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  • 1. Abrahamsson, C.
    et al.
    Siahpoosh, M.
    Altskär, Annika
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Nyden, M.
    Composite silica gel as test bed for flow in nano porous materials2011Ingår i: European Cells and Materials, ISSN 1473-2262, E-ISSN 1473-2262, Vol. 21, nr SUPPL.1, s. 27-Artikel i tidskrift (Refereegranskat)
  • 2.
    Abrahamsson, Christoffer K.
    et al.
    Chalmers University of Technology, Sweden.
    Nordstierna, Lars
    Chalmers University of Technology, Sweden.
    Bergenholtz, Johan
    University of Gothenburg, Sweden.
    Altskär, Annika
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Nyden, Magnus
    University of South Australia, Australia.
    Magnetically induced structural anisotropy in binary colloidal gels and its effect on diffusion and pressure driven permeability2014Ingår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 10, nr 24, s. 4403-4412Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the synthesis, microstructure and mass transport properties of a colloidal hydrogel self-assembled from a mixture of colloidal silica and nontronite clay plates at different particle concentrations. The gel-structure had uniaxial long-range anisotropy caused by alignment of the clay particles in a strong external magnetic field. After gelation the colloidal silica covered the clay particle network, fixing the orientation of the clay plates. Comparing gels with a clay concentration between 0 and 0.7 vol%, the magnetically oriented gels had a maximum water permeability and self-diffusion coefficient at 0.3 and 0.7 vol% clay, respectively. Hence the specific clay concentration resulting in the highest liquid flux was pressure dependent. This study gives new insight into the effect of anisotropy, particle concentration and bound water on mass transport properties in nano/microporous materials. Such findings merit consideration when designing porous composite materials for use in for example fuel cell, chromatography and membrane technology.

  • 3.
    Altskär, Annika
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Andersson, R.
    Boldizar, A.
    Koch, K.
    Stading, Mats
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Rigdahl, M.
    Some effects of processing on the molecular structure and morphology of thermoplastic starch2008Ingår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 71, nr 4, s. 591-597Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hydroxypropylated and oxidised potato starch (HONPS) was used together with glycerol and water to produce thermoplastic starch. The amount of glycerol was kept constant at 22 parts by weight per 100 parts of dry starch. The thermoplastic starch was converted into films/sheets using three different processing techniques; casting, compression moulding and film blowing. The last two methods represent typical thermoplastic conversion techniques requiring elevated processing temperatures. By means of size-exclusion chromatography, it was found that compression moulding and film blowing led to some degradation of high-molecular weight amylopectin as well as of high-molecular weight amylose-like molecules. The degradation was significantly less pronounced for the cast films. The morphology of the specimens was quite complex and phase separations on different levels were identified. In the cast films and, to a lesser extent, in the compression-moulded specimens, a fine network structure could be distinguished. Such a structure could however not be ascertained in the film-blown material and this is discussed in terms of the thermo-mechanical treatment of the starch materials. © 2007 Elsevier Ltd. All rights reserved.

  • 4.
    Barreto, Carlos
    et al.
    University of Oslo, Norway; Norner AS, Norway.
    Altskär, Annika
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Fredriksen, Siw Bodil
    Norner AS, Norway.
    Hansen, Eddy Walther
    University of Oslo, Norway.
    Rychwalski, Rodney W.
    Chalmers University of Technology, Sweden.
    Multiwall carbon nanotube/PPC composites: Preparation, structural analysis and thermal stability2013Ingår i: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 49, nr 8, s. 2149-2161Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The focus of this report concerns the preparation nanocomposites from poly(propylene carbonate) (PPC) and multiwall carbon nanotubes (MWNTs). A solvent route using tetrahydrofuran, ethoxylated non- ionic surfactants combined with sonication was found to be successful in deagglomerating and dispersing the nanotubes. Transmission electron microscopy revealed highly disentangled and dispersed nanotubes and was supported by the qualitative stability evaluations. The morphology and molecular mobility of the prepared nanocomposites (0.5, 3.0 and 5.0 wt% of nanotubes) were characterized by rheology, microscopy, low-field solid-state nuclear magnetic resonance, and electrical conductivity. The networking of nanotubes was highest with a stearyl alcohol ethoxylate surfactant, and was found to improve with the sonication time. Nanotube percolation was established, both rheologically and electrically, from a filler content of approximately 0.5 wt%. A higher tendency toward particle agglomeration was observed at higher MWNT loadings. Only minor changes in the glass transition temperature were measured presumably due to the presence of solvent and surfactant residues. The thermal stability was marginally improved by increasing the loading and dispersion of the nanotubes, and appeared to be modified by solvent and surfactant residues.

  • 5. Bernin, D.
    et al.
    Hermansson, Ann-Marie
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Van Ruijven, M.
    Altskär, Annika
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Strom, A.
    Rudemo, M.
    Microstructure of polymer hydrogels studied by pulsed field gradient NMR diffusion and TEM methods2011Ingår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 7, nr 12, s. 5711-5716Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The microstructure of various alginate gels have been studied by pulsed field gradient NMR (PFG NMR) and transmission electron microscopy (TEM). The reduced diffusivity of dendrimer diffusion within the gels has been obtained from PFG NMR diffusion experiments. The polymer strand radius, an important microstructural property, has been extracted from various diffusion models. The results agree well with the polymer strand radii obtained from image analysis of the corresponding TEM micrographs. © 2011 The Royal Society of Chemistry.

