Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 5.003
Filtrar
1.
Int J Prosthodont ; 33(1): 99-104, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31860919

RESUMO

PURPOSE: To establish a complete digital workflow for the design and manufacture of sports mouthguards and to observe preliminary clinical effects. MATERIALS AND METHODS: Eighteen healthy participants were included in this study. The self-controlled method was applied, and all participants were provided with two types of mouthguards. Digital mouthguards were designed and milled using CAD/CAM with polyetheretherketone, and conventional mouthguards were fabricated using the vacuum pressure-forming method with ethylene vinyl acetate. The order of wearing was determined using a random number table, and the washout period between was set as 1 month. Degrees of satisfaction in terms of retention, appearance, occlusal comfort, and labial comfort were evaluated. Distribution of occlusal force was tested using the T-scan analysis system. Participants were also asked to choose one mouthguard for future use. RESULTS: The complete workflow of digitally designed and manufactured sports mouthguards was successfully established. No significant difference was noted in retention between the types of mouthguard. The appearance score (P = .025), occlusal comfort score (P = .030), and labial side comfort score (P = .003) of the digital mouthguard group were significantly higher compared to the conventional mouthguard group. T-scan analysis results showed that in centric occlusion, participants exhibited occlusal contact in the second molar alone while wearing conventional mouthguards, while the occlusal force was uniformly distributed with digital mouthguards. Sixteen participants selected the digital mouthguard for future use. CONCLUSION: Digital design and manufacture of sports mouthguards improved the occlusal design and greatly simplified and optimized the conventional fabrication process.


Assuntos
Protetores Bucais , Esportes , Desenho de Equipamento , Vácuo , Fluxo de Trabalho
2.
Food Chem ; 308: 125570, 2020 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-31648089

RESUMO

The effect of pre-treatment (dipping and vacuum impregnation in lemon juice solution), freezing and frozen storage (FS) on single and total polyphenols (free and conjugated) content and antioxidant activity (AOA) of organic and conventional apples, was investigated. Fresh organic and conventional fruits showed different profiles of free and conjugated polyphenols while their total phenolic content and AOA were similar. Organic and conventional apple tissues showed different physiological responses to physical stresses described by changes in phenolic profiles. Vacuum impregnation in lemon juice affected the polyphenols extractability of both the organic and conventional apples and favored their enrichment with bioactive compounds (AOA = +11.5%). FS decreased the single and conjugated polyphenols content of the pre-treated apple samples and the effect was different between organic and conventional fruits. After FS, not pre-treated organic apples showed a lower AOA reduction than the conventional ones (-13% vs -25%), while no differences were found on pre-treated samples.


Assuntos
Antioxidantes/análise , Malus/química , Polifenóis/análise , Citrus/química , Alimentos Orgânicos/análise , Congelamento , Frutas/química , Sucos de Frutas e Vegetais , Vácuo
3.
J Sci Food Agric ; 100(1): 102-109, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31436308

RESUMO

BACKGROUND: The combination of sugar osmotic dehydration and microwave vacuum drying is an effective method for the dehydration of blackberries, the retention of their antioxidant properties, and the extension of their shelf life. Mass transfer during the osmotic dehydration of blackberries in sugar solution was investigated together with its influence on microwave vacuum drying characteristics, and the retention rate of anthocyanins in dried frozen blackberries. RESULTS: The concentrations of the osmotic solutions that were tested contained 40%, 50%, and 60% sugar, and the osmotic solution temperatures were 30 °C, 40 °C, and 50 °C. The solution-to-blackberry mass ratio was 10:1 (w/w) and the process duration varied from 0 to 5 h. A two-parameter mathematical model was used to describe mass transfer in the osmotic dehydration of blackberry samples and estimate moisture loss and solid gain in the final equilibrium. The results showed that the dehydration rate and solid gain rate of the blackberries increased with an increase in osmotic concentration, osmotic time, and the temperature of the solution under certain experimental conditions. The effective diffusivity of moisture and solute were estimated using the analytical solution of Fick's second law of diffusion. The moisture and effective diffusivities of sugar in the above osmotic dehydration conditions were in the range of 1.77 × 10-9 -2.10 × 10-9 and 1.36 × 10-9 -1.60 × 10-9 m2 .s-1 , respectively. CONCLUSION: The pretreatment of sugar osmosis greatly reduced the microwave vacuum drying time in the latter part of the dehydration period and increased anthocyanin retention. © 2019 Society of Chemical Industry.


