Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 3.801
Filtrar
1.
Inorg Chem ; 58(17): 11382-11388, 2019 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-31402664

RESUMO

Enzyme-like metal-organic frameworks (MOFs) are currently one type of starring material in the fields of artificial enzymes and analytical sensing. However, there has been little progress in making use of the MOF structures based on the catalytically active metal center with multiple valences. Herein, we report a mixed-valence Ce-MOF (Ce-BPyDC) that can exhibit both oxidase-like and peroxidase-like activities. Ce-BPyDC was synthesized by a facile hydrothermal method, which preserves the rare coexistence of Ce(III) and Ce(IV) in the MOF structure. The enzymatic studies demonstrated the enzyme-like activities of Ce-BPyDC follow the Michaelis-Menten kinetics and are strongly dependent on temperature, pH, and reaction time. Ce-BPyDC was also revealed to exert high catalytic activity that could transcend horseradish peroxidase and other MOF nanozymes, due to the redox-active Ce(III)/Ce(IV) cycles inside. Furthermore, the simple synthesis, high nanozyme activity, and great stability of Ce-BPyDC motivated us to establish a colorimetric biosensing platform using 3,3',5,5'-tetramethylbenzidine as a color reagent. Adopting this strategy, we established a visual, sensitive, and selective colorimetric method for ascorbic acid (AA) detection, for which the linear interval and limit of detection were 1-20 and 0.28 µM, respectively. The successful AA detection in real juice samples implies the promising use of such mixed-valence MOF nanozymes in food and biomedical samples.


Assuntos
Técnicas Biossensoriais , Cério/química , Colorimetria , Estruturas Metalorgânicas/química , Ácido Ascórbico/análise , Catálise , Concentração de Íons de Hidrogênio , Estruturas Metalorgânicas/síntese química , Temperatura Ambiente
2.
Food Chem ; 298: 125080, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31260985

RESUMO

Propolis extract was investigated as potential substitute for sorbate in orangeade. Extract was prepared by using aqueous solution of hydroxypropyl-beta-cyclodextrins. Propolis extract was incorporated in non-carbonated orange soft drinks and its antioxidant activity, microbiological stability and color changes were estimated and compared to those of orangeade containing potassium sorbate. l-Ascorbic acid (AsA) degradation at concentrations 0.13 and 1.3% w/w was investigated in the presence of propolis during storage using High Performance Liquid Chromatography-Ion Exclusion Column (HPLC-IEC). The results indicate that the rate of degradation decreased with an increase in ascorbic acid concentration, while addition of propolis affected the degradation rate of samples containing a high AsA concentration. The antifungal effect of propolis extract, potassium sorbate and their combination was assayed. Results showed the inhibition of Aspergillus spp. and B. bruxellensis inhibited in low combined concentrations antimicrobials, while Aspergillus spp. and T. macrosporus were inhibited at 450 mg/g propolis extract.


Assuntos
Bebidas , Conservação de Alimentos/métodos , Conservantes de Alimentos/química , Própole/química , Anti-Infecciosos , Antifúngicos/farmacologia , Antioxidantes/química , Ácido Ascórbico/análise , Ácido Ascórbico/química , Aspergillus/efeitos dos fármacos , Cromatografia Líquida de Alta Pressão/métodos , Cor , Microbiologia de Alimentos , Extratos Vegetais/química , Própole/farmacologia , Ácido Sórbico/farmacologia
3.
Food Chem ; 299: 125116, 2019 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-31295637

RESUMO

The effects of exogenous melatonin treatment on the enzymatic browning and nutritional quality of fresh-cut pear fruit were investigated. Fresh-cut fruit soaked with 0, 0.05, 0.1 and 0.5 mM melatonin were stored at 4 °C. Our results showed that 0.1 mM melatonin treatment was optimal for reducing the surface browning and maintaining the titratable acidity of the fresh-cut fruit, which significantly decreased MDA and H2O2 contents and the growth of microorganism, enhanced total phenolic content and antioxidant capacity, and delayed the reduction of ascorbic acid. Furthermore, melatonin treatment at 0.1 mM decreased the expression of genes involving in enzymatic browning pathway including POD, PPO1, PPO5 and LOX1, and reduced PPO activity. Moreover, this treatment increased the expression of PAL and CHS, and enhanced PAL and CHS activities. These results showed that melatonin treatment might be a promising strategy to alleviate browning and improve the nutritional quality of fresh-cut pear fruit.


