Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 7 de 7
Filtrar
Mais filtros

Base de dados
País como assunto
Tipo de documento
Intervalo de ano de publicação
1.
Molecules ; 21(12)2016 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-28009849

RESUMO

Catechins are polyphenolic phytochemicals with many important physiological activities that play a multifaceted health care function in the human body, especially in the prevention of cardiovascular disease. In this paper, various experimental and clinical studies have revealed the role of catechins in the prevention and treatment of cardiovascular disorders, and we review the preventive effects of catechins on cardiovascular disease from the following aspects: Regulating lipid metabolism, regulating blood lipid metabolism, vascular endothelial protection, and reducing blood pressure.


Assuntos
Antioxidantes/farmacologia , Doenças Cardiovasculares/prevenção & controle , Catequina/farmacologia , Endotélio Vascular/efeitos dos fármacos , Chá/química , Pressão Sanguínea/efeitos dos fármacos , Doenças Cardiovasculares/sangue , Doenças Cardiovasculares/fisiopatologia , Endotélio Vascular/metabolismo , Endotélio Vascular/fisiopatologia , Humanos , Metabolismo dos Lipídeos/efeitos dos fármacos , Prevenção Primária
2.
PLoS One ; 13(3): e0193393, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29494626

RESUMO

In the present work, a novel infrared-assisted extraction coupled to headspace solid-phase microextraction (IRAE-HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS) was developed for rapid determination of the volatile components in green tea. The extraction parameters such as fiber type, sample amount, infrared power, extraction time, and infrared lamp distance were optimized by orthogonal experimental design. Under optimum conditions, a total of 82 volatile compounds in 21 green tea samples from different geographical origins were identified. Compared with classical water-bath heating, the proposed technique has remarkable advantages of considerably reducing the analytical time and high efficiency. In addition, an effective classification of green teas based on their volatile profiles was achieved by partial least square-discriminant analysis (PLS-DA) and hierarchical clustering analysis (HCA). Furthermore, the application of a dual criterion based on the variable importance in the projection (VIP) values of the PLS-DA models and on the category from one-way univariate analysis (ANOVA) allowed the identification of 12 potential volatile markers, which were considered to make the most important contribution to the discrimination of the samples. The results suggest that IRAE-HS-SPME/GC-MS technique combined with multivariate analysis offers a valuable tool to assess geographical traceability of different tea varieties.


Assuntos
Cromatografia Gasosa-Espectrometria de Massas , Chá/química , Compostos Orgânicos Voláteis/análise , Análise por Conglomerados , Análise Discriminante , Raios Infravermelhos , Análise dos Mínimos Quadrados , Análise Multivariada , Microextração em Fase Sólida , Chá/metabolismo , Compostos Orgânicos Voláteis/isolamento & purificação
3.
J Food Sci ; 83(6): 1668-1675, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29806704

RESUMO

In this study, a Box-Behnken design was used to explore the effect of a new technology on green tea fragrance improvement and to optimize fragrance-improving with a bilayer far-infrared fragrance-improving machine with temperature and humidity control. Based on the results of previous single-factor experiments, the main biochemical composition and sensory evaluation scores of the fragrance-improved samples were used as investigation indices. The new fragrance-improving technology was compared with the traditional far-infrared fragrance-improving process, roller pot fragrance improvement, and hot air rotary fragrance improvement. The results show that the optimal parameter combination of the new technology consists of a temperature of 128.00 °C, relative humidity of 70.00 g/h, and transmission speed of 435.00 r/min. With these process parameters, the amino acids, tea polyphenols, flavonoids, soluble sugar, catechins, and caffeine in the fragrance-improved samples reached 3.86%, 32.29%, 5.59%, 4.45%, 8.97%, and 2.75%, respectively. The quality material weight value was 11.72%. The shape, color, taste, and aroma of the fragrance-improved samples made using these parameters were found to be best, with a sensory quality score of 87.40, which is significantly higher than that of other fragrance-improving methods. The energy consumption was 0.19 RMB/kg, which was reduced by more than 50% compared with the other methods, and the production efficiency was more than 30% higher than the traditional methods. This new far-infrared fragrance-improving technology overcomes the yellowish and grayish color of fragrance-improved tea samples that is caused by the traditional fragrance-improving approach, and will provide technical guidance for actual green tea production. PRACTICAL APPLICATION: Our proposed approach innovatively integrates humidity and rotational speed as factors for fragrance improvement in Chinese tea process. The findings of this work provide new technical for fragrance improvement processes.


Assuntos
Manipulação de Alimentos , Raios Infravermelhos , Odorantes/análise , Folhas de Planta/efeitos da radiação , Chá/efeitos da radiação , Temperatura , Cafeína/análise , Catequina/análise , Bases de Dados Factuais , Flavonoides/análise , Folhas de Planta/química , Polifenóis/análise , Paladar , Chá/química
4.
Chem Commun (Camb) ; (4): 407-9, 2007 Jan 28.
Artigo em Inglês | MEDLINE | ID: mdl-17220986

RESUMO

One-dimensional zigzag coordination chains in four different directions are hierarchically entangled to generate an unprecedented 3D interwoven framework, which exhibits permanent porosity and guest selectivity.

5.
J Zhejiang Univ Sci B ; 18(6): 544-548, 2017 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-28585431

RESUMO

Tea is one of the three greatest beverages in the world. In China, green tea has the largest consumption, and needle-shaped green tea, such as Maofeng tea and Sparrow Tongue tea, accounts for more than 40% of green tea (Zhu et al., 2017). The appearance of green tea is one of the important indexes during the evaluation of green tea quality. Especially in market transactions, the price of tea is usually determined by its appearance (Zhou et al., 2012). Human sensory evaluation is usually conducted by experts, and is also easily affected by various factors such as light, experience, psychological and visual factors. In the meantime, people may distinguish the slight differences between similar colors or textures, but the specific levels of the tea are hard to determine (Chen et al., 2008). As human description of color and texture is qualitative, it is hard to evaluate the sensory quality accurately, in a standard manner, and objectively. Color is an important visual property of a computer image (Xie et al., 2014; Khulal et al., 2016); texture is a visual performance of image grayscale and color changing with spatial positions, which can be used to describe the roughness and directivity of the surface of an object (Sanaeifar et al., 2016). There are already researchers who have used computer visual image technologies to identify the varieties, levels, and origins of tea (Chen et al., 2008; Xie et al., 2014; Zhu et al., 2017). Most of their research targets are crush, tear, and curl (CTC) red (green) broken tea, curly green tea (Bilochun tea), and flat-typed green tea (West Lake Dragon-well green tea) as the information sources. However, the target of the above research is to establish a qualitative evaluation method on tea quality (Fu et al., 2013). There is little literature on the sensory evaluation of the appearance quality of needle-shaped green tea, especially research on a quantitative evaluation model (Zhou et al., 2012; Zhu et al., 2017).


Assuntos
Camellia sinensis/anatomia & histologia , Chá , Inteligência Artificial , China , Cor , Técnicas de Apoio para a Decisão , Humanos , Dinâmica não Linear , Chá/normas
6.
Food Chem ; 192: 470-6, 2016 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-26304374

RESUMO

The present study aims to improve the sweet aftertaste and overall acceptability of green tea infusion by hydrolyzing (-)-epigallocatechin gallate (EGCG) and (-)-epicatechin gallate (ECG) with tannase. The results showed that the intensity of the sweet aftertaste and the score of overall acceptability of the green tea infusion significantly increased with the extension of the hydrolyzing treatment. (-)-Epigallocatechin (EGC) and (-)-epicatechin (EC) were found to be the main contributors for the sweet aftertaste, based on a trial compatibility with EGCG, ECG, EGC, and EC monomers, and a synergistic action between EGC and EC to sweet aftertaste was observed. A 2.5:1 (EGC/EC) ratio with a total concentration of 3.5 mmol/L gave the most satisfying sweet aftertaste, and the astringency significantly inhibited the development of the sweet aftertaste. These results can help us to produce a tea beverage with excellent sweet aftertaste by hydrolyzing the green tea infusion with tannase.


Assuntos
Hidrolases de Éster Carboxílico/metabolismo , Paladar , Chá/química , Catequina/análogos & derivados , Catequina/análise , Catequina/metabolismo , Hidrólise , Extratos Vegetais/química
7.
Food Chem ; 172: 831-5, 2015 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-25442627

RESUMO

The effects of Ca(2+), caffeine and polyphenols on the formation of reversible tea sediments (RTS) and irreversible tea sediments (IRS) in green tea infusion were studied. Adding Ca(2+) (2 mmol/l) was found to increase the formation of RTS by 8% and IRS by 92%, while adding chelating ions of Na2EDTA significantly decreased the amount of RTS by 14.6%, but not the amount of IRS. Under acid conditions, Ca(2+) combined with oxalic ions to form indissoluble oxalate that is the principal constituent of IRS, despite the existence of the chelating ions. Decaffeination largely inhibited the formation of RTS (73%) and IRS (60%), even in the presence of Ca(2+). The amount of sediment could be reduced by removing polyphenols using polyvinyl-polypyrrolidone. The results suggest that sediment formation in green tea infusions can be inhibited by lowering the concentration of Ca(2+), caffeine or polyphenols.


Assuntos
Camellia sinensis/química , Preparações de Plantas/química , Chá/química , Ácidos/química , Cafeína/química , Cálcio/química , Precipitação Química , Oxalatos/química , Polifenóis/química
SELEÇÃO DE REFERÊNCIAS
Detalhe da pesquisa