Assuntos
Antocianinas/química , Dessecação/métodos , Manipulação de Alimentos/métodos , Rubus/química , Dessecação/instrumentação , Manipulação de Alimentos/instrumentação , Frutas/química , Micro-Ondas , Osmose , Temperatura Ambiente , Vácuo , Água/análise
4.
Food Chem ; 306: 125625, 2020 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-31606635

RESUMO

A novel ultrasonic-assisted vacuum drying technique for dehydrating garlic slices to give high quality products was developed. Garlic slices were dried at 60 °C using four methods: ultrasonic-assisted vacuum drying (USVD), vacuum drying (VD), ultrasonic-assisted drying (USD), and convective drying (CD, the control with no vacuum or ultrasonic applied). Drying kinetics, water-content changes, and properties of the garlic slices were assessed. Univariate linear and partial-least-squares regression models were used to predict the properties from low-field nuclear magnetic resonance parameters. USVD gave the shortest drying time (180 min less than CD) and provided a better garlic color and texture, and allicin retention rate than the other methods. Higher correlations between low-field nuclear magnetic resonance parameters and quality properties were found by partial-least-squares regression (PLSR) than by univariate analysis, with the analysis results being credible. Overall, ultrasonic-assisted vacuum drying produced high-quality products with its properties predicted well by low-field nuclear magnetic resonance.


Assuntos
Dessecação/métodos , Alho/química , Ultrassom , Cor , Cinética , Espectroscopia de Ressonância Magnética , Vácuo
5.
Biochemistry (Mosc) ; 84(9): 1107-1115, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31693470

RESUMO

Using absorption spectroscopy in the visible/near-IR and mid-IR regions, spectral and photochemical properties of isolated reaction centers (RCs) from Rhodobacter sphaeroides R-26 were studied in dried films on the inorganic support surface (quartz or CaF2 plates) under vacuum dehydration conditions (10-2 or 7·10-5 mm Hg). Three detergents, N,N-dimethyldodecylamine N-oxide (LDAO), Triton X-100 (TX100), and n-dodecyl-ß-D-maltoside (DM), were tested for their ability to stabilize the RC-detergent complexes in the vacuum-dried state. It was shown that in the presence of LDAO, RC complexes underwent destruction in vacuum. In contrast, DM provided an environment that minimized irreversible disruptive changes in the RCs in vacuum. The effects of vacuum dehydration on the RC-DM films included a small increase in the content of α-helices in the RC protein, a short-wavelength reversible shift in the optical transitions of pigments, and minor changes in the electronic structure of the P+ dimer. The films retained their photochemical activity upon excitation with high-intensity light (200 mW/cm2). TX100 also helped to maintain spectral and functional properties of the RCs in vacuum; however, in this case, the stabilizing effect was less pronounced than in the presence of DM, especially, at high detergent concentrations. The results are discussed within the framework of a model suggesting that the detergent-protein interactions and the properties of detergent micelles play a dominant role in maintaining the structure of the RCs upon vacuum dehydration of the RC complexes. The obtained data can be useful for developing hybrid photoconverting systems based on bacterial RCs.


Assuntos
Complexo de Proteínas do Centro de Reação Fotossintética/metabolismo , Rhodobacter sphaeroides/metabolismo , Vácuo , Processos Fotoquímicos , Rhodobacter sphaeroides/isolamento & purificação , Espectrofotometria Ultravioleta , Espectroscopia de Infravermelho com Transformada de Fourier , Propriedades de Superfície
7.
J Contemp Dent Pract ; 20(7): 857-862, 2019 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-31597809

RESUMO

AIM: The aim of this article is to provide an insight into the various modalities of retention and types of appliance used in achieving this objective. BACKGROUND: Maintaining the orthodontically treated teeth in their corrected position is a challenging and ominous task since the inception of this specialty. Orthodontic retainers play a pivotal role in preventing posttreatment tooth movement, thereby maintaining the esthetic, function, and stability of the stomatognathic system. RESULTS: An extensive study of literature suggests that there are significant variations in the results describing the effectiveness, cost factors, survival times, oral hygiene status, and regimen of various orthodontic retention appliances. In terms of patient's satisfaction and speech articulation, vacuum-formed retainers (VFRs) are better than Hawley retainers. Occlusal contacts are better achieved with Hawley retainers than VFRs. CONCLUSION: Currently, there is insufficient high-quality evidence in favor of a particular retention appliance/regime or protocol. There is a need for further evidence-based high-quality studies/randomize controlled trial studies (RCTs) to evaluate different orthodontic retention appliances and regime after the orthodontic treatment. CLINICAL SIGNIFICANCE: Irrespective of the appliance, the patients should be prepared for a long-term or indefinite retention phase following orthodontic treatment to prevent relapse.


