| 1. |
- da Cruz Francisco, José, et al.
(författare)
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Phase behavior of the monoolein-water system - The effects of addition of the hydrocarbon 1,8-cineole and supercritical carbon dioxide
- 2004
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Ingår i: Journal of Supercritical Fluids. - : Elsevier BV. - 0896-8446. ; 31:3, s. 263-271
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Tidskriftsartikel (refereegranskat)abstract
- The results of a study on the phase behavior of the monoolein/water system with the addition of the hydrocarbon 1,8-cineole (C10H18O) and supercritical carbon dioxide at 15 MPa is presented. To two mixtures consisting of 9 and 18 wt.% water in monoolein, 5, 10, and 20 wt.% cineole were added and heated to between 35 and 80 degreesC at atmospheric pressure and in the presence of supercritical carbon dioxide. The phase changes were followed by deuterium nuclear magnetic resonance (H-2 NMR), light microscopy, and ocular inspection. The mesomorphic structures developed in the 9 wt.% water sample suffered little change due to the presence of the supercritical carbon dioxide. However, in the mixture with 18 wt.% water, the native phase structures were dramatically affected and an isotropic fluid phase developed. The addition of cineole has lowered the LC-L-alpha --> LC-H-Pi phase transition in the samples with 9 and 18 wt.% water in monoolein. The surplus of supercritical carbon dioxide in the samples has resulted in similar developments. Regardless of the amount of cineole present in the system, only the isotropic fluid phase was observed in the samples with 18 wt.% water in monoolein. (C) 2004 Elsevier B.V. All rights reserved.
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| 2. |
- da Cruz Francisco, José, et al.
(författare)
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Phase behavior of the system lecithin-water - The effects of addition of the hydrocarbon 1,8-cineole and supercritical carbon dioxide
- 2004
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Ingår i: Journal of Supercritical Fluids. - : Elsevier BV. - 0896-8446. ; 31:3, s. 255-262
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Tidskriftsartikel (refereegranskat)abstract
- The phase behavior of lecithin and water mixtures with addition of the hydrocarbon 1,8-cineole (C10H18O) was investigated using light microscopy and H-2 NMR at atmospheric pressure and with a surplus of supercritical carbon dioxide (15 MPa) between 35 and 80degreesC. The lecithin-water (LW) mixtures consisted of 10 and 20wt.% water in lecithin to which 5, 10, and 20wt.% cineole and supercritical carbon dioxide were added. The addition of cineole to the 10wt.% water in lecithin samples has affected the original lamellar liquid crystalline phase present and mainly transformed it into the reversed hexagonal phase at cineole concentration of 10wt.% and higher. This phase however Only Occurred when 20 wt.% cineole were added to the lecithin samples with 20wt.% water which otherwise was lamellar. The addition of supercritical carbon dioxide to the lecithin/water samples in the absence of cineole resulted in a liquid crystalline lamellar (LC-L-alpha) phase and was the same as in the original phase structure at atmospheric pressure. In the lecithin/water samples with cineole, the addition of supercritical carbon had little effect on the structure. (C) 2004 Elsevier B.V. All rights reserved.
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| 3. |
- Francisco, J D, et al.
(författare)
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Liquid crystalline properties and extractability of monoolein-water systems by supercritical carbon dioxide
- 2003
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Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects. - 0927-7757. ; 213:1, s. 69-78
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Tidskriftsartikel (refereegranskat)abstract
- The influence of phase structure on the extraction recovery of monoolein from monoolein-water systems by supercritical carbon dioxide was investigated. Two monoolein-water mi tures at concentrations of 9 wt% water and 18 wt% water, respectively, were studied. H-2-NMR was used to monitor changes of the phase structures in supercritical conditions. The results showed that the phase structure and the water-monoolein interactions play a role on the extraction yield. The monoolein recovery was higher in the 9 wt% water sample in which L-alpha phase was present compared to the 18 wt% water sample in which the L-alpha melted to yield a L-2 phase. When the phase structures were the same in both samples, the extraction recovery was determined by the solubility properties of the components of the system. The changes due to the presence of supercritical carbon dioxide were shown also to depend on the water concentration of the monoolein-water mixture besides the temperature. The 18 wt% mixture showed a L-2 phase structure in all the range of the temperature investigated while the 9 wt% water mixture showed phase changes from L-alpha phase to L-2 phase in the same temperature range. (C) 200 Elsevier Science B.V. All rights reserved.
