炒绿茶的主要品质成分;分析了野化白云茶鲜叶加工黄茶过程中的依工艺阶段取8个茶样（茶青、杀青叶、揉捻叶、再炒叶（除水叶）、闷黄24 h、闷黄48 h、闷黄72 h、毛茶）可培养菌种的变化。野化白云茶与烘青绿茶、半烘半炒绿茶比较,除氨基酸、咖啡碱含量略有下降外,水浸出物含量分别高出4.80%、7.11%,可溶性糖含量分别高出0.41%、0.36%,茶多酚含量、儿茶素总含量呈下降趋势,酯型儿茶素总量下降21.62 mg/g、19.08 mg/g,EGCG下降9.99 mg/g、6.98 mg/g,GCG下降14.23 mg/g、13.80 mg/g,以上成分变化均差异显著（p<0.05）;非酯型儿茶素组分中除C减小2.49 mg/g、1.75 mg/g（p<0.05）外,其余非酯型儿茶素组分和总含量变化差异不显（p>0.05）;闷黄24 h,酵母菌数量明显,至72 h霉菌成优势菌种（3.5×105 CFU/g）;分离鉴出8株微生物,包括1株拟盘多毛孢属,4株青霉属,1株枝孢属及2株酵母菌属,其中Penicillium exsudans菌首次从茶叶加工中和茶叶中分离并鉴定。说明闷黄使茶叶水溶性物质、可溶性糖增加,茶多酚、酯型儿茶素下降,闷黄阶段有微生物繁殖并参与黄茶品质的形成。     

红紫芽品种的茶类适制性研究

以不同季节红叶1号、红叶2号、丹妃三个红紫芽品种（系）为供试原料制成绿茶、白茶和红茶,通过茶叶品质分析及感官审评方法综合评价了红紫芽茶树品种（系）的茶类适制性。结果表明,同一品种（系）制成的绿茶和白茶理化成分含量高于对应的红茶。绿茶中各理化成分含量最高,可溶性糖含量三季平均为4.24%~4.69%,而红茶则为3.54%~3.96%。氨基酸含量在白茶中高于绿茶和红茶,白茶中含量达3.40%以上,而红茶和绿茶中含量在3%左右。红紫芽绿茶中花青素含量夏季>秋季>春季,夏季含量为0.086%~0.115%;除了春季白茶检出痕量的花青素外,其余不同季节的白茶和红茶均未检出花青素。感官审评结果表明,白茶普遍具有优雅、浓郁的花香或果香,滋味甜醇鲜爽的特点;红茶普遍具有甜香浓郁、滋味甜醇鲜爽的特点;绿茶品质成分丰富,汤色呈红紫色。研究认为,红紫芽茶更适合制作红茶和白茶,而制成的绿茶则可以作为一种新型特异茶饮进行推广。本研究为红紫芽茶的深入利用提供了理论基础和实践依据。     

Tentative identification,quantitation, and principal component analysis of green pu-erh,green, and white teas using UPLC/DAD/MS

Tea (Camellia sinensis L.), an important drink and a natural medicine for thousands of years, contains many health beneficial compounds. Growing season, geographical region, and fermentation methods create many variations in tea compositions, which contribute to each tea’s uniqueness. In this study, a simple, rapid, and efficient ultra-performance liquid chromatography (UPLC) method combined with diode array detector (DAD) and mass spectroscopic (MS) detection and chemometrics analysis was used to analyse three different types of teas (green pu-erh, green tea, white tea). Using the developed method, 68 compounds were identified and 54 were quantified based on retention times, UV spectra, and MS spectra by referencing to available standards and data in the literatures. The results showed the chemical differences between the tested teas. Principal component analysis (PCA) was applied to classify and distinguish between tea samples.     

Analysis of free amino acids in Chinese teas and flower of tea plant by high performance liquid chromatography combined with solid-phase extraction

An effective liquid chromatographic method that involved precolumn derivatisation with o-phthaladehyde combined with solid-phase extraction has been developed for the determination of free amino acids in tea. Firstly, tea infusion was treated by C18 cartridge before derivatisation, resulting in great improvement of separation by Zorbax Eclipse XDB-C₁₈ column. Then, the contents of free amino acids in Chinese green, black, and Oolong teas and the flower of plant Camellia sinensis have been determined. The results showed that theanine was the most abundant amino acid in teas, and green tea contained much higher amounts of free amino acids than fermented ones. While the contents and composition of free amino acids in tea flower were quite different from those of teas. The tea flower contained much higher content of free amino acids. Furthermore, although theanine was the most abundant amino acid in tea flower as tea, histidine became the second one.     