Assuntos
Contenções Ortodônticas , Satisfação do Paciente , Humanos , Desenho de Aparelho Ortodôntico , Recidiva , Técnicas de Movimentação Dentária , Vácuo
8.
Chem Commun (Camb) ; 55(83): 12507-12510, 2019 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-31576386

RESUMO

Charge reduction and neutralization of electro-sprayed peptides are realized by selective gas-phase photocleavage of tailored covalent tags. The concept is demonstrated with four model peptides in positive and negative ion modes and tagged insulin as the largest construct.


Assuntos
Insulina/química , Peptídeos/química , Vácuo , Íons/química , Estrutura Molecular , Processos Fotoquímicos
9.
Water Sci Technol ; 80(4): 773-783, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31661456

RESUMO

Benzotriazoles (BTs) attract increasing concerns because of abundant presence in environmental water bodies. In this study, degradation of 1H-benzotriazole (1H-BT) was performed by a customized vacuum ultraviolet (VUV) device emitting 185 + 254 nm (VUV/UV-C) irradiation. Degradation of 1H-BT presented an apparent rate constant reached 8.17 × 10-4 s-1. Degradation mechanisms included 185 + 254 nm photodegradation and radical reaction. The later one may be the predominant one, which presented a k·OH-1H-BT at (7.3 ± 0.8) × 109 M-1 s-1. Effects of anions revealed that VUV interception and radical trapping were the dominant restraining factors. Degradation of 1H-BT can be attributed to VUV induced radical-based oxidation. Radical-induced addition, substitution and fracture generated abundant hydroxylated and open-loop products during 10-45 min. Identification using reactive oxygen species and apoptosis in Escherichia coli was conducted. Variations of these two indicators revealed that the incomplete degradation products presented higher toxicities than 1H-BT, and a further mineralization reduced their toxicities. In the pure water solution with little impurities, VUV can induce efficient degradation of 1H-BT, suggesting its potential for eliminating and detoxifying MPs.


Assuntos
Poluentes Ambientais , Poluentes Químicos da Água , Estudos Prospectivos , Triazóis , Raios Ultravioleta , Vácuo
10.
J Chromatogr A ; 1604: 460473, 2019 Oct 25.
Artigo em Inglês | MEDLINE | ID: mdl-31472937

RESUMO

A solvent-assisted vacuum desorption method is developed and combined with gas chromatography-tandem mass spectrometry (GC-MS/MS) for quick determination of soil PAHs. With the assistance of a reduced pressure of 0.0001 kPa and the DMSO/acetone (1:1) mixed solvent, this method allows desorption of PAHs in a moderate temperature of 160 °C. Analytes were trapped in a collection tube and eluted with n-hexan for GC-MS/MS analysis. The entire procedure can be completed within 20 min. In order to validate this method for determining soil PAHs, the solvent-assisted vacuum desorption method, Soxhlet extraction and ASE extraction were applied in different samples of real contaminated soils. Most HMW PAHs showed similar concentrations, yet LMW PAHs with solvent-assisted vacuum desorption presented significantly higher concentrations than those with conventional methods, such as NAP, ANY, ANA and FLU. Further investigation revealed that solvent-assisted vacuum desorption is capable of improving both the extractability and collection efficiency of those four LMW PAHs in real contaminated soil. This method enables desorption of HMW PAHs and provides the additional benefit of improved extractability and collection efficiency for LMW PAHs.