  • 6.
    Craig, Marina
    et al.
    Chalmers University of Technology, Sweden; Mölnlycke Health Care, Sweden.
    Altskär, Annika
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience. Chalmers University of Technology, Sweden.
    Nordstierna, Lars
    Chalmers University of Technology, Sweden.
    Holmberg, Krister
    Chalmers University of Technology, Sweden.
    Bacteria-triggered degradation of nanofilm shells for release of antimicrobial agents2016Ingår i: Journal of materials chemistry. B, ISSN 2050-750X, E-ISSN 2050-7518, Vol. 4, nr 4, s. 672-682Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Due to an increase in lifestyle diseases in the developed world, the number of chronic wounds is increasing at a fast pace. Chronic wound infections are common and systemic antibiotics are usually used as a treatment. In this paper we describe an approach to encapsulate antimicrobial agents in hollow microcapsules covered with a nanofilm shell that degrades through the action of a virulence factor from Pseudomonas aeruginosa. The shell was assembled using the layer-by-layer (LbL) technique with poly-l-lysine and hyaluronic acid. The microcapsules were loaded with a model substrate or a drug. By crosslinking the components in the nanofilm, the film remained intact when exposed to human wound proteases. However, the film was degraded and the drug exposed when in contact with Pseudomonas aeruginosa's Lys-X specific protease IV. The antimicrobial efficacy of the drug-loaded microcapsules was confirmed by exposure to virulent Pseudomonas aeruginosa. The current study contributes to the establishment of a release platform for targeted treatment of topical infections with the aim of minimizing both overexposure to drugs and development of bacterial resistance.

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  • 7. Fransson, S.
    et al.
    Loren, Niklas
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Altskär, Annika
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Hermansson, Ann-Marie
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Effect of confinement and kinetics on the morphology of phase separating gelatin-maltodextrin droplets2009Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 10, nr 6, s. 1446-1453Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 8.
    Gmoser, Rebecca
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel.
    Bordes, Romain
    Chalmers University of Technology, Sweden.
    Nilsson, Gustav
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel.
    Altskär, Annika
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel.
    Stading, Mats
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel. Chalmers University of Technology, Sweden.
    Loren, Niklas
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel. Chalmers University of Technology, Sweden.
    Berta, Marco
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel.
    Effect of dispersed particles on instant coffee foam stability and rheological properties2017Ingår i: European Food Research and Technology, ISSN 1438-2377, E-ISSN 1438-2385, Vol. 243, nr 1, s. 115-121Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Properties of instant coffee foam constitute the focus of this study. The coffee, obtained from commercial sources, was dispersed in water at a concentration in the range of standard use. The resulting solution contained a substantial amount of micron and submicron size particles that were filtered with membranes having difference size cut-offs in order to investigate the relationship foam properties—particles size. The foams produced from these solutions have been imaged by confocal laser scanning microscopy, and their moduli and stability have been measured by oscillatory rheology, using an in-house developed rheometric set-up. The results show that particles larger than 0.8 µm have little effect on the reduction of drainage while a clear strengthening effect on the foam was evident. This was a result of their diffusion to the lamellae borders, which increases the viscosity of the liquid–air interface. Particles smaller than 0.2 µm affect bubble coarsening and likely hinder the migration of soluble surface active species to the bubble surface. Particles also participate in the stabilization of the air–water interface, and this affects both the foam stability and mechanical properties. Established models developed for ideal foam systems containing particles are difficult to apply due to the complexity of the system studied. Despite this limitation, these results provide increased understanding of the effect of particles on instant coffee foams.

  • 9.
    Gustafsson, Hanna
    et al.
    Chalmers University of Technology, Sweden.
    Isaksson, Simon
    Chalmers University of Technology, Sweden.
    Altskär, Annika
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience.
    Holmberg, Krister
    Chalmers University of Technology, Sweden.
    Mesoporous silica nanoparticles with controllable morphology prepared from oil-in-water emulsions2016Ingår i: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 467, s. 253-260Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Mesoporous silica nanoparticles are an important class of materials with a wide range of applications. This paper presents a simple protocol for synthesis of particles as small as 40. nm and with a pore size that can be as large as 9. nm. Reaction conditions including type of surfactant, type of catalyst and presence of organic polymer were investigated in order to optimize the synthesis. An important aim of the work was to understand the mechanism behind the formation of these unusual structures and an explanation based on silica condensation in the small aqueous microemulsion droplets that are present inside the drops of an oil-in-water emulsion is put forward.

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  • 10.
    Gómez-Martínez, Diana
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik. Universidad de Huelva, Spain.
    Altskär, Annika
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Stading, Mats
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik. Chalmers University of Technology, Sweden.
    Correlation between viscoelasticity, microstructure, and molecular properties of zein and pennisetin melts2012Ingår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 125, nr 3, s. 2245-2251Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cereals are a large source of biopolymers, where mainly the starch is used for food and feed. A rapidly growing cereal application is the production of biofuel, mainly produced from corn in the US. The starch is fermented to ethanol leaving spent grain rich in cereal proteins as a by-product. The corn protein zein is currently extracted on a large scale and used in, for example, material applications. Similarly, pennisetin can be extracted from pearl millet, a crop critical for food security in sub-Saharan Africa. The formation of viscoelastic melts is crucial for (bio)plastics production and the viscoelasticity, microstructure, and molecular properties of zein and pennisetin melts were determined here. The proteins were mixed with plasticizers (polyethyleneglycol or glycerol/citric acid) to form melts. The melts displayed a phase separated microstructure with protein-rich and plasticizer-rich regions with distinctly separate T gs. The pennisetin melts formed cross-links at temperatures above 60°C, which could be related to the high content of cysteine and methionine, as compared to zein. As a consequence, pennisetin melts showed a more thermocomplex behavior than zein melts. For zein melts, the mixture of glycerol and citric acid interacted with protein in addition to being a plasticizer causing a high-molecular weight shoulder in the molecular weight distribution. The study showed that, although both zein and pennisetin form viscoelastic melts, the choice of plasticizer strongly affects both melt structure and physical properties.

