茶叶提取物体外抗氧化活性与其功能性成分含量的相关性研究

分别选取信阳毛尖、红碎茶、普洱熟茶为典型不发酵、全发酵及后发酵茶种,测定其醇提物及水提物中的主要成分,并以氧自由基的吸收能力(ORAC)和DPPH自由基的清除能力为指标,比较各样品体外抗氧化活性,采用功能化合物重组模型,探究茶叶提取物抗氧化活性的主要贡献物质。结果表明:茶叶醇提物中茶多酚、咖啡因及醇溶蛋白的含量较高,其ORAC值及DPPH自由基清除能力均较对应水提物强;茶叶水提物功能性组分以茶多酚、茶多糖及氨基酸为主,都具有一定的抗氧化活性。其中茶多酚含量,尤其是酯型儿茶素(ECG和EGCG)含量是影响茶叶提取物抗氧化活性的主要因素。重组试验结果表明,儿茶素和没食子酸是不发酵茶(信阳毛尖)提取物的主要抗氧化组分,但并不是红碎茶、普洱熟茶等发酵茶中的主要抗氧化成分。     

茶叶中有效成分综合提取的研究

以绿茶为原料，采用ZJL大孔离了交换树脂和ZJX大孔吸附树脂从茶叶的浸提液中提取茶氨酸、咖啡因、茶多酚和茶多糖。通过对树脂的静态、动态吸附性能的实验研究，确定了咖啡因、茶氨酸、茶多酚及茶多糖联合分离提取的工艺。研究结果表明：该工艺能有效的从茶叶中提取咖啡因、茶氨酸和茶多酚，提取的咖啡因纯度达83．23％，提取率为1．9％，茶氨酸纯度达85．43％，提取率为0．94％，提取的茶多酚纯度达95．62％，提取率为12．35％，且茶多酚中的咖啡因含量低于0．7％，茶多糖的纯度达51％，提取率为1．1％。     

Simultaneous purification of tea polyphenols and caffeine from discarded green tea by macroporous adsorption resins

To separate and purify tea polyphenols and caffeine from discarded green tea crude extract with macroporous adsorption resins (MARs), the adsorption properties of twenty kinds of MARs are systematically evaluated. The results show that GS-18 has higher separation efficiency than other MARs, and the experimental data fit best to the pseudo-second-order kinetic model. And adsorption isotherms and thermodynamics of tea polyphenols and caffeine on GS-18 are investigated. The separation parameters of tea polyphenols and caffeine from discarded green tea crude extract are optimized according to dynamic adsorption/desorption experiments with the column packed with GS-18. Through only one cycle treatment, the content of tea polyphenols increases 3.0-fold from 20 to 60 % with a recovery yield of 91 % and that of caffeine increases 3.1-fold from 7 to 22 % with a recovery yield of 98 %. The results demonstrate that the method of MARs will provide useful help for the development of large-scale separation of tea polyphenols and caffeine from discarded green tea in industry.     

High-efficient column chromatographic extraction of curcumin from Curcuma longa

Curcumin is an important food additive and a potential therapeutic agent for various diseases from turmeric, the rhizome of Curcuma longa L. High-efficient column chromatographic extraction (CCE) procedures were developed for the extraction of curcumin from turmeric. Turmeric powder was loaded into a column with 2-fold 80% ethanol. The column was eluted with 80% ethanol at room temperature. For quantitative analysis with a non-cyclic CCE, 8-fold eluent was collected as extraction solution. For large preparation with a cyclic CCE, only the first 2-fold of eluent was collected as extraction and other eluent was sequentially circulated to the next columns. More than 99% extraction rates were obtained through both CCE procedures, compared to a 59% extraction rate by the ultrasonic-assisted maceration extraction with 10-fold 80% ethanol. The CCE procedures are high-efficient for the extraction of curcumin from turmeric with minimum use of solvent and high concentration of extraction solution.     