Assuntos
Monitoramento Ambiental/métodos , Cromatografia Gasosa-Espectrometria de Massas , Hidrocarbonetos Policíclicos Aromáticos/análise , Poluentes do Solo/análise , Solo/química , Solventes/química , Vácuo
11.
Water Res ; 166: 115061, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31522015

RESUMO

Vacuum UV (VUV) technologies have recently attracted high interest due to their high efficacy in generating reactive oxygen species (ROS). To date, no systematic study of the modes of action of the integrated VUV/Fe(II)/H2O2 process against contaminants elimination exists; the present study reports the oxidation of MTBE in a new light-assisted Fenton-process, by employing either narrowband UVC (254 nm) or VUV (185 and 254 nm) irradiation, in a comparative evaluation. The processes under investigation were the UVC- or VUV/Fe(II)/H2O2 sensitized ones and their constituents, i.e. Fe(II)/H2O2, VUV, VUV/Fe(II), VUV/H2O2, VUV/Fe(II)/H2O2, as well as the UVC, UVC/H2O2 and UVC/Fe(II)/H2O2. We scrutinize the operational parameters of the VUV-assisted process, its enhancements and synergies, comparison with the UVC-based ones, as well as their inflicted pathways towards MTBE degradation. Complete degradation and 87.8% mineralization of 50 mg/L MTBE was achieved in the VUV/Fe(II)/H2O2 process (0.9 mM Fe(II) and 3 mM H2O2), at near-neutral pH (reaction times: ∼30 and 60 min, respectively). Irradiation with VUV light was found to act synergistically and in high kinetic rates enhancement compared to the UVC source, sensitizing the Fenton process for effective oxidation of MTBE in the aqueous solution. A scavenger study and degradation by-products investigation has been performed, leading to a mechanistic pathway proposition, elucidating MTBE degradation. The VUV/Fe(II)/H2O2 process demonstrated potential applicability in the field since it could efficiently treat (100% degradation and 86.4% mineralization) groundwater spiked with MTBE, operated either under batch or continuous-flow mode. The findings clearly indicates the VUV-assisted Fenton as an emerging and viable technology for field application to treat the MTBE-contaminated effluents or waters.


Assuntos
Éteres Metílicos , Poluentes Químicos da Água , Compostos Ferrosos , Peróxido de Hidrogênio , Concentração de Íons de Hidrogênio , Oxirredução , Vácuo
12.
J Environ Manage ; 249: 109435, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31450199

RESUMO

Source separation of human urine has not been widely adopted because of scaling on urine collecting fixtures and lack of verified technologies for on-site utilization of waterless urine. This study investigated the effects of flushing liquid, temperature and urease amendment on hydrolysis of urea to ammonia, explored ammonia recovery via vacuum stripping in connection with phosphorus recovery via struvite precipitation in different sequences, and performed economic analysis of a proposed nutrient recovery strategy. It was found that acetic acid could be dosed at 0.05-0.07 N to flush urine-diverting toilets and urinals for hygiene and prevention of scaling. However, a high dosage of 0.56 N completely inhibited urea hydrolysis. Source-separated urine could be stored at 25 °C with ample urease for complete urea hydrolysis within approximately 20 h. Fully hydrolyzed waterless urine contained 9.0-11.6 g/L ammonia-N, 0.53-0.95 g/L phosphate-P and only 2.3-9.1 mg/L magnesium. When magnesium was supplemented to attain the optimum Mg2+: PO43- molar concentration ratio of 1.0 in hydrolyzed urine, batch operation of a pilot-scale air-lift crystallizer removed 93-95% of phosphate and produced 3.65-4.93 g/L struvite in 1-5 h. Batch operation of a pilot-scale vacuum stripping - acid absorption system for 12 h stripped 72-77% of ammonia and produced 37.6-39.7 g/L (NH4)2SO4. Compared with the ammonia → phosphorus recovery sequence, the struvite precipitation → vacuum stripping sequence produced more struvite and ammonium sulfate. The strategy of urea hydrolysis → struvite precipitation → vacuum stripping of ammonia is a sustainable alternative to the conventional phosphorus fertilizer production and ammonia synthesis processes.