  • 11.
    Hagsten, Carin
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience. Lund University, Sweden.
    Altskär, Annika
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience.
    Gustafsson, Stefan
    Chalmers University of Technology, Sweden.
    Loren, Niklas
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience.
    Hamberg, Lars
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience.
    Innings, Fredrik
    Tetra Pak Processing Systems, Sweden.
    Paulsson, Marie
    Lund University, Sweden.
    Nylander, Tommy
    Lund University, Sweden.
    Composition and structure of high temperature dairy fouling2016Ingår i: Food Structure, ISSN 2213-3291, Vol. 7, s. 13-20Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The fouling structure and composition is dependent on the product, but also on the heating process applied to it. The structure will have profound effect on the cleaning process and the down time in the production plant. Here, the structure of high temperature (137 °C) milk fouling has been investigated, which so far has not been sufficiently studied in a systematic way. This particular fouling has a high content of the mineral calcium phosphate and a relatively low concentration of protein. Wide angle X-ray diffraction (WAXD) reveals a crystalline structure of calcium phosphate in agreement to the chemical analysis of the bulk layer. Microscopic investigations visualize the heterogeneous structure and energy dispersive X-ray spectroscopy (EDX) shows a spatial variation of the elements through the radius of the sample.

  • 12.
    Hagsten, Carin
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel. Lund University, Sweden.
    Altskär, Annika
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel.
    Gustafsson, Stefan
    Chalmers University of Technology, Sweden.
    Loren, Niklas
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel. Chalmers University of Technology, Sweden.
    Trägårdh, Christian
    Lund University, Sweden.
    Innings, Fredrik
    Tetra Pak Processing Systems, Sweden.
    Hamberg, Lars
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel.
    Paulsson, Marie
    Lund University,Sweden.
    Nylander, Tommy
    Lund University, Sweden.
    Structural and compositional changes during UHT fouling removal—Possible mechanisms of the cleaning process2019Ingår i: Food Structure, ISSN 2213-3291, Vol. 21, artikel-id 100118Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ultra-high temperature (UHT) treatment of milk forms a deposit or fouling in the processing equipment that is mineral-based with an enclosed protein network. This study addresses the fundamental mechanisms that control the removal of this deposit. For this purpose, the structural and compositional changes during the cleaning process have been studied. The structure analysis was performed with scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) on samples that were quenched at different stages of the cleaning process. It was found for acid cleaning that the mineral content is rapidly decreasing in the fouling layer as the cleaning continues, but there is still an intact protein structure with the similar thickness as the original fouling. For alkali cleaning, part of the protein structure was subsequently removed from the outside towards the stain-less steel as a function of time, while the mineral structure was mostly remaining. The break-up of the organic network structure, which likely involves depolymerization of protein aggregates, were found to control the cleaning efficiency. The weakening of the protein network facilitates the removal of the UHT fouling layer during the acid cleaning step and allow for an efficient cleaning cycle. The chemical reactions that occur within the fouling layer between the hydroxyl ions and the protein network was modeled according to a depolymerization reaction and a mechanistic model of the cleaning process is presented. © 2019

  • 13.
    Hamngren Blomqvist, C.
    et al.
    Chalmers University of Technology, Sweden.
    Gebäck, T.
    Chalmers University of Technology, Sweden .
    Altskär, Annika
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel. Chalmers University of Technology, Sweden.
    Hermansson, Ann-Marie
    Chalmers University of Technology, Sweden .
    Gustafsson, S.
    Chalmers University of Technology, Sweden .
    Loren, Niklas
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel. Chalmers University of Technology, Sweden .
    Olsson, E.
    Chalmers University of Technology, Sweden .
    Interconnectivity imaged in three dimensions: Nano-particulate silica-hydrogel structure revealed using electron tomography2017Ingår i: Micron, ISSN 0968-4328, E-ISSN 1878-4291, Vol. 100, s. 91-105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have used Electron Tomography (ET) to reveal the detailed three-dimensional structure of particulate hydrogels, a material category common in e.g. controlled release, food science, battery and biomedical applications. A full understanding of the transport properties of these gels requires knowledge about the pore structure and in particular the interconnectivity in three dimensions, since the transport takes the path of lowest resistance. The image series for ET were recorded using High-Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF-STEM). We have studied three different particulate silica hydrogels based on primary particles with sizes ranging from 3.6 nm to 22 nm and with pore-size averages from 18 nm to 310 nm. Here, we highlight the nanostructure of the particle network and the interpenetrating pore network in two and three dimensions. The interconnectivity and distribution of width of the porous channels were obtained from the three-dimensional tomography studies while they cannot unambiguously be obtained from the two-dimensional data. Using ET, we compared the interconnectivity and accessible pore volume fraction as a function of pore size, based on direct images on the nanoscale of three different hydrogels. From this comparison, it was clear that the finest of the gels differentiated from the other two. Despite the almost identical flow properties of the two finer gels, they showed large differences concerning the accessible pore volume fraction for probes corresponding to their (two-dimensional) mean pore size. Using 2D pore size data, the finest gel provided an accessible pore volume fraction of over 90%, but for the other two gels the equivalent was only 10–20%. However, all the gels provided an accessible pore volume fraction of 30–40% when taking the third dimension into account.