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| 4. |
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| 5. |
- Landström, K, et al.
(författare)
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Competitive protein adsorption between ß-casein and ß-lactoglobulin during spray-drying: effect of calcium induced association
- 2003
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Ingår i: Food Hydrocolloids. - : Fairleigh Dickinson University Press. - 0268-005X .- 1873-7137. ; 17, s. 103-116
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Tidskriftsartikel (refereegranskat)abstract
- Competitive adsorption between ß-casein and ß-lactoglobulin (ß-Lg) during spray-drying was studied by the new surface sensitive technique using fluorescence quenching of pyrene labelled protein at the powder surface. The difference in competitiveness of -casein when present as monomers and as associated into micellar like structures were studied. Results were compared with the adsorption of single proteins at the powder surface. The adsorption of monomeric ß-casein alone gave an apparent surface load of ≈1 mg/m2 at a protein concentration of 0.3% dry weight and then remained constant with an increasing protein concentration. In the presence of Ca2+, associated ß-casein gave a lower affinity adsorption than monomeric ß-casein and did not reach a plateau value, instead it continued to increase with an increasing protein concentration. ß-Lg showed a low-affinity adsorption during spray-drying compared to monomeric ß-casein, although not as low as associated ß-casein. Competitive adsorption between monomeric ß-casein and ß-Lg resulted in a higher apparent surface load of ß-casein than ß-Lg at both protein concentrations studied (total 0.3 and 3.3% dry weight). However, in an associated form ß-casein was less competitive than ß-Lg. At a low bulk protein concentration (0.3% dry weight) ß-Lg dominated the powder surface, whereas at a higher concentration (3.3% dry weight) there was little difference between the proteins. The results indicate that the competitiveness of a protein during spray-drying is highly influenced by the ability of the protein to attach and rearrange at the droplet's air–water interface during the spray-drying process
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| 6. |
- Lofborg, N., et al.
(författare)
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Molecular exchange in thermal equilibrium between dissolved and crystalline tripalmitin by NMR
- 2003
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Ingår i: Journal of the American Oil Chemists Society. - : Wiley. - 0003-021X .- 1558-9331. ; 80:12, s. 1187-1192
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Tidskriftsartikel (refereegranskat)abstract
- An NMR technique to measure exchange kinetics at thermal equilibrium in dispersions of moderately soluble crystalline material is presented. By monitoring the exchange of molecules between pools in solid and dissolved form, one can characterize the surface specific exchange rate. Illustrative experiments were performed in a model system with beta-type crystals of tripalmitin as the solid phase and tripalmitin, a fraction of it deuterated, dissolved in a medium-chain TG oil as the liquid phase. The concentration of deuterated tripalmitin in the solvent was followed by H-2 NMR after the crystals, which initially lack deuterated tripalmitin, were immersed in the liquid. The variation of the H-2 concentration in the solvent provided the surface specific exchange rate. No systematic errors, due to the slight difference in properties of the deuterated tripalmitin compared to hydrogenated tripalmitin, were observed. The methodology worked well between crystal concentrations of 2 and 4 wt%.
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| 7. |
- Löfberg, N, et al.
(författare)
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Exchange rate between crystalline tripalmitin and liquid triglyceride oil analysed by NMR.
- 2003
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Ingår i: Journal of the American Oil Chemists Society. - 0003-021X. ; 80:12, s. 1187-1192
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Tidskriftsartikel (refereegranskat)abstract
- An NMR technique to measure exchange kinetics at thermal equilibrium in dispersions of moderately soluble crystalline material is presented. By monitoring the exchange of molecules between pools in solid and dissolved form, one can characterize the surface specific exchange rate. Illustrative experiments were performed in a model system with b-type crystals of tripalmitin as the solid phase and tripalmitin, a fraction of it deuterated, dissolved in a medium-chain TG oil as the liquid phase. The concentration of deuterated tripalmitin in the solvent was followed by 2H NMR after the crystals, which initially lack deuterated tripalmitin, were immersed in the liquid. The variation of the 2H concentration in the solvent provided the surface specific exchange rate. No systematic errors, due to the slight difference in properties of the deuterated tripalmitin compared to hydrogenated tripalmitin, were observed. The methodology worked well between crystal concentrations of 2 and 4 wt%.