茯砖茶优势菌株分离鉴定及发酵低级绿茶分析

对湖南白沙溪茯砖茶中的优势菌株进行分离、纯化,并通过形态学分析和ITS序列比对进行鉴定。以云南大叶种低级绿茶为原料进行纯菌发酵,分析发酵液主要成分含量的变化。结果表明：从湖南白沙溪茯砖茶中分离得到的4 株优势菌株,其中J1被鉴定为谢瓦曲霉（Aspergillus chevalieri）;J2、J3和J4均被鉴定为冠突曲霉（Aspergillus cristatus）。分别采用鉴定得到的4?株菌株对云南大叶种低级绿茶进行发酵,发现发酵液中茶多酚、总黄酮含量均显著降低;茶褐素含量均显著增加。与未发酵的空白对照组相比,总生物碱含量在谢瓦曲霉作用下显著增加,在冠突曲霉作用下显著降低;儿茶素各组分含量变化差异较大,其中酯型儿茶素含量均显著下降,而表儿茶素、没食子儿茶素、表没食子儿茶素3?种非酯型儿茶素均显著增加;茶黄素在谢瓦曲霉J1和冠突曲霉J2、J3作用下显著减少,在冠突曲霉J4作用下显著增加;氨基酸各组分含量也具有显著变化。发酵前后主要成分含量变化的分析可为云南大叶种低级绿茶高值化产品的开发提供技术和数据支撑。     

Trace metals and flavonoids in different types of tea

The mineral and flavonoid contents of commercially available different types of teas (premium black, flavored black, green, and fruit tea) and the infusions produced from them were determined. Studied teas differed in the contents of elements between their raw materials and infusions. Iron and copper exhibited the lowest efficiency of extraction by hot water. For the most popular black tea brand (Lipton® Yellow label) the efficiency of metal extraction decreased in the order: Co>Mn>Ni>Zn>Cu>Fe. Flavored black Citrus tea infusion had the highest content of Co and Ni, while Yellow label and Green Indonesia are a good source of Fe, Mn, and Zn. Flavonoids were predominantly present as glycosides. Rutin was present at much higher levels in black and green teas. Significant amounts of naringin and hesperidin were determined in tea infusions with citrus aromas or fruits.     

不同产地绿茶饮料香气特征及差异分析

利用顶空固相微萃取与气相色谱-质谱联用法并结合相关性与气味活度值分析研究了不同产地绿茶饮料挥发性风味成分物质含量及构成差异。结果表明：低糖型绿茶饮料的香气总量要远高于无糖型,且不同产地绿茶饮料主要香气物质组成不同,主要共性成分是芳樟醇和柠檬烯;其中中国大陆饮料中含量较高的有酯类、酮类和烯类,日本饮料以醇类、烯类和醛类为主,中国台湾饮料中醇类、酯类的含量较高,而烯类含量很低。其中有10 个香气组分与香气评分相关性较高,主要是反-氧化芳樟醇（0.93**）与花香呈显著正相关,顺-3-己烯醇（0.90*）和β-环柠檬醛（0.92**）与清香呈显著正相关,β-紫罗酮（－0.92**）与果香呈显著负相关,β-大马烯酮（0.95**）与甜香呈显著正相关,1-乙基吡咯（0.87*）与烘焙香呈显著正相关;6 个气味活度值较高的组分分别是β-大马烯酮、β-紫罗酮、芳樟醇、大马酮、癸醛和柠檬烯,它们对整体香气贡献较大。     

Melatonin contents in mulberry (Morus spp.) leaves: Effects of sample preparation,cultivar, leaf age and tea processing