Assuntos
Frutas/efeitos dos fármacos , Melatonina/farmacologia , Valor Nutritivo , Pyrus/efeitos dos fármacos , Antioxidantes/análise , Antioxidantes/metabolismo , Ácido Ascórbico/análise , Ácido Ascórbico/metabolismo , Armazenamento de Alimentos , Frutas/química , Frutas/metabolismo , Frutas/microbiologia , Regulação da Expressão Gênica de Plantas/efeitos dos fármacos , Peróxido de Hidrogênio/análise , Peróxido de Hidrogênio/metabolismo , Malondialdeído/análise , Malondialdeído/metabolismo , Fenóis/análise , Pyrus/química , Pyrus/genética , Pyrus/metabolismo
4.
Food Chem ; 298: 125069, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31260991

RESUMO

The effects of ethanol treatment on quality characteristics of cherry tomatoes were investigated over 11 days of storage at room temperature (25 °C). Results showed that sensory quality was improved after ethanol treatment, with redder, softer fruits at the edible stage (11 days) compared with control fruit. In addition, the contents of ascorbic acid, sucrose and fructose were elevated after ethanol treatment as well as the concentration of 6-methyl-5-hepten-2-one. Conversely, decreased levels of methyl salicylate (MeSA), guaiacol, (Z)-3-hexenal and (E)-2-hexenal were observed. Selected consumers showed a preference for ethanol-treated cherry tomato fruits compared with controls. Taken together, 0.1% ethanol application has the potential to improve the quality characteristics of cherry tomatoes stored at room temperature.


Assuntos
Etanol/farmacologia , Lycopersicon esculentum/efeitos dos fármacos , Aldeídos/química , Ácido Ascórbico/análise , Cromatografia Líquida de Alta Pressão , Análise Discriminante , Aromatizantes/análise , Frutas/química , Frutas/efeitos dos fármacos , Frutas/metabolismo , Humanos , Análise dos Mínimos Quadrados , Lycopersicon esculentum/química , Lycopersicon esculentum/metabolismo , Salicilatos/química , Açúcares/análise , Temperatura Ambiente , Compostos Orgânicos Voláteis/análise , Compostos Orgânicos Voláteis/isolamento & purificação
5.
Food Chem ; 300: 125195, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31326676

RESUMO

Presence of pungent gingerols in ginger oleoresin makes it an ideal natural flavoring candidate for the food industry. The study reports its incorporation for synergistic enhancement of flavor and nutraceutical portfolio of candied mango. The process is systematically optimized at bench-scale for gingerols infusion and subsequent candying treatment in a range of hypo and hypertonic osmotic solutions for critical transport properties. After that, optimization of the drying process and the scale-up study was conducted with a 200 folds increase in the batch size. Collated effects of multistep optimization resulted in 85.6, 76.8, 60.2% retention in ß-carotene, total phenolics, Vitamin C, respectively, along with minor color difference and significant improvement in sensory scores over fresh mango. Mass transfer and quality parameters were comparable in both scales, implying excellent repeatability and scalability of the process. Compared with a similar commercial product, substantial improvement in quality characteristics along with 376.7% reduction in overall processing time was achieved.


Assuntos
Doces , Catecóis/química , Álcoois Graxos/química , Aromatizantes/química , Indústria de Processamento de Alimentos/métodos , Mangifera/química , Ácido Ascórbico/análise , Ácido Ascórbico/química , Cor , Dessecação/métodos , Suplementos Nutricionais/análise , Qualidade dos Alimentos , Frutas/química , Gengibre/química , Humanos , Fenóis/análise , Fenóis/química , Paladar , beta Caroteno/análise , beta Caroteno/química
6.
Plant Foods Hum Nutr ; 74(3): 334-341, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31175546

