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1.
J Agric Food Chem ; 67(37): 10401-10411, 2019 Sep 18.
Artigo em Inglês | MEDLINE | ID: mdl-31441654

RESUMO

This research applied inhibitors to reduce the content of cooked off-flavor components (dimethyl sulfide, dimethyl disulfide, dimethyl trisulfide, and 3-(methylthio)propanaldehyde) in heat-treated melon juice. The effects of glucose oxidase (GOD) on the formation and release of these four volatile sulfur compounds were also investigated. Results showed that GOD strongly inhibited the formation of the four compounds. In GOD-treated melon juice, S-methylmethionine was strongly protonated and not easily degraded into dimethyl sulfide. Moreover, the release of the dimethyl sulfide that did form was restrained by the hydrophobic interactions of gluconic acid and oxidation by hydrogen peroxide. In addition, gluconic acid (or glucose) and hydrogen peroxide could form a stable complex with methionine in an acidic matrix and thus prevented the methionine from producing 3-(methylthio)propanaldehyde, dimethyl disulfide, and dimethyl trisulfide by the Maillard reaction during heat processing.


Assuntos
Cucurbitaceae/química , Aromatizantes/química , Sucos de Frutas e Vegetais/análise , Culinária , Cucurbitaceae/enzimologia , Frutas/química , Frutas/enzimologia , Glucose Oxidase/química , Temperatura Alta , Humanos , Reação de Maillard , Odorantes/análise , Proteínas de Plantas/química , Compostos de Enxofre/química , Paladar
2.
J Agric Food Chem ; 67(31): 8599-8608, 2019 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-31287302

RESUMO

Because foods are perceived through combined inputs from taste and odor, which are determined by the concentration of the individual odor and taste molecules, the unified high-throughput quantitation of volatile odorants and non-volatile tastants with the very same instrumental setup has been a long-standing but yet unmet dream. The research presented here for the first time demonstrates, after only minimal sample workup, the highly accurate, rapid, and sensitive unified quantitation of odorants and tastants of key flavor molecules in apple juice on a single ultra-high-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) platform over a large dynamic range of up to 6 orders of magnitude. While flavor-active aldehydes, ketones, and organic acids were analyzed after derivatization with 3-nitrophenylhydrazine, taste-active polyphenols and odor-active esters were directly analyzed by means of UHPLC-MS/MS with and without target analyte enrichment through stir-bar sorptive extraction. This "unified flavor quantitation" approach holds promise to accelerate the transition of today's labor and time-consuming, low-throughput analysis of odorants and tastants into a new era of high-performance quantitation of key flavor molecules.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Aromatizantes/química , Ensaios de Triagem em Larga Escala/métodos , Odorantes/análise , Espectrometria de Massas em Tandem/métodos , Sucos de Frutas e Vegetais/análise , Malus/química , Compostos Orgânicos Voláteis/química
3.
J Chromatogr A ; 1602: 178-187, 2019 Sep 27.
Artigo em Inglês | MEDLINE | ID: mdl-31301797

RESUMO

A magnetic porous covalent triazine-based organic polymer (M-PCTP) was synthesized by co-precipitation method. The M-PCTP combined both the properties of the PCTP and the magnetism of Fe3O4 nanoparticles, possessing highly porous structure and good magnetism. It was used as a magnetic solid phase extraction (MSPE) adsorbent to extract carbamate pesticides (propoxur, carbaryl, isoprocarb, fenobcarb and diethofencarb) from lemonade and grape juice samples prior to high performance liquid chromatography-mass spectrometric detection. Under the optimal conditions, a good linearity for the real samples was received in the range from 0.10-0.90 to 80.00 ng mL-1 with the correlation coefficients of 0.9882-0.9983. The method recoveries for the five carbamates were 86.3-108.0%. The limits of detection were 0.02-0.20 ng mL-1 for lemonade sample, and 0.04-0.30 ng mL-1 for grape juice sample. The M-PCTP also demonstrated good extraction capabilities for other different kinds of organic compounds including chlorophenols and polycyclic aromatic hydrocarbons.


