Browsing by Author "Skurtys, O."
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- ItemFormation of bubbles and foams in gelatine solutions within a vertical glass tube(2008) Skurtys, O.; Bouchon Aguirre, Pedro Alejandro; Aguilera, José Miguel
- ItemFormation of O/W macroemulsions with a circular microfluidic device using saponin and potato starch(ELSEVIER SCI LTD, 2009) Skurtys, O.; Aguilera, J. M.The formation of O/W macroemulsions stabilized by a non-ionic surfactant (Quillaja saponin) and gelatinized starch was investigated using a flow focusing device consisting of circular microchannels. Droplets of hot oil (T(oil) = 338 K) were dispersed into an aqueous solution of saponin and potato starch granules. The oil fraction varied between 0.9% and 5% (dilute macroemulsions) while the starch-to-saponin concentration ratio, a, ranged between 0 and 187.5. The heat transfer from the hot oil droplet (340 to 725 mu m in diameter) induced the gelatinization of the adjacent starch granules to create a thin-shell around the oil droplet. In order to optimize the droplet generation, the physical properties of fluids were determined and the interactions between saponin and gelatinized starch granules were studied by measuring the specific conductivity. In particular, the onset, peak and end temperatures of starch gelatinization were determined. For various a, the monodispersed regime was determined by measuring the oil droplet volume V(drop). For all cases studied, Vdrop followed a power dependence with the flow rate of the aqueous phase but the exponents were different (0.65 < n < 0.9). The formation process, i.e. the dripping and jetting regime, and the generation time of oil droplets were also detailed. (C) 2009 Elsevier Ltd. All rights reserved.
- ItemPhysical properties of emulsion-based hydroxypropyl methylcellulose films: Effect of their microstructure(ELSEVIER SCI LTD, 2012) Zuniga, R. N.; Skurtys, O.; Osorio, F.; Aguilera, J. M.; Pedreschi, F.The initial characteristics of emulsions and the rearrangement of the oil droplets in the film matrix during film drying, which defines its microstructure, has an important role in the physical properties of the emulsion-based films. The objective of this work was to study the effect of the microstructure (two droplet size distributions) and stability (with or without surfactant) of HPMC oil-in-water emulsions over physical properties of HPMC emulsion-based edible films. HPMC was used to prepare sunflower oil-in-water emulsions containing 0.3 or 1.0% (w/w) of oil with or without SOS, as surfactant, using an ultrasonic homogenizer. Microstructure, rheological properties and stability of emulsions (creaming) were measured. In addition, microstructure, coalescence of oil droplets, surface free energy, optical and mechanical properties and water vapor transfer of HPMC films were evaluated. Image analysis did not show differences among droplet size distributions of emulsions prepared at different oil contents: however, by using SOS the droplet size distributions were shifted to lower values. Volume mean diameters were 3.79 and 3.77 mu m for emulsions containing 0.3 and 1.0% without surfactant, respectively, and 2.72 and 2.71 mu m for emulsions with SOS. Emulsions formulated with 1.0% of oil presented higher stability, with almost no change during 5 and 3 days of storage, for emulsions with and without SOS, respectively. Internal and surface microstructure of emulsion-based films was influenced by the degree of coalescence and creaming of the oil droplets. No effect of microstructure over the surface free energy of films was found. The incorporation of oil impaired the optical properties of films due to light scattering of light. Addition of oil and SOS decreased the stress at break of the emulsion-based films. The replace of HPMC by oil and SOS produce a lower "amount" of network structure in the films, leading to a weakening of their structure. The oil content and SDS addition had an effect over the microstructure and physical properties of HPMC-based emulsions which lead to different microstructures during film formation. The way that oil droplets were structured into the film had an enormous influence over the physical properties of HPMC films. (C) 2012 Elsevier Ltd. All rights reserved.
- ItemStructuring bubbles and foams in gelatine solutions within a circular microchannel device(ACADEMIC PRESS INC ELSEVIER SCIENCE, 2008) Skurtys, O.; Aguilera, J. M.A flow-focusing device with circular cross-section to produce monodispersed air bubbles and foams in several gelatine solutions is presented. Four flow regimes were studied by varying the gas pressure: dripping, bi-disperse bubbly, bubbly and foam flows. Bubble formation at the flow-focusing exit is discussed in detail and compared with that in rectangular microchannels. The bubble volume was shown to depend on the viscosity of the gelatine solution but not on the surface tension. For the bubbly flow, the frequency of bubble formation in this geometry was similar to that found in rectangular microchannels. For the foam flow the frequency was independent of the pressure. Study in the outlet microchannel for the bubbly and foam flows showed that the gas flow followed a power law with the applied pressure. Finally, the viscous resistance was measured and a pressure drop law was determined for each regime. (C) 2007 Elsevier Inc. All rights reserved.
- ItemStudy on image analysis application for identification Quinoa seeds (Chenopodium quinoa Willd) geographical provenance(ELSEVIER SCIENCE BV, 2010) Medina, W.; Skurtys, O.; Aguilera, J. M.In quality control procedures of biological materials, the geographical provenance is an important information to know. Image analysis is an accessible method that can provide this data. In this work, the geographical provenance of 25 varieties of quinoa seeds, cultivated in Europe and South America was identified from 38 averaged measurements as geometric dimensions, morphological features, fractal dimensions and color features. Principal component analysis (PCA) and hierarchical cluster analysis carried out with all of data allowed to distinguish the five varieties cultivated in Europe. They were located in one sector of the tridimensional PCA scatter plot, where 75% of the variability are expressed, and in one cluster of the UPGMA dendrogram with a cophenetic correlation coefficient of 0.7. (C) 2009 Elsevier Ltd. All rights reserved.
- ItemWetting Behavior of Chitosan Solutions on Blueberry Epicarp With or Without Epicuticular Waxes(2015) Skurtys, O.; Velásquez, Patricia; Osorio, F.