RESUMO

The aim of the study was to investigate the potential of using ß-glucan as wall material to microencapsulate the elderberry extract. Firstly, the extract was obtained by the water-acetone extraction method to extract mainly anthocyanins from ground dried fruits. The extract was mixed with wall materials: maltodextrin-ß-glucan mixture and the control sample as a widely used combination of maltodextrin and arabic gum (92.5:7.5). In the examined samples the content of ß-glucan was 0.5, 1, 2 and 3%. Properties of encapsulated extracts of final powders were measured using particle size and morphology, encapsulation efficiency, color measurement, total anthocyanin and ascorbic acid content (TAC and TAAC) methods. Our results indicated that the ß-glucan wall material samples had higher process quality compared to control samples. Addition of ß-glucan insignificantly decreases encapsulation efficiency. Among powders with ß-glucan content, the powder with 1% ß-glucan content was characterized by the smallest (24 µm) particle size. The sample with 2% ß-glucan content had the highest water solubility and polydispersity index. Due to the encapsulation efficiency, moisture content, and water solubility index, the optimum condition of microencapsulation process for elderberry extract was for samples with 0.5% ß-glucan as wall material content. To conclude, due to high molecular weight of ß-glucan the higher than 0.5% ratio of ß-glucan is not recommended for spray-drying method. However, small quantity of health-beneficial ß-glucan could act as potential encapsulation agent in clean label products to replace Arabic gum.


Assuntos
Antocianinas/análise , Ácido Ascórbico/análise , Composição de Medicamentos/métodos , Extratos Vegetais/química , Sambucus nigra/química , beta-Glucanas/química , Dessecação , Frutas/química , Goma Arábica/química , Tamanho da Partícula , Polissacarídeos/química , Pós , Solubilidade , Água/química
7.
Plant Foods Hum Nutr ; 74(3): 350-357, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31209702

RESUMO

Thirteen fruits, eight legumes and three tubers consumed in the Andean regions of Ecuador were studied to determine their bioactive compounds, organic acids, sugars content, total antioxidant capacity, as well as to determine which among them showed the greatest contribution in terms of antioxidant activity and which compounds contributed to it. Among fruits, taxo fruits (Passiflora mollissima (Kunth) L.H. Bailey) presented the highest values of total phenolic, carotene content, and total antioxidant capacity. The ají ratón (Capsicum chinense Jacq) showed the highest content of vitamin C. Taxo showed the highest content of ß carotene, whilst lycopene was identified only in guayaba fruits (Psidium guajava L.) and ají ratón was the principal source of lutein. In legumes, chocho perla (Lupinus mutabilis Sweet) showed the highest values for both total phenolic and flavonoid content, whilst frejol negro (Phaseolus vulgaris L.) and frejol canario (Vigna unguiculata (L.) Walp) showed the highest values for FRAP and DPPH assay, respectively. Between tubers, the jícama (Smallanthus sonchifolius (Poepp.) H. Rob.) had the majors values in terms of total phenolic, flavonoid content, and total antioxidant capacity. In terms of total antioxidant capacity, taxo fruits have the highest contribution in terms of total antioxidant capacity, whilst the dendogram shown the occurrence of five distinct groups in which taxo was located in the first largest group. Our data contributing towards gaining better knowledge about the Andean Ecuadorian diet and the composition of Andean food in order to estimate dietary intakes of health-promoting components.


Assuntos
Antioxidantes/análise , Asteraceae/química , Capsicum/química , Fabaceae/química , Promoção da Saúde , Passiflora/química , Ácido Ascórbico/análise , Carotenoides/análise , Equador , Flavonoides/análise , Frutas/química , Fenóis/análise , Compostos Fitoquímicos/análise , Tubérculos/química , beta Caroteno/análise
8.
Ultrason Sonochem ; 57: 108-115, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31208605

RESUMO

Efficiency of blue (462 ±â€¯3 nm) light emitting diode (LED) illumination to inactivate Escherichia coli and Staphylococcus aureus in the presence of exogenous photosensitizer (curcumin) was studied in freshly squeezed orange juice. Further, the combinational effect of ultrasound (US), photosensitizer (PS) and blue light (BL) on inactivation of microbes was evaluated. The effect of process parameters such as concentration of PS, US and volume of the juice on E. coli and S. aureus inactivation was also investigated. The US alone and PS + BL treatments resulted in 3.02 ±â€¯0.52 and 1.06 ±â€¯0.13 log reduction of E. coli; 0.18 ±â€¯0.14 and 2.34 ±â€¯0.13 log reduction of S. aureus, respectively. The combination of PS + US + BL treatment at optimized conditions resulted in 2.35 ±â€¯0.16 log reduction of S. aureus. An additive effect on the inactivation of E. coli (4.26 ±â€¯0.32 log reduction) was observed with PS + US + BL combination treatment. The US treatment showed significant change in cloud value, colour and browning index of orange juice. The combinational non-thermal processes (PS + BL and PS + US + BL) did not have any significant effect on total phenolic content, total flavonoid content, and hesperidin content of the orange juice. However, these processes affected ascorbic acid content and antioxidant activity negatively. Thus, this study indicated that photodynamic inactivation of E. coli and S. aureus using LED-based photosensitization in fruit juices could be a potential method for microbial inactivation. Nevertheless, the effect on quality parameters needs to be considered while optimizing the process.