Assuntos
Carbamatos/isolamento & purificação , Cromatografia Líquida de Alta Pressão , Análise de Alimentos/métodos , Espectrometria de Massas , Praguicidas/análise , Extração em Fase Sólida , Sucos de Frutas e Vegetais/análise , Magnetismo , Hidrocarbonetos Policíclicos Aromáticos/análise , Polímeros/química , Porosidade
4.
J Agric Food Chem ; 67(33): 9344-9353, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31361957

RESUMO

Anthocyanins determine the color and potential health-promoting properties of red fruit juices, but the juices contain remarkably less anthocyanins than the fruits, which is partly caused by the interactions of anthocyanins with the residues of cell wall polysaccharides like pectin. In this study, pectin was modified by ultrasound and enzyme treatments to residues of polysaccharides and oligosaccharides widely differing in their molecular weight. Modifications decreased viscosity and degrees of acetylation and methylation and released smooth and hairy region fragments. Native and modified pectin induced different effects on the concentrations of individual anthocyanins after short-term and long-term incubation caused by both hydrophobic and hydrophilic interactions. Results indicate that both pectin and anthocyanin structure influence these interactions. Linear polymers generated by ultrasound formed insoluble anthocyanin complexes, whereas oligosaccharides produced by enzymes formed soluble complexes with protective properties. The structure of the anthocyanin aglycone apparently influenced interactions more than the sugar moiety.


Assuntos
Antocianinas/química , Beta vulgaris/química , Pectinas/química , Acetilação , Cor , Frutas/química , Sucos de Frutas e Vegetais/análise , Interações Hidrofóbicas e Hidrofílicas , Metilação , Peso Molecular , Ultrassom , Viscosidade
5.
Anal Chim Acta ; 1078: 182-188, 2019 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-31358218

RESUMO

Early detection of toxic proteases in food matrices plays a major role in preventing the occurrence of diseases as well as outbreaks. However, on-site detection of proteases, for instance, botulinum, anthrax and cholera in food matrices remains challenging due to their extremely low lethal dose levels. Here, we report a lateral flow assay (LFA) in a dipstick format for on-site visual detection of proteases in food matrices. The light chain of BoNT serotype A (BoNT/A LC) is used as a model system for validation of the proposed assay using magnetic beads conjugated to a synthetic peptide that provide a specific cleavage site for BoNT/A LC. Magnetic beads serve as both reporters for visual detection and as facilitators for sample clean-up, owing to the efficient magnetic separation protocol adopted. Digestion of the peptide substrate by BoNT/A LC for 5 h followed by the dipstick assay yields a reduction in color intensity of the test line on the dipstick compared to the control line obtained using an un-cleaved peptide substrate. Concentration dependent responses for the assay in carrot juice were obtained with a limit of detection (LOD) of 1 nM/2.5 nM (with/without amplification), also supported by RGB (ΔE) analysis, indicating the potential of the proposed methodology for on-site assaying of proteases in food matrices. Unlike typical affinity-based assays that yield a collective response for the active and inactive forms of the proteases, the proposed functional LFA targets only the active form, thereby enabling a more precise analysis for preventing potential false-positives. The proposed approach could be extended for detection of BoNT serotypes and other proteases in food matrices, upon utilizing appropriate substrates with specific cleavage sites.


Assuntos
Bioensaio/métodos , Toxinas Botulínicas Tipo A/análise , Sucos de Frutas e Vegetais/análise , Sequência de Aminoácidos , Anticorpos/imunologia , Toxinas Botulínicas Tipo A/química , Daucus carota/química , Limite de Detecção , Fenômenos Magnéticos , Peptídeos/química , Polietilenoglicóis/química , Estudo de Prova de Conceito , Estreptavidina/química
6.
Food Chem ; 298: 124971, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31260997

RESUMO

The BRS Violeta grape presents pulp and skin with high content of phenolic compounds (PCs) and intense purplish color. It was used as raw material for the production of juice and dehydrated products using foam mat drying at 60, 70 and 80 °C and freeze drying (control). HLPC-DAD-ESI-MSn allowed the evaluation of the quantitative and qualitative changes of the main PCs (anthocyanins, flavonols and hydroxycinnamic acid derivatives (HCAD)) present in the grapes during the processing. The use of the steam extraction method to obtain grape juice allowed a greater extraction of flavonols and, mainly derivatives of hydroxycinnamic acids, when compared with anthocyanins. Drying at 70 °C was the most suitable for the preservation of the PCs and, at the same time, for the reduction of the processing time. The powdered products presented considerable concentrations of total PCs (3-5 mg/g) and antioxidant activity (32-79 (DPPH) or 17-27 (FRAP) mg/g).