Assuntos
Nitrogênio , Fósforo , Precipitação Química , Humanos , Hidrólise , Fosfatos , Estruvita , Urina , Vácuo
13.
Waste Manag ; 97: 140-148, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31447021

RESUMO

An environmentally benign vacuum pyrolysis (VP) approach is employed to recover Li and Co from spent LiCoO2-based lithium-ion batteries (LIBs). First, the electroactive materials were separated from the current collector by the VP method from 623 to 823 K with an attempt to choose an appropriate temperature. Then, the as-received cathode materials were mixed with different amounts of graphite from the anode to selectively convert LiCoO2 to Co or CoO and Li2CO3 by carbothermic reduction under vacuum and at 873 to 1273 K. After carbothermic reduction, the pyrolyzed powder was leached in water to separate Li2CO3 from Co/CoO. By alternating the C/LiCoO2 mass ratio and the pyrolysis temperature, a recovery rate reaches over 93% for Li and 99% for Co. Finally, the recovered CoO and Li2CO3 were used to regenerated LiCoO2 that delivered a specific capacity of 145 mAh g-1 at 1C and retaining 93% of the initial capacity after 100 cycles. Overall, a multi-vacuum-pyrolysis approach offers a closed-loop route for the management of spent LIBs without using any hazardous chemicals.


Assuntos
Lítio , Pirólise , Fontes de Energia Elétrica , Reciclagem , Vácuo
14.
Forensic Sci Int ; 302: 109900, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31382222

RESUMO

Currently, forensic drug experts are facing chemical identification challenges with the increasing number of new isomeric forms of psychoactive substances occurring in case samples. Very similar mass spectra for these substances could easily result in misidentification using the regular GC-MS screening methods in combination with colorimetric testing in forensic laboratories. Building on recent work from other groups, this study demonstrates that GC-VUV is a powerful technique for drug isomer differentiation, showing reproducible and discriminating spectra for aromatic ring-isomers. MS and VUV show complementary selectivity as VUV spectra are ring-position specific whereas MS spectra are characteristic for the amine moieties of the molecule. VUV spectra are very reproducible showing less than 0.1‰ deviation in library match scores and therefore small spectral differences suffice to confidently distinguish isomers. In comparison, MS match scores gave over 10‰ deviation and showed significant overlap in match score ranges for several isomers. This poses a risk for false positive identifications when assigning compounds based on retention time and GC-MS mass spectrum. A strategy was developed, based on Kernel Density Estimations of match scores, to construct Receiver Operating Characteristic (ROC) curves and estimate likelihood ratios (LR values) with respect to the chemical differentiation of drug related isomers. This approach, and the added value of GC-VUV is demonstrated with the chemical analysis of several samples from drug case work from the Amsterdam area involving both compounds listed in Dutch drug legislation (3,4-MDMA; 3,4-MDA; 4-MMC; 4-MEC and 4-FA) as well as their unlisted and thus uncontrolled isomers (2,3-MDMA; 2,3-MDA; 2- and 3-MMC; 2- and 3-MEC and 2- and 3-FA).


Assuntos
Cromatografia Gasosa/métodos , Isomerismo , Espectrofotometria Ultravioleta/métodos , Medicamentos Sintéticos/química , Vácuo , Cromatografia Gasosa-Espectrometria de Massas
16.
Am J Orthod Dentofacial Orthop ; 156(2): 186-192, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31375228

RESUMO

INTRODUCTION: The purpose of this study was to compare and evaluate salivary microbial levels and periodontal status in patients using a fixed lingual retainer, a removable vacuum-formed retainer, or a Hawley retainer after orthodontic treatment with fixed appliances. METHODS: Forty-five patients who finished their orthodontic treatment with fixed appliances and were about to start the retention phase were randomly divided into the following 3 groups of 15 individuals each: the fixed lingual retainer group, the vacuum-formed retainer group, and the Hawley retainer group. Periodontal measurements, such as the plaque index, gingival index, probing depth, and bleeding on probing, were obtained at the following 4 time points: at debonding (T0) and 1 week (T1), 5 weeks (T2), and 13 weeks (T3) after debonding. Saliva samples were collected 3 times in total: at T0, T2, and T3. A quantitative analysis for Streptococcus mutans and Lactobacillus casei was performed with the use of real-time polymerase chain reaction. The Kruskal-Wallis test and 1-way analysis of variance were used for the statistical comparisons of the groups. RESULTS: No statistically significant difference in salivary S mutans and L casei levels was found among the 3 groups (P >0.05). They showed no statistically significant differences in plaque index, gingival index, bleeding on probing, and probing depth values (P >0.05). All periodontal parameters showed statistically significant decreases from T0 to T3 in all 3 groups (P <0.001). The S mutans and L casei levels were decreased significantly from T2 to T3 in the lingual retainer and Hawley retainer groups, whereas they decreased significantly from T0 to T3 in the vacuum-formed retainer group. CONCLUSIONS: Fixed and removable orthodontic retainers do not differ in salivary S mutans and L casei levels and periodontal status. With all retainers, regardless of whether they are fixed or removable, oral hygiene improved after orthodontic treatment with fixed appliances.


Assuntos
Aparelhos Ortodônticos Fixos/efeitos adversos , Aparelhos Ortodônticos Removíveis/efeitos adversos , Contenções Ortodônticas/efeitos adversos , Índice Periodontal , Saliva/microbiologia , Adolescente , Adulto , Análise de Variância , Criança , DNA Bacteriano , Índice de Placa Dentária , Feminino , Humanos , Lactobacillus casei , Masculino , Higiene Bucal , Desenho de Aparelho Ortodôntico , Ortodontia Corretiva/efeitos adversos , Ortodontia Corretiva/instrumentação , Streptococcus mutans , Vácuo , Adulto Jovem
17.
Water Res ; 164: 114918, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31377528

RESUMO

1,4-Dioxane is one of the most persistent organic micropollutants and is quite difficult to remove via conventional drinking water treatment consisting of coagulation, sedimentation, and sand filtration. Vacuum ultraviolet (VUV) treatment has recently been found to show promise as a treatment method for 1,4-dioxane removal, but the associated decomposition rate of 1,4-dioxane is known to be very sensitive to water quality characteristics. Some computational models have been proposed to predict the decomposition rate of micropollutants during VUV treatment, but the effects of only bicarbonate and natural organic matter have been considered in the models. In the present study, we attempted to develop a versatile computational model for predicting the behavior of 1,4-dioxane during VUV treatment that took into account the effects of other coexisting inorganic ions commonly found in natural waters. We first conducted 1,4-dioxane decomposition experiments with low-pressure mercury lamps and test waters that had been prepared by adding various inorganic ions to an aqueous phosphate buffer. The apparent decomposition rate of 1,4-dioxane was suppressed when bicarbonate, chloride, and nitrate were added to the test waters. Whereas bicarbonate and chloride directly suppressed the apparent decomposition rate by consuming HO•, nitrate became influential only after being transformed into nitrite by concomitant UV light (λ = 254 nm) irradiation. Cl-related radicals (Cl• and Cl2•-) did not react with 1,4-dioxane directly. A computational model consisting of 31 ordinary differential equations with respect to time that had been translated from 84 reactions (10 photochemical and 74 chemical reactions) among 31 chemical species was then developed for predicting the behavior of 1,4-dioxane during VUV treatment. Nine of the parameters in the ordinary differential equations were determined by least squares fitting to an experimental dataset that included different concentrations of bicarbonate, chloride, nitrate, and nitrite. Without further parameter adjustments, the model successfully predicted the behavior of 1,4-dioxane during VUV treatment of three groundwaters naturally contaminated with 1,4-dioxane as well as one dechlorinated tap water sample supplemented with 1,4-dioxane.


Assuntos
Poluentes Químicos da Água , Purificação da Água , Dioxanos , Oxirredução , Raios Ultravioleta , Vácuo
18.
J Food Sci ; 84(9): 2467-2474, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31449337

RESUMO

The antioxidant stability of minced pork treated with thyme and oregano essential oils (EOs) was determined. Minced pork containing different concentrations (0%, 0.3%, 0.6%, or 0.9%) of thyme (TEO) or oregano essential oil (OEO) and packaged under vacuum or modified atmosphere (MAP) (30%O2 /50%CO2 /20%N2 ) was evaluated within 15 days of refrigeration (3 ± 1 °C) storage. EOs were examined for scavenging capacity toward 2,2-diphenyl-1-picrylhydrazyl, nitric oxide radicals, and hydroxyl, and inhibition of lipid peroxidation and ferric ion reducing antioxidant power (butylated hydroxytoluene was used as positive controls). The order of antioxidative effectiveness was as follows: butylated hydroxytoluene > OEO > TEO, with significant differences between agents (P < 0.05). Lipid oxidation in meat was determined by monitoring malondialdehyde (MDA) formation and lipolysis was assessed by measuring the acidity index immediately and after 3, 6, 9, 12, and 15 days of storage. EOs significantly (P < 0.05) increased the stability of minced pork with respect to lipid oxidation compared with the control, and the antioxidative effect was dose-dependent. Moreover, vacuum packaging resulted in mince with significantly lower oxidation and lipolysis levels than modified atmosphere packaged mince (P < 0.05). The results demonstrate that both EOs examined effectively reduced lipid oxidation in raw pork mince after 2 weeks' storage. PRACTICAL APPLICATION: The natural food preservatives market is growing rapidly, as is high demand for organic foods. These results are likely to be of interest to the scientists, researchers, and persons who work in the meat industry. Results and discussion can contribute to a better understanding of antioxidative properties of essential oils in food model. Furthermore, no study has reported the effect of these MAP on pork oxidative stability.