Assuntos
Escherichia coli/efeitos dos fármacos , Escherichia coli/efeitos da radiação , Microbiologia de Alimentos , Sucos de Frutas e Vegetais/microbiologia , Luz , Fármacos Fotossensibilizantes/farmacologia , Staphylococcus aureus/efeitos dos fármacos , Staphylococcus aureus/efeitos da radiação , Ondas Ultrassônicas , Antioxidantes/análise , Ácido Ascórbico/análise , Contagem de Colônia Microbiana , Escherichia coli/isolamento & purificação , Flavonoides/análise , Sucos de Frutas e Vegetais/análise , Hesperidina/análise , Valor Nutritivo , Fenóis/análise , Espectrofotometria/métodos , Staphylococcus aureus/isolamento & purificação
9.
Food Chem Toxicol ; 131: 110594, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31226431

RESUMO

The phytochemical composition and the antioxidant and anti-inflammatory activities of a mixture of 23 plants, named Horchata, traditionally consumed in Ecuador, have been evaluated. The study was carried out using the hydroalcoholic extract (HHext) and infusion (IHext) of the horchata plant mixture. It was verified that thermal treatment affected the contents of vitamin C and carotenoids, but hardly those of polyphenols, which would be the main bioactive compounds in the infusion, the common form of preparation of horchata for consumption. Among phenolic compounds, caffeoylquinic acids, flavones and flavonols (mostly quercetin glycosides) were prominent. Both HHext and IHext extracts managed to protect RAW 264.7 macrophages against LPS-induced cytotoxic damage, increasing the levels of endogenous antioxidant enzymes and modulating the production of pro-inflammatory and anti-inflammatory cytokines. Greater protective effects were obtained for HHext compared to IHext, which was in agreement with its higher content of phenolic compounds favoured by a more efficient extraction in the hydroalcoholic medium. Nonetheless, the infusion still maintained a significant antioxidant and anti-inflammatory activity, which would support the protective effects on health traditionally attributed to its consumption by the population.


Assuntos
Anti-Inflamatórios/farmacologia , Antioxidantes/farmacologia , Extratos Vegetais/farmacologia , Animais , Anti-Inflamatórios/química , Anti-Inflamatórios/isolamento & purificação , Antioxidantes/química , Antioxidantes/isolamento & purificação , Ácido Ascórbico/análise , Biomarcadores/metabolismo , Carotenoides/análise , Equador , Inflamação/induzido quimicamente , Interleucina-10/metabolismo , Interleucina-6/metabolismo , Lipopolissacarídeos , Camundongos , Nitritos/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Extratos Vegetais/química , Extratos Vegetais/isolamento & purificação , Plantas Medicinais/química , Polifenóis/análise , Células RAW 264.7 , Temperatura Ambiente , Fator de Necrose Tumoral alfa/metabolismo
10.
Food Chem ; 293: 278-284, 2019 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-31151612

RESUMO

A headspace sampling-gas chromatography/mass spectrometry (HS-GC/MS) method using mild HS conditions (40 °C, 30 min) was established, validated in terms of specificity, linearity (1.75-87.65 ng mL-1), precision (0.3-9.1% RSD), and accuracy (81.1-117.7%); and applied for the monitoring of 900 commercial beverage samples of six different types. These mild (low-temperature) conditions were compared with 1) optimized (high-temperature) conditions and 2) a liquid-phase microextraction method involving no heat treatment. This method was desirable because a high equilibrium temperature induced artefactual benzene formation from benzoate and ascorbic acid. In a 2IV8-3 fractional factorial design, eight variables-ascorbic acid, benzoate, benzaldehyde, Cu2+, Fe2+, riboflavin, pyridoxine, and heat treatment-were tested as potential factors affecting benzene formation. All variables except Fe2+ and pyridoxine significantly affected benzene formation, both individually and interactively. The present study suggests an accurate and reliable method for benzene analysis and provides strategies to prevent unintentional benzene formation in beverages.


