The Experts below are selected from a list of 96636 Experts worldwide ranked by ideXlab platform
Margaret M. Robins - One of the best experts on this subject based on the ideXlab platform.
-
emulsions Creaming and rheology
Current Opinion in Colloid and Interface Science, 2002Co-Authors: Margaret M. Robins, Andrew D. Watson, Peter J WildeAbstract:Emulsions remain of key interest to major sectors of the food industry. Recent advances include the development of novel scaling approaches to modelling of rheology, and the use of new characterisation techniques such as high frequency compressive oscillation, diffusing wave spectroscopy and magnetic resonance imaging.
-
emulsions Creaming phenomena
Current Opinion in Colloid and Interface Science, 2000Co-Authors: Margaret M. RobinsAbstract:Recent years have seen advances in the monitoring of emulsion stability, particularly multiple-point techniques using optical, ultrasonic and NMR sensors. In parallel, there has been interest in the mechanisms of Creaming and phase separation, leading to progress in the theoretical interpretation of the process.
-
I. Creaming Behavior.
Journal of colloid and interface science, 1998Co-Authors: Pretima Manoj, Annette Fillery-travis, Andrew D. Watson, David J. Hibberd, Margaret M. RobinsAbstract:We report an experimental investigation on the Creaming behavior of flocculated, polydisperse, oil-in-water emulsions. Flocculation is by addition of a depletion flocculant, the polymer hydroxyethylcellulose (HEC), at a range of concentrations. The Creaming behavior is dependent on the oil volume fraction and polymer concentration. At low concentrations of HEC, the droplets cream either individually or in two populations, a flocculated phase, and a coexistent phase of individual droplets. At higher HEC concentrations, the droplets appear to cream as a single entity, with a sharp lower boundary, separating the region with droplets from a clear serum at the base of the container. In these emulsions, and in some of the coexistent ones, there is a significant delay before Creaming starts. Once started they cream at a constant rate. We have identified the continuous phase viscosity as a major factor. The aim of this work is to elucidate the mechanisms underlying the delay before Creaming. We propose that as soon as they flocculate, the emulsions form space-filling structures, which slowly rearrange until channels are formed that allow the flow of bulk continuous phase to the base of the container. Scaling arguments are presented that suggest the delay could be related to the single-droplet diffusion rate. Copyright 1998 Academic Press.
-
i Creaming behavior
Joint International Conference on Information Sciences, 1998Co-Authors: Pretima Manoj, Andrew D. Watson, David J. Hibberd, Annette Fillerytravis, Margaret M. RobinsAbstract:Abstract We report an experimental investigation on the Creaming behavior of flocculated, polydisperse, oil-in-water emulsions. Flocculation is by addition of a depletion flocculant, the polymer hydroxyethylcellulose (HEC), at a range of concentrations. The Creaming behavior is dependent on the oil volume fraction and polymer concentration. At low concentrations of HEC, the droplets cream either individually or in two populations, a flocculated phase, and a coexistent phase of individual droplets. At higher HEC concentrations, the droplets appear to cream as a single entity, with a sharp lower boundary, separating the region with droplets from a clear serum at the base of the container. In these emulsions, and in some of the coexistent ones, there is a significant delay before Creaming starts. Once started they cream at a constant rate. We have identified the continuous phase viscosity as a major factor. The aim of this work is to elucidate the mechanisms underlying the delay before Creaming. We propose that as soon as they flocculate, the emulsions form space-filling structures, which slowly rearrange until channels are formed that allow the flow of bulk continuous phase to the base of the container. Scaling arguments are presented that suggest the delay could be related to the single-droplet diffusion rate.
Julian D Mcclements - One of the best experts on this subject based on the ideXlab platform.
-
influence of ph and carrageenan type on properties of β lactoglobulin stabilized oil in water emulsions
Food Hydrocolloids, 2005Co-Authors: Eric A. Decker, Julian D McclementsAbstract:Abstract The influence of pH and carrageenan type (ι, κ, and λ) on the properties of β-lactoglobulin (β-Lg) stabilized oil-in-water emulsions was investigated by particle charge, particle size distribution, Creaming stability, and optical microscopy measurements. Emulsions containing droplets stabilized by β-Lg were produced by homogenization, and then adjusted to a particular pH (3, 5 or 6) before carrageenan solution (0 to 0.15 wt%) of the same pH was added. At pH 3 and 5, there was a pronounced decrease in droplet charge with increasing polysaccharide concentration for all carrageenan types, suggesting adsorption of carrageenan to the droplet surfaces. Extensive droplet aggregation and Creaming were observed in these emulsions when the carrageenan concentration exceeded a particular level, indicating that carrageenan destabilized the emulsions. At pH 6, the droplet charge decreased when ι- or λ-carrageenan were added to the emulsions suggesting surface adsorption, but did not significantly change when κ-carrageenan was added. The mean particle diameter remained relatively small in all emulsions at pH 6 indicating no strong flocculation or coalescence occurred, however only the emulsions containing ι-carrageenan were stable to Creaming after 1 week storage. We propose that ι-carrageenan, which had the most densely charged helix structure, was most effective at creating highly charged interfacial membranes, thereby reducing the tendency for depletion flocculation to occur.