不同贮藏时间普洱生茶水提物的特征性成分分析

以同公司、同批号、不同贮藏时间的普洱生茶(7542)为研究对象,真空冷冻干燥制备普洱生茶水提取物,利用分光光度计和超高效液相色谱-串联质谱(ultra performance liquid chromatography-tandem mass spectrometry,UPLC-MS/MS)检测其内含成分,并进行主成分分析(principal component analysis,PCA)和聚类分析(cluster analysis,CA),得出不同贮藏时间普洱生茶水提物的特征性成分和聚类树状图。结果表明,不同贮藏时间的普洱生茶水提物,随着贮藏时间的延长,茶多酚、儿茶素和游离氨基酸呈逐渐下降趋势,黄酮呈逐渐上升趋势,可溶性总糖和咖啡碱呈不规则变化;不同贮藏时间的普洱生茶提取物经UPLC-MS/MS共检测到107种化合物,经PCA,得到不同贮藏时间普洱生茶水提物的特征性成分包括柠檬酸、没食子酸、表儿茶素、茶氨酸、咖啡碱、表没食子儿茶素没食子酸酯等26种物质;CA表明,贮藏年份越接近的普洱生茶水提物样越易聚为一类,贮藏时间达到3 a和8 a时,茶叶聚类分类发生较大变化。     

Comparison of Conventional and Ultrasound Assisted Extraction Techniques of Yellow Tea and Bioactive Composition of Obtained Extracts

Yellow tea is the least investigated type of tea (Camellia sinensis), therefore, this study is focused on characterization of bioactive content of yellow tea extracts as well as application of inovative extraction techniques (ultrasound bath and probe) compared to conventional extraction, in water and aqueous ethanol media. Comparison of obtained extracts was based on total flavonoid (TFC) and nonflavonoid (TNC) content, HPLC analysis of individual polyphenols and methylxanthines, and antioxidant capacity. The highest TFC was detected in extracts obtained by ultrasound probe assisted extraction in aqueous ethanol as an extraction medium and the lowest in extracts obtained by ultrasound bath extraction (water and aqueous ethanol) with a trend of increase with prolonged extraction time. Conventional extraction was successful when combined with 75% aqueous ethanol as an extraction medium. Results of HPLC analysis and antioxidant capacity assays were generally in compliance with these results. This study proves that ultrasound probe extraction could succesfully be used for extraction of polyphenols and methylxanthines from yellow tea.     

Comparison of extraction and isolation efficiency of catechins and caffeine from green tea leaves using different solvent systems

Catechins from green tea (Camellia sinensis L.) have received considerable attention due to their beneficial effects on human health, such as antioxidant and anticancer activities. Optimisation of extraction conditions of the catechins from green tea leaves was performed using different solvents (ethanol or distilled water), different extraction methods (ultrasound‐assisted, room temperature or reflux extractions) and various extraction times (0.5–24 h). The optimal extraction conditions were determined using 40% ethanol with ultrasound‐assisted extraction method for 2 h at 40 °C. In addition, two isolation methods for the recovery of catechins from green tea extracts were compared using different solvent combinations (chloroform/ethyl acetate versus ethyl acetate/dichloromethane). The results showed that the ethyl acetate/dichloromethane system could achieve much higher content of catechins than the other isolation approaches, indicating the method that extract catechins first with organic solvent such as ethyl acetate before removing caffeine is much effective than removing caffeine first when organic solvents are used for the recovery of catechins without caffeine from green tea extracts.     

Extraction of active ingredients from green tea (Camellia sinensis): Extraction efficiency of major catechins and caffeine

