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  • 1. Andersson, H.
    et al.
    Öhgren, Camilla
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Johansson, Daniel
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Kniola, Magda
    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.
    Extensional flow, viscoelasticity and baking performance of gluten-free zein-starch doughs supplemented with hydrocolloids2011In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 25, no 6, p. 1587-1595Article in journal (Refereed)
    Abstract [en]

    Viscoelastic doughs of zein and starch were prepared at 40 °C, above the glass transition temperature of zein. The effects of hydrocolloid supplementation with hydroxypropyl methylcellulose (HPMC) or oat bran with a high content of ?-glucan (28%) were investigated by dynamic measurements in shear, confocal laser scanning microscopy (CLSM) and Hyperbolic Contraction Flow. Zein-starch dough without hydrocolloids exhibited rapid age-related stiffening, believed to be caused by cross-links between peptide chains. A prolonged softness was attributed to doughs containing hydrocolloids, with the oat bran exhibiting the most pronounced reduction in age-related stiffening. Moreover, CLSM-images of dough microstructure revealed that a finer fibre network may be formed by increased shearing through an addition of viscosity-increasing hydrocolloids, a reduction in water content in the dough or the use of appropriate mixing equipment. The Hyperbolic Contraction Flow measurements showed that doughs containing hydrocolloids had high extensional viscosities and strain hardening, suggesting appropriate rheological properties for bread making. Zein-starch dough without hydrocolloids showed poor bread making performance while hydrocolloid additions significantly improved bread volume and height. Although the hydrocolloid supplemented doughs had similar extensional rheological properties and microstructures, a fine crumb structure was attributed only to bread containing HPMC, marking the importance of surface active components in the liquid-gas interface of dough bubble walls. Zein could not mimic the properties of gluten on its own, but hydrocolloids did positively affect the structural and rheological properties of zein, which yielded dough similar to wheat dough and bread with increased volume. © 2011 Elsevier Ltd.

  • 2. Brink, J.
    et al.
    Langton, Maud
    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.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Simultaneous analysis of the structural and mechanical changes during large deformation of whey protein isolate/gelatin gels at the macro and micro levels2007In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 21, no 3, p. 409-419Article in journal (Refereed)
    Abstract [en]

    The effect of microstructure on the fracture properties of whey protein isolate (WPI) gels with varying amounts of gelatin was analysed on the macro (mm scale) and micro (?m scale) levels. Eight percent WPI particulate gels with 0-6% gelatin were prepared at a pH near the isoelectric point of whey protein. The tensile stage was placed directly under the confocal laser-scanning microscope (CLSM). The structural changes of the gel during the deformation are visualized in series of micrographs with simultaneous recording of stress and strain data with the tensile stage. The pure whey protein gel exhibited uneven failure at the macro level, where the crack propagated between the whey protein clusters, whereas the crack propagated smoothly through the gelatin phase in the whey/gelatin gel system. At higher magnification the pure WPI protein gel showed porous failure behaviour and gradually ruptured. The WPI gel with high gelatin concentration followed the rheological response of the gelatin phase, resulting in stretched failure behaviour with rapid rupture. The micro strain was calculated directly from micrographs, with the pure WPI gel reaching a seven times higher micro strain than the macro strain. The difference between micro and macro strain decreases with increasing gelatin concentration. Threshold crack propagation values were identified at both the macro and micro levels, and the start of structural failure was observed long before any mechanical response. The fracture dynamics of mixed biopolymer gels can be analysed with this approach both structurally and rheologically at different length scales, contributing to a more comprehensive understanding of the failure behaviour. © 2006 Elsevier Ltd. All rights reserved.