  • 14.
    Hamngren Blomqvist, Charlotte
    et al.
    Chalmers University of Technology, Sweden.
    Abrahamsson, Christoffer
    Chalmers University of Technology, Sweden.
    Gebäck, Tobias
    Chalmers University of Technology, Sweden.
    Altskär, Annika
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden.
    Hermansson, Anne-Marie
    Chalmers University of Technology, Sweden.
    Nyden, Magnus
    Chalmers University of Technology, Sweden; University of South Australia, Australia.
    Gustafsson, Stefan
    Chalmers University of Technology, Sweden.
    Loren, Niklas
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden.
    Olsson, Eva
    Chalmers University of Technology, Sweden.
    Pore size effects on convective flow and diffusion through nanoporous silica gels2015Ingår i: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 484, s. 288-296Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Material structure has great impact on mass transport properties, a relationship that needs to be understood on several length scales. Describing and controlling the properties of flow through soft materials are both challenges concerning the industrial use of gel structures. This paper reports on how the porous structure in nanoporous materials affects the water transport through them. We used three different silica gels with large differences in the pore sizes but of equal silica concentration. Particle morphology and gel structure were studied using high-resolution transmission electron microscopy and image analysis to estimate the pore size distribution and intrinsic surface area of each gel. The mass transport was studied using a flow measurement setup and nuclear magnetic resonance diffusometry. The average pore size ranged from approximately 500 nm down to approximately 40 nm. An acknowledged limit for convective flow to occur is in the pore size range between 100 and 200 nm. The results verified the existence of a non-linear relationship between pore size and liquid flow at length scales below 500 nm, experimentally. A factor of 4.3 in flow speed separated the coarser gel from the other two, which presented almost identical flow speed data despite a factor 3 in pore size difference. In the setup, the mass transport in the gel with the largest pores was flow dominated, while the mass transport in the finer gels was diffusion dominated. Besides providing new insights into mass transport as a function of pore sizes, we conclude that three-dimensional analysis of the structures is needed for a comprehensive understanding of the correlation between structure and mass transport properties.

  • 15.
    Hermansson, Elin
    et al.
    Chalmers University of Technology, Sweden.
    Schuster, Erich
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden.
    Lindgren, Lars
    Chalmers University of Technology, Sweden; Mölnlycke Health Care, Sweden.
    Altskär, Annika
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden.
    Ström, Anna
    Chalmers University of Technology, Sweden.
    Impact of solvent quality on the network strength and structure of alginate gels2016Ingår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 144, s. 289-296Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The influence of the mixture of water and alcohols on the solubility and properties of alginate and its calcium-induced gels is of interest for the food, wound care and pharmaceutical industries. The solvent quality of water with increasing amounts of ethanol (0-20%) on alginate was studied using intrinsic viscosity. The effect of ethanol addition on the rheological and mechanical properties of calcium alginate gels was determined. Small-angle X-ray scattering and transmission electron microscopy were used to study the network structure. It is shown that the addition of ethanol up to 15% (wt) increases the extension of the alginate chain, which correlates with increased moduli and stress being required to fracture the gels. The extension of the polymer chain is reduced at 20% (wt) ethanol, which is followed by reduced moduli and stress at breakage of the gels. The network structure of gels at high ethanol concentrations (24%) is characterized by thick and poorly connected network strands.

  • 16. Hillerstrom, A.
    et al.
    Andersson, M.
    Pedersen, J.S.
    Altskär, Annika
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Langton, Maud
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Van Stam, J.
    Transparency and wettability of PVP/PDMS-IPN synthesized in different organic solvents2009Ingår i: Journal of Applied Polymer Science, ISSN 0021-8995, E-ISSN 1097-4628, Vol. 114, nr 3, s. 1828-1839Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An interpenetrating polymer network (IPN) combining a hydrophobic polymer (polydimethylsiloxane, PDMS) and a hydrophilic polymer (polyvinylpyrrolidone, PVP) was synthesized in different solvents via a two-step preparation method. The solvent used during polymerization of the IPN showed a significant impact on the properties of the PVP/PDMS-IPN. The choice of solvent was affecting both the wettability and transparency of the PVP/ PDMS-IPN. The PVP/PDMS-IPNs turned hydrophilic in all the solvents used in this study, but the transition from a hydrophobic to a hydrophilic PVP/PDMS-IPN occurred at lower PVP concentration if a solvent with similar solubility parameter as PVP was chosen. Also, the PVP/PDMS-IPNs were transparent when the samples were polymerized in a good solvent for PVP. It was concluded that the properties of the PVP/PDMS-IPN can be tuned by the selection of the solvent used during polymerization. The size of the PVP phase domains in the PVP/PDMS-IPNs were analyzed with X-ray scattering techniques (SAXS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and differential scanning calorimetry (DSC), and the sizes of the domains were found to be smaller than 350 nm. © 2009 Wiley Periodicals, Inc.

  • 17.
    Langton, Maud
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Jordansson, E.
    Altskär, Annika
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Sorensen, C.
    Hermansson, Ann-Marie
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Microstructure and image analysis of mayonnaises1999Ingår i: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 13, nr 2, s. 113-125Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The microstructure of full-fat mayonnaise was characterised at different structural levels by using confocal laser scanning microscopy, CLSM, and transmission electron microscopy on freeze-etched samples. The size of droplets varied, and in 80% mayonnaise many very small droplets were found between larger droplets. The colloidal structural parameters were quantified on CLSM images. A stereological approach was used to estimate the droplet size, the interfacial surface area between the fat phase and water phase, and the size of the egg yolk aggregates. The mayonnaise samples were produced by a cold process line in a pilot plant equipment. A two-level fully factorial experimental design was used, with the processing parameters, (speed of the emulsification cylinder, the speed of the visco-rotor and the out-temperature) as design variables. The results showed that the speed of the emulsification cylinder had a main effect on the size of the droplets. No other effects were found when the speed of the emulsification cylinder was high. When the speed was slow, however, an interaction effect was found on the size of the droplets. The distribution of egg yolk was affected by the processing conditions and by the quality of the egg yolk. The storage modulus G? had higher values when the mayonnaise was formed of smaller droplets at a high emulsification cylinder speed. Lower values of G? were found when the mayonnaise was formed of larger droplets produced by a slower emulsification cylinder speed. © 1999 Elsevier Science Ltd.