Assuntos
Benzeno/síntese química , Bebidas/análise , Cromatografia Gasosa-Espectrometria de Massas/métodos , Artefatos , Ácido Ascórbico/análise , Benzaldeídos/análise , Benzoatos/análise , Ácido Benzoico/análise , Cobre/análise , Compostos Ferrosos/análise , Temperatura Alta , Piridoxina/análise , Reprodutibilidade dos Testes , Riboflavina/análise , Microextração em Fase Sólida
11.
Food Chem ; 295: 530-536, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31174792

RESUMO

In this work, new detection route for ascorbic acid was designed. First, highly luminescent sulfur and nitrogen doped graphene quantum dots (S,N-GQDs) were prepared via simple hydrothermal method using citric acid and thiourea as the C, N and S sources respectively. The prepared S,N-GQDs are characterized by XRD, HRTEM, FTIR, EDS and PL. Investigations showed that prepared S,N-GQDs have a good photostability and excitation-dependent emission fluorescence. Prepared S,N-GQDs showed maximum excitation wavelength and emission wavelength at 400 and 462 nm, respectively. In the following, prepared S,N-GQDs were applied as a photoluminescence probe for detection of ascorbic acid (AA). The designed sensor was based on "off-on" detection mode. The developed sensor had a linear response to AA over a concentration range of 10-500 µM with a detection limit of 1.2 µM. The regression equation is Y = 0.0014 X + 1.2036, where Y and X denote the fluorescence peak intensity and AA concentration, respectively.


Assuntos
Ácido Ascórbico/análise , Grafite/química , Pontos Quânticos/química , Espectrometria de Fluorescência/métodos , Limite de Detecção , Nanoestruturas/química , Nitrogênio/química , Enxofre/química
12.
Food Chem ; 295: 172-179, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31174747

RESUMO

The effects of 10 and 20 days of fermentation followed by freeze-drying on the vitamin C and fatty acids contents, chemical conversions and overall chemical composition of Jerusalem artichoke were studied. Fermentation between the 10th and 20th days increased content of all saturated fatty acids and two of the four unsaturated fatty acids. The only fatty acid content that decreased was that of C18:1 cis 9 acid, which was suggested to be converted to other fatty acids. The experimental data, which were supported by energetical feasibility, suggested the reaction pathways of the mutual conversions of fatty acids and confirmed the decreased vitamin C content during fermentation. Discriminant modelling of the spectral data successfully distinguished the fresh, 10 days and 20 days fermented samples. The correlation of the spectral and reference data allowed to construct reference models for predicting the content of vitamin C and C18:1 cis 9 fatty acid.


Assuntos
Ácido Ascórbico/metabolismo , Ácidos Graxos/metabolismo , Helianthus/química , Silagem , Ácido Ascórbico/análise , Ácidos Graxos/análise , Fermentação , Análise de Alimentos/estatística & dados numéricos , Liofilização , Helianthus/metabolismo , Modelos Estatísticos , Silagem/análise , Espectrofotometria Infravermelho/estatística & dados numéricos
13.
Food Chem ; 297: 124954, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31253296

RESUMO

In this study, fruits of two nectarine cultivars, harvested at commercial ripeness, were sorted into three density groups. Physicochemical parameters (mean weight, firmness, dry matter, soluble solids content, titratable acidity) and the levels of sugars, organic acids, vitamin C, polyphenols and volatiles were then determined at harvest and after ripening. A sensory ranking test was also performed on ripened nectarines to compare quality attributes (firmness, sweetness, acidity, and aroma). In both cultivars, ripened nectarines of higher density had significantly higher levels of dry matter, soluble solids content, sugars, ascorbic acid, polyphenols and volatiles. Among polyphenols, the levels of hydroxycinnamic acids were 30-40% significantly higher in nectarines of higher density. Among volatiles, levels of lactones, well-known key aroma compounds in nectarines, were also 2-3 times significantly higher in ripened fruits of higher density. Consistent with these results, nectarines of higher density were significantly ranked sweeter and more aromatic in both cultivars.


