| 11. |
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| 12. |
- Fransson, S., et al.
(författare)
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Effect of confinement and kinetics on the morphology of phase separating gelatin-maltodextrin droplets
- 2009
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 10:6, s. 1446-1453
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Tidskriftsartikel (refereegranskat)abstract
- The effect of confinement on the structure evolution and final morphology during phase separation and gelation of gelatin and maltodextrin was investigated and compared to the structures seen in bulk phase. Emulsion droplets with diameters from 4 to 300 ?m were analyzed using confocal laser scanning microscopy and image analysis. With the confocal laser scanning microscope it was possible to follow the entire phase separating process inside the droplets in real-time. The samples were either quenched directly from 70°C down to 20°C or exposed to holding times at 40°C. Different cooling procedures were studied to examine the structure evolution both before and after gelation in the restricted geometries. The concentration of the biopolymer mixture was kept constant at 4 w/w% gelatin and 6 w/w% maltodextrin. The results revealed that the size of the confinement had a great effect on both the initiation of phase separation and the final morphology of the microstructure inside the emulsion droplets. The phase separation in small droplets was observed to occur at a temperature above the phase separating temperature for bulk. Small droplets had either a microstructure with a shell of maltodextrin and core of gelatin or a microstructure where the two biopolymers had formed two separate bicontinuous halves. The initiation of phase separation in large droplets was similar to what was seen in bulk. The microstructure in large droplets was discontinuous, resembling the morphology in bulk phase. The kinetics had an effect on the character of the maltodextrin inclusions, as the cooling procedure of a direct quench gave spherical inclusions with an even size distribution, while a holding time at 40°C resulted in asymmetrical and elongated inclusions. © 2009 American Chemical Society.
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| 13. |
- Gatenholm, P., et al.
(författare)
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Hygiene: Jellyfish are blueprint for new absorbent materials
- 2007
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Ingår i: Medical Textiles. - 0266-2078. ; :FEB., s. 9-
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Tidskriftsartikel (refereegranskat)abstract
- Four years ago, scientists from the Chalmers University of Technology and the Swedish Institute for Food and Biotechnology initiated a project aimed at examining the little-known mechanisms of jellyfish. The group found out that the jellyfish's structure is made of interacting proteins and polysaccharides that are built up in a highly hierarchic fashion. Ions were also found to play a key role in the mechanism.
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| 14. |
- Hamberg, Lars, et al.
(författare)
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Aggregation, viscosity measurements and direct observation of protein coated latex particles under shear
- 2001
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Ingår i: Food Hydrocolloids. - 0268-005X .- 1873-7137. ; 15:2, s. 139-151
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Tidskriftsartikel (refereegranskat)abstract
- The aggregation under shear, of latex particles coated with whey protein isolate was monitored, in a continuous phase with a complex behaviour in relation to temperature dependence and shear thinning. The monitoring was done with viscosity measurements and microscopy. An aggregating dispersion of whey coated polystyrene latex particles, salt, sucrose and gelatine was sheared in a rheometer at shear rates between 0.05 and 5 s-1. The viscosity was monitored as a function of time during a temperature increase from 30 to 60°C. The viscosity curves were interpreted with the aid of additional information from light microscopy micrographs. The aggregation was clearly visible as an increase in viscosity. Aggregation was observed to initiate at a temperature between 40 and 50°C. Unbound protein, i.e. protein not a part of particle coating, was found to be essential for the aggregation of latex particles. After aggregation, a shear thinning behaviour was detected. This was due to two phenomena: structural changes of the aggregates and shear thinning behaviour of the dispersion. The build-up of the aggregates was followed by direct observation in a confocal laser scanning microscope. A sequence of micrographs was taken, in an unstopped 3-D flow field generated in a four-roll mill, which showed the evolution of the size of the aggregates. The micrographs were in good agreement with the viscosity measurements. This showed that the four-roll mill and a confocal laser scanning microscope is a useful tool for studying aggregation in an undisturbed 3-D flow. © 2001 Elsevier Science Ltd.
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| 15. |
- Hamberg, Lars, et al.
(författare)
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Shapes and shaping of biopolymer drops in a hyperbolic flow
- 2003
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Ingår i: Food Hydrocolloids. - 0268-005X .- 1873-7137. ; 17:5, s. 641-652
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Tidskriftsartikel (refereegranskat)abstract
- The shaping of drops in a model system based on ? -carrageenan-emulsion drops in the millimetre range in silicon oil has been studied. The drops were shaped by exposing them to drag forces in a hyperbolic flow, while their shape was fixed simultaneously by introducing gel formation of the biopolymer in the drop. The shape and the shaping process were studied and evaluated with image analysis of macrograph sequences of the shaping. The effect of process conditions, flow speed and cooling temperature on the final shape and shape progress was investigated as well as the effect of different ?-carrageenan drop characteristics, such as drop viscosity and gel strength. Drop viscosity was altered by addition of locust bean gum, LBG, and the gel strength was altered by addition of ions. The ?-carrageenan solutions in the drop were characterised by rheological investigations. With the same type of flow, different shapes could be achieved with small process changes and with high reproducibility. The fixation of the characteristic drop features, perimeter, area, Feret's X and Y, does not occur at the same time and position. For the different process parameters investigated, a change in speed affected the process in a similar way to a change in the viscosity ratio. This applies if the viscosity ratio is changed at a constant temperature, but if the change in the viscosity ratio is temperature-induced, the effect is different. The final shape of the produced drops could be graded into three classes, correlated to the position in the flow field where the drops were fixed. A shape map of the different drop shapes obtained was presented. © 2003 Elsevier Science Ltd. All rights reserved.