  • 18.
    Longfils, Marco
    et al.
    Chalmers University of Technology, Sweden; University of Gothenburg, Sweden.
    Röding, Magnus
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel.
    Altskär, Annika
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel.
    Schuster, Erich
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel.
    Loren, Niklas
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel.
    Sarkka, Aila
    Chalmers University of Technology, Sweden; University of Gothenburg, Sweden.
    Rudemo, Mats
    Chalmers University of Technology, Sweden; University of Gothenburg, Sweden.
    Single particle raster image analysis of diffusion for particle mixtures2018Ingår i: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818, Vol. 269, nr 3, s. 269-281Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recently we complemented the raster image correlation spectroscopy (RICS) method of analysing raster images via estimation of the image correlation function with the method single particle raster image analysis (SPRIA). In SPRIA, individual particles are identified and the diffusion coefficient of each particle is estimated by a maximum likelihood method. In this paper, we extend the SPRIA method to analyse mixtures of particles with a finite set of diffusion coefficients in a homogeneous medium. In examples with simulated and experimental data with two and three different diffusion coefficients, we show that SPRIA gives accurate estimates of the diffusion coefficients and their proportions. A simple technique for finding the number of different diffusion coefficients is also suggested. Further, we study the use of RICS for mixtures with two different diffusion coefficents and investigate, by plotting level curves of the correlation function, how large the quotient between diffusion coefficients needs to be in order to allow discrimination between models with one and two diffusion coefficients. We also describe a minor correction (compared to published papers) of the RICS autocorrelation function. Lay description Diffusion is a key mass transport mechanism for small particles. Efficient methods for estimating diffusion coefficients are crucial for analysis of microstructures, for example in soft biomaterials. The sample of interest may consist of a mixture of particles with different diffusion coefficients. Here, we extend a method called Single Particle Raster Image Analysis (SPRIA) to account for particle mixtures and estimation of the diffusion coefficients of the mixture components. SPRIA combines elements of classical single particle tracking methods with utilizing the raster scan with which images obtained by using a confocal laser scanning microscope. In particular, single particles are identified and their motion estimated by following their center of mass. Thus, an estimate of the diffusion coefficient will be obtained for each particle. Then, we analyse the distribution of the estimated diffusion coefficients of the population of particles, which allows us to extract information about the diffusion coefficients of the underlying components in the mixture. On both simulated and experimental data with mixtures consisting of two and three components with different diffusion coefficients, SPRIA provides accurate estimates and, with a simple criterion, the correct number of mixture components is selected in most cases.

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  • 19.
    Lopez-Sanches, Patricia
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel. Maurten AB, Sweden.
    Fredriksson, Nils
    Maurten AB, Sweden.
    Larsson, Anette
    Chalmers University of Technology, Sweden.
    Altskär, Annika
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel. Chalmers University of Technology, Sweden.
    Ström, Anna K.
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel. Chalmers University of Technology, Sweden.
    High sugar content impacts microstructure, mechanics and release of calcium-alginate gels2018Ingår i: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 84, s. 26-33Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of calcium-alginate gels as carriers of food and pharmaceutical compounds is of great interest due the versatile properties of such systems. In this work, we investigated the influence of sugars (glucose:fructose) as co-solutes (15–60% (wt)) on the physico-chemical properties of calcium-alginate gel particles. Sugar concentrations above 15% (wt) reduced extensibility of alginate molecules, as shown by intrinsic viscosity measurements, and lead to a more open or less connected gel network with aggregated alginate strands. Furthermore, it is shown for the first time that sugar impacted swelling-deswelling ability of calcium alginate gels under simulated gastric (pH 1.2) and intestinal (pH 6.6) conditions. Release of sugar from calcium alginate gels with 15% (wt) and 30% (wt) sugar was close to Fickian diffusion mechanism, in both simulated gastric and intestinal fluid, with diffusion coefficient close to that previously reported for calcium-alginate gels with lower sugar contents. However, release from 60% (wt) gels in gastric fluid was slower than for 15 and 30% (wt) and, there was a drastic shrinkage of the gels under acid conditions. In intestinal fluid 60% (wt) gels showed slower release than gels with lower sugar content, this was hypothesised to be due to the lower surface area of these gels. Understanding the structure-function relationship of these gels is key to the successful design of delivery systems for food and biotechnological applications.

  • 20.
    Lopez-Sanchez, Patricia
    et al.
    Maurten AB, Sweden.
    Fredriksson, Nils
    Maurten AB, Sweden.
    Larsson, Anette
    Chalmers University of Technology, Sweden.
    Altskär, Annika
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel. Chalmers University of Technology, Sweden.
    Ström, Anna
    Chalmers University of Technology, Sweden.
    High sugar content impacts microstructure, mechanics and release of calcium-alginate gels2018Ingår i: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 84, s. 26-33Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The use of calcium-alginate gels as carriers of food and pharmaceutical compounds is of great interest due the versatile properties of such systems. In this work, we investigated the influence of sugars (glucose:fructose) as co-solutes (15–60% (wt)) on the physico-chemical properties of calcium-alginate gel particles. Sugar concentrations above 15% (wt) reduced extensibility of alginate molecules, as shown by intrinsic viscosity measurements, and lead to a more open or less connected gel network with aggregated alginate strands. Furthermore, it is shown for the first time that sugar impacted swelling-deswelling ability of calcium alginate gels under simulated gastric (pH 1.2) and intestinal (pH 6.6) conditions. Release of sugar from calcium alginate gels with 15% (wt) and 30% (wt) sugar was close to Fickian diffusion mechanism, in both simulated gastric and intestinal fluid, with diffusion coefficient close to that previously reported for calcium-alginate gels with lower sugar contents. However, release from 60% (wt) gels in gastric fluid was slower than for 15 and 30% (wt) and, there was a drastic shrinkage of the gels under acid conditions. In intestinal fluid 60% (wt) gels showed slower release than gels with lower sugar content, this was hypothesised to be due to the lower surface area of these gels. Understanding the structure-function relationship of these gels is key to the successful design of delivery systems for food and biotechnological applications.