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| 8. |
- Richardson, Gisela, et al.
(författare)
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The function of alpha-crystalline emulsifiers on expanding foam surfaces
- 2004
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Ingår i: Food Hydrocolloids. - : Elsevier BV. - 0268-005X. ; 18:4, s. 655-663
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Tidskriftsartikel (refereegranskat)abstract
- The expanding capacity and the stabilizing function of an alpha-crystalline emulsifier on the bubble surfaces during and after expansion of a sugar foam were examined by volume measurements, confocal laser scanning microscopy (CLSM), freeze-etching and transmission electron microscopy (TEM) and oscillatory theological measurements. 0.2-10% (w/w) emulsifier, either a polyglycerol ester mixed with monoglycerides (PGE/MG) in alpha-gel form or sodium oleate in micellar form, was mixed into a 65% sucrose solution in a specially designed vessel at a pressure of 1-5 bar. The foam produced was expanded to ambient pressure before measurements were made. The total volume of the foam was shown to increase proportionally to the expansion with both emulsifiers. With PGE/MG, small bubbles were produced (1-4 mum). With oleate, the bubbles became much larger (5-25 mum) and more coalescence could be observed. The storage modulus of the foam was shown to depend on the bubble sizes, the volume fraction of air and also the emulsifier. The foam stabilized with PGE/MG was stiff at a high concentration of emulsifier, while the micelle forming emulsifier remained more liquid-like. A possible explanation was that the alpha-crystalline PGE/MG emulsifier formed aggregates and caused an attractive bridging interaction between the bubbles, which resulted in a higher storage modulus. The micellar oleate did not cause any bubble bridging. (C) 2003 Elsevier Ltd. All rights reserved.
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| 9. |
- Wang, Ke, et al.
(författare)
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Phase Behavior and Phase Structure of a Cationic Fluorosurfactant in Water
- 2000
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 16:3, s. 1042-9
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Tidskriftsartikel (refereegranskat)abstract
- The phase behavior of the cationic fluorocarbon surfactant 1,1,2,2-tetrahydroperfluorodecylpyridinium chloride in water has been studied using small-angle X-ray and 2H NMR spectroscopy as the main techniques. The following phase sequence was found: micellar (L1), hexagonal (HI), centered rectangular (R; spacegroup c2mm) and centered trigonal (T, spacegroup Rm) with increasing surfactant concentration. At higher concentrations evidence for random mesh phase and a lamellar phase was found, at high temperatures a bicontinuous cubic phase was found. Compared to a cationic hydrocarbon surfactant of similar hydrophobicity, the occurrence of the intermediate phases is more extensive in the phase diagram, and the fluorocarbon surfactant prefers to form intermediate phases instead of a cubic phase. The surface curvature of the aggregates changes from highly curved cylindrical structures of the hexagonal phase to the planar bilayer structure of the lamellar phase over a sequence of geometries that allow the average of the mean curvature to change gradually as water content is decreased.
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| 10. |
- Waninge, Rianne, et al.
(författare)
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Cryo-TEM of isolated milk fat globule membrane structures in cream
- 2004
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084. ; 6:7, s. 1518-1523
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Tidskriftsartikel (refereegranskat)abstract
- This study has focused on structures formed through the release of lipid membrane material from milk fat globules. The aim of the study was to describe vesicles in the cream plasma and processing-induced vesicular structures in cream and buttermilk. The dairy samples were divided into three fractions through centrifugation, using DO for density control. These fractions were examined using cryogenic transmission electron microscopy (cryo-TEM). The cream layer contains submicron-sized emulsion droplets, which are spherical and partly covered with loosely associated protein aggregates. The structures of the coalescence-induced vesicles are mostly unilamellar but bilamellar and multilamellar vesicles are also present. Some spherical structures are observed but facetted particles dominate. In the buttermilk sample, spherical and slightly deformed vesicles are visible but no facetted structures are observed. The butter oil serum sample shows interesting membrane vesicle-fat globule aggregate. These types of structures were also visible in the skim milk sample. The results show that that vesicular material may be found in a range of dairy products. To our knowledge this is the first time that the existence of these types of structure has been unambiguously demonstrated in these systems.
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