The effect of different extraction set-ups that influence the extraction efficiency of catechins and caffeine from green tea leaves (variety Fanning Belas, China) were studied using different aqueous and pure solvents (acetone, ethanol, methanol, acetonitrile, water), different temperatures (60, 80, 95 and 100 °C) and times (5–240 min). Raw extracts were analysed for contents of major catechins (EC, EGC, ECG, EGCG), caffeine, proanthocyanidins and flavonols (myricetin, caempherol, quercetin). Starting material was found to contain 191 g major catechins/kg material, 36 g caffeine/kg material and 5.2 g flavonols/kg material on a dry mass basis. The content of major catechins in green tea extracts varied from approximately 280–580 g/kg dry extract, with extraction efficiencies of major catechins varying from 61% to almost 100%. Content of caffeine in extract was in the range of 75 g/kg, where its extraction efficiency varied from 62% to 76%. Average extraction yield was 30% with exceptions when using pure acetone and acetonitrile, where extraction yield was about 3%. Contents of flavonols and proanthocyanidins were in the ranges 6–20 and 12–19 g/kg, respectively. Different extraction procedures with water were also investigated and optimal conditions determined: maximum achieved extraction efficiency of catechins with water was obtained at 80 °C after 20 min (97%) and at 95 °C after 10 min of extraction (90%). Degradation of catechins was observed at higher extraction temperatures and with prolonged extraction times. Using a lower ratio of solvent to material, extraction efficiencies were increased by applying a multi-step extraction procedure. Optimal extraction procedure was then performed using decaffeinated green tea leaves, which were obtained by high-pressure extraction with CO₂, when 98% of caffeine was selectively isolated without significant impact on valuable catechins.     

冲泡条件对恩施玉露绿茶茶汤品质的影响

对恩施玉露绿茶茶汤品质在不同冲泡条件下的变化进行探讨,采用分析化学手段和量化感官分析方法鉴定了沸水(100℃,5 min)、常温水(25℃,2 h)及冷水(4℃,6 h)冲泡后茶汤呈味成分、挥发性成分与感官分属性,并建立了两者的相关性。结果表明:沸水冲泡法的茶汤花香和甜香高,滋味较浓,带有苦涩味;低温和常温冲泡下的茶汤以清香和果香为主,滋味鲜醇,无苦涩味,且有回甘。沸水冲泡条件下的茶多酚、儿茶素、咖啡碱、水浸出物和总糖含量都显著高于冷泡茶,常温冲泡下的茶氨酸和精氨酸含量最高。香气成分上表现为冷泡茶的醛类和酮类含量都明显增加,而芳香烃类物质明显减少,醇类在热泡茶汤中含量最高。进一步的相关性研究发现,有7个呈味成分和10个香气组分分别与滋味和香气分属性间相关性较高,呈味成分包括茶多酚、咖啡碱、茶氨酸等,呈香成分包括二甲硫、己醛、芳樟醇、柠檬烯等,这些成分对不同冲泡条件下绿茶风味变化及感官分属性有重要的贡献。      

Stop for tea? Enzyme inhibitors from tea – what good are they?

Tea possesses many bioactive components including polyphenols, theanine and caffeine. Inhibitory effect of these components on the various enzymes involved in some chronic diseases was reviewed in this study. Many studies revealed that anti‐obesity of tea was mainly ascribed to the polyphenols which could inhibit the activity of the enzymes related to diet metabolism such as α‐amylase, α‐glucosidase and lipase. Inhibitory effect of catechins and caffeine against β‐ and γ‐secretase, acetylcholinesterase, protein kinase C and histone deacetylase might be responsible for the prevention from nervous system diseases. Cytochrome P450 enzymes, cytosolic sulfotransferases, cyclooxygenase‐2 and phosphoinositide‐3‐kinase could be efficiently suppressed by catechins, which would decrease the risk of cancer initiation and proliferation; theanine could lower the activity of some anticarcinogen‐activated enzymes and alleviate the adverse effect of cancer cure. Catechins and caffeine exhibited significant inhibition against the matrix metalloproteinases, histidine decarboxylase and many kinases related to inflammation. Thus, catechins, theanine and caffeine might be employed as inhibitors of the enzymes associated with these chronic diseases.     

Comparison of the main compounds in Fuding white tea infusions from various tea types

The purpose of this study was to compare the main components, and particularly catechins, caffeine, theanine, free amino acids, and water extracts, in Bai Hao Yin Zhen, Bai Mu Dan, and Shou Mei Fuding white tea infusions brewed at different temperatures, and their contributions to taste were estimated by dose-over-threshold value. Infusion temperature had a distinct effect on the main components extracted, and 100 °C was found to be optimal for extracting catechins and caffeine. However, the effect of temperature on theanine, free amino acids, and water extracts varied with tea type. Bai Mu Dan and Shou Mei yielded a higher content of the major compounds than did Bai Hao Yin Zhen. Thus, infusion temperature had a large effect on extracting the main compounds, and the differences in content between the three white teas presumably reflected differences in the harvest time, processing method or leaf shape.     

Green tea from purple leaf coloured tea clones in Kenya- their quality characteristics

The Kenyan tea industry wishes to diversify its tea products, and in line with this, anthocyanin – rich teas were developed at the Tea Research Foundation of Kenya. These teas have purple-coloured leaves and the green colour is masked. In total, 12 accessions of the purple leaf coloured teas and 2 standard tea varieties were studied. Clones Hanlu and Yabukita are Chinese and Japanese tea varieties, respectively, known for good green tea, and they were used as reference standards. Little if any research had been done to characterize the quality of these purple leaf coloured teas and this study investigated their total polyphenols (TPP), catechins, caffeine, gallic acid and theanine. These are the major green tea quality parameters. Results showed that the new Kenyan tea clones had higher total polyphenols than had the reference standard tea varieties, which had 17.2% and 19.7% while the lowest among the Kenyan clones was 20.8%. On catechin quality index, K-purple and TRFK 91/1 showed high index values of 15.9 and 13.3, respectively, while clones TRFK 83/1 and 73/5 showed low index values of 0.74 and 1.0, respectively. Hanlu had the highest caffeine level with 2.42% while clones TRFK KS 3, TRFK KS 2 and TRFK 83/1 had relatively high caffeine levels among the purple leaf coloured teas, with 2.33%, 2.22% and 2.21%, respectively. Clone TRFK 73/5 had the lowest caffeine content, with 1.16%. Theanine analysis showed that most purple leaf coloured teas had more theanine than had the reference standard clones, except TRFK 83/1 and K-purple, which were lower than the reference standard clones. The implication of the green tea chemical quality parameters is also discussed. It is concluded that all the studied clones/varieties have above the minimum 14% of total polyphenols. Clones K-purple and TRFK 91/1 showed high green tea quality indices with the latter doubling with high levels of theanine; hence its highly recommended for green tea manufacture.     

Valorisation of theanine from decaffeinated tea dust in bakery functional food

Nowadays, consumers appreciate the positive properties of decaffeinated tea for their well‐being. During decaffeination process, a very fine tea dust powder is obtained as by‐product, which contains the same quantity of bioactives as decaffeinated tea: the antioxidant polyphenols and the amino acid theanine. The aim was to add value to theanine gained from black tea powder dust and to develop theanine‐enriched bread. A theanine containing powder was obtained by column separation of decaffeinated tea dust extract and spray‐drying using carrier supports. This powder contains also the very polar compounds from decaffeinated tea such as amino acids, sugars and minerals. Breads with 110, 220 and 330 ppm of theanine, respectively, were prepared with the theanine powder. Physical properties, theanine and total polyphenolic content in bread were analysed. Bread and other bakery food serve as good products to add value to bioactive tea dust ingredients.     

金花白茶加工过程中主要滋味物质的动态变化

以2017年福建寿眉散茶为原料,按照渥堆、汽蒸、压制定型、发花、干燥等加工工艺制成金花白茶。通过对加工过程中8个有代表性的工艺节点取样检测,以探明金花白茶加工过程中茶多酚、儿茶素、咖啡碱、氨基酸、水浸出物、可溶性糖、黄酮、茶三素等主要滋味物质含量的动态变化,并探究各类滋味物质的动态变化对其滋味品质的影响。结果表明,金花白茶加工过程中,茶多酚、儿茶素、游离氨基酸、可溶性糖、茶黄素及茶红素含量均逐渐降低,金花白茶较原料降幅分别为24.26%、52.89%、27.44%、9.38%、48.83%及30.96%。黄酮总量、没食子酸及茶褐素含量逐渐增加,金花白茶较原料增幅分别为20.46%、10.92%及77.31%。水浸出物、咖啡碱、茶氨酸含量略有增加,增幅为2.89%、7.70%、8.63%。这些变化有利于金花白茶滋味浓醇厚不苦涩,汤色红浓明亮品质的形成。同时结合感官审评发现,茶多酚、茶黄素、咖啡碱、游离氨基酸及茶褐素均与金花白茶滋味品质显著或极显著相关。     

Interaction mechanisms between caffeine and polyphenols in infusions of Camellia sinensis leaves

Black tea infusions of Camellia sinensis leaves were studied for the influence of water composition, especially calcium content, on the amount of extracted organic matter and on the interactions between caffeine and polyphenols. The higher the calcium content, the lower the extraction of caffeine and polyphenols in acidic media. In alkaline media, besides the calcium effect, polyphenols are oxidized. Caffeine NMR chemical shifts varied depending on the water used showing modified interactions. Using model solutions, polyphenols seem to be responsible for these changes in the case of ultra pure water, but in the case of alkaline solutions, the data in model solutions are different from tea infusions implying that other compounds should interact. Moreover, epigallocatechin gallate (EGCg) and epigallocatechin are the polyphenols interacting most strongly with caffeine in infusions and not EGCg and epicatechin gallate as thought before.     

Influence of extraction conditions on polyphenols content and cream constituents in black tea extracts

Increase in water‐to‐tea ratio and extraction time increased polyphenols recovery as well as extractable‐solids‐yield (ESY) in black tea extracts. Polyphenols content‐in‐extracted solids (PES) used as a tea quality parameter, was significantly higher at 50:1 water‐to‐tea ratio and favourably improved only up to 60 min. Extending the extraction period beyond 40 min degraded theaflavins (TF) and also affected the recovery of major catechins. Although tea cream content showed a decrease with increase in water‐to‐tea ratio, the content was nearly the same (1.80–1.89%) in all these extracts when measured at a uniform 0.5% solids concentration. The extraction conditions displayed a similar influence on the other tea cream components, namely, caffeine, calcium, pectin and protein. The conditions optimised (50:1 water‐to‐tea ratio and 40 min) based on higher PES and TF/TR ratio gave a maximum PES of 0.566 g g^?1 and TF of 0.46% (black tea) in the extract.     

Sustainable extraction of proteins and bioactive substances from pomegranate peel (Punica granatum L.) using pressurized liquids and deep eutectic solvents

Pomegranate peel is a source of proteins, bioactive peptides, and phenolic compounds. The simultaneous extraction of these compounds required the use of polluting solvents and reagents that are non-suitable. This work targets the development of green methodologies based on pressurized liquids (PLE) or deep eutectic solvents (DES) for the extraction of these compounds. Extracts were digested with different proteolytic enzymes and different functionalities (antioxidant, hypocholesterolemia, and antihypertensive capacities) were evaluated. Highly antioxidant and hypocholesterolemic extracts and hydrolysates were obtained using PLE while high antihypertensive capacity was observed in the hydrolysates from proteins extracted using DES. Peptides and polyphenols were identified by HPLC-ESI-Q-TOF/MS. Higher amounts of peptides were shown in hydrolysates from DES extracts while hydrolysates from PLE extracts presented higher amounts of phenolic compounds. Some peptides were assigned to proteins from Punica granatum. Both green methods improved the extraction of bioactive compounds from pomegranate peel compared to the non-sustainable method.Industrial relevanceThe development of green methodologies which employ sustainable solvents such as pressurized liquids (PLE) and deep eutectic solvents (DES) allows extracting proteins and bioactive compounds from pomegranate peel. In addition, these solvents improve the extraction of health beneficial compounds compared to the non-sustainable and polluting solvents. Therefore, they could be used for the development of nutraceuticals and functional foods or even in medicinal, cosmetic, and pharmaceutical preparations.     

蒙顶甘露名茶主要滋味成分及香气组分检测分析

采用常规分析法与高效液相色谱、气相色谱-质谱分析法相结合对蒙顶甘露茶的主要滋味成分、游离氨基酸组分和香气组分进行检测,并就内含成分与品质风味的关系进行探究。结果表明,主要滋味成分茶多酚、儿茶素、咖啡碱、可溶性糖和氨基酸的全含量为（23.98±0.26）%、（17.52±0.05）%、（4.26±0.21）%、（4.85±0.12）%和（4.66±0.16）%,酚氨比值为3.95～7.43;日常饮茶冲泡时,第2次泡滋味感官评分（28.9±0.2）最高,品质风味好,其主要成分包括茶多酚、咖啡碱、可溶性糖和游离氨基酸,浸出质量浓度分别为262.2、63.9、66.5 mg/250 mL和89.3 mg/250 mL,酚氨比值较小,为2.93;蒙顶甘露茶中含有18 种游离氨基酸组分,其中茶氨酸高达20.46 mg/g,占51.5%;蒙顶甘露茶中酯型儿茶素组分表儿茶素没食子酸酯和表没食子儿茶素没食子酸酯的含量分别为3.39%、6.97%;检测到51 种香气组分,主要是醇类（12 种）和酯类（9 种）,其中芳樟醇、β-紫罗兰酮、橙花叔醇和反-橙花叔醇含量较高,这些组分共同成为嫩香持久馥郁的香气物质基础。     

不同等级金牡丹乌龙茶品质和矿质元素差异分析

以不同等级金牡丹乌龙茶为试材,测定了不同等级金牡丹乌龙茶的感官审评得分、品质指标（茶多酚、咖啡碱、8种儿茶素、可溶性糖、游离氨基酸、茶氨酸、水浸出物和总黄酮）和8种矿质元素含量。等级越高的金牡丹乌龙茶水浸出物含量越高,特等奖水浸出物含量比一等奖和优质奖分别高1.07%和1.75%,且差异均达到显著水平（P<0.05）。咖啡碱、可溶性糖和总黄酮含量均为低等级显著高于高等级（P<0.05）。三个等级的茶多酚含量之间没有显著差异（P>0.05）。特等奖的酚氨比要显著低于一等奖和优质奖（P<0.05）。优质奖的茶氨酸含量要显著低于特等奖和一等奖（P<0.05）。线性回归分析表明,游离氨基酸和总黄酮与审评得分呈显著线性负相关（P<0.05）,可溶性糖与审评得分呈极显著线性负相关（P<0.01）,而水浸出物与审评得分呈极显著线性正相关（P<0.01）。不同等级金牡丹乌龙茶除Mn和Fe外,大多数矿质元素之间不存在显著差异（P>0.05）。限制性主坐标分析表明,品质指标结合限制性主坐标分析可以很好的区分金牡丹乌龙茶等级差异,R值达1.00。但矿质元素结合限制性主坐标分析并不能很好的区分不同等级金牡丹乌龙茶的品质差异。研究结果为金牡丹乌龙茶品质鉴定提供相关参考依据。     

乳酸菌发酵对红茶饮料营养成分、香气成分及抗氧化活性的影响

以植物乳杆菌菌剂发酵红茶饮料为研究对象,分别采用酒石酸铁比色法、茚三酮比色法和标准碱滴定法测定红茶发酵前后的茶多酚、茶氨酸、咖啡碱及乳酸含量;采用4种不同体外抗氧化模型来考察红茶饮料发酵前后的抗氧化活性;并采用顶空固相微萃取结合气相色谱-质谱联用技术分析红茶发酵前后主要香气成分。结果表明,发酵后红茶饮料茶多酚和咖啡碱含量比发酵前稍有下降,茶氨酸含量较发酵前显著上升(P0.05);对部分自由基的清除能力较发酵前略有下降;醇类和酮类等香气成分在发酵后较发酵前有明显增加,有利于提升红茶的香气品质。