  • 21.
    Loren, Niklas
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Altskär, Annika
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Hermansson, Ann-Marie
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Structure evolution during gelation at later stages of spinodal decomposition in gelatin/maltodextrin mixtures2001Ingår i: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 34, nr 23, s. 8117-8128Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The kinetics of phase separation and gelation in kinetically trapped gelatin/maltodextrin/water gels was studied using confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM). The time evolution of the morphology was followed by CLSM during temperature quenches from 60°C to between 1 and 40°C. The maltodextrin concentration was varied between 2.25% and 7.5% (w/w), and the gelatin concentration was held constant at 4% (w/w). Spinodal decomposition, self-similar growth, percolation-to-cluster transition, coalescence, and diffusion of maltodextrin inclusions were observed during the progress of gelation. The start and completion of these processes, the onset of phase separation, and the relative rates of phase separation and gelation were found to determine the morphology. The characteristic wavelength showed a crossover in its growth rate power law from one-third to one in a slowly gelling, near-symmetric system. Droplet and bicontinuous morphologies were observed in off-symmetric and near-symmetric quenches, respectively. Secondary phase separation occurred at low temperatures and near-symmetric composition. Partial coalescence and contracted flocculation were observed during the progress of gelation. Stereological measurements showed that the size of maltodextrin inclusions increases and that the volume fraction decreases with increasing quench temperature. In addition, the number of the maltodextrin inclusions decreases with increasing quench temperature.

  • 22.
    Malmgren, Bozena
    et al.
    Tetra Pak Dairy, Sweden.
    Ardö, Ylva
    University of Copenhagen, Denmark.
    Langton, Maud
    SLU Swedish University of Agricultural Sciences, Sweden.
    Altskär, Annika
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel.
    Bremer, Maria G.E.G.
    RIKILT Institute of Food Safety, The Netherlands.
    Dejmek, Petr
    Lund University, Sweden.
    Paulsson, Marie
    Lund University, Sweden.
    Changes in proteins, physical stability and structure in directly heated UHT milk during storage at different temperatures2017Ingår i: International Dairy Journal, ISSN 0958-6946, E-ISSN 1879-0143, Vol. 71, s. 60-75Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Changes occurring in directly heated UHT milk were studied during storage at 5, 22, 30 and 40 °C. Industrially produced UHT milk samples were analysed for changes in enzymatic activity, protein modification, destabilisation of casein micelles and relocation of milk proteins in relation to sedimentation and gel formation. Sedimentation occurred at all temperatures, and the protein composition of the sediments reflected the composition of its liquid phase; however, there was no α-lactalbumin, β-lactoglobulin or κ-casein present in sediments. Tendrils composed of β-lactoglobulin and κ-casein were seen on casein micelles after UHT treatment and grew in length prior to gelation. High degrees of lactosylation of proteins and peptides were clearly correlated with the absence of gelation and long tendrils. Gelled samples showed complete hydrolysis of intact β-casein, and limited lactosylation of β-lactoglobulin and κ-casein.

  • 23.
    Ovaska, Sami-Seppo
    et al.
    Lappeenranta University of Technology, Finland.
    Hiltunen, Salla
    Lappeenranta University of Technology, Finland.
    Ernstsson, Marie
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor, Material och ytteknik.
    Schuster, Erich
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design.
    Altskär, Annika
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design.
    Backfolk, Kaj
    Lappeenranta University of Technology, Finland.
    Characterization of rapeseed oil/coconut oil mixtures and their penetration into hydroxypropylated-starch-based barrier coatings containing an oleophilic mineral2016Ingår i: Progress in organic coatings, ISSN 0300-9440, E-ISSN 1873-331X, Vol. 101, s. 569-576Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A study was conducted that demonstrated that the blending of edible oils leads to changes in surface tension, thermal properties, viscosity, and oil penetration times through a barrier-coated paperboard. The results emphasize the significance of testing the oil and grease resistance (OGR) oil blends in order-to verify the suitability of the packaging material for real-life end-use applications. The results of the OGR determinations suggest that hydroxypropylated-starch-based composite coatings containing an oleophilic high aspect ratio mineral can be tailored for food shaving different fatty acid compositions by varying the pigmentation level. Compared to standard OGR tests, confocal laser scanning microscopy (CLSM)-based techniques make it possible to evaluate the oil penetration time and its diffusion behavior very accurately, both inside the coating layer and in the bulk matrix. It was found that, at room temperature, coconut oil tends to crystallize inside the substrate, inducing swelling of the coating layer, which probably has an influence on the physicomechanical properties of the packaging material.

  • 24.
    Qasi, Waqas
    et al.
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel. Chalmers University of Technology, Sweden.
    Wiklund, Johan
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel.
    Ekberg, Olle
    Lund University, Sweden .
    Altskär, Annika
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel.
    Stading, Mats
    RISE - Research Institutes of Sweden (2017-2019), Biovetenskap och material, Jordbruk och livsmedel. Chalmers University of Technology, Sweden.
    Shear and extensional rheology of commercial thickeners used for dysphagia management2017Ingår i: Journal of texture studies, ISSN 0022-4901, E-ISSN 1745-4603, Vol. 48, nr 6, s. 507-517Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    People who suffer from swallowing disorders, commonly referred to as dysphagia, are often restricted to a texture-modified diet. In such a diet, the texture of the fluid is modified mainly by the addition of gum or starch-based thickeners. For optimal modification of the texture, tunable rheological parameters are shear viscosity, yield stress, and elasticity. In this work, the flow properties of commercial thickeners obtained from major commercial suppliers were measured both in shear and extensional flow using a laboratory viscometer and a newly developed tube viscometry technique, termed Pulsed Ultrasound Velocimetry plus Pressure Drop (PUV+PD). The two methods gave similar results, demonstrating that the PUV+PD technique can be applied to study flow during the swallowing process in geometry similar to that of the swallowing tract. The thickeners were characterized in relation to extensional viscosity using the Hyperbolic Contraction Flow (HCF) method, with microscopy used as a complementary method for visualization of the fluid structure. The gum-based thickeners had significantly higher extensional viscosities than the starch-based thickeners. The rheological behavior was manifested in the microstructure as a hydrocolloid network with dimensions in the nanometer range for the gum-based thickeners. The starch-based thickeners displayed a granular structure in the micrometer range. In addition, the commercial thickeners were compared to model fluids (Boger, Newtonian and Shear-thinning) set to equal shear viscosity at 50s−1 and it was demonstrated that their rheological behavior could be tuned between highly elastic, extension-thickening to Newtonian. This article is protected by copyright. All rights reserved.

