Mara Gabriela Novy Quadri

Flat microfiltration mullite (3Al₂O₃2SiO₂) membranes were prepared via phase-inversion tape casting method. The sintering temperature has been reduced from 1700°C to 1450°C by adding 3 wt.% of magnesium oxide (MgO) as a sintering aid. The effect of this compound on the membrane properties was systematically investigated. The presence of MgO promoted at the same time a change in membrane morphology resulting in a symmetric structure, which is opposite to the asymmetrical structure obtained for mullite membranes prepared without this sintering aid. Porosity of 38.9% and average pore size of 2.33 μm was achieved. Water and n-heptane vapor adsorption analysis showed an increment in hydrophilic behavior due to MgO. The reduction of sintering temperature from 1700°C (MgO free) to 1450°C (MgO added) produced mechanical stable samples with flexural strength about 15.3 MPa. The membrane was resistant enough to withstand the water flux permeation test up to 3 bar. Compared to the pure mullite membranes, the MgO containing sample displayed higher water permeation fluxes, which might be related to both the larger superficial pore size and its hydrophilicity.

Maltodextrin (MD) and two types of gum arabic (IRX 40642 and IRX 49345) were used to encapsulate anthocyanins of red cabbage. The solution of the encapsulated dye was evaluated by polarized light microscopy. The spray-dried powder (microspheres) containg anthocyanins (red cabbage juice obtained by disintegration and filtration) and encapsulating agent was characterized by Scanning Electron Microscopy (SEM) and water sorption isotherms; the product color characterization was measured using software of imaging analysis (Mathematica). The microspheres showed that in gum arabic solutions, the dye was located at the wall. Specifically, dried gum arabic microspheres had a better quality than that produced by the maltodextrin because the MD does not form microsphere, but serving only as wall material. GAB isotherm was well fitted on experimental water sorption data. Through the color parameters quantified in CIELab and CIELCH systems for anthocyanin solutions in the presence of three studied encapsulating agents, it was possible to observe that maltodextrin had little effect on the coloring of the dye solution, for example, through the analysis of the hue parameter H, which was least affected by changes in concentration or pH from 5.0 to 3.0. The gum arabic IRX 40642 showed an oxidized hue, while gum arabic IRX 49345 gave similar colors to the original dye at concentrations less or equal to 10%. Even with some limitations, it was concluded that the gums used in this study are suitable for the encapsulation of red cabbage anthocyanins.

Mucilages are heteropolysaccharides with rich monosaccharide composition. They are capable of forming films that are brittle and fragile, and in order to obtain flexible materials, plasticizers must be added. The present study aims to evaluate the physicochemical properties of mucilage‐based films produced with Cereus hildmannianus and different glycerol concentrations by the casting technique. Transparent and yellowish films were obtained by the addition of glycerol, which also improved handleability, evidenced by increased elongation, and reduced tensile strength and Young's modulus. Thermal gravimetric analysis and differential thermal analysis revealed that glycerol presence reduced the thermal stability, showing the influence of a plasticizer over the polymer structure. Water absorption capacity and contact angle were reduced with the increase of plasticizer concentration; on the other hand, the water vapor permeability increased, as expected, due to the hydrophilic nature of glycerol. The results indicated the potential application of C. hildmannianus mucilage as a promising material to produce edible films. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45223.

The influence of the concentration, viscosity, electrical conductivity and Bloom index of gelatin solutions on the electrospinning process and the fibrous membrane formed was evaluated. Electrospun membranes were produced at different concentrations for three Bloom values (90, 250 and 280); the solutions were evaluated in terms of viscosity and electrical conductivity and the fibrous membranes by SEM and tensile tests. Results indicate that the electrospinning was most successful when the solution viscosity was within the range of 300 to 700 mPa·s, regardless of the type of gelatin used in the investigated conditions. The average fiber diameter increased with the increased solution viscosity and the relationship between them was well described by a linear equation. With regard to the mechanical properties, GeB250 and GeB280 fibrous membranes showed elongation, on average, at least ten times higher than that of GeB90 membranes.

In this research, cellulose nanocrystals (CNs) were extracted from corn cobs by 2,2,6,6,‐tetramethylpiperidine‐1‐oxyl radical‐mediated oxidation combined with ultrasonic treatment for the first time. These CNs were then used as a mechanical reinforcement agent and barrier in chitosan‐based bionanocomposite films. Birefringence analyses under crossed polarizers indicated the presence of isolated nanocrystals in suspension, which was later confirmed by TEM analysis. The crystallinity index obtained from X‐ray diffraction was 92.4%. The incorporation of these nanoparticles into a filmogenic matrix of chitosan made it possible to obtain bionanocomposite films with improved properties. The water‐vapor permeability was reduced by 70%, whereas the tensile strength and Young's modulus increased by up to 136 and 224% respectively. The developed films were applied as interleaving of sliced cheese, and the efficiency was assessed by investigation of adhesion between the surfaces and by comparing its properties with two commercial interleaving products (polyethylene (PE), and Greasepel paper (GP)). Concluding, the developed films showed a substantial potential to be exploited as an interleaving film, owing to its excellent mechanical properties, permeability, hydrophobicity, and low surface adhesion compared to pure chitosan, PE, and GP films. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43033.

A eletrofiação é uma tecnologia em que forças elétricas são aplicadas em polímero fundido ou em solução para a fabricação de fibras ultrafinas com di...

Mucilagens de diferentes fontes e seus derivados são considerados seguros para o consumo humano, sendo um potencial hidrocolóide para ser utilizado em diversa...

O jaracatiá (Carica quercifolia (A. St.-Hil.) Hieron) pertence à família Caricaceae e ao gênero Vasconcellea, o qual possui 21 espécies. O foco do presente...