The effects of sample preparation, cultivar, leaf age and tea processing on melatonin content of mulberry (Morus spp.) leaves were investigated. Sample preparation using ultrasonic technique in combination with solid phase extraction resulted in high recovery rate (76%), when compared to homogenisation in combination with liquid–liquid extraction procedure (12% recovery rate). The melatonin contents in mulberry leaves harvested from three major cultivars (Buriram 60, Sakonnakhon and Khunphai) grown in Thailand were identified and quantified using high-performance liquid chromatography combined with fluorescence detector. The average melatonin content of the mulberry leaves cv. Buriram 60 (279.6 ng/g dry weight (DW)) was higher than those of cv. Sakonnakhon (100.5 ng/g DW) and cv. Khunphai (40.7 ng/g DW). The melatonin contents of all cultivars tested were highest in the tip of the leaves, followed by that in the young leaves, whereas the lowest was found in the old leaves. The melatonin contents of the two types of tea produced from mulberry leaves cv. Buriram 60 were also determined. Heat treatment during tea processing decreased the melatonin content in mulberry leaves cv. Buriram 60 by approximately 87%, when compared to that of the fresh leaves. However, there were no significant differences between the melatonin contents of the mulberry leaf tea produced with blanching (mulberry green tea) and those produced without blanching (mulberry black tea).     

汉中绿茶中6 种矿质元素含量及其溶出特性

采用原子吸收光谱法测定汉中绿茶主栽地区的7 个品种茶叶消化液和茶叶水浸出液中Mn、Zn、Fe、Cu、Ni、Cr 6 种矿质元素的含量。以这些矿质元素的含量及其溶出率作为另一种分析评价汉中绿茶品质的依据,实验回收率在92.70%～102.55%之间,相对标准偏差在10%以下。结果表明：采用原子吸收光谱法能准确测定绿茶及绿茶水浸出物中的矿质元素的含量,且方法简单、快捷;从溶出率和矿质元素的含量来看,相对其他几个供试品种而言,有机锌硒茶、鹏翔茶粉、汉中仙毫和汉中绿茶品质较好。     

红茶、绿茶、乌龙茶活性成分抗氧化性研究

目的与方法：通过醇提得到各种茶多酚提取液,酒石酸亚铁法测定了多酚的含量;水提得到各种茶多糖提取液,用硫酸- 苯酚法测定其中多糖的含量。通过DPPH·法、水杨酸法及邻苯三酚法测定不同茶叶中多酚、多糖含量对自由基的清除作用的影响,对比研究八种茶叶的抗氧化能力。结果：不同茶叶中多糖的含量从2.19%增大到2.89% (半发酵乌龙茶＞红茶＞绿茶),抗氧化能力：红茶＞绿茶＞乌龙茶(DPPH·法);红茶＞绿茶＞乌龙茶(水杨酸法);红茶＞乌龙茶＞绿茶(邻苯三酚法);不同茶叶中多酚的含量从1.71% 增大到9.75% (绿茶＞半发酵乌龙茶＞红茶);结论：茶多糖和多酚是茶叶的主要抗氧化成分。绿茶的抗氧化作用主要来自茶多酚,红茶的抗氧化作用主要来自茶多糖。除乌龙茶多糖提取液外,两种抗氧化成分的抗氧化能力与其含量成量效关系。     

云南“紫娟”晒青绿茶和大叶晒青绿茶的化学成分比较研究

目的:比较云南特种"紫娟"晒青绿茶和常规大叶晒青绿茶的化学成分。方法:测定云南特种"紫娟"晒青绿茶和常规大叶晒青绿茶的常规成分、酚类物质及香气成分。结果:两种茶样水浸出物、总灰分、水溶性总糖、多糖、蛋白质及游离氨基酸总量差异较小,"紫娟"晒青绿茶的矿物质元素铁、锰分别是大叶晒青绿茶的1.25倍和1.15倍,大叶晒青绿茶的硫含量是"紫娟"晒青绿茶的2.83倍;"紫娟"晒青绿茶中的亮氨酸、酪氨酸和精氨酸含量高于大叶晒青绿茶;两种茶样的酚类物质差异较大。"紫娟"晒青绿茶的茶多酚、原花青素、花青素、茶褐素、总儿茶素含量分别为21.83%、20.23%、1.16%、2.38%、7.25%,较大叶晒青绿茶分别高5.03%、2.47%、1.16%、0.85%、0.88%,两者的儿茶素单体组成也有较大差异;"紫娟"晒青绿茶的挥发性物质中醇类、醛类分别比大叶晒青绿茶高5.18%和4.15%,酯类、羧酸类化合物分别比大叶晒青绿茶低3.00%和3.29%。结论:云南特种"紫娟"晒青绿茶和常规大叶晒青绿茶的化学成分差异较大。