Assuntos
Antioxidantes/análise , Indústria de Processamento de Alimentos/métodos , Sucos de Frutas e Vegetais , Fenóis/análise , Vitis/química , Antocianinas/análise , Cromatografia Líquida de Alta Pressão , Cor , Ácidos Cumáricos/análise , Flavonóis/análise , Liofilização , Sucos de Frutas e Vegetais/análise , Pós , Espectrometria de Massas por Ionização por Electrospray , Temperatura Ambiente
7.
Food Chem ; 300: 125178, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31326677

RESUMO

In this work, a sensitive and stable ZrO2-Cu(I) nanosphere mesoporous material modified non-enzymatic glucose sensor has been developed through simple, low cost chemistry. ZrO2-Cu(I) material was obtained by controlled co-precipitation method under ultra dilution conditions. Cyclic voltammetric tests were performed in order to evaluate the electrocatalytic activity ZrO2-Cu(I) modified electrode. The modified electrode showed high sensitivity, wide linear range and very low detection limit of 0.25 mM, this indicates that the modified sensor is competent with that reported earlier. Spherical morphology of the active material, alkaline environment and presence of +1 copper have significantly enhanced the electro-catalytic oxidation of glucose on carbon paste platform. Also, the fabricated electrode showed excellent anti-interference nature. Electro-catalytic oxidation of glucose was demonstrated in real raw unpurified orange juice, this shows the selective electrocatalytic activity of the ZrO2-Cu(I) nanosphere material towards glucose even in the presence of interferrants.


Assuntos
Citrus sinensis/química , Técnicas Eletroquímicas/instrumentação , Técnicas Eletroquímicas/métodos , Eletrodos , Glucose/análise , Carbono/química , Catálise , Cobre/química , Análise de Alimentos/instrumentação , Análise de Alimentos/métodos , Sucos de Frutas e Vegetais/análise , Glucose/química , Limite de Detecção , Nanosferas/química , Oxirredução , Zircônio/química
8.
Food Chem ; 300: 125168, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31330368

RESUMO

This study reports a clear-cut relationship of the technological use of specific filter aids with highly variable vanadium levels in beer, wine, and fruit juices. First, the previously reported broad range of vanadium levels was confirmed in 68 commercial beverages by ICP-MS. Since cloudy apple juices exhibited significantly lower vanadium amounts than clear apple juices, filter aids used for clarification were analyzed and found to contain substantial and highly variable amounts of vanadium, particularly in all analyzed diatomite (38-368 mg vanadium per kg filter aid), but not in perlite products (<4 mg/kg). Subsequent pilot-scale precoat filtration experiments (170 L/batch) proved vanadium to be released from diatomite (Kieselguhr), increasing its levels from ca. 2.1-2.6 µg/kg unfiltered to 27-201 µg/kg filtered juice, depending on the use of diatomites high or low in vanadium. Thus, filter aid selection was shown to modulate the vanadium concentrations in clarified beverages.


Assuntos
Bebidas/análise , Filtração/instrumentação , Vanádio/análise , Óxido de Alumínio , Cerveja/análise , Terra de Diatomáceas/análise , Terra de Diatomáceas/química , Filtração/métodos , Contaminação de Alimentos/análise , Sucos de Frutas e Vegetais/análise , Malus , Dióxido de Silício , Vinho/análise
9.
J Sci Food Agric ; 99(13): 5953-5961, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31215031

RESUMO

BACKGROUND: The development of rapid methods for the determination of the soluble solids content (SSC) and total phenolic content (TPC) in fruit juices is of great interest. Soluble solids content is related to sensory attributes, whereas TPC is related to the antioxidant capacity of juices. The aim of this study was to develop and optimize the calibration models for the prediction of the SSC and TPC of strawberry juices from the spectra of fruit and juices. RESULTS: Near infrared (NIR) spectra were measured for strawberry fruit and ultraviolet (UV), visible (VIS), and NIR spectra were measured for juices. The partial least squares regression models were validated using the test sample set and their predictive ability was evaluated on the basis of determination coefficients (R2 P ) and root mean square error of prediction (RMSEP). For SSC the models with high predictive ability were obtained using spectra of fruit (R2 P = 0.929, RMSEP = 0.46%) or juices (R2 P = 0.979, RMSEP = 0.25%) in the NIR range. The optimal models for TPC were obtained using NIR spectra of fruit (R2 P = 0.834, RMSEP = 130.8 mg GA L-1 ) or UV-VIS-NIR spectra of juices (R2 P = 0.844, RMSEP = 126.7 mg GA L-1 ). CONCLUSION: The results show the potential of spectroscopy for predicting quality parameters of strawberry juices from the juice spectra itself or non-destructively from the fruit spectra. They may contribute to the development of fruit sorting systems to optimize their use in juice production, as well as fast-screening methods for quality control of juices. © 2019 Society of Chemical Industry.