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| 16. |
- Hamberg, Lars, et al.
(författare)
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Shaping of gelling biopolymer drops in an elongation flow
- 2002
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 252:2, s. 297-308
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Tidskriftsartikel (refereegranskat)abstract
- Shaping, defined as deformation in combination with gel formation of gelatine and ?-carrageenan drops in an elongation flow, was studied. The focus was to investigate the possibility of shaping and fixating small drops in the diameter range 20 to 229 ?m. In the shaping progress and the influence of experimental properties, the viscosity, temperature, and flow of the deforming fluid were examined on the final drop shape. In the experiments a hot emulsion of an aqueous biopolymer solution in silicone oil was injected into cold silicone oil where a deforming elongation flow field existed. After injection, a temperature decrease in the drops resulted in a gel formation of the biopolymer and a fixation of the deformed drop in the flow. The shape was measured and the effect on the drop aspect ratio was determined by image analysis. Over the total drop diameter range, ?-carrageenan was more ellipsoid-shaped than gelatine, with a maximum aspect ratio of 6 compared to 4 for gelatine. For small drops, around 22 ?m, it is possible to shape ?-carrageenan, but for gelatine small drops tend to be unaffected. An increase in viscosity, temperature, and flow resulted in an increase in the final fixated shape of the drops. The differences in drop deformation between the biopolymers were explained by drop-viscosity/oil differences and differences in the kinetics of gel formation. The different gel formation kinetics resulted in a short, well-defined, shaping process for ?-carrageenan, while for gelatine the process was more complex, with both deformation and relaxation present at different stages. © 2002 Elsevier Science (USA).
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| 17. |
- Hermansson, Ann-Marie
(författare)
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Biofysik hos sönderdelat kött.
- 1984
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Ingår i: Livsmedelsteknik. ; 26:6-7, s. 241-243
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 18. |
- Hermansson, Ann-Marie, et al.
(författare)
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Characterization of protein gels by scanning and transmission electron microscopy : A methodology study of soy protein gels
- 1981
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 81:2, s. 519-530
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Tidskriftsartikel (refereegranskat)abstract
- Different preparation techniques for scanning (SEM) and for transmission electron microscopy (TEM) were compared in order to characterize the structure of protein gels. SEM specimens were prepared by chemical fixation, dehydration, and critical-point drying. TEM specimens were prepared by using techniques of thin-sectioning and freeze-fracturing/etching. Thin sections were made after varying fixation and staining conditions. For freeze-fracturing/etching, the standard freezing procedure both using and omitting cryoprotectants (glycerol), as well as a particular modification of the "soil-emulsion" freezing technique without cryoprotective pretreatment were used. Finally, critical-point dried specimens (produced for SEM) were freeze-etched after infiltration with dioxane. The various techniques of preparation were applied to soy protein gels made in distilled water and in 0.2M NaCl under well defined conditions. The gel structures differed with regard to the state of aggregation which depended on the presence or absence of NaCl. The network structure was found to be of two levels. First, there was an orientation on the molecular level in the form of strands and fine ring structures. Second, there was a coarser network with voids of the magnitude of ?0.2 ?m. The pore size distribution of the latter network was found to be very sensitive to environmental factors such as low ionic strength and presence of cryoprotectants mainly due to swelling. The information obtained by the various techniques generally showed good agreement and were complementary. Distinct preparation artifacts caused by improper freezing or critical-point drying were also revealed. © 1981 Academic Press, Inc. All rights of reproduction in any form reserved.
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| 19. |
- Hermansson, Ann-Marie, et al.
(författare)
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Developments in the understanding of starch functionality
- 1996
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Ingår i: Trends in Food Science & Technology. - 0924-2244 .- 1879-3053. ; 7:11, s. 345-353
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Tidskriftsartikel (refereegranskat)abstract
- In this article, we describe how starch functionality can be explained in terms of structure. The behaviour of different types of starches is demonstrated by showing how the microstructure of potato and wheat starch is related to their rheological properties. The results illustrate the structural importance of amylose and amylopectin. The microstructure of a completely new type of genetically engineered potato amylopectin starch is presented for the first time.
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| 20. |
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