  • 25.
    Schuster, Erich
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik. Chalmers University of Technology, Sweden.
    Eckardt, Johanna
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik. Chalmers University of Technology, Sweden.
    Hermansson, Ann-Marie
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik. Chalmers University of Technology, Sweden.
    Larsson, Anette
    Chalmers University of Technology, Sweden.
    Loren, Niklas
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik. Chalmers University of Technology, Sweden.
    Altskär, Annika
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik. Chalmers University of Technology, Sweden.
    Microstructural, mechanical and mass transport properties of isotropic and capillary alginate gels2014Ingår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 10, nr 2, s. 357-366Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Macroscopically homogeneous and inhomogeneous calcium alginate gels are formed via internal or external addition of various amounts of calcium to an alginate solution. The externally formed gels contain parallel aligned capillary structures. The mechanical and mass transport properties and the microstructure of the differently set gels were characterized by rheological measurements, fluorescence recovery after photobleaching (FRAP) and transmission electron microscopy (TEM). TEM images show a zone of distorted anisotropic gel structure in the vicinity of the capillaries as well as indications of a lower degree of void connectivity. The diffusion rates of dextran at large distances from the capillaries were fast and capillary gels showed a plastic behaviour in comparison to the internally set gels. The results presented show large functional differences between the internally and externally set gels, which cannot be explained by the presence of capillaries alone.

  • 26.
    Schuster, Erich
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden.
    Sott, Kristin
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden.
    Ström, Anna
    Chalmers University of Technology, Sweden.
    Altskär, Annika
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden.
    Smisdom, Nick
    Hasselt University, Belgium; Flemish Institute for Technological Research, Belgium.
    Gebäck, Tobias
    Chalmers University of Technology, Sweden.
    Loren, Niklas
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden.
    Hermansson, Anne-Marie
    Chalmers University of Technology, Sweden.
    Interplay between flow and diffusion in capillary alginate hydrogels2016Ingår i: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 12, nr 17, s. 3897-3907Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Alginate gels with naturally occurring macroscopic capillaries have been used as a model system to study the interplay between laminar flow and diffusion of nanometer-sized solutes in real time. Calcium alginate gels that contain homogeneously distributed parallel-aligned capillary structures were formed by external addition of crosslinking ions to an alginate sol. The effects of different flow rates (0, 1, 10, 50 and 100 μl min-1) and three different probes (fluorescein, 10 kDa and 500 kDa fluorescein isothiocyanate-dextran) on the diffusion rates of the solutes across the capillary wall and in the bulk gel in between the capillaries were investigated using confocal laser scanning microscopy. The flow in the capillaries was produced using a syringe pump that was connected to the capillaries via a tube. Transmission electron microscopy revealed an open aggregated structure close to the capillary wall, followed by an aligned network layer and the isotropic network of the bulk gel. The most pronounced effect was observed for the 1 nm-diameter fluorescein probe, for which an increase in flow rate increased the mobility of the probe in the gel. Fluorescence recovery after photobleaching confirmed increased mobility close to the channel, with increasing flow rate. Mobility maps derived using raster image correlation spectroscopy showed that the layer with the lowest mobility corresponded to the anisotropic layer of ordered network chains. The combination of microscopy techniques used in the present study elucidates the flow and diffusion behaviors visually, qualitatively and quantitatively, and represents a promising tool for future studies of mass transport in non-equilibrium systems.

  • 27. Sharafi, Nooshin
    et al.
    Sepehri, Sobhan
    RISE Research Institutes of Sweden, Digitala system, Smart hårdvara.
    Andersson, Johanna
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Jordbruk och livsmedel.
    Lopez-Sanchez, Patricia
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Jordbruk och livsmedel.
    Schaller, Vincent
    RISE Research Institutes of Sweden, Digitala system, Smart hårdvara.
    Altskär, Annika
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Jordbruk och livsmedel.
    Grüttner, Cordula
    micromod Partikeltechnologie GmbH, Germany.
    Stading, Mats
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Jordbruk och livsmedel.
    Johansson, Christer
    RISE Research Institutes of Sweden, Digitala system, Smart hårdvara.
    Nanorheological analysis of xanthan/water solutions using magnetic nanoparticles with different particle sizes2020Ingår i: Annual Transactions of the Nordic Rheology Society, Vol. 28, s. 147-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We have studied nanorheological properties (viscosity and shear moduli) of aqueous xanthan solutions, in the oscillation frequency range up to 10 kHz by using magnetic particles that undergo Brownian relaxation and frequency dependent AC susceptibility (ACS). We used two magnetic nanoparticle (MNP) systems with different mean particle sizes of 80 nm and 100 nm. The determined viscosity and shear modulus of the diluted xanthan solutions from the ACS measurement of the two particle systems agree with traditional oscillatory rheological measurements. However, there is a particle size dependency that could be explained by comparing particles sizes with the xanthan microstructure