Assuntos
Fragaria/química , Sucos de Frutas e Vegetais/análise , Espectrofotometria/métodos , Espectroscopia de Luz Próxima ao Infravermelho/métodos , Calibragem , Frutas/química , Análise dos Mínimos Quadrados , Controle de Qualidade
10.
J Sci Food Agric ; 99(13): 5994-6000, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31215047

RESUMO

BACKGROUND: Dynamic high-pressure microfluidization (DHPM) is an emerging and promising technique for continuous production of fluid foods. This study aimed to investigate the influence of DHPM and conventional homogenization (CH) on the quality of peach juice. Processing was performed by passing peach juice through CH at 20 MPa and DHPM at 20-160 MPa for one or three passes. The effect of DHPM pressure and passing number were also assessed. RESULTS: The results indicate that DHPM could maintain the antioxidant activity of peach juice much better than CH processing. Total phenolic compounds were decreased by 11.7% and 7.9%-15.8% through CH and DHPM processing in different conditions. Moreover, particle size, non-enzymatic browning index and turbidity decreased significantly under DHPM and CH processing, and decreased more and more with the increasing of DHPM pressure and treatment times. However, vitamin C content and zeta-potential did not reveal remarkable variation before and after these two types of processing. CONCLUSION: Taken together, DHPM is able to maintain the quality and stability of peach juice, which can be a reliable technological alternative to CH to produce fresh-like peach juices. © 2019 Society of Chemical Industry.


Assuntos
Manipulação de Alimentos/métodos , Sucos de Frutas e Vegetais/análise , Preparações de Plantas/química , Prunus persica/química , Manipulação de Alimentos/instrumentação , Fenóis/química , Pressão
11.
Plant Foods Hum Nutr ; 74(3): 383-390, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31228035

RESUMO

Orange juice is an important source of flavanones in the Western diet. However, little is known of the variation in flavanone content of shop-bought orange juice with pulp (OJP) or without pulp (OJ), nor the impact of pulp on the fate of flavanones in the gut. Total phenols, total flavonoids, antioxidant capacity, hesperidin and narirutin, and dietary fibre were measured in six orange juice brands sold as OJP and OJ. The inclusion of pulp had little impact on fibre content. Apart from total phenols (OJ: 208.4 ± 10.7 µg gallic acid equivalents (GAE) ml-1; OJP: 225.9 ± 16.7 µg GAE ml-1, P < 0.05), there were no differences between OJ and OJP. The fate of flavanones in OJ and OJP (Tropicana) were further compared using in vitro gastrointestinal (GI) models. After in vitro upper GI digestion, recovery of hesperidin was higher in OJ compared with OJP (89 ± 6 vs. 68 ± 3%, P = 0.033). After 2 h colonic fermentation, hesperidin was 1.2 fold higher in OJP than OJ. However, after 24 h colonic fermentation there was no significant difference between juices in terms of hesperidin, hesperetin, narirutin, naringenin and catabolites. In conclusion, the amount of pulp included in these shop-bought orange juices had little impact on flavanone metabolism in models of the GI tract. The effects of greater amounts of orange pulp remain to be determined.


Assuntos
Antioxidantes/análise , Citrus sinensis/química , Flavanonas/análise , Flavonoides/análise , Sucos de Frutas e Vegetais/análise , Fenóis/análise , Bactérias/metabolismo , Fibras na Dieta/análise , Digestão , Dissacarídeos/análise , Fermentação , Flavanonas/metabolismo , Trato Gastrointestinal/metabolismo , Trato Gastrointestinal/microbiologia , Hesperidina/análise , Humanos
12.
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
13.
Ultrason Sonochem ; 57: 73-88, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31208621

RESUMO

Recently, ultrasound has been widely used in the researches in the food science and technology. Among the food materials, fruits, juices and dairy products are strongly sensitive to ultrasound-based techniques. In this review paper, applications of ultrasound in terms of high and low-power modes in processing, instrumentation and control of the industrial operations are studied in the fruit, juice and dairy sectors of the food science and technology by emphasizing the principles of these techniques and their physicochemical effects on the products. Also, a comprehensive analysis of these methods and important factors influencing their performance are presented, along with the advantages and the drawbacks of each ultrasound-assisted techniques. The solutions for better productivity of this technique would be presented and future trend of this technology would be outlined. By studying the latest researches and advances in the field of ultrasound applications, it has been confirmed that this technique can be helpful in accelerating processes, reducing energy requirements, increasing productivity, and producing better quality food materials in the fields of fruits, juices and dairy products. Notwithstanding, in order to solve the challenges ahead, and for potential applications of ultrasound technology, further researches need to be expanded in the areas mentioned. Also, with the advancement of technology, more advanced equipment, ultrasound transducers and instrumentations would be introduced that needs to be applied in this regard, to solve the current challenges.


Assuntos
Laticínios/análise , Análise de Alimentos/métodos , Manipulação de Alimentos/métodos , Indústria Alimentícia/organização & administração , Sucos de Frutas e Vegetais/análise , Frutas/química , Controle de Qualidade , Ondas Ultrassônicas , Antioxidantes/análise , Fenóis/análise , Proteínas de Plantas/análise
14.
Food Chem ; 293: 144-150, 2019 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-31151594

RESUMO

Nobiletin, a polymethoxyflavone mainly found in citrus fruits, have been reported to exhibit various beneficial biological activities for human health. It is an important bioactive compound in traditional Chinese medicine, Pericarpium Citri Reticulatae and Fructus Aurantii. To detect the contents of nobiletin in citrus and herb samples, we developed an indirect competitive enzyme-linked immunosorbent assay (icELISA) based on monoclonal antibodies. It possessed a median inhibition concentration (IC50) of 2.43 ±â€¯0.19 ng/mL and a working range of 0.52-12.3 ng/mL. The assay exhibited the average recoveries of 72.5-85.3% in citrus peel, pulp and juice samples. Moreover, eleven citrus cultivars samples and four herb samples were also detected by the icELISA. The nobiletin content varied in different citrus cultivars samples and herb samples, which were confirmed by the ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS). These results indicated that the developed immunoassay was suitable for detecting nobiletin in citrus and herb samples.


Assuntos
Citrus/química , Flavonas/análise , Anticorpos Monoclonais/imunologia , Citrus/metabolismo , Ensaio de Imunoadsorção Enzimática , Flavonas/química , Flavonas/imunologia , Frutas/química , Frutas/metabolismo , Sucos de Frutas e Vegetais/análise , Haptenos/química , Haptenos/imunologia , Medicina Tradicional Chinesa
15.
Food Chem ; 293: 151-160, 2019 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-31151596

RESUMO

Blackcurrant juices were prepared without enzyme (NEB-juice) and with conventional enzyme-aided berry pressing (EB-juice). Juices were pasteurized and stored at ambient temperature (in light and dark conditions) and at +4 °C for a 1-year period of time. Volatile composition and odor attributes were followed by HS-SPME-GC-MS and a sensory panel, respectively. Volatiles were decreased in the EB-juice, showing 100-fold lower contents of the main terpenoids, e.g., α-pinene, δ-3-carene, limonene, terpinolene, bornyl acetate and ß-caryophyllene; whereas esters, such as methyl butanoate and ethyl butanoate, showed 2- and 4-fold lower contents for the EB-juice. Pasteurization produced minor changes in both juices. Volatiles decreased during storage at room temperature while at +4 °C esters and eucalyptol were kept at 100%. The descriptive sensory analysis reported a significant decrease (p < 0.05) of the berry-like odor after 12-month storage at RT. Storage at +4 °C for 12 months did not affect the odor quality.


Assuntos
Sucos de Frutas e Vegetais/análise , Ribes/química , Compostos Orgânicos Voláteis/análise , Manipulação de Alimentos , Cromatografia Gasosa-Espectrometria de Massas , Humanos , Odorantes/análise , Pasteurização , Ribes/metabolismo , Microextração em Fase Sólida , Temperatura Ambiente , Terpenos/análise , Compostos Orgânicos Voláteis/isolamento & purificação
16.
Food Chem ; 293: 220-225, 2019 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-31151604

RESUMO

This study was conducted for quantitative determination of quercetin in food and fruit juice samples based on a green, fast, and accurate method namely, micro-cloud point extraction (MCPE). The proposed MCPE is essentially a miniaturized form of traditional cloud point extraction (CPE) in which only a few microliters of micellar extracting phase is sufficient for determination. Factors influencing the extraction efficiency, such as amount of Triton X-114 (5%, v/v), effect of pH, amount of Na2SO4 salt (5%, w/v) and time of centrifugation were investigated and optimized by experimental design. Under the optimized condition, the calibration range was found to be linear over 10-100 ng mL-1 with the limit of detection of 2.2 ng mL-1. The relative standard deviation of 2.8%, was obtained on a 30 ng mL-1quercetin standard solution (n = 3). Finally, the proposed method was successfully applied for the determination of quercetin in onion, tomato, apple and orange juice samples.


Assuntos
Análise de Alimentos/métodos , Sucos de Frutas e Vegetais/análise , Quercetina/análise , Calibragem , Centrifugação , Fracionamento Químico , Concentração de Íons de Hidrogênio , Limite de Detecção , Lycopersicon esculentum/química , Lycopersicon esculentum/metabolismo , Cebolas/química , Cebolas/metabolismo , Polietilenoglicóis/química , Quercetina/isolamento & purificação , Espectrofotometria/normas
17.
Anal Bioanal Chem ; 411(20): 5023-5031, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31177332

RESUMO

A simple method to determine hazardous silver nanoparticles (AgNPs) based on ionic liquid (IL) dispersive liquid-liquid microextraction and back-extraction is described. This approach involves AgNP stabilization using a cationic surfactant followed by extraction from the sample matrix by means of an IL as an extraction phase. Certain ILs have high affinity for metals, and preliminary experiments showed that those ILs consisting of imidazolium cation efficiently extracted AgNPs in the presence of a cationic surfactant and a chelating agent. Afterward, histamine was used as a dispersing agent to promote phase transfer of differently coated AgNPs from the IL in aqueous solution to be subsequently analyzed by UV-visible spectrometry. The analytical procedure allows AgNPs to be recovered from the sample matrix in an aqueous medium, the enrichment factor being up to 4, preserving both AgNP size and AgNP shape as demonstrated by transmission electron microscopy images and the localized surface plasmon resonance band characteristic of each AgNP. The present method exhibited a linear response for AgNPs in the range from 3 to 20 µg/mL, the limit of detection being 0.15 µg/mL. Method efficiency was assessed in spiked orange juice and face cream, yielding recoveries ranging from 75.7% to 96.6%. The method was evaluated in the presence of other nanointerferents (namely, gold nanoparticles). On the basis of diverse electrophoretic mobilities and surface plasmon resonance bands for metal nanoparticles, capillary electrophoresis was used to prove the lack of interaction of the target AgNPs with gold nanoparticles during the whole protocol; thus, interferents do not affect AgNP determination. As a consequence, the analytical approach described has great potential for the analysis of engineered nanosilver in consumer products. Graphical abstract Simple protocol for the determination of silver nanoparticles (AgNPs) based on dispersive liquid-liquid extraction with a specific short alkyl side chain ionic liquid and their quantitative detection with a UV-visible spectrometer. HMIM•PF6 1-hexyl-3-methylimidazolium hexafluorophosphate, NP nanoparticle, SPR surface plasmon resonance.


Assuntos
Cosméticos/química , Sucos de Frutas e Vegetais/análise , Líquidos Iônicos/química , Microextração em Fase Líquida/métodos , Nanopartículas Metálicas/análise , Prata/química , Artefatos , Estudos de Viabilidade , Limite de Detecção , Nanopartículas Metálicas/química , Espectrofotometria Ultravioleta/métodos , Ressonância de Plasmônio de Superfície
18.
Food Chem ; 297: 124930, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31253279

RESUMO

A new microfluidic chemiluminescence (MF-CL) method for rapidly assaying the total antioxidant capacity (TAC) of apple and pomegranate juices and honey samples was developed. The method exploited the NaHCO3-H2O2-Co2+ CL reaction. It was found that gallic acid (GA), catechin, caffeic acid, ferulic acid and rutin, as selected phenolic antioxidants, could suppress the CL reaction. The linear range and limit of detection of the method for the antioxidants were as follows: 0.5-3 mg L-1 and 0.27 mg L-1 for GA, 0.2-5.0 mg L-1 and 0.17 mg L-1 for catechin, 0.03-2.0 mg L-1 and 0.03 mg L-1 for caffeic acid, 0.3-2.0 mg L-1 and 0.23 mg L-1 for ferulic acid and 0.3-4.0 mg L-1 and 0.15 mg L-1 for rutin. GA was used as the standard, and the TAC of the fruit juices and honey samples as presented as GA equivalents (GAE). MF-CL was compared with DPPH and Folin-Ciocalteau (FC) methods.


Assuntos
Antioxidantes/química , Sucos de Frutas e Vegetais/análise , Mel/análise , Dispositivos Lab-On-A-Chip , Medições Luminescentes/métodos , Cobalto/química , Ácido Gálico/química , Peróxido de Hidrogênio/química , Medições Luminescentes/instrumentação , Bicarbonato de Sódio/química
19.
Int. j. cardiovasc. sci. (Impr.) ; 32(3): 238-246, May-June 2019. graf
Artigo em Inglês | LILACS | ID: biblio-1002226

RESUMO

Grapes and its derivatives (wines and juices) are rich in polyphenols that have high antioxidant and vasodilator capacity. These biological activities may vary in the juices marketed and produced in different regions of Brazil. Objectives: To determine the antioxidant and vasorelaxant effects of grape juice samples produced in different regions of Brazil. Methods: The content of phenolic compounds and antioxidant capacity were evaluated by the methods of Folin-Ciocalteau, DPPH, ABTS and a new electroanalytical approach (differential pulse voltammetry - DPV). Vasodilator effects were analyzed in isolated aorta from rats in an organ bath. Results: The samples from RJ and SP presented respectively the higher and lower phenolic content and also antioxidant capacity by the methods used (ABTS and DPPH). The results of the electrochemical index corroborate to the other tests, with the best results to RJ (21.69 ± 3.15 µA/V) and worse to the SP sample (11.30 ± 0.52 µA/V). In the vascular reactivity studies, the relaxation induced by each sample presented more distinct differences, following the order: RJ (87.9 ± 4.8%) > RS1 (71.6 ± 8.6%) > GO (56.2 ± 7.2%) > SP (39.9 ± 7.8%) > PR (39.4 ± 9.5%) > RS2 (19.5 ± 6.2%). Inhibition of endothelial NO practically abolished (p < 0.001) the relaxation for all samples, except one. Conclusion: The phenolic content and antioxidant capacity vary greatly among samples. The results obtained for the order of antioxidant activity were: RJ > RS1 > GO > RS2 > PR > SP. The juices were able to induce vascular relaxation at quite varied levels, and the RJ sample the most effective. The L-NAME practically blocked all samples except one (RS2)


Assuntos
Animais , Ratos , Vasodilatação , Vasodilatadores/análise , Brasil/epidemiologia , Vitis , Antioxidantes/farmacologia , Doenças Cardiovasculares/prevenção & controle , Análise de Variância , Ratos Wistar , Modelos Animais , Células Endoteliais , Técnicas Eletroquímicas , Polifenóis , Sucos de Frutas e Vegetais/análise , Hipertensão , Neoplasias/prevenção & controle
20.
Food Chem ; 295: 637-645, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31174806

RESUMO

Sauvignon blanc grape samples (n = 21) from across a single Geographical Indication of South Australia were analysed for thiol precursors and amino acids, and fermented in an identical laboratory-scale fermentation trial to investigate the intraregional pattern of varietal thiols in the wines. Precursors and thiols exhibited obvious intraregional diversity, and notably, stronger correlations were observed between a number of amino acids and thiol precursors (especially with glutamic acid, r ≤ -0.73) rather than free thiols. Additionally, pre-fermentation freezing (-20 °C, 1 month) was applied to five selected fresh grape samples and their juices, followed by identical fermentation. In comparison to wines from fresh grapes or frozen juices, significant elevation of varietal thiols (up to 10-fold) occurred in the wines derived from frozen grapes, with parallel increases of precursors (up to 19-fold) in juices from frozen berries. These novel results may lead to new strategies for thiol enhancement during winemaking.


Assuntos
Aminoácidos/análise , Compostos de Sulfidrila/análise , Vitis/química , Vinho/análise , Diamino Aminoácidos/análise , Cromatografia Líquida de Alta Pressão , Congelamento , Sucos de Frutas e Vegetais/análise , Análise de Componente Principal , Austrália do Sul , Espectrometria de Massas em Tandem , Vitis/metabolismo
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