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Goran T. Vladisavljevic - One of the best experts on this subject based on the ideXlab platform.
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influence of process parameters on Droplet Size Distribution in spg membrane emulsification and stability of prepared emulsion Droplets
Journal of Membrane Science, 2003Co-Authors: Goran T. Vladisavljevic, H SchubertAbstract:SPG membranes were used to prepare monodispersed O/W and W/O/W emulsions over a wide range of membrane wall shear stress (0.37–40 Pa), dispersed phase content (1–20 vol.%) and transmembrane pressure. Although the most uniform Droplets were prepared at the membrane wall shear stress of 30 Pa, a monodispersed O/W emulsion can be even obtained at the wall shear stress of 0.37 Pa, corresponding to laminar flow regime of continuous phase inside the membrane tube. The minimum Droplet Size somewhat decreased with time, probably due to gradual activation of smaller pores. There was no significant difference in the Size Distribution curve of pure oil Droplets of O/W emulsions and W/O drops of W/O/W emulsions, if they were both prepared under the same conditions. No significant change in Droplet Size Distribution of prepared O/W emulsions was observed during the storage time of up to 159 days.
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Preparation and analysis of oil-in-water emulsions with a narrow Droplet Size Distribution using Shirasu-porous-glass (SPG) membranes☆
Desalination, 2002Co-Authors: Goran T. Vladisavljevic, Helmar SchubertAbstract:Abstract Shirasu-porous-glass (SPG) membranes with a mean pore Size from 0.4–6.6 μm were used to produce O/W emulsions consisting of vegetable (rape seed) oil as the dispersed phase and Span 80 dissolved in demineralized water as the continuous phase. The emulsion Droplets with a mean Droplet Size 3.5 times larger than the mean pore Size and the span of the Droplet Size Distribution between 0.26 and 0.45 were produced using 2% emulsifier at a transmembrane pressure slightly exceeding the capillary pressure. Under these conditions the dispersed phase flux through the membrane was in the range of 0.7–7 1·m−2·h−1 and only about 2% of the pores were active. However, if the transmembrane pressure was considerably higher than the capillary pressure, the dispersed phase flux strongly increased and Droplets with a broad Droplet Size Distribution were produced. The hydraulic resistance of the SPG membrane was inversely proportional to the square of the mean pore Size, which is in agreement with the Hagen-Poiseuille law. The membrane porosity is independent on the pore Size and ranged from 53–60%.
A Guerrero - One of the best experts on this subject based on the ideXlab platform.
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temperature and ph as factors influencing Droplet Size Distribution and linear viscoelasticity of o w emulsions stabilised by soy and gluten proteins
Food Hydrocolloids, 2010Co-Authors: Carlos Bengoechea, Alberto Romero, Felipe Cordobes, Jose Manuel Aguilar, A GuerreroAbstract:Abstract The influence of pH and two post-emulsification treatments (pH modification and thermal cycles) over linear dynamic viscoelasticity and Droplet Size Distribution, DSD, of O/W emulsions (75% oil) stabilized either by soy protein isolate, SPI, or wheat gluten, WG were studied in the present work. Rheological properties and Droplet Size of fresh emulsions showed an important dependence on pH as a consequence of the role of electrostatic interactions, not being possible to obtain a stable emulsion for pH values close to the protein isoelectric point, pI, (4–5 for SPI and 6 for WG). In order to overcome this inconvenient, an alternative emulsification procedure, basically consisting in a modification of pH after emulsification (indirect emulsification), was successfully developed. Emulsions obtained after this post-emulsification treatment, showed higher elastic ( G ′) and loss ( G ″) moduli and also larger oil Droplets than fresh emulsions prepared at the same pH. Moreover, the application of upward/downward temperature cycles from 20 to 70 °C to emulsions directly prepared at a pH yielded to significantly higher values of the rheological functions when compared to those found for fresh emulsions. Accordingly, both post-emulsification treatments lead to apparent enhancements in emulsion rheology and microstructure, which is indicative of a good potential to improve long-term emulsion stability.