Assuntos
Frutas/química , Prunus persica/química , Açúcares/análise , Compostos Orgânicos Voláteis/análise , Ácido Ascórbico/análise , Análise de Alimentos/métodos , Qualidade dos Alimentos , Frutas/fisiologia , Humanos , Odorantes/análise , Polifenóis/análise , Paladar
14.
Talanta ; 201: 295-300, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31122426

RESUMO

A novel single-walled carbon nanotubes array-modified glassy carbon electrode (SWCNTs array-GCE) has been fabricated through a simple electrochemical technique. Benefitting from their vertically aligned configuration on the electrode surface, the modified single-walled carbon nanotubes can be used more efficiently in comparison with other modified method. The as-fabricated SWCNTs array-GCE can separate the anodic oxidation potential of dopamine (DA), uric acid (UA) and ascorbic acid (AA) with well-defined peak separation in the presence of each other, and thus employs as a new electrochemical sensor for selective determination of DA and UA. It can make a further improvement of the electrocatalytic ability of the electrode to perform an acetone pretreatment to SWCNTs array-GCE before electrochemical detection, which has been confirmed by atomic force microscope and electrochemical impedance spectroscopic measurements. Especially, unlike other carbon nanotubes-based electrode at which only two redox pairs are observed for dopamine oxidations, a third two-electron oxidation of 5,6-dihydroxyindole to indole-5,6-quinone can be clearly observed at acetone-pretreated SWCNTs array-GCE, showing the excellent electrocatalytic performance of as-fabricated electrode toward dopamine. The practicability of SWCNTs array-GCE was evaluated for the selective detection of DA and UA in real sample solutions of human serum and urine. It revealed acceptable recovery results in the range of 94-104%, indicating that it might be a promising platform for further biosensor development.


Assuntos
Dopamina/sangue , Técnicas Eletroquímicas/métodos , Nanotubos de Carbono/química , Ácido Úrico/urina , Ácido Ascórbico/análise , Ácido Ascórbico/química , Dopamina/química , Técnicas Eletroquímicas/instrumentação , Eletrodos , Humanos , Indóis/química , Limite de Detecção , Oxirredução , Ácido Úrico/química
15.
Talanta ; 201: 388-396, 2019 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-31122439

RESUMO

Ascorbic acid (AA) is an essential vitamin and plays an irreplaceable role in humans' daily life. Therefore, it is of profound significance to develop effective strategies for AA sensing. Herein, a novel bi-functional sensing strategy was developed by using carbon dots (CDs) and MnO2 nanosheet as the fluorometric/magnetic signal source. When AA was absence, the fluorescence of CDs was quenched by MnO2 nanosheet due to the inner filter effect. Neither the fluorescence nor magnetic signal of the nanoprobe can be detected. In the presence of AA, a redox reaction occurred between MnO2 nanosheet and AA resulting in the generation of magnetic resonance imaging (MRI) response Mn2+ and decomposing of MnO2 nanosheet structure, thus leading to the recovery of CDs fluorescence. The detection limit of the AA was determined to be 2.89 µM with a linear range of 0-80 µM in fluorescence mode, and detection limit of 0.776 µM with a linear range of 0-80 µM in MRI mode when used transverse relaxation rate as signal. Furthermore, the developed fluorometric/magnetic bi-functional nanoprobe showed good biocompatibility, high response rate, high selectivity towards AA and could be used to analyses AA in real samples. Moreover, in vivo imaging of AA in mice was achieved in magnetic mode. The fluorometric/magnetic bi-function sensor for AA detection was introduced, which provided a novel strategy for sensor design based on CDs.


Assuntos
Ácido Ascórbico/análise , Corantes Fluorescentes/química , Imagem por Ressonância Magnética/métodos , Compostos de Manganês/química , Óxidos/química , Pontos Quânticos/química , Espectrometria de Fluorescência/métodos , Animais , Ácido Ascórbico/química , Ácido Ascórbico/metabolismo , Fluorescência , Corantes Fluorescentes/toxicidade , Limite de Detecção , Fenômenos Magnéticos , Masculino , Camundongos Endogâmicos BALB C , Oxirredução , Óxidos/toxicidade , Pontos Quânticos/toxicidade
16.
Talanta ; 200: 186-192, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31036172

RESUMO

In this work, different paper surface modification strategies were compared to obtain an amine functionalized SBA-15 (N-SBA-15) composite for paper-based device development. The synthesized N-SBA-15 was characterized by N2 adsorption-desorption isotherm, and infrared spectroscopy (FTIR), and it was incorporated to different polymer matrices (κ-carrageenan (CA), polyvinyl alcohol (PVA) and polyethylenimine (PEI)) for the development of the composite modified paper-based device. The retention, interactions, and morphology of the obtained composites were investigated by absorbance measurement, FTIR and scanning electron microscopy (SEM), respectively. To demonstrate the applicability of the modified paper-based device, ascorbic acid (AA) quantification was carried out. Horseradish peroxidase (HRP) was immobilized onto the modified paper surface. HRP in the presence of H2O2 catalyzes the oxidation of 10-acetyl-3,7-dyhidroxyphenoxazine (ADHP) to highly fluorescent resorufin, which was measured by LIF detector. Thus, when AA was added to the solution, it decreases the relative fluorescence signal proportionally to the AA concentration. The linear range from 50 nmol L-1 to 1500 nmol L-1 and a detection limit of 15 nmol L-1 were obtained for AA quantitation. The obtained results allowed us to conclude that N-SBA-15/PEI composite could be considered an excellent choice for the paper-based device modification procedure due to its inherent simplicity, low cost, and sensitivity.


Assuntos
Ácido Ascórbico/análise , Papel , Polímeros/química , Dióxido de Silício/química , Adsorção , Peroxidase do Rábano Silvestre/química , Peroxidase do Rábano Silvestre/metabolismo , Peróxido de Hidrogênio/química , Nitrogênio/química , Tamanho da Partícula , Dióxido de Silício/síntese química , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície
17.
Ultrason Sonochem ; 56: 240-253, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31101259

RESUMO

In considering the adverse nutritional and flavor consequences of thermal pasteurization on fruit juices, freshly squeezed and unpasteurized fruit juices, commonly called raw juices, are of increasing demand as they are served in bars, restaurants and at home. Apparently, due to lack of controlled processing regime as did in a juice factory, the raw juice often undergoes a rapid phase separation and is at the risk of microbial unsafety. To this end, an attempt of cold ultrasound treatment (CUT, 87.52 W/cm2, 10 °C) was implemented to a raw tomato juice up to 30 min. Appreciatively, the physical stability, nutritional value and microbial safety substantially improved. On a CUT time scale, cloud stability and total phenolic content continuously increased; the total plate count was adversely altered; the rheological parameters (viscosity, thixotropy and shear-thinning tendency) and total carotenoids obtained shared a parabolic changing pattern but peaked at 15 min and 10 min, respectively. Finally, the ascorbic acid sharply increased at an earlier stage (5 min), and then remained stable throughout the whole process. Notably, the occurrences of these improvements are of spatial-temporal nature and resulted from different cavitation induced stress fields. At the initial stage, CUT chiefly worked via the mechanical field with the particles in pulp phase, making them smaller and releasing the soluble materials into serum phase. When the particles larger than approximately of 160 µm were completely disintegrated, the CUT entered its second stage and mainly functioned in the serum phase via both mechanical and chemical fields. As a result, the serum pectin and carotenoids were depolymerized and degraded, respectively. The present results are valuable in uncovering the mechanism and kinetics underlying the ultrasound treatment of fruit juices and the present CUT is highly recommended due to its high maneuverability and excellent performance.


Assuntos
Temperatura Baixa , Qualidade dos Alimentos , Inocuidade dos Alimentos , Sucos de Frutas e Vegetais/análise , Lycopersicon esculentum/química , Sonicação/métodos , Paladar , Antioxidantes/análise , Ácido Ascórbico/análise , Carotenoides/análise , Sucos de Frutas e Vegetais/microbiologia , Fenóis/análise , Reologia , Análise Espaço-Temporal
18.
J Food Sci ; 84(6): 1340-1345, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-31112293

RESUMO

Barley sprouts and wheat sprouts have received much interest as functional foods in many countries. In this study, the effects of heat processing and extraction temperature on the bioactive components and antioxidative properties were examined in barley and wheat sprout teas. Both barley and wheat sprout teas were processed with two different methods (steaming or pan-roasting). Crude protein was increased, and moisture content was the lowest, in the roasted barley and wheat sprout teas. Total phenolics content and flavonoid contents were significantly higher in the roasted teas than in the steamed teas. Vitamin C content was the highest after an extraction temperature of 55 °C (24.05 mg/mL) in the roasted wheat sprout tea. Both roasted barley and wheat sprout teas exhibited the most antioxidative effects in vitro, demonstrated by 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging and nitrite-scavenging activities. Therefore, the roasting method can be considered an appropriate technique for the production of barley and wheat sprout teas. PRACTICAL APPLICATION: Barley and wheat sprouts have received much attention in recent years as functional food materials in many countries and can be consumed as a form of tea. Heat processing methods such as steaming and roasting were applied and compared to increase the bioactive components and antioxidative activity in barley and wheat sprout teas. We found that roasting showed higher bioactive components and antioxidative activity than steaming in both barley and wheat sprout teas. In addition, wheat sprouts tea showed better bioactive components and antioxidative activity compared with the barley sprout tea.


Assuntos
Antioxidantes/farmacologia , Bebidas/análise , Hordeum/química , Temperatura Alta , Extratos Vegetais/farmacologia , Plântula/química , Triticum/química , Antioxidantes/análise , Ácido Ascórbico/análise , Ácido Ascórbico/farmacologia , Compostos de Bifenilo/metabolismo , Culinária , Flavonoides/análise , Flavonoides/farmacologia , Humanos , Fenóis/análise , Fenóis/farmacologia , Picratos/metabolismo , Extratos Vegetais/química , Chá
19.
Talanta ; 200: 300-306, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31036188

RESUMO

In this work, the low-cost nitrogen-doped graphene-like mesoporous nanosheets (N-GMNs) was synthesized from the biomass waste of okara for the first time for the construction of a nonenzymatic amperometric vitamin C biosensor. The N-GMNs modified glassy carbon electrode (N-GMNs/GCE) shows much lower overpotential for the electrooxidation of vitamin C comparing to the traditional GCE as well as the GCE modified by carbon nanotubes (CNTs/GCE), indicating the promising of N-GMNs/GCE for the sensitive and selective nonenzymatic amperometric vitamin C biosensing. As a nonenzymatic amperometric biosensor for vitamin C, the N-GMNs/GCE shows a higher sensitivity (144.65 µA mM-1 cm-2), a wider linear range (10-5640 µmol L-1) and a lower detection limit (0.51 µmol L-1) than GCE, CNTs/GCE or some of recently reported nanomaterials-based electrochemical vitamin C biosensors. Especially, the vitamin C concentration in real samples of commercial beverage, vitamin C injection and commercial juice can be determined by the proposed N-GMNs/GCE with satisfied results. Therefore, the utilization of okara as the raw material for the synthesis of nanostructured carbon of N-GMNs is a green method to fabricate an advanced and low-cost electrode material for developing the nonenzymatic electrochemical biosensor for vitamin C detection.


Assuntos
Ácido Ascórbico/análise , Grafite/química , Nanoestruturas/química , Nitrogênio/química , Resíduos/análise , Biomassa , Técnicas Biossensoriais/economia , Técnicas Eletroquímicas/economia , Eletrodos , Grafite/economia , Nanoestruturas/economia , Nitrogênio/economia , Tamanho da Partícula , Porosidade , Propriedades de Superfície , Água/química
20.
J Sci Food Agric ; 99(12): 5541-5549, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31106435

RESUMO

BACKGROUND: The production of fruit and vegetables rich in health-promoting components in an eco-friendly context represents the winning answer to the world population demand for food. In this study, the effects of different treatments on the yield and fruit chemical characteristics of tomato (Solanum lycopersicum L.) are reported. The treatments included three inducers of plant defence responses (chitosan, Trichoderma harzianum T-22 and Bacillus subtilis QST713) applied alone or before Cucumber mosaic virus infection. Fruit production and antioxidant compounds were investigated by ultrahigh-performance liquid chromatography (UHPLC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). RESULTS: Compared to control fruit harvested from untreated and healthy plants, treatment with QST713 increased the fruit number. Furthermore, plant treatments with T22, QST713 and chitosan alone enhanced fruit carotenoids (lutein and ß-carotene), ascorbic acid and phenolic acids (caffeoyl glucoside and p-coumaroyl glucoside). In parallel, compared to fruit harvested from only CMV-infected plants, treatments with T22, QST713 and chitosan before CMV enhanced fruit ascorbic acid and flavonoids (quercetin 3-O-xylosyl-rutinoside and rutin). CONCLUSION: Antioxidant compounds of tomato fruit can increase with the application of the plant defence inducers, thus protecting both the consumer and plant health. © 2019 Society of Chemical Industry.


Assuntos
Antioxidantes/química , Cucumovirus/fisiologia , Lycopersicon esculentum/química , Lycopersicon esculentum/virologia , Doenças das Plantas/virologia , Inoculantes Agrícolas/fisiologia , Ácido Ascórbico/análise , Bacillus subtilis/fisiologia , Carotenoides/análise , Cromatografia Líquida , Frutas/química , Frutas/microbiologia , Frutas/virologia , Lycopersicon esculentum/microbiologia , Espectrometria de Massas em Tandem , Trichoderma/fisiologia
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA