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  • 1.
    de Kort, Daan W
    et al.
    Wageningen University, The Netherlands; TI-COAST, The Netherlands.
    Schuster, Erich
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Hoeben, Freek J M
    TI-COAST, The Netherlands; SyMO-Chem B.V, The Netherlands.
    Barnes, Ryan
    University of California, USA.
    Emondts, Meike
    University of California, USA.
    Janssen, Henk M
    TI-COAST, The Netherlands; SyMO-Chem B.V, The Netherlands.
    Loren, Niklas
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Han, Songi
    University of California, USA.
    Van As, Henk
    Wageningen University, The Netherlands; TI-COAST, The Netherlands.
    van Duynhoven, John P M
    Wageningen University, The Netherlands; TI-COAST, The Netherlands ; Unilever R&D, The Netherlands.
    Heterogeneity of Network Structures and Water Dynamics in κ-Carrageenan Gels Probed by Nanoparticle Diffusometry.2018In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 34, no 37Article in journal (Refereed)
    Abstract [en]

    A set of functionalized nanoparticles (PEGylated dendrimers, d = 2.8-11 nm) was used to probe the structural heterogeneity in Na+/K+ induced κ-carrageenan gels. The self-diffusion behavior of these nanoparticles as observed by 1H pulsed-field gradient NMR, fluorescence recovery after photobleaching, and raster image correlation spectroscopy revealed a fast and a slow component, pointing toward microstructural heterogeneity in the gel network. The self-diffusion behavior of the faster nanoparticles could be modeled with obstruction by a coarse network (average mesh size <100 nm), while the slower-diffusing nanoparticles are trapped in a dense network (lower mesh size limit of 4.6 nm). Overhauser dynamic nuclear polarization-enhanced NMR relaxometry revealed a reduced local solvent water diffusivity near 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO)-labeled nanoparticles trapped in the dense network, showing that heterogeneity in the physical network is also reflected in heterogeneous self-diffusivity of water. The observed heterogeneity in mesh sizes and in water self-diffusivity is of interest for understanding and modeling of transport through and release of solutes from heterogeneous biopolymer gels.

  • 2. Deschout, H.
    et al.
    Hagman, Joel
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Fransson, S.
    Jonasson, J.
    Rudemo, M.
    Loren, Niklas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Straightforward FRAP for quantitative diffusion measurements with a laser scanning microscope2010In: Optics Express, ISSN 1094-4087, E-ISSN 1094-4087, Vol. 18, no 22, p. 22886-22905Article in journal (Refereed)
    Abstract [en]

    Confocal or multi-photon laser scanning microscopes are convenient tools to perform FRAP diffusion measurements. Despite its popularity, accurate FRAP remains often challenging since current methods are either limited to relatively large bleach regions or can be complicated for non-specialists. In order to bring reliable quantitative FRAP measurements to the broad community of laser scanning microscopy users, here we have revised FRAP theory and present a new pixel based FRAP method relying on the photo bleaching of rectangular regions of any size and aspect ratio. The method allows for fast and straightforward quantitative diffusion measurements due to a closed-form expression for the recovery process utilizing all available spatial and temporal data. After a detailed validation, its versatility is demonstrated by diffusion studies in heterogeneous biopolymer mixtures. © 2010 Optical Society of America.

  • 3. 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 droplets2009In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 10, no 6, p. 1446-1453Article in journal (Refereed)
    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.

  • 4. Fransson, S.
    et al.
    Peleg, O.
    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.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Kroger, M.
    Modelling and confocal microscopy of biopolymer mixtures in confined geometries2010In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 6, no 12, p. 2713-2722Article in journal (Refereed)
  • 5.
    Gmoser, Rebecca
    et al.
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Bordes, Romain
    Chalmers University of Technology, Sweden.
    Nilsson, Gustav
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Altskär, Annika
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Stading, Mats
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience. Chalmers University of Technology, Sweden.
    Loren, Niklas
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience. Chalmers University of Technology, Sweden.
    Berta, Marco
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Effect of dispersed particles on instant coffee foam stability and rheological properties2017In: European Food Research and Technology, ISSN 1438-2377, E-ISSN 1438-2385, Vol. 243, no 1, p. 115-121Article in journal (Refereed)
    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.

  • 6. Guillot, G.
    et al.
    Loren, Niklas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Rudemo, M.
    Spatial prediction of weed intensities from exact count data and image-based estimates2009In: Journal of the Royal Statistic Society, Series C: Applied Statistics, ISSN 0035-9254, E-ISSN 1467-9876, Vol. 58, no 4, p. 525-542Article in journal (Refereed)
    Abstract [en]

    Collecting weed exact counts in an agricultural field is easy but extremely time consuming. Image analysis algorithms for object extraction applied to pictures of agricultural fields may be used to estimate the weed content with a high resolution (about 1 m2), and pictures that are acquired at a large number of sites can be used to obtain maps of weed content over a whole field at a reasonably low cost. However, these image-based estimates are not perfect and acquiring exact weed counts also is highly useful both for assessing the accuracy of the image-based algorithms and for improving the estimates by use of the combined data. We propose and compare various models for image index and exact weed count and we use them to assess how such data should be combined to obtain reliable maps. The method is applied to a real data set from a 30-ha field. We show that using image estimates in addition to exact counts allows us to improve the accuracy of maps significantly. We also show that the relative performances of the methods depend on the size of the data set and on the specific methodology (full Bayes versus plug-in) that is implemented. © 2009 Royal Statistical Society.

  • 7.
    Gårdebjer, Sophie
    et al.
    Chalmers University of Technology, Sweden.
    Gebäck, Tobias
    Chalmers University of Technology, Sweden.
    Andersson, Torbjörn
    Chalmers University of Technology, Sweden; Tetra Pak AB, Sweden.
    Fratini, Enrico
    University of Florence, Italy.
    Baglioni, Pietro
    University of Florence, Italy.
    Bordes, Romain
    Chalmers University of Technology, Sweden.
    Viridén, Anna
    Chalmers University of Technology, Sweden; AstraZeneca, Sweden.
    Nicholas, Mark
    Chalmers University of Technology, Sweden; AstraZeneca, Sweden.
    Loren, Niklas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden.
    Larsson, Anette
    Chalmers University of Technology, Sweden.
    The impact of interfaces in laminated packaging on transport of carboxylic acids2016In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 518, p. 305-312Article in journal (Refereed)
    Abstract [en]

    The permeability of oleic and acetic acid through low density polyethylene (LDPE) and ethylene acrylic acid (EAA) have been measured using diffusion cells. In addition, the permeability through combinations of LDPE and EAA in the form of laminates with different numbers of layers has been determined. Oleic acid shows an almost 30 times higher permeability compared to acetic acid, which was partly explained by the adsorption of oleic acid to the film surface during the permeability experiment. In addition, the permeability is lower for both oleic and acetic acid in the laminates compared to the pure films. The decreased permeability can be explained by the presence of crystalline domains close to the interface. This is supported by SAXS data which suggests an ordering of polymer chains in the EAA film close to the interface. In summary, the results show that it is possible to create barrier materials with decreased permeability, which is interesting for example in the packaging industry.

  • 8.
    Hagman, Joel
    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.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Effect of gelatin gelation kinetics on probe diffusion determined by FRAP and rheology2010In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 11, no 12, p. 3359-3366Article in journal (Refereed)
    Abstract [en]

    The time-dependent diffusion and mechanical properties of gelatin in solution, in the gel state, and during the sol/gel transition were determined using fluorescence recovery after photobleaching (FRAP) and rheology. The parameters in the experimental design were 2% w/w and 5% w/w gelatin concentration; 15, 20, and 25?C end quench temperatures; and Na 2-fluorescein, 10 kDa FITC-dextran, and 500 kDa FITC-dextran as diffusion probes. The samples were monitored in solution at 60?C, during quenching, for 75 min at end quench temperatures and after 1, 7, and 14 days of storage at the end quench temperature. The effect of temperature on the probe diffusion was normalized by determining the free diffusion of the probes in pure water for the different temperatures. The results gained by comparing FRAP and rheology showed that FRAP is able to capture structural changes in the gelatin before gelation occurs, which was interpreted as a formation of transient networks. This was clearly seen for 2% w/w gelatin and 20 and 25?C end quench temperatures. The structural changes during sol/gel transition are detected only by the larger probes, giving information about the typical length scales in the gelatin structure. The normalized diffusion rate increased after 7 and 14 days of storage. This increase was most pronounced for fluorescein but was also seen for the larger probes. © 2010 American Chemical Society.

  • 9.
    Hagman, Joel
    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.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Probe diffusion in ?-carrageenan gels determined by fluorescence recovery after photobleaching2012In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 29, no 1, p. 106-115Article in journal (Refereed)
    Abstract [en]

    The effects of free volume and heterogeneity on probe diffusion in . ?-carrageenan gels were determined by fluorescence recovery after photobleaching (FRAP) and rheology. By changing the ionic conditions, biopolymer concentration and end temperature, different microstructures and aggregation kinetics in the . ?-carrageenan gels were evaluated. The results of the FRAP measurements were compared to transmission electron microscopy (TEM) and nuclear magnetic resonance diffusometry (NMRd) data from previous studies. The results showed that the free diffusion rates of the probe (FITC dextran) in water were influenced by both temperature and ionic conditions. The free diffusion values were used for normalization of the diffusion rates in the . ?-carrageenan gel measurements. The compatibility between FITC dextran with different molecular weights (10 and 500 kDa) and . ?-carrageenan was evaluated. The results showed that the larger FITC dextran probe phase separates; therefore only the 10 kDa FITC dextran probe was used in the FRAP experiments. FRAP measurements and NMRd probe diffusion in combination with TEM in . ?-carrageenan revealed that the void space, degree of aggregation and heterogeneity influence the probe diffusion rate. The . ?-carrageenan gelation was analyzed at different end temperatures using rheology and FRAP. The FITC dextran probe diffusion was not influenced by . ?-carrageenan aggregation, regardless of rheological gelation kinetics and storage modulus near the gel point. This indicates that the average void space between the gel strands is larger than the size of the probe. Good correlation between the microstructure and the probe diffusion rate in . ?-carrageenan gel with different ionic conditions and constant biopolymer concentration were obtained with TEM and FRAP. © 2012 Elsevier Ltd.

  • 10.
    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 fouling2016In: Food Structure, ISSN 2213-3291, Vol. 7, p. 13-20Article in journal (Refereed)
    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.

  • 11.
    Hagsten, Carin
    et al.
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience. Lund University, Sweden.
    Altskär, Annika
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Gustafsson, Stefan
    Chalmers University of Technology, Sweden.
    Loren, Niklas
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience. Chalmers University of Technology, Sweden.
    Trägårdh, Christian
    Lund University, Sweden.
    Innings, Fredrik
    Tetra Pak Processing Systems, Sweden.
    Hamberg, Lars
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Paulsson, Marie
    Lund University,Sweden.
    Nylander, Tommy
    Lund University, Sweden.
    Structural and compositional changes during UHT fouling removal—Possible mechanisms of the cleaning process2019In: Food Structure, ISSN 2213-3291, Vol. 21, article id 100118Article in journal (Refereed)
    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

  • 12.
    Hamngren Blomqvist, C.
    et al.
    Chalmers University of Technology, Sweden.
    Gebäck, T.
    Chalmers University of Technology, Sweden .
    Altskär, Annika
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience. 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, Bioscience and Materials, Agrifood and Bioscience. 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 tomography2017In: Micron, ISSN 0968-4328, E-ISSN 1878-4291, Vol. 100, p. 91-105Article in journal (Refereed)
    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.

  • 13.
    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 gels2015In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 484, p. 288-296Article in journal (Refereed)
    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.

  • 14.
    Hermansson, Ann-Marie
    et al.
    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.
    Loren, Niklas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    New approaches to characterizing food microstructures.2000In: MRS Bulletin, no Dec, p. 30-36Article in journal (Other academic)
  • 15. Jonasson, J.K.
    et al.
    Hagman, J.
    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.
    Bernin, D.
    NydEn, M.
    Rudemo, M.
    Pixel-based analysis of FRAP data with a general initial bleaching profile2010In: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818, Vol. 239, no 2, p. 142-153Article in journal (Refereed)
  • 16. Jonasson, J.K.
    et al.
    Loren, Niklas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Olofsson, P.
    Nyden, M.
    Rudemo, M.
    A pixel-based likelihood framework for analysis of fluorescence recovery after photobleaching data2008In: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818, Vol. 232, no 2, p. 260-269Article in journal (Refereed)
    Abstract [en]

    A new framework for the estimation of diffusion coefficients from data on fluorescence recovery after photobleaching (FRAP) with confocal laser scanning microscopy (CLSM) is presented. It is a pixel-based statistical methodology that efficiently utilizes all information about the diffusion process in the available set of images. The likelihood function for a series of images is maximized which gives both an estimate of the diffusion coefficient and a corresponding error. This framework opens up possibilities (1) to obtain localized diffusion coefficient estimates in both homogeneous and heterogeneous materials, (2) to account for time differences between the registrations at the pixels within each image, and (3) to plan experiments optimized with respect to the number of replications, the number of bleached regions for each replicate, pixel size, the number of pixels, the number of images in each series etc. To demonstrate the use of the new framework, we have applied it to a simple system with polyethylene glycol (PEG) and water where we find good agreement with diffusion coefficient estimates from NMR diffusometry. In this experiment, it is also shown that the effect of the point spread function is negligible, and we find fluorochrome-concentration levels that give a linear response function for the fluorescence intensity. © 2008 The Authors.

  • 17.
    Karlsson, Kristina
    et al.
    Chalmers University of Technology, Sweden.
    Larsson, Emanuel
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Loren, Niklas
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Stading, Mats
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience. Chalmers University of Technology, Sweden.
    Rigdahl, Mikael
    Chalmers University of Technology, Sweden.
    Extrusion Parameters for Foaming of a β-Glucan Concentrate2019In: Journal of polymers and the environment, ISSN 1566-2543, E-ISSN 1572-8919, Vol. 27, no 6, p. 1167-1177Article in journal (Refereed)
    Abstract [en]

    Plastics is a group of materials commonly encountered on a daily basis by many people. They have enabled rapid, low-cost manufacturing of products with complicated geometries and have contributed to the weight reduction of heavy components, especially when produced into a foamed structure. Despite the many advantages of plastics, some drawbacks such as the often fossil-based raw-material and the extensive littering of the material in nature, where it is not degraded for a very long time, needs to be dealt with. One way to address at least one of the issues could be to use polymers from nature instead of fossil-based ones. Here, a β-glucan concentrate originating from barley was investigated. The concentrate was processed into a foam by hot-melt extrusion, and the processing window was established. The effect of different blowing agents was also investigated. Water or a combination of water and sodium bicarbonate were used as blowing agents, the latter apparently giving a more uniform pore structure. The porous structure of the foamed materials was characterized mainly by using a combination of confocal laser scanning microscope and image analysis. The density of the samples was estimated and found to be in a similar range as some polyurethane foams. A set of 3D parameters were also quantified on two selected samples using X-ray microtomography in combination with image analysis, where it was indicated that the porous structure had a pre-determined direction, which followed the direction of the extrusion process. © 2019, The Author(s).

  • 18. Kvarnstrom, M.
    et al.
    Westergard, A.
    Loren, Niklas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Nyden, M.
    Brownian dynamics simulations in hydrogels using an adaptive time-stepping algorithm2009In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 79, no 1, p. 16102-Article in journal (Refereed)
    Abstract [en]

    The adaptive time-stepping algorithm for Brownian simulation of solute diffusion in three-dimensional complex geometries previously developed by the authors of this paper was applied to heterogeneous three-dimensional polymer hydrogel structures. The simulations were performed on reconstructed three-dimensional hydrogels. The obstruction effect from the gel strands on water and diffusion of dendrimers with different sizes were determined by simulations and compared with experimental nuclear magnetic resonance diffusometry data obtained from the same material. It was concluded that obstruction alone cannot explain the observed diffusion rates, but an interaction between the dendrimers and the gel strands should be included in the simulations. The effect of a sticky-wall interaction potential with geometrically distributed residence times on the diffusion rate has been studied. It was found that sticky-wall interaction is a possible explanation for the discrepancy between simulated and experimental diffusion data for dendrimers of different sizes diffusing in hydrogels. © 2009 The American Physical Society.

  • 19.
    Kvist, Patric
    et al.
    Chalmers University of Technology, Sweden.
    Schuster, Erich
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience. Chalmers University of Technology, Sweden.
    Loren, Niklas
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience. Chalmers University of Technology, Sweden.
    Rasmuson, Anders
    Chalmers University of Technology, Sweden.
    Using fluorescent probes and FRAP to investigate macromolecule diffusion in steam-exploded wood2018In: Wood Science and Technology, ISSN 0043-7719, E-ISSN 1432-5225, Vol. 52, no 5, p. 1395-1410Article in journal (Refereed)
    Abstract [en]

    Diffusion of fluorescently labeled dextran of varying molecular weight in wood pretreated by steam explosion was studied with a confocal microscope. The steam explosion experiments were conducted at relatively mild conditions relevant for materials biorefinery at a pressure of 14 bars for 10 min. The method of fluorescence recovery after photobleaching (FRAP) was used to perform diffusion measurements locally in the wood microstructure. It was found that the FRAP methodology can be used to observe differences in the diffusion coefficient based on localization in the microstructure, i.e., earlywood, latewood, and cell wall. Microscopic changes due to steam explosion were seen to increase diffusion of the smaller 3-kDa dextran diffusion probe in the earlywood, while the latewood structure was not affected in any significant way. Macroscopic changes to the structure in the form of ruptures due to the steam explosion pretreatment were observed to increase the rate of diffusion for the larger 40-kDa dextran probe.

  • 20.
    Longfils, M.
    et al.
    Chalmers University of Technology, Sweden; University of Gothenburg, Sweden.
    Röding, Magnus
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Altskar, Annika
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Schuster, Erich
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Loren, Niklas
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Sarkka, A.
    Chalmers University of Technology, Sweden; University of Gothenburg, Sweden.
    Rudemo, M.
    Chalmers University of Technology, Sweden; University of Gothenburg, Sweden.
    Single particle raster image analysis of diffusion for particle mixtures2018In: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818, Vol. 269, no 3, p. 269-281Article in journal (Refereed)
    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.

  • 21.
    Longfils, M.
    et al.
    Chalmers University of Technology, Sweden; University of Gothenburg, Sweden.
    Schuster, Erich
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Loren, Niklas
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Särkä, A.
    Chalmers University of Technology, Sweden; University of Gothenburg, Sweden.
    Rudemo, M.
    Chalmers University of Technology, Sweden; University of Gothenburg, Sweden.
    Single particle raster image analysis of diffusion2017In: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818, Vol. 266, no 1, p. 3-14Article in journal (Refereed)
    Abstract [en]

    As a complement to the standard RICS method of analysing Raster Image Correlation Spectroscopy images with estimation of the image correlation function, we introduce the method SPRIA, Single Particle Raster Image Analysis. Here, we start by identifying individual particles and estimate the diffusion coefficient for each particle by a maximum likelihood method. Averaging over the particles gives a diffusion coefficient estimate for the whole image. In examples both with simulated and experimental data, we show that the new method gives accurate estimates. It also gives directly standard error estimates. The method should be possible to extend to study heterogeneous materials and systems of particles with varying diffusion coefficient, as demonstrated in a simple simulation example. A requirement for applying the SPRIA method is that the particle concentration is low enough so that we can identify the individual particles. We also describe a bootstrap method for estimating the standard error of standard RICS.

  • 22.
    Longfils, Marco
    et al.
    Chalmers University of Technology, Sweden.
    Schuster, Erich
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design.
    Särkkä, Aila
    Chalmers University of Technology, Sweden.
    Loren, Niklas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design.
    Rudemo, Mats
    Chalmers University of Technology, Sweden.
    Single particle raster image diffusion analysis2015In: Proceedings of the 14th International Congress for Stereology and Image Analysis, 2015, , p. 3Conference paper (Refereed)
  • 23.
    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 mixtures2001In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 34, no 23, p. 8117-8128Article in journal (Refereed)
    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.

  • 24.
    Loren, Niklas
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design.
    Hagman, Joel
    RISE, SP – Sveriges Tekniska Forskningsinstitut.
    Jonasson, Jenny K.
    Chalmers University of Technology, Sweden.
    Deschout, Hendrik
    Ghent University, Belgium.
    Bernin, Diana
    Chalmers University of Technology, Sweden.
    Cella-Zanacchi, Francesca
    Istituto Italiano di Tecnologia, Italy.
    Diaspro, Alberto
    Istituto Italiano di Tecnologia, Italy.
    McNally, James G.
    Helmholtz Center Berlin, Germany.
    Ameloot, Marcel
    Hasselt University, Belgium.
    Smisdom, Nick
    Hasselt University, Belgium.
    Nyden, Magnus
    University of South Australia, Australia.
    Hermansson, Anne-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design.
    Rudemo, Mats
    Chalmers University of Technology, Sweden.
    Braeckmans, Kevin
    Ghent University, Belgium.
    Fluorescence recovery after photobleaching in material and life sciences: putting theory into practice2015In: Quarterly reviews of biophysics (Print), ISSN 0033-5835, E-ISSN 1469-8994, Vol. 48, no 3, p. 323-387Article in journal (Refereed)
    Abstract [en]

    Fluorescence recovery after photobleaching (FRAP) is a versatile tool for determining diffusion and interaction/binding properties in biological and material sciences. An understanding of the mechanisms controlling the diffusion requires a deep understanding of structure-interaction-diffusion relationships. In cell biology, for instance, this applies to the movement of proteins and lipids in the plasma membrane, cytoplasm and nucleus. In industrial applications related to pharmaceutics, foods, textiles, hygiene products and cosmetics, the diffusion of solutes and solvent molecules contributes strongly to the properties and functionality of the final product. All these systems are heterogeneous, and accurate quantification of the mass transport processes at the local level is therefore essential to the understanding of the properties of soft (bio)materials. FRAP is a commonly used fluorescence microscopy-based technique to determine local molecular transport at the micrometer scale. A brief high-intensity laser pulse is locally applied to the sample, causing substantial photobleaching of the fluorescent molecules within the illuminated area. This causes a local concentration gradient of fluorescent molecules, leading to diffusional influx of intact fluorophores from the local surroundings into the bleached area. Quantitative information on the molecular transport can be extracted from the time evolution of the fluorescence recovery in the bleached area using a suitable model. A multitude of FRAP models has been developed over the years, each based on specific assumptions. This makes it challenging for the non-specialist to decide which model is best suited for a particular application. Furthermore, there are many subtleties in performing accurate FRAP experiments. For these reasons, this review aims to provide an extensive tutorial covering the essential theoretical and practical aspects so as to enable accurate quantitative FRAP experiments for molecular transport measurements in soft (bio)materials.

  • 25.
    Loren, Niklas
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Hagslatt, H.
    Nyden, M.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Water mobility in heterogeneous emulsions determined by a new combination of confocal laser scanning microscopy, image analysis, nuclear magnetic resonance diffusometry, and finite element method simulation2005In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 122, no 2, p. 24716-Article in journal (Refereed)
    Abstract [en]

    Nuclear magnetic resonance (NMR) diffusometry and confocal laser scanning microscopy (CLSM) were combined in a quantitative way in finite element calculations of water propagation in CLSM images obtained from a very heterogeneous emulsion. The propagators calculated on the basis of microstructure were Fourier transformed and subsequently compared with the echo decays obtained by the NMR diffusometry method. The results showed very good agreement between microstructure based calculations and experiments, indicating that the short gradient pulse approximation in the NMR diffusometry experiment holds for a certain q range. Furthermore, the CLSM was able to achieve a relevant two-dimensional microstructure although some discrepancy at low q values was noted. This effect is attributed to the inherent three-dimensional connectivity between the water domains in this type of structures, making the calculations slightly underestimate the water diffusion at longer distances. © 2005 American Institute of Physics.

  • 26.
    Loren, Niklas
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Hamberg, Lars
    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.
    Measuring shapes for application in complex food structures2006In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 20, no 5, p. 712-722Article in journal (Refereed)
    Abstract [en]

    The image analysis method of Fourier shape description is implemented to analyse shaped food microstructural entities, independent of their complexity, because entity shape is an important and nearly unexploited possibility for designing food material properties. The method is described in four steps: the accuracy of image acquisition, representation of the object outline, calculation of components and interpretation of the components, all focusing on colloidal food system applications. Three different common food systems are used to emphasise the possibilities that Fourier shape description offers for food structure design and food processing. Fourier shape measurements make it possible to quantify, present a typical shape and determine the distribution of shape independently of size of model food suspension consisting of complex shaped entities. This was done in an automatic and replicable way. The time evolution of entities structured in a flow field during model processing is analysed using Fourier shape descriptors. Graphs of time-dependent, low order single Fourier components allow control of the entity shape during processing. Differences in the shape of water domains in heterogeneous emulsions are quantified and classified on different length scales using a multivariate hypothesis test. © 2005 Elsevier Ltd. All rights reserved.

  • 27.
    Loren, Niklas
    et al.
    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.
    Phase separation and gel formation in kinetically trapped gelatin/maltodextrin gels.2000In: International Journal of Biological Macromolecules, Vol. 27, p. 249-262Article in journal (Refereed)
  • 28.
    Loren, Niklas
    et al.
    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.
    Williams, M.A.K.
    Lundin, Leif
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Foster, T.J.
    Hubbard, C.D.
    Phase separation induced by conformational ordering of gelatin in gelatin/maltodextrin mixtures2001In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 34, no 2, p. 289-297Article in journal (Refereed)
    Abstract [en]

    Mixtures of gelatin and maltodextrin in aqueous solution have been quenched to temperatures at which they are initially miscible but where gelatin ordering is initiated. In many cases phase separation was observed to occur after a significant time delay, and the dependence of these delays on quench temperature and biopolymer concentration has been studied in detail using turbidity measurements and confocal laser scanning microscopy (CLSM). Furthermore, by observing the optical rotation (OR) and turbidity of the system simultaneously, the gelatin helix content and the time delay before the onset of phase separation were monitored concurrently. The observed delay times were found to correspond to the time taken for the development of a certain degree of gelatin ordering, which drives the separation process. A further consequence of gelatin ordering is the viscosifying of the solution and, at sufficient concentrations, the formation of a gel. Therefore, rheological measurements have been used in addition to turbidity measurements and CLSM in order to monitor further the structural development of the systems. A comparison of the data obtained from these techniques shows that while the development of a certain elasticity will trap the system morphology, this elasticity is not directly related to that found at the gel point. At low maltodextrin concentrations, where phase separation was not detected by turbidity, transmission electron microscopy (TEM) has been used to examine the microstructure on a smaller length scale.

  • 29.
    Loren, Niklas
    et al.
    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.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Confocal fluorescence microscopy (CLSM) for food structure characterisation2007In: Understanding and Controlling the Microstructure of Complex Foods, p. 232-260Article in journal (Refereed)
    Abstract [en]

    * Introduction * Principles of modern CLSM * CLSM and the study of food structure * Application of CLSM to food systems * Measuring and modelling using CLSM images * Conclusions and future trends * References. © 2007 Woodhead Publishing Limited. All rights reserved.

  • 30.
    Loren, Niklas
    et al.
    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.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Confocal laser scanning microscopy and image analysis of kinetically trapped phase-separated gelatin/maltodextrin gels1999In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 13, no 2, p. 185-198Article in journal (Refereed)
    Abstract [en]

    The effect of phase separation on the gelatin/maltodextrin systems has been studied using confocal laser scanning microscopy and image analysis. Stereological image analysis has been used to analyse the effect of different cooling rates, holding times, holding temperatures and gelatin types on the microstructure at pH 5.3. The quantified microstructural parameters were the volume-weighted mean volume, the interfacial area and the area fraction. A factorial experimental design was used, with cooling rate (0.2°C/min, 1°C/min, 10°C/min), holding time (0 min, 10 min, 20 min), holding temperature (20°C, 25°C, 30°C), and two different gelatin types (LH, PS) as design parameters. Gelatin lime hide (LH) has an isoelectric point of pH 4.7, and gelatin pig skin (PS), has an isoelectric point of pH 9.1. The composition was kept constant at 4% gelatin and 5% maltodextrin. The results showed that the phase-separated system was gelatin continuous. The size of the maltodextrin inclusions decreases with increasing cooling rate and was largest at the lowest cooling rate (0.2°C/min). Gelatin PS has larger maltodextrin inclusions and a smaller interfacial area than gelatin LH. The size of the maltodextrin inclusions varied in diameter between 3 and 10 ?m for gelatin LH and between 3 and 18 ?m for gelatin PS. The size of the maltodextrin inclusions increases with increasing holding time and was largest at 20 min. The interfacial area increases with increasing cooling rates and was largest at 10°C/min. A region was found where the phase separation and the gel formation competed with each other in connection with mobility. The residence time in that region and how fast the sample proceeds through it, are important for the morphology of the resulting microstructure. © 1999 Elsevier Science Ltd.

  • 31.
    Loren, Niklas
    et al.
    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.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Determination of temperature dependent structure evolution by fast-Fourier transform at late stage spinodal decomposition in bicontinuous biopolymer mixtures.2002In: Journal of Chemical Physics, Vol. 116, no 23, p. 10536-10546Article in journal (Refereed)
  • 32.
    Loren, Niklas
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Nyden, M.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Determination of local diffusion properties in heterogeneous biomaterials2009In: Advances in Colloid and Interface Science, ISSN 0001-8686, E-ISSN 1873-3727, Vol. 150, no 1, p. 42139-Article in journal (Refereed)
    Abstract [en]

    The coupling between structure and diffusion properties is essential for the functionality of heterogeneous biomaterials. Structural heterogeneity is defined and its implications for time-dependent diffusion are discussed in detail. The effect of structural heterogeneity in biomaterials on diffusion and the relevance of length scales are exemplified with regard to different biomaterials such as gels, emulsions, phase separated biopolymer mixtures and chocolate. Different diffusion measurement techniques for determination of diffusion properties at different length and time scales are presented. The interplay between local and global diffusion is discussed. New measurement techniques have emerged that enable simultaneous determination of both structure and local diffusion properties. Special emphasis is given to fluorescence recovery after photobleaching (FRAP). The possibilities of FRAP at a conceptual level is presented. The method of FRAP is briefly reviewed and its use in heterogeneous biomaterials, at barriers and during dynamic changes of the structure is discussed. © 2009 Elsevier B.V. All rights reserved.

  • 33.
    Loren, Niklas
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Shtykova, L.
    Kidman, Siw
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Jarvoll, P.
    Nyden, M.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Dendrimer diffusion in ?-carrageenan gel structures2009In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 10, no 2, p. 275-284Article in journal (Refereed)
    Abstract [en]

    The effect of the ?-carrageenan concentration on gel microstructure and self-diffusion of polyamideamine dendrimers has been determined by transmission electron microscopy (TEM), image analysis, and nuclear magnetic resonance (NMR) diffusometry. Different salt conditions of KCl, NaCl, and mixtures thereof allowed for formation of significantly different microstructures. The ?-carrageenan concentrations were varied between 0.25 and 3.0 w/w% for a salt mixture containing 20 mM KCl and 200 mM NaCl gels and between 0.5 and 4.0 w/w% for 250 mM NaCl gels. Furthermore, the effect of potassium ion concentration on the gel structure and the dendrimer diffusion rate was determined. The potassium ion concentration was varied between 20 mM KCl and 200 mM KCl. Two different dendrimer generations with significant difference in size were used: G2 and G6. Dendrimers were found to be sensitive probes for determination of the effect of the gel microstructure on molecular diffusion rate. A qualitative comparison between TEM micrographs, NMR diffusometry data and image analysis showed that the gel structure has a large impact on the dendrimers diffusion in ?-carrageenan gels. It was found that diffusion was strongly influenced by the ?-carrageenan concentration and the dendrimer generation. Small voids in the gel network gave strongly reduced diffusion. Image analysis revealed that the interfacial area between the gel network and the surrounding water phase correlated well with the dendrimer diffusion. © 2009 American Chemical Society.

  • 34.
    Lorén, N
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Structure evolution during phase separation and gelation of biopolymer mixtures.2001Report (Refereed)
  • 35. Lundell, C.
    et al.
    Walkenström, Pernilla
    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.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Influence of elongational flow on phase separated inclusions within gelling biopolymer drops2004In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 18, no 5, p. 805-815Article in journal (Refereed)
    Abstract [en]

    Drops of an immiscible biopolymer mixture containing maltodextrin/gelatine were shaped and set in an elongational flow in a flow cell called 4-RM. The kinetics of phase separation as well as the kinetics of gel formation were governed by the temperature differences which appear as the 60°C maltodextrin/gelatine mixture reaches the 10°C silicon oil in the 4-RM. The shape and inner structure of the drops were visualized with the help of a confocal laser scanning microscope (CLSM). The result showed that the solution phase separated into gelatine-rich and a maltodextrin-rich phase during the short time it takes to gel the particle, i.e. in approximately 2 s. It was found that the shape of the phase separated inclusions was affected by the elongational flow. Mixtures of a 10% constant gelatine concentration and a 2-15% maltodextrin concentration were evaluated. The size of the inclusions within the phase separated drops increases as the maltodextrin concentration increases. At a maltodextrin concentration of 12%, the phase inversion has occurred. Shape transfer between the drop and its inclusions was investigated. The length to width ratios of the drops and its inclusions were compared and it was found that for the gelatine-continuous drop created at a flow rate of 10 rpm the ratio responds well. A comparison of the Taylor parameter calculated from viscosity data before gel formation and image analysis of experimental results showed that deformation takes place within the critical stage of gel formation. © 2004 Elsevier Ltd. All rights reserved.

  • 36. Mohlin, K.
    et al.
    Loren, Niklas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Nyden, M.
    Water pores in alkyl ketene dimer (AKD) dispersions studied by NMR diffusometry and optical microscopy2007In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 297, no 42007, p. 114-121Article in journal (Refereed)
    Abstract [en]

    Water borne alkyl ketene dimer (AKD) dispersions have been investigated by means of optical microscopy and NMR diffusometry (NMR-D). In two different formulations, different amounts of entrapped water in pores with different sizes are obtained, which can be compared to a water-in-oil-in-water (w/o/w) dispersion. It is shown that the amount of entrapped water inside the AKD particles can conveniently be measured with the NMR-D technique. The pore size is however not obtained correctly from the NMR-D experiment. Due to the small size of the water pores, the pore size is underestimated when measured with NMR-D. This effect is investigated in more detail by Brownian dynamic simulations from which a correction factor is obtained that allows a more correct value of the pore size from NMR-D measurements. When the pore size is too small to be observed by optical microscopy, typically below 0.5 ?m, NMR diffusometry combined with Brownian dynamic simulations are shown to be a rapid and reliable tool for quantifying the porosity in these types of systems. © 2006 Elsevier B.V. All rights reserved.

  • 37. Nisslert, R.
    et al.
    Kvarnstrom, M.
    Loren, Niklas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Nyden, M.
    Rudemo, M.
    Identification of the three-dimensional gel microstructure from transmission electron micrographs2007In: Journal of Microscopy, ISSN 0022-2720, E-ISSN 1365-2818, Vol. 225, no 1, p. 42298-Article in journal (Refereed)
    Abstract [en]

    Mass transport in gels depends crucially on local properties of the gel network. We propose a method for identifying the three-dimensional (3D) gel microstructure from statistical information in transmission electron micrographs. The gel strand network is modelled as a random graph with nodes and edges (branches). The distribution of edge length, the number of edges at nodes and the angles between edges at a node are estimated from transmission electron micrographs by image analysis methods. The 3D network is simulated by Markov chain Monte Carlo, with a probability function based on the statistical information found from the micrographs. The micrographs are projections of stained gel strands in slices, and we derive a formula for estimating the thickness of the stained gel slice based on the total projected gel strand length and the number of times that gel strands enter or exit the slice. © 2007 The Authors.

  • 38. Petersson, M.
    et al.
    Loren, Niklas
    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.
    Characterization of phase separation in film forming biopolymer mixtures2005In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 6, no 2, p. 932-941Article in journal (Refereed)
    Abstract [en]

    Enhanced, tailor-made films can be achieved by combining the good gas barrier of the hydrophilic high amylose maize starch (hylon) with the water resistance of the hydrophobic protein zein. Two polymers are not always miscible in solution, and the phase separation behavior of the mixture is therefore important for the final film structure and its properties. Phase separation of a mixture of these two biopolymers was induced either by cooling, which was observed as growing droplets of the hylon phase which in some cases also formed small aggregates, or by solvent evaporation and studied in real-time in a confocal laser scanning microscope. Solvent evaporation had a much stronger effect on phase separation. During the early stage of phase separation, hylon formed large aggregates and subsequently smaller droplets coalesced with other droplets or large hylon aggregates. The later part of the separation seemed to take place through spinodal decomposition. © 2005 American Chemical Society.

  • 39.
    Pihl, Maria
    et al.
    Chalmers University of Technology, Sweden.
    Kolman, Krzysztof
    Chalmers University of Technology, Sweden.
    Lotsari, Antiope
    Chalmers University of Technology, Sweden.
    Ivarsson, Marie
    Chalmers University of Technology, Sweden.
    Schüster, Erich
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience. Chalmers University of Technology, Sweden.
    Loren, Niklas
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience. Chalmers University of Technology, Sweden.
    Bordes, Romain
    Chalmers University of Technology, Sweden.
    Silica-based diffusion probes for use in FRAP and NMR-diffusometry2019In: Journal of Dispersion Science and Technology, ISSN 0193-2691, E-ISSN 1532-2351, Vol. 40, no 4, p. 555-562Article in journal (Refereed)
    Abstract [en]

    Development of multi-purpose probes for mass transport measurements is of importance to gain knowledge in diffusional behaviour in heterogeneous structures such as food, hygiene or pharamceuticals. By combining different techniques, such as Fluorescence Recovery After Photobleaching (FRAP) and Nuclear Magnetic Resonance Diffusometry (NMR-d), information of both local and global diffusion can be collected and used to gain insights on for example material heterogeneities and probe-material interactions. To obtain a FRAP-responsive probe, fluorescent silica particles were produced using fluorescent preconjugates added in a modified Stöber process. A NMR-d responsive moiety was introduced by derivatizing the fluorescent silica particles with polyethylene glycol. The particle size distributions were determined by dynamic light scattering and transmission electron microscopy and these measurements were compared to value extrapolated from diffusion measurements using FRAP and NMR-d. The good agreement between the FRAP and NMR-d measurements demonstrates the potential of multi-purpose probes for future applications concerning mass transport at local and global scale simultaneously. © 2018, © 2018 The Author(s).

  • 40.
    Röding, Magnus
    et al.
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Gaska, Karolina
    Chalmers University of Technology, Sweden .
    Kádár, Roland
    Chalmers University of Technology, Sweden.
    Loren, Niklas
    Chalmers University of Technology, Sweden.
    Computational Screening of Diffusive Transport in Nanoplatelet-Filled Composites: Use of Graphene To Enhance Polymer Barrier Properties2017In: ACS Applied Nano Materials, ISSN 2574-0970Article in journal (Refereed)
    Abstract [en]

    Motivated by the substantial interest in various fillers to enhance the barrier properties of polymeric films, especially graphene derivatives, we perform a computational screening of obstructed diffusion to explore the design parameter space of nanoplatelet-filled composites synthesized in silico. As a model for the nanoplatelets, we use circular and elliptical nonoverlapping and impermeable flat disks, and diffusion is stochastically simulated using a random-walk model, from which the effective diffusivity is calculated. On the basis of ∼1000 generated structures and diffusion simulations, we systematically investigate the impact of different nanoplatelet characteristics such as orientation, layering, size, polydispersity, shape, and amount. We conclude that the orientation, size, and amount of nanoplatelets are the most important parameters and show that using nanoplatelets oriented perpendicular to the diffusion direction, under reasonable assumptions, with approximately 0.2% (w/w) graphene, we can reach 90% reduction and, with approximately 1% (w/w) graphene, we can reach 99% reduction in diffusivity, purely because of geometrical effects, in a defect-free matrix with perfect compatibility. Additionally, our results suggest that the existing analytical models have some difficulty with extremely large aspect ratio (extremely flat) nanoplatelets, which calls for further development.

  • 41.
    Röding, Magnus
    et al.
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Lacroix, Leander
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Krona, Annika
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Gebäck, Tobias
    Chalmers University of Technology, Sweden.
    Loren, Niklas
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience. Chalmers University of Technology, Sweden.
    A Highly Accurate Pixel-Based FRAP Model Based on Spectral-Domain Numerical Methods2019In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 116, no 7, p. 1348-1361Article in journal (Refereed)
    Abstract [en]

    We introduce a new, to our knowledge, numerical model based on spectral methods for analysis of fluorescence recovery after photobleaching data. The model covers pure diffusion and diffusion and binding (reaction-diffusion) with immobile binding sites, as well as arbitrary bleach region shapes. Fitting of the model is supported using both conventional recovery-curve-based estimation and pixel-based estimation, in which all individual pixels in the data are utilized. The model explicitly accounts for multiple bleach frames, diffusion (and binding) during bleaching, and bleaching during imaging. To our knowledge, no other fluorescence recovery after photobleaching framework incorporates all these model features and estimation methods. We thoroughly validate the model by comparison to stochastic simulations of particle dynamics and find it to be highly accurate. We perform simulation studies to compare recovery-curve-based estimation and pixel-based estimation in realistic settings and show that pixel-based estimation is the better method for parameter estimation as well as for distinguishing pure diffusion from diffusion and binding. We show that accounting for multiple bleach frames is important and that the effect of neglecting this is qualitatively different for the two estimation methods. We perform a simple experimental validation showing that pixel-based estimation provides better agreement with literature values than recovery-curve-based estimation and that accounting for multiple bleach frames improves the result. Further, the software developed in this work is freely available online.

  • 42.
    Röding, Magnus
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden; University College London, Australia.
    Schuster, Erich
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden.
    Logg, Katarina
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience, Structure Design. Chalmers University of Technology, Sweden.
    Lundman, Malin
    Chalmers University of Technology, Sweden; SCA Hygiene Products, Sweden.
    Bergström, Per
    Chalmers University of Technology, Sweden; SCA Hygiene Products, Sweden.
    Hanson, Charlotta
    Chalmers University of Technology, Sweden; SCA Hygiene Products, Sweden.
    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.
    Computational high-throughput screening of fluid permeability in heterogeneous fiber materials2016In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 12, no 29, p. 6293-6299Article in journal (Refereed)
    Abstract [en]

    We explore computational high-throughput screening as a design strategy for heterogeneous, isotropic fiber materials. Fluid permeability, a key property in the design of soft porous materials, is systematically studied using a multi-scale lattice Boltzmann framework. After characterizing microscopic permeability as a function of solid volume fraction in the microstructure, we perform high-throughput computational screening of in excess of 35000 macrostructures consisting of a continuous bulk interrupted by spherical/elliptical domains with either lower or higher microscopic permeability (hence with two distinct microscopic solid volume fractions and therefore two distinct microscopic permeabilities) to assess which parameters determine macroscopic permeability for a fixed average solid volume fraction. We conclude that the fractions of bulk and domains and the distribution of solid volume fraction between them are the primary determinants of macroscopic permeability, and that a substantial increase in permeability compared to the corresponding homogenous material is attainable.

  • 43.
    Röding, Magnus
    et al.
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience. Chalmers University of Technology, Sweden.
    Svensson, Peter
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Loren, Niklas
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience. Chalmers University of Technology, Sweden.
    Functional regression-based fluid permeability prediction in monodisperse sphere packings from isotropic two-point correlation functions2017In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 134, p. 126-131Article in journal (Refereed)
    Abstract [en]

    We study fluid permeability in random sphere packings consisting of impermeable monodisperse hard spheres. Several different pseudo-potential models are used to obtain varying degrees of microstructural heterogeneity. Systematically varying solid volume fraction and degree of heterogeneity, virtual screening of more than 10,000 material structures is performed, simulating fluid flow using a lattice Boltzmann framework and computing the permeability. We develop a well-performing functional regression model for permeability prediction based on using isotropic two-point correlation functions as microstructural descriptors. The performance is good over a large range of solid volume fractions and degrees of heterogeneity, and to our knowledge this is the first attempt at using two-point correlation functions as functional predictors in a nonparametric statistics/machine learning context for permeability prediction.

  • 44.
    Schuster, Erich
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Eckardt, Johanna
    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.
    Larsson, A.
    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.
    Microstructural, mechanical and mass transport properties of isotropic and capillary alginate gels2014In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 10, no 2, p. 357-366Article in journal (Refereed)
    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. © 2014 The Royal Society of Chemistry.

  • 45.
    Schuster, Erich
    et al.
    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.
    Öhgren, Camilla
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Rudemo, M.
    Loren, Niklas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Interactions and diffusion in fine-stranded beta-lactoglobulin gels determined via FRAP and binding2014In: Biophysical Journal, ISSN 0006-3495, E-ISSN 1542-0086, Vol. 106, no 1, p. 253-262Article in journal (Refereed)
    Abstract [en]

    The effects of electrostatic interactions and obstruction by the microstructure on probe diffusion were determined in positively charged hydrogels. Probe diffusion in fine-stranded gels and solutions of ?-lactoglobulin at pH 3.5 was determined using fluorescence recovery after photobleaching (FRAP) and binding, which is widely used in biophysics. The microstructures of the ?-lactoglobulin gels were characterized using transmission electron microscopy. The effects of probe size and charge (negatively charged Na2-fluorescein (376Da) and weakly anionic 70kDa FITC-dextran), probe concentration (50 to 200 ppm), and ?-lactoglobulin concentration (9% to 12% w/w) on the diffusion properties and the electrostatic interaction between the negatively charged probes and the positively charged gels or solutions were evaluated. The results show that the diffusion of negatively charged Na2-fluorescein is strongly influenced by electrostatic interactions in the positively charged ?-lactoglobulin systems. A linear relationship between the pseudo-on binding rate constant and the ?-lactoglobulin concentration for three different probe concentrations was found. This validates an important assumption of existing biophysical FRAP and binding models, namely that the pseudo-on binding rate constant equals the product of the molecular binding rate constant and the concentration of the free binding sites. Indicators were established to clarify whether FRAP data should be analyzed using a binding-diffusion model or an obstruction-diffusion model. © 2014 by the Biophysical Society.

  • 46.
    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 hydrogels2016In: Soft Matter, ISSN 1744-683X, E-ISSN 1744-6848, Vol. 12, no 17, p. 3897-3907Article in journal (Refereed)
    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.

  • 47.
    Sott, Kristin
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Geback, T.
    Pihl, M.
    Loren, Niklas
    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.
    Heintz, A.
    ?PIV methodology using model systems for flow studies in heterogeneous biopolymer gel microstructures2013In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 398, p. 262-269Article in journal (Refereed)
    Abstract [en]

    A methodology for studying flow in heterogeneous soft microstructures has been developed. The methodology includes: (1) model fractal or random heterogeneous microstructures fabricated in PDMS and characterised using CLSM; (2) ?PIV measurements; (3) Lattice-Boltzmann simulations of flow. It has been found that the flow behaviour in these model materials is highly dependent on pore size as well as on the connectivity and occurrence of dead ends. The experimental flow results show good agreement with predictions from the Lattice-Boltzmann modelling. These simulations were performed in geometries constructed from 3D CLSM images of the actual PDMS structures. Given these results, mass transport behaviour may be predicted for even more complex structures, like gels or composite material in, e.g., food or biomaterials. This is a step in the direction towards predictive science with regards to tailoring soft biomaterials for specific mass transport properties. © 2013 Elsevier Inc.

  • 48.
    Svanberg, Lina
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Ahrné, Lilia
    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.
    Windhab, E.
    A method to assess changes in mechanical properties of chocolate confectionery systems subjected to moisture and fat migration during storage2012In: Journal of texture studies, ISSN 0022-4901, E-ISSN 1745-4603, Vol. 43, no 2, p. 106-114Article in journal (Refereed)
    Abstract [en]

    An Instron universal testing machine was used to assess fundamental parameters, such as Young's modulus, tensile strength and tensile strain, in order to determine the effect of fat and moisture migration on the mechanical properties of chocolate during storage. Two thin steel anchorages were inserted into each end of the chocolate samples during molding. These anchorages were used to mount the samples in the instrument without inducing stresses prior to the start of the experiment. Longitudinal forces applied to the chocolate provided a measure of the strength of the bond between different chocolate components (nonfat solids and cocoa butter). The new method proved to be a valid technique that can be used to measure fundamental mechanical parameters and quantify the impact of fat or moisture migration. © 2011 Wiley Periodicals, Inc.

  • 49.
    Svanberg, Lina
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Ahrné, Lilia
    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.
    Windhab, E.
    Effect of pre-crystallization process and solid particle addition on microstructure in chocolate model systems2011In: Food Research International, ISSN 0963-9969, E-ISSN 1873-7145, Vol. 44, no 5, p. 1339-1350Article in journal (Refereed)
    Abstract [en]

    The microstructure of chocolate model systems was investigated at the meso (~. 10. ?m), micro (~. 50. ?m), and macro (0.1-1 mm) scales simultaneously, to examine effect of pre-crystallization process and/or solid particle addition on the formation of a dense structure. The structure density was quantified by measuring the diffusion rate of small molecules at different length scales. At the meso scale, fluorescence recovery after photobleaching (FRAP) was utilized to quantify local diffusion rate solely in the fat phase, whereas high-performance liquid chromatography (HPLC) measurements were made to assess the global diffusion of the same molecules at the macro scale. Both techniques were used in combination with microstructure characterization using confocal laser scanning microscopy (micro scale) and supported by differential scanning calorimeter melting curves for estimating cocoa butter polymorphism. Both FRAP and HPLC analysis generated relevant information on the effect of pre-crystallization and solid particle addition on the structure density. FRAP measurements gave detailed information on microstructure heterogeneity or homogeneity in the cocoa butter, whereas HPLC clearly revealed the impact of solid particles on the structure density. Combining the two techniques revealed that a compact and homogeneous structure obtained through optimized pre-crystallization is required at all times, i.e., immediately after cooling and throughout the product's shelf life, to retard global diffusion in confectionery systems. © 2011 Elsevier Ltd.

  • 50.
    Svanberg, Lina
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Ahrné, Lilia
    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.
    Windhab, E.
    Effect of sugar, cocoa particles and lecithin on cocoa butter crystallisation in seeded and non-seeded chocolate model systems2011In: Journal of Food Engineering, ISSN 0260-8774, E-ISSN 1873-5770, Vol. 104, no 1, p. 70-80Article in journal (Refereed)
    Abstract [en]

    The effect of major chocolate ingredients (sugar, cocoa particles and lecithin), in combination with the two pre-crystallization techniques, seeding and non-seeding, was investigated with respect to the kinetics of cocoa butter crystallisation and the resulting microstructure. Confocal laser scanning microscopy (CLSM) was used to monitor microstructural evolution under dynamic thermal conditions. DSC measurements and image analysis were also applied in order to quantify the impacts of processing and formulation on microstructure. All ingredients and pre-crystallisation techniques considered proved to have a large impact on fat crystallisation kinetics and the resulting microstructure. Seeded samples tended to form multiple nucleation sites, inducing rapid growth of a crystal network. The non-seeded samples showed an altering structure, with some domains developing large spherical crystals while in other domains a more heterogeneous microstructure resulted. Lecithin showed a remarkable impact on crystallisation kinetics in both the seeded and non-seeded samples. For the seeded samples, the effect was most noteworthy in samples containing cocoa butter and sugar, where lecithin significantly reduced the induction time. In the absence of seeds, lecithin itself acted as the nucleation site for fat crystallisation. © 2010 Elsevier Ltd. All rights reserved.

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