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influence of ph on linear viscoelasticity and Droplet Size Distribution of highly concentrated o w crayfish flour based emulsions
Food Hydrocolloids, 2009Co-Authors: Alberto Romero, Felipe Cordobes, A GuerreroAbstract:In the present work, the influence of pH on stability of oil-in-water (O/W; 75 wt%/25 wt%) emulsions stabilized by crayfish flour (CF) has been studied. CF (containing ca. 65 wt%) showed poor functionality in a wade range of pH, which inhibits formation of stable emulsions. An indirect procedure has been developed in order to obtain emulsion at a broad pH range, including isoelectric point (pI) value. The emulsions have been characterized by means of linear dynamic viscoelasticity and Droplet Size Distribution (DSD) analysis. These emulsions present a behaviour characteristic of highly concentrated emulsions with a well-developed plateau region. The most unfavourable DSD and linear viscoelastic results correspond to the pI. A significant improvement takes place as the pH value departs from the pI. An exception for linear viscoelasticity results have been found at pH 10, which is close to the pI for rod segments of myofibrillar proteins. Stability of these emulsions has been studied by following the evolution of DSD and linear viscoelastic parameters along time. The poorer results in emulsion stability correspond to pH values close to the pI, at which the increase in Droplet Size or uniformity parameter as well as the decrease in the plateau modulus become more pronounced. Conversely, the stability significantly improves as the pH departs from pI.
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rheology and Droplet Size Distribution of emulsions stabilized by crayfish flour
Food Hydrocolloids, 2008Co-Authors: Alberto Romero, Felipe Cordobes, Maria Cecilia Puppo, A Guerrero, Carlos BengoecheaAbstract:Abstract Highly concentrated oil-in-water (o/w) emulsions stabilized by crayfish flour at high pH were characterized by means of linear dynamic viscoelasticity and Droplet Size Distribution (DSD) analysis. Power consumption and temperature were recorded as a function of emulsification time at different agitation speeds. The emulsions studied followed a gel-like behavior, characterized by G′ being about one order of magnitude higher than G″ within the experimental frequency range. This behavior was characteristic of highly concentrated emulsions with a well-developed plateau region. Increase in both energy input and crayfish flour concentration yielded higher values of linear viscoelasticity functions and lower Droplet Size, which suggested an enhancement of the elastic network and an increase in emulsion stability. The evolution of plateau modulus and Sauter diameter was studied at different concentrations of crayfish flour (0.25–6.25 wt%) over storage time at 5 °C. The microstructure of these emulsions was characterized by using confocal laser scanning microscopy (CLSM).
H Schubert - One of the best experts on this subject based on the ideXlab platform.
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influence of process parameters on Droplet Size Distribution in spg membrane emulsification and stability of prepared emulsion Droplets
Journal of Membrane Science, 2003Co-Authors: Goran T. Vladisavljevic, H SchubertAbstract:SPG membranes were used to prepare monodispersed O/W and W/O/W emulsions over a wide range of membrane wall shear stress (0.37–40 Pa), dispersed phase content (1–20 vol.%) and transmembrane pressure. Although the most uniform Droplets were prepared at the membrane wall shear stress of 30 Pa, a monodispersed O/W emulsion can be even obtained at the wall shear stress of 0.37 Pa, corresponding to laminar flow regime of continuous phase inside the membrane tube. The minimum Droplet Size somewhat decreased with time, probably due to gradual activation of smaller pores. There was no significant difference in the Size Distribution curve of pure oil Droplets of O/W emulsions and W/O drops of W/O/W emulsions, if they were both prepared under the same conditions. No significant change in Droplet Size Distribution of prepared O/W emulsions was observed during the storage time of up to 159 days.
Andy Chan - One of the best experts on this subject based on the ideXlab platform.
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cfd study of distillation sieve tray flow regimes using the Droplet Size Distribution technique
Journal of The Taiwan Institute of Chemical Engineers, 2014Co-Authors: Aldo Malvin, Andy ChanAbstract:Abstract A good understanding on the characteristics of sieve tray flow regimes is one of the keys to achieve an efficient distillation operation. A 3-D computational fluid dynamics (CFD) model based on the volume-of-fluid (VOF) and the large eddy simulation (LES) has been developed to simulate the complex flow phenomena in a sieve tray. The analysis of Droplet Size Distribution (DSD), which was made possible by the use of VOF model, was then carried out to characterize the prevailing flow regime. The obtained results are in good agreement with the experimental data available in the literature in terms of the prediction of clear liquid height. The results obtained from the DSD analysis reveal that the sphere equivalent Droplet diameter, ddrop,eq, is inversely proportional to the gas superficial velocity, and is directly proportional to the liquid volumetric flow rate, QLo. Approaching the froth-to-spray transition regime, ddrop,eq was found to range from 0.008 m to 0.0114 m. These findings may serve as valuable information in assisting tray designers and process engineers to decide on ranges of operating conditions which allows the attainment of high efficiency distillation operation, and also providing some insights into future development of sieve tray technology.
Alberto Romero - One of the best experts on this subject based on the ideXlab platform.
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temperature and ph as factors influencing Droplet Size Distribution and linear viscoelasticity of o w emulsions stabilised by soy and gluten proteins
Food Hydrocolloids, 2010Co-Authors: Carlos Bengoechea, Alberto Romero, Felipe Cordobes, Jose Manuel Aguilar, A GuerreroAbstract:Abstract The influence of pH and two post-emulsification treatments (pH modification and thermal cycles) over linear dynamic viscoelasticity and Droplet Size Distribution, DSD, of O/W emulsions (75% oil) stabilized either by soy protein isolate, SPI, or wheat gluten, WG were studied in the present work. Rheological properties and Droplet Size of fresh emulsions showed an important dependence on pH as a consequence of the role of electrostatic interactions, not being possible to obtain a stable emulsion for pH values close to the protein isoelectric point, pI, (4–5 for SPI and 6 for WG). In order to overcome this inconvenient, an alternative emulsification procedure, basically consisting in a modification of pH after emulsification (indirect emulsification), was successfully developed. Emulsions obtained after this post-emulsification treatment, showed higher elastic ( G ′) and loss ( G ″) moduli and also larger oil Droplets than fresh emulsions prepared at the same pH. Moreover, the application of upward/downward temperature cycles from 20 to 70 °C to emulsions directly prepared at a pH yielded to significantly higher values of the rheological functions when compared to those found for fresh emulsions. Accordingly, both post-emulsification treatments lead to apparent enhancements in emulsion rheology and microstructure, which is indicative of a good potential to improve long-term emulsion stability.
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influence of ph on linear viscoelasticity and Droplet Size Distribution of highly concentrated o w crayfish flour based emulsions
Food Hydrocolloids, 2009Co-Authors: Alberto Romero, Felipe Cordobes, A GuerreroAbstract:In the present work, the influence of pH on stability of oil-in-water (O/W; 75 wt%/25 wt%) emulsions stabilized by crayfish flour (CF) has been studied. CF (containing ca. 65 wt%) showed poor functionality in a wade range of pH, which inhibits formation of stable emulsions. An indirect procedure has been developed in order to obtain emulsion at a broad pH range, including isoelectric point (pI) value. The emulsions have been characterized by means of linear dynamic viscoelasticity and Droplet Size Distribution (DSD) analysis. These emulsions present a behaviour characteristic of highly concentrated emulsions with a well-developed plateau region. The most unfavourable DSD and linear viscoelastic results correspond to the pI. A significant improvement takes place as the pH value departs from the pI. An exception for linear viscoelasticity results have been found at pH 10, which is close to the pI for rod segments of myofibrillar proteins. Stability of these emulsions has been studied by following the evolution of DSD and linear viscoelastic parameters along time. The poorer results in emulsion stability correspond to pH values close to the pI, at which the increase in Droplet Size or uniformity parameter as well as the decrease in the plateau modulus become more pronounced. Conversely, the stability significantly improves as the pH departs from pI.
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rheology and Droplet Size Distribution of emulsions stabilized by crayfish flour
Food Hydrocolloids, 2008Co-Authors: Alberto Romero, Felipe Cordobes, Maria Cecilia Puppo, A Guerrero, Carlos BengoecheaAbstract:Abstract Highly concentrated oil-in-water (o/w) emulsions stabilized by crayfish flour at high pH were characterized by means of linear dynamic viscoelasticity and Droplet Size Distribution (DSD) analysis. Power consumption and temperature were recorded as a function of emulsification time at different agitation speeds. The emulsions studied followed a gel-like behavior, characterized by G′ being about one order of magnitude higher than G″ within the experimental frequency range. This behavior was characteristic of highly concentrated emulsions with a well-developed plateau region. Increase in both energy input and crayfish flour concentration yielded higher values of linear viscoelasticity functions and lower Droplet Size, which suggested an enhancement of the elastic network and an increase in emulsion stability. The evolution of plateau modulus and Sauter diameter was studied at different concentrations of crayfish flour (0.25–6.25 wt%) over storage time at 5 °C. The microstructure of these emulsions was characterized by using confocal laser scanning microscopy (CLSM).