-
probing floc structure by ultrasonic spectroscopy viscometry and Creaming measurements
Langmuir, 2000Co-Authors: Ratjika Chanamai, And Norbert Herrmann, Julian D McclementsAbstract:Information about the structural organization of droplets within flocculated monodisperse emulsions was obtained using ultrasonic spectroscopy, dynamic shear rheometry, and Creaming-rate measurements. The ultrasonic attenuation and velocity spectra (from 1 to 150 MHz), apparent viscosity (from 0.01 to 1 Pa), and Creaming rate of a series of nonflocculated, 14 vol % silicone oil-in-water emulsions stabilized by SDS were measured at 25 °C. Measurements were then repeated after the droplets had been flocculated by adding either SDS micelles (0−80 mM) or NaCl (0−400 mM) to the aqueous phase. Differences in the ultrasonic, rheological, and Creaming properties of the flocculated emulsions were interpreted in terms of differences in the spatial distribution of the droplets within the flocs. By combining ultrasound, rheological, and Creaming measurements, it was possible to obtain information about floc structure that was not available using each technique individually.
-
Creaming stability of flocculated monodisperse oil in water emulsions
Joint International Conference on Information Sciences, 2000Co-Authors: Ratjika Chanamai, Julian D McclementsAbstract:Abstract The influence of droplet flocculation on the Creaming stability of monodisperse n -hexadecane oil-in-water emulsions was studied. The Creaming velocity of emulsions with different droplet radii (0.43 and 0.86 μm), droplet concentrations (1–67 vol%), and sodium dodecyl sulfate (SDS) concentrations (7–80 mM) were measured. Depletion flocculation was observed in the emulsions when the aqueous phase SDS concentration exceeded a particular level (∼40 mM for 0.43-μm droplets and ∼15 mM for 0.86-μm droplets). Creaming was monitored by measuring the back-scattered light from an emulsion as a function of its height. The Creaming velocity increased with increasing flocculation and decreased with increasing droplet concentration. These results have important implications for the formulation of emulsion-based materials.
David Julian Mcclements - One of the best experts on this subject based on the ideXlab platform.
-
Stabilization of Soybean Oil Bodies Using Protective Pectin Coatings Formed by Electrostatic Deposition
Journal of agricultural and food chemistry, 2008Co-Authors: Daigo Iwanaga, Jochen Weiss, Eric A. Decker, David A. Gray, David Julian McclementsAbstract:Soybeans contain oil bodies that are naturally coated by a layer of phospholipids and proteins. In nature, this coating protects the oil bodies from environmental stresses and could be utilized by food manufacturers for the same purpose. However, natural oil bodies are physically unstable to aggregation because of the relatively weak electrostatic repulsion between them, which limits their application in many foods. In this study, oil bodies were extracted from soybean using an aqueous extraction method and then coated by a pectin layer using electrostatic deposition. The influence of NaCl (0–500 mM), pH (2–8), and freeze–thaw cycling (−20 °C, 22 h/40 °C, 2 h) on the properties and stability of the oil bodies coated by the pectin layer was analyzed using ζ-potential, particle size, and Creaming stability measurements. These results suggest that pectin-coated oil bodies have similar or improved stability compared to uncoated oil bodies and may provide a new way of creating functional soy products for use i...
-
dependence of Creaming and rheology of monodisperse oil in water emulsions on droplet size and concentration
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2000Co-Authors: Ratjika Chanamai, David Julian McclementsAbstract:Abstract The influence of droplet concentration (1–67 vol.%) and size (r=0.43 and 0.86 μm) on the Creaming stability and rheology of monodisperse n-hexadecane oil-in-water emulsions stabilized by sodium dodeycl sulfate (SDS) was studied. Creaming was monitored by measuring the back-scattered light from an emulsion as a function of its height. Apparent viscosity and shear modulus were measured using a dynamic shear rheometer. The Creaming velocity of the emulsions decreased with increasing droplet concentration. The apparent viscosity of the emulsions increased with increasing droplet concentration, decreasing droplet size and decreasing shear stress. Emulsions gained elastic characteristics and did not exhibit Creaming when the droplet concentration exceeded about 40% because of close packing of the droplets. The viscosity and Creaming behavior of monodisperse emulsions could be described using the same equations as for monodisperse suspensions.
Alan L Kelly - One of the best experts on this subject based on the ideXlab platform.
-
factors affecting the Creaming of human milk
International Dairy Journal, 2020Co-Authors: F Meng, T Uniackelowe, Elisa Lanfranchi, G Meehan, C A Oshea, P F Fox, Thom Huppertz, C A Ryan, Alan L KellyAbstract:Abstract The Creaming properties of human milk have not been widely studied to date, and a mechanism for this phenomenon is not known. Here, the natural Creaming of human milk, as affected by temperature and pre-treatments, was studied using dynamic light-scattering. The Creaming rate of human milk increased with temperature in the range 5 °C–40 °C. Freezing human milk at −20 °C and thawing at room temperature had little influence on Creaming. Compared with bovine milk, human milk showed a faster Creaming rate at 40 °C, but a slower rate at 5 °C, suggesting a lack of cold agglutination; the mechanisms of Creaming were also shown to differ in response to heat treatment. This study expands the current knowledge on milk Creaming, and may have potential application to storage and handling of human milk in hospitals or homes, therefore supporting optimal nutrition of infants.
-
high pressure induced changes in the Creaming properties of bovine milk
Innovative Food Science and Emerging Technologies, 2003Co-Authors: Thom Huppertz, P F Fox, Alan L KellyAbstract:Abstract Creaming of raw whole bovine milk at refrigeration temperatures is generally regarded as an undesirable phenomenon; traditionally, Creaming is prevented by homogenising the milk. The effects of high pressure (HP) processing on the Creaming of raw whole bovine milk were examined in this study. HP treatment at pressures ≤250 MPa increased the rate and level of Creaming, whereas treatment at ≥400 MPa reduced both of these parameters. On treatment at 200 or 600 MPa, Creaming increased or decreased, respectively, with increasing treatment time. At 400 MPa, HP-induced changes in the rate and level of Creaming were strongly treatment time-dependent. Treatment at 100–600 MPa for 0–60 min had little effect on milk fat globule size, whereas the viscosity of skimmed milk increased with increasing pressure and treatment time. The amount of milk protein associated with the milk fat globules was increased by HP treatment, the extent of the increase being maximal at 200 MPa. Although increased viscosity and the level of protein associated with the fat globules may partially explain the reduced rate and level of Creaming, HP-induced aggregation and denaturation of agglutinins and lipoproteins are likely to have significant effects on HP-induced changes in the Creaming characteristics of milk.
Eric Dickinson - One of the best experts on this subject based on the ideXlab platform.
-
Creaming and rheology of oil in water emulsions containing sodium dodecyl sulfate and sodium caseinate
Joint International Conference on Information Sciences, 2000Co-Authors: Eric Dickinson, Christos RitzoulisAbstract:The Creaming and rheology of fine n-tetradecane oil-in-water emulsions at pH 6.8 containing the commercial protein sodium caseinate and the ionic surfactant sodium dodecyl sulfate (SDS) have been studied, and an overview diagram relating surfactant composition and Creaming stability has been constructed. The presence of both SDS and sodium caseinate in an emulsion system increases the overall stability with respect to Creaming. Excess SDS promotes destabilization through fast Creaming; this can be attributed to depletion flocculation brought about by unadsorbed surfactant micelles. Addition of sodium caseinate was found to reduce this effect, even at relatively high SDS concentrations. The behavior of the caseinate + SDS emulsions is thus different from the behavior of the previously reported caseinate + Tween 20 systems, where the combination of the two surface-active agents was found to reduce the emulsion stability, as indicated by fast Creaming and shear-thinning rheology. Addition of sodium chloride was found to increase the extent of non-Newtonian behavior and to enhance the degree of Creaming for SDS-containing emulsions. Increased caseinate levels in these systems seem to offer some stabilization through reduction of the shear-thinning character and improvement in Creaming stability. These phenomena can be explained in terms of a considerable amount of SDS binding to the protein, which reduces the amount of SDS available to promote protein displacement and depletion flocculation. In contrast to the SDS systems, the properties of equivalent emulsions containing caseinate + nonionic surfactant Tween 20 are relatively insensitive to salt content.
-
modeling of combined Creaming and flocculation in emulsions
Journal of Colloid and Interface Science, 1997Co-Authors: Valerie J Pinfield, Eric Dickinson, Malcolm J W PoveyAbstract:A computer model is presented which simulates the simultaneous Creaming and flocculation of emulsions. A cubic lattice model is used, with particles bonding together and breaking apart according to predefined probabilities. Creaming and diffusion are included, with different rates for different sizes of floc. Results are presented in the form of concentration profiles as a function of height, and as the variation of the pseudo-fractal dimension of the particle networks formed. In the numerical simulations, an increase in Creaming rate was observed before a particle network formed which prevented further Creaming. A sharp serum interface was seen. In the presence of bond breakage, Creaming proceeded for a longer period and a more compact network was formed. These results explain some features observed experimentally in Creaming and flocculating emulsions, but do not reproduce the rapid serum development seen in some cases.
-
interpretation of ultrasound velocity Creaming profiles
Ultrasonics, 1996Co-Authors: Valerie J Pinfield, Malcolm J W Povey, Eric DickinsonAbstract:Ultrasound velocity measurements are used to observe the Creaming behaviour of dispersions. A simple relationship between velocity and concentration is required in order to calculate the dispersed phase concentration profiles from velocity measurements. A method is proposed by which the concentration profiles can be calculated with a knowledge of only the continuous phase velocity and the initial dispersed phase concentration. The method is applicable whether or not the Urick equation applies, and without a knowledge of all the physical parameters required for a full scattering theory calculation. This renormalisation technique is applied to experimental measurements of Creaming in a sunflower oil in water emulsion. Some restrictions on the method are presented.