  • 28.
    Tibäck, Evelina
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Svelander, C.A.
    Ahrné, Lilia
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Altskär, Annika
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Alminger, M.A.G.
    Langton, Maud
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Mechanical and thermal pretreatments of crushed tomatoes: Effects on consistency and in vitro accessibility of lycopene2009Ingår i: Journal of Food Science, ISSN 0022-1147, E-ISSN 1750-3841, Vol. 74, nr 7, s. E386-E395Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effects of mechanical and thermal treatments on the consistency and in vitro lycopene accessibility of crushed tomatoes were evaluated. Different crushing intensities and a subsequent heat treatment carried out as a heat shock (95 °C for 8 min) or a boiling step (100 °C for 20 min) were examined. Additional homogenization was compared with milder crushing regarding the effect on lycopene content and in vitro accessibility. Textural properties, polygalacturonase and pectinmethylesterase activity, pectin degree of methoxylation, lycopene content, and in vitro lycopene accessibility were evaluated. Microstructure was studied using both light and transmission electron microscopy. Crushing and subsequent heating affected the pectin degree of methoxylation and the consistency of the crushed tomatoes. The mechanical and thermal treatments did not affect the lycopene content to any great extent; however, in vitro accessibility seemed to improve with extensive crushing followed by heating. Crushing or homogenization in itself was not enough to increase in vitro lycopene accessibility. © 2009 Institute of Food Technologists®.

  • 29.
    Wallin, Maria
    et al.
    Chalmers University of Technology, Sweden.
    Altskär, Annika
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design.
    Nordstierna, Lars
    Chalmers University of Technology, Sweden.
    Andersson, Martin
    Chalmers University of Technology, Sweden.
    Meso-ordered PEG-based particles2015Ingår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 31, nr 1, s. 13-16Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the formation of meso-ordered hydrogel particles by cross-linking poly(ethylene glycol) diacrylate (PEG-DA) in the presence of surfactants in a confined environment. The results demonstrated that well-ordered mesoporous hydrogel particles having a pore size of about 5 nm could be formed. It is suggested that these meso-ordered hydrogel particles might have unique drug-delivery capabilities

  • 30.
    Wojno, Sylwia
    et al.
    Chalmers University of Technology, Sweden.
    Ahlinder, Astrid
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Jordbruk och livsmedel.
    Altskär, Annika
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Jordbruk och livsmedel.
    Stading, Mats
    RISE Research Institutes of Sweden, Bioekonomi och hälsa, Jordbruk och livsmedel. Chalmers University of Technology, Sweden.
    Abitbol, Tiffany
    RISE Research Institutes of Sweden, Bioekonomi och hälsa. EPFL, Switzerland.
    Kádár, Roland
    Chalmers University of Technology, Sweden.
    Percolation and phase behavior in cellulose nanocrystal suspensions from nonlinear rheological analysis2023Ingår i: Carbohydrate Polymers, ISSN 0144-8617, E-ISSN 1879-1344, Vol. 308, artikel-id 120622Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We examine the influence of surface charge on the percolation, gel-point and phase behavior of cellulose nanocrystal (CNC) suspensions in relation to their nonlinear rheological material response. Desulfation decreases CNC surface charge density which leads to an increase in attractive forces between CNCs. Therefore, by considering sulfated and desulfated CNC suspensions, we are comparing CNC systems that differ in their percolation and gel-point concentrations relative to their phase transition concentrations. The results show that independently of whether the gel-point (linear viscoelasticity, LVE) occurs at the biphasic - liquid crystalline transition (sulfated CNC) or at the isotropic - quasi-biphasic transition (desulfated CNC), the nonlinear behavior appears to mark the existence of a weakly percolated network at lower concentrations. Above this percolation threshold, nonlinear material parameters are sensitive to the phase and gelation behavior as determined in static (phase) and LVE conditions (gel-point). However, the change in material response in nonlinear conditions can occur at higher concentrations than identified through polarized optical microscopy, suggesting that the nonlinear deformations could distort the suspensions microstructure such that for example a liquid crystalline phase (static) suspension could show microstructural dynamics similar to a biphasic system.

  • 31.
    Öhgren, Camilla
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Loren, Niklas
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Altskär, Annika
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Hermansson, A.-M.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Surface-directed structure formation of β-lactoglobulin inside droplets2011Ingår i: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 12, nr 6, s. 2235-2242Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The morphology of β-lactoglobulin structures inside droplets was studied during aggregation and gelation using confocal laser scanning microscopy (CLSM) equipped with a temperature stage and transmission electron microscopy (TEM). The results showed that there is a strong driving force for the protein to move to the interface between oil and water in the droplet, and the β-lactoglobulin formed a dense shell around the droplet built up from the inside of the droplets. Less protein was found inside the droplets. The longer the β-lactoglobulin was allowed to aggregate prior to gel formation, the larger the part of the protein went to the interface, resulting in a thicker shell and very little material being left inside the droplets. The droplets were easily deformed because no network stabilizes them. When 0.5% emulsifier, polyglycerol polyresinoleat (PGPR), was added to the oil phase, the β-lactoglobulin was situated both inside the droplets and at the interface between the droplets and the oil phase; when 2% PGPR was added, the β-lactoglobulin structure was concentrated to the inside of the droplets. The possibility to use the different morphological structures of β-lactoglobulin in droplets to control the diffusion rate through a β-lactoglobulin network was evaluated by fluorescence recovery after photobleaching (FRAP). The results show differences in the diffusion rate due to heterogeneities in the structure: the diffusion of a large water-soluble molecule, FITC-dextran, in a dense particulate gel was 1/4 of the diffusion rate in a more open particulate β-lactoglobulin gel in which the diffusion rate was similar to that in pure water.

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