Assuntos
Antioxidantes/química , Conservação de Alimentos/métodos , Conservantes de Alimentos/química , Carne/análise , Óleos Voláteis/química , Origanum/química , Extratos Vegetais/química , Thymus (Planta)/química , Animais , Embalagem de Alimentos , Oxirredução , Refrigeração , Suínos , Vácuo
19.
J Food Sci ; 84(8): 2171-2180, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31313307

RESUMO

Amadori rearrangement product (ARP) derived from glutamic acid (Glu) and xylose (Xyl) was prepared by aqueous Maillard reaction. Subsequently, ion exchange chromatography, MS, and NMR were used for purification and identification, confirming that the molecular formula of ARP was C10 H17 NO8 , namely N-(1-deoxy-α-D-xylulos-1-yl)-glutamic acid, with a molecular mass of 279 Da. To improve the aqueous yield of ARP, a thermal reaction coupled with vacuum dehydration was used and the yield of ARP was increased from 2.07% to 75.11%. Furthermore, flavor formation capacity of ARP by a thermal treatment simulated to a baking process was compared with Maillard reaction products, Maillard-dehydration reaction products, and Glu-Xyl mixture. The results indicated that a larger amount of volatile flavor compounds and a biscuit-like, burnt aroma was generated rapidly from the mixture of ARP and unreacted Glu-Xyl, which could be a potential flavor enhancer for baked foods. PRACTICAL APPLICATION: Maillard reaction performed in aqueous medium through thermal reaction combined with vacuum dehydration is a novel and practical technology that could be widely used to produce Maillard reaction intermediates (MRIs), such as Amadori or Heyns rearrangement products, which are regarded as significant nonvolatile aroma precursors and have stable physical and chemical properties compared with Maillard reaction products (MRPs). MRI derived from glutamic acid and xylose is a potential substitute of MRPs for flavorings preparation and shows a great capacity to generate fresh flavors in a short time at high temperature, which meets the requirements of baking foods. Therefore, the new developed method could be a promising tool for MRI preparation and application in food and flavoring industries.


Assuntos
Aromatizantes/química , Ácido Glutâmico/química , Produtos Finais de Glicação Avançada/química , Temperatura Alta , Reação de Maillard , Odorantes/análise , Paladar , Vácuo , Xilose/química
20.
Food Chem ; 299: 125117, 2019 Nov 30.
Artigo em Inglês | MEDLINE | ID: mdl-31288164

RESUMO

This work evaluated nutritional and organoleptic properties of murta, a Chilean native berry, impregnated with Lactobacillus casei var. rhamnosus and dehydrated by different methods: freeze- (FD), convective- (CD) and vacuum- (VD) drying. Scanning electron microscopy revealed that L. casei localized at the peduncle and near the peduncle of the impregnated fruit. Murta enriched with probiotics contained higher L. casei viable counts after dehydration with FD compared to CD and VD methods. Overall, drying resulted in a decrease in crude fibre and phenolic compounds, which was attributed to L. casei metabolic activity suggesting that murta berries could act as prebiotics for L. casei. Among drying methods, L. casei enriched FD murta presented less alterations in the microstructure, less drying-induced damage and obtained a higher sensory acceptability score than CD and VD murta. Taken together, these results will contribute to the development of functional foods from regional products improving local economy.


Assuntos
Frutas/química , Lactobacillus rhamnosus , Myrtaceae/química , Chile , Dessecação , Fibras na Dieta/análise , Liofilização , Frutas/microbiologia , Humanos , Lactobacillus rhamnosus/crescimento & desenvolvimento , Myrtaceae/microbiologia , Fenóis/análise , Prebióticos , Probióticos , Sensação , Vácuo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA