绿茶、红茶加工工艺对茶鲜叶中多酚类物质的影响

采用槠叶种一芽二、三叶鲜叶,按照传统的加工工艺分别制成绿茶和红茶。以鲜叶为对照,应用分光光度法和RP—HPLC法对绿茶、红茶的多酚类物质进行了分析,结果表明:与鲜叶相比,(1)绿茶中多酚类物质总量保持不变,而红茶中多酚类物质总量下降了43.8%;(2)绿茶中儿茶素总量几乎不变,而红茶下降了80.6%;(3)红茶中茶黄素和茶红素分别上升了565.5%和74.5%。     

Bioactivities and sensory evaluation of Pu-erh teas made from three tea leaves in an improved pile fermentation process

Two commercial Pu-erh teas, 15-year-old Ta-Huang-In and 25-year-old Ta-Hon-In, were used for screening some species of fungi, yeasts, and bacteria, and six of them were isolated and identified as Actinoplanes aurantiacus, Actinoplanes pallidoaurantiacus, Actinoplanes purpeobrunneus, Streptomyces bacillaris, Streptomyces cavourensis subsp. cavourensis, and Streptomyces cinereus. They were selected for inoculated into thee tea leaves (Yun Nan from China, TTES-12 and C. S. Oolong from Taiwan) and fermented for 180 days. The total polyphenols and GABA content, and DPPH radical scavenging effects were determined to examine the tea infusion quality. The samples inoculated with S. cinereus had the highest total polyphenols content and maximum capacity to scavenge DPPH radicals; the highest GABA content was obtained while the sample inoculated with S. bacillaris. Further comparison of these samples with two commercial Pu-erh teas of different ages (Ta-Huang-In, 15-year storage and Ta-Hon-In, 25-year storage) showed that DPPH radical scavenging activity and GABA content of S. bacillaris and S. cinereus fermented tea leaf were higher than these two commercial teas. Sensory evaluation also demonstrated that the taste, flavor, and overall acceptance did not had significant differences between the experimental tea leaves and commercial samples. The present studies revealed that the fresh tea leaves inoculated with the suitable microbes in short period of time will possess a high-quality tea infusion as long-term storage Pu-erh tea.     

Antioxidant and anti-glycation properties of Thai herbal teas in comparison with conventional teas

Fifteen Thai herbal teas in comparison with teas of Camellia sinensis, were studied for their antioxidants and anti-glycation properties in correlation with their total phenolics, flavonoids, and non-flavonoids contents. Significant differences were observed among the tea infusions. Only stevia and sappan herbal teas had primary antioxidants and anti-glycation capacities comparable to C. sinensis. However, purple velvet, mulberry and false mallow herbal teas were exceptionally stronger in metal chelating capacity than the C. sinensis teas. Principal component analysis showed that total phenolics, particularly flavonoids highly correlated with primary antioxidants and anti-glycation. Cluster analysis showed that the properties of stevia and sappan herbal teas were similar to green, black and oolong teas. Some common, but rarely mentioned, Thai herbal teas could be choices of interest for healthy beverages and could be new dietary sources for bioactive compounds.     

Influence of withering, including leaf handling, on the manufacturing and quality of black teas - a review

Literature on the influence of withering on maceration, fermentation and drying and on black tea quality is reviewed. The importance of including the handling of the leaf in the field and during transportation as an integral part of withering is stressed. The influence of physical and chemical changes in the green leaf, during withering, on the quality of black teas is discussed. Withering practices vary with climate, producing region, the type of manufacturing process and demands by the markets. Mechanised withering may improve quality by reduced handling of the leaf. The influence of plucking standards on withering and the effect of withering on the storage of tea are discussed.     

The synergistic potential of various teas,herbs and therapeutic drugs in health improvement: a review

Tea is one of the most widely consumed non‐alcoholic beverages in the world next to water. It is classified as Camellia sinensis and non‐Camellia sinensis (herbal teas). The common bioactive compounds found mainly in green teas are flavan‐3‐ols (catechins) (also called flavanols), proanthocyanidins (tannins) and flavonols. Black tea contains theaflavins and thearubigins and white tea contains l ‐theanine and gamma‐aminobutyric acid (GABA), while herbal teas contain diverse polyphenols. Phytochemicals in tea exhibit antimicrobial, anti‐diabetic and anti‐cancer activities that are perceived to be helpful in managing chronic diseases linked to lifestyle. Many of these phytochemicals are reported to be biologically active when combined. Knowledge of the synergistic interactions of tea with other teas or herbs in terms of biological activities will be of benefit for therapeutic enhancement. There is evidence that various types of teas act synergistically in exhibiting health benefits to humans, improving consumer acceptance and economic value. Similar observations have been made when teas and herbs or medicinal drugs were combined. The aim of this review is to highlight potential beneficial synergies between combinations of different types of teas, tea and herbs, and tea and medicinal drugs. © 2017 Society of Chemical Industry     

茶叶中农残检测改良方法

食品农残检测中,超临界流体萃取,固相微萃取,在线HPLC萃取等先进的样品提取手段和气质联用法、高效液相色谱法、超临界流体色谱法等高级的检测手段不断涌现,使农残检测取得了越来越理想的效果,但由于这些方法需要昂贵的设备和特殊的仪器,     

Gravimetric determination of soluble phenolics including tannins from leaves by precipitation with trivalent ytterbium

A method for the gravimetric determination of soluble phenolics based on precipitation with trivalent ytterbium is described. Solutions of ytterbium-precipitated phenolics can be prepared in order to study u.v. absorbance, colorimetric assays for phenolics, protein precipitation and cellulase inhibition. The method was applied to mature leaves of 10 East African browse species in the diets of goats and camels. There was a large range in ytterbium-precipitated phenolics (Yb-ppt), from 50% dry matter (DM) in Acacia nilotica to less than 15% in Acacia brevispica and Cadaba farinosa. Results from u.v. absorbance and the Folin-Ciocalteu assay on solutions of ytterbium-precipitated phenolics indicated that ytterbium precipitates many types of phenolics including proanthocyanidins. The vanillin-HCl and n-butanol-HCl assays for proanthocyanidins separated the samples into two groups with high or low levels. The group with high levels of proanthocyanidins had greater protein precipitation capacity and cellulase inhibition at similar amounts of Yb-ppt. The results indicate that the method may be useful in nutritional studies involving browse and other forages. Gravimetric analysis avoids problems associated with colorimetric assays because it does not rely on the use of standards. The preparation of solutions of Yb-precipitated phenolics allows direct comparison between amount and nutritional effects such as protein precipitation and enzyme inhibition.     

Pyrrolizidine and tropane alkaloids in teas and the herbal teas peppermint,rooibos and chamomile in the Israeli market

Dehydro pyrrolizidine alkaloids (dehydro PAs) are carcinogenic phytotoxins prevalent in the Boraginaceae, Asteraceae and Fabaceae families. Dehydro PAs enter the food and feed chain by co-harvesting of crops intended for human and animal consumption as well as by carry-over into animal-based products such as milk, eggs and honey. Recently the occurrence of dehydro PAs in teas and herbal teas has gained increasing attention from the EU, due to the high levels of dehydro PAs found in commercially available teas and herbal teas in Germany and Switzerland. Furthermore, several tropane alkaloids (TAs, e.g. scopolamine and hyoscyamine) intoxications due to the consumption of contaminated herbal teas were reported in the literature. The aim of the present study was to determine the dehydro PAs and TAs levels in 70 pre-packed teabags of herbal and non-herbal tea types sold in supermarkets in Israel. Chamomile, peppermint and rooibos teas contained high dehydro PAs levels in almost all samples analysed. Lower amounts were detected in black and green teas, while no dehydro PAs were found in fennel and melissa herbal teas. Total dehydro PAs concentrations in chamomile, peppermint and rooibos teas ranged from 20 to 1729 μg/kg. Except for black tea containing only mono-ester retrorsine-type dehydro PAs, all other teas and herbal teas showed mixed patterns of dehydro PA ester types, indicating a contamination by various weed species during harvesting and/or production. The TA levels per teabag were below the recommended acute reference dose; however, the positive findings of TAs in all peppermint tea samples warrant a more extensive survey. The partially high levels of dehydro PAs found in teas and herbal teas present an urgent warning letter to the regulatory authorities to perform routine quality control analysis and implement maximum residual levels for dehydro PAs.     

Long-term acceptability and choice of teas differing in sweetness

We measured people’s choice and changes in choice of three types of tea, each at a low and an optimum level of sweetness. Twenty-eight tea drinkers participated in an initial taste test session and 20 additional consumption sessions. During the first session they tasted the six tea samples, ranked them in order of preference, and otherwise familiarized themselves with the samples prior to the long-term experiment. In each of the 20 consumption sessions they selected a tea, drank it, rated how well they liked it, how tired they were of it, and their satisfaction with having chosen it. We observed four choice patterns: constant-switcher, acquired-liker, non-switcher, and systematic-switcher. Over the 20 sessions the liking of the low-sweet tea increased and the tiredness ratings of the optimum-sweet tea increased. These changes, however, did not increase the frequency with which they chose the low sweet teas. Initial liking significantly predicted choice for about half the panelists.     

Heavy metal content of black teas consumed in Iran

Tea (Camellia sinensis) is the most widely consumed beverage in several parts of the world. Tea consumption is a major component of the traditional Iranian diet; however, limited data are available indicating heavy metals content of this beverage. This study aimed to assess concentrations of heavy metals, including copper, lead, cadmium, chromium and mercury as well as minerals like zinc and iron in black tea samples. Atomic absorption spectrometry was used to determine the elements of interest in 20 brands of black tea that are widely consumed among Iranians. The mean concentrations were 28.8 for Zn, 135.2 for Fe, 15.9 for Cu and 8.2 for Cr (mg kg^?1) and 134.5 for Cd, 209.5 for Pb and 40 for Hg (µg kg^?1). It is concluded that tea consumption can be a possible source of some heavy metal intake for the Iranian population.     

The nature of the oxygenated fatty acids present in Malva parviflora seed oil

The seed oil of Malva parviflora L. (Malvaceae) is known to contain glycerides of cyclopropene (malvalic and sterculic), cyclopropane (dihydromalvalic and dihydrosterculic), epoxy, and conjugated dienol acids. By preparative thin layer chromatography, the epoxy and conjugated dienol acids were isolated as their methyl esters. These were characterised as cis-12, 13-epoxy-cis-9-octadecenoic (vernolic) acid, and 13-hydroxy-cis-9, trans-11-octadecadienoic (coriolic) acid.     

福建省地产茶叶中14种元素的分析与研究

目的了解福建省不同地区不同茶叶中铅、砷、铜、铁、锰、锌、镉、铝、硒、镍、铬、钴、锡、铋等14种元素的含量分布,为茶叶资源的开发利用提供科学依据。方法从福建省主要产茶地区的产地和市场随机抽取9个茶叶品种共112份样品,用微波消解-电感耦合等离子体质谱法(ICP-MS)测定样品中14种元素含量。结果 9种茶叶中14种元素的含量水平分别为:锰135～1 797 mg/kg,铝69～1 126 mg/kg,铁37～371 mg/kg,锌3.93～90.05 mg/kg,铜2.25～43.66 mg/kg,镍0.95～7.40 mg/kg,铅0.29～5.45 mg/kg,铬0.10～2.39 mg/kg,钴0.018～0.67 mg/kg,硒0.020～0.68 mg/kg,镉0.014～0.24 mg/kg,砷0.023～0.30 mg/kg,锡0.010～0.49 mg/kg,铋0.006～0.073 mg/kg,铅合格率为99.1%,铬、镉、砷合格率为100%。结论福建省地产茶叶中都富含锰、铝、铁、锌、铜。铬、镉、砷、铅等有害元素污染水平较轻,且不同地区不同茶叶中元素含量存在差异。     

桑叶保健袋泡茶的研制

通过对桑叶制茶工艺的研究,确定了桑叶茶的最佳杀青方法,并以花茶、大枣、枸杞、黄芪为辅料进行调配,既提高了桑叶茶的营养保健作用,又改善了桑叶茶的风味,并利用正交试验确定了主辅料的最佳配比。     

含生物类黄酮的植物叶在焙烤类保健食品中的应用

蓼科植物苦荞麦、蔷薇科植物山楂、桑科植物桑树与银杏科植物银杏的叶中含有丰富的生物类黄酮物质,其保健功能和开发利用价值受到了国内外学者的普遍关注,欧美及日本等国对生物类黄酮的性质和保健作用已作了深入的基础性研究,我国卫生部新食品资源评审委员会于１９９２也已批准银杏叶提取物作为新的食品添加剂。 一、生物类黄酮的性质和保健作用 生物类黄酮属植物次级代谢产物,是一组存在于植物叶、花及果实中的天然色素,因多呈黄色而称为类黄酮。动物不能合成类黄酮,植物是富含生物类黄酮的主要食物来源。生物类黄酮无毒性,在高级动…     

桑叶复合保健饮料的研制

以桑叶为主要原料,添加适量新鲜果汁及其它原辅料,研制出口感优良、风味独特、营养丰富、质量稳定的桑汁保健饮料。探讨桑叶提取液的脱苦方法,通过正交实验确定了饮料的最佳配方。     

豆腐柴保健饮料的研制

以豆腐柴叶为主要原料,白砂糖、蜂蜜、柠檬酸为辅料,加工制成具有保健功能的饮料。实验对豆腐柴保健饮料的生产工艺、配方和技术进行了研究,并测定了饮料中蛋白质和黄酮的含量。实验结果表明,豆腐柴叶的最佳浸提条件为:浸提温度60℃,浸提时间30min,料液比1:25。豆腐柴保健饮料的最佳配方为:豆腐柴浸提液40%,白砂糖6%,柠檬酸0.15%,蜂蜜2%。饮料中蛋白质的含量为6.41mg/100mL,黄酮的含量为37.45mg/100mL。     

Milk minerals (including trace elements) and bone health

Osteoporosis is a global health problem that will take on increasing significance as people live longer and the world's population continues to increase in number. Thus, there is an urgent need to develop and implement nutritional approaches and policies for the prevention and treatment of osteoporosis. However, to develop preventative strategies, it is important to determine which modifiable factors, especially nutritional factors, are able to improve bone health throughout life. The present review will firstly, and very briefly, define the principal disease of bone mass (i.e., osteoporosis) and its risk factors, and will then focus on the importance of ‘milk minerals’ in bone health. While there are 20 essential minerals, and all of these are present in milk at some concentration, for the purposes of this review only a selected number of minerals (calcium, phosphorus, magnesium, sodium, potassium and zinc) will be discussed in relation to bone health.