  • 3.
    Chen, Si-Qian
    et al.
    Dongguan University of Technology, China.
    Lopez-Sanchez, Patricia
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Wang, Dongjie
    Tianjin University of Science and Technology, China.
    Mikkelsen, Deidre
    The University of Queensland, Australia.
    Gidley, Michael J
    The University of Queensland, Australia.
    Mechanical properties of bacterial cellulose synthesised by diverse strains of the genus Komagataeibacter2018In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 81, p. 87-95Article in journal (Refereed)
    Abstract [en]

    Bacterial cellulose (BC) has several current and potential future uses in the food industry because of its ability to form hydrogels with distinctive properties. The texture of BC hydrogels is determined by both the cellulose fibre network and the internal dispersed water. In this study, mechanical properties of hydrated BC synthesised by six different strains of Komagataeibacter genus were investigated with regards to their extensibility, compressive strength, relaxation ability, viscoelasticity and poroelasticity. The stress/strain at failure and Young's modulus were assessed by uniaxial tensile testing. The compressive strength, relaxation ability and viscoelasticity were measured via a series of compression and small amplitude oscillatory shear steps. A poroelastic constitutive modelling simulation was used to investigate the mechanical effects of water movement. The morphology of the BC fibril network under compression was observed via scanning electron microscopy. Results showed that the mechanics of BC were highly dependent on the cellulose concentration, as well as the morphology of the fibril network. BC synthesised by ATCC 53524 was the most concentrated (0.71 wt%), and exhibited high tensile properties, stiffness and storage moduli; whereas comparatively low mechanical properties were noted for BC produced by ATCC 700178 and ATCC 10245, which contained the lowest cellulose concentration (0.18 wt%). Small deformation responses (normal stress, G') scaled with cellulose concentration for all samples, whereas larger deformation responses (Young's modulus, poroelasticity) depended on both cellulose concentration and additional factors, presumably related to network morphology. Increasing concentration and compressive coalescence of fibres in the integrated BC network reduced both the relaxation of the normal stress and the movement of water. This research aids the selection of bacterial strains to modulate the texture and mechanical properties of hydrated BC-based food systems. 

  • 4.
    Dedinaite, A
    et al.
    YKI – Ytkemiska institutet.
    Claesson, PM
    YKI – Ytkemiska institutet.
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    Campbell, B
    Interactions between hydrophilic surfaces in triglyceride media - information obtained from surface force measurements1997In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 11, p. 7-12Article in journal (Refereed)
    Abstract [en]

    The application of surface force measurements for modelling the behaviour of food colloid system, in particular dispersions of hydrophilic particles in oil continuous media, is discussed. Interactions between two mica surfaces across a triglyceride, triolein, in anhydrous state and containing different amounts of dissolved water, have been investigated. The water content influences the layering of triolein molecules at the surfaces and whereby their interactions. The relation between surface force data (e.g. the magnitude of the force barrier and the adhesion force) to the properties of colloidal systems is discussed. Further, the importance of capillary condensation for particle interactions in triolein saturated with water is demonstrated.

  • 5. Fäldt, P
    et al.
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    Spray-dried whey protein/lactose/soybean oil emulsions. 1. Surface composition and particle structure1996In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 10, p. 421-429Article in journal (Refereed)
    Abstract [en]

    Emulsions made of whey protein, lactose and soy bean oil were spray-dried and the chemical surface composition of the dried powders estimated by electron spectroscopy for chemical analysis (ESCA). In particular, the ability of whey protein to encapsulate fat is enlightened. Additionally, the structure of the spray-dried powder particles was studied by scanning electron microscopy. The powders were examined after storage in both dry and humid atmosphere (relative humidity 75 %, 4 days). It was found that the ability of whey protein to encapsulate soy-bean oil is rather low as compared to sodium caseinate with a large part of the powder surface covered by fat after spray-drying. After storage in humid atmosphere there is a release of encapsulated oil onto the powder surface in most cases, and a fat coverage increase. The release of fat onto the powder surfaces causes the particle structure to change dramatically for powders containing a critical amount of lactose. Such powders agglomerate and lose structure completely. In comparison, powders containing no lactose under humid conditions also causes a release of fat onto the powder, however in this case particle structure remains intact. Powders containing only a small amount of lactose, up to about 25 % of emulsion dry weight, do not exhibit a release of fat onto the powder surfaces after storage under humid conditions and the structure of these powder particles do not change. Presence of lactose in whey protein stabilized emulsions, however, do not increase fat encapsulation by whey protein, as reported earlier for sodium caseinate stabilized emulsions that were spray-dried. During spray-drying of whey protein/lactose solutions there is a strong overrepresentation of surface-active whey protein on the powder surface. Whey protein coverage increases even further when the powders are stored under humid conditions, also making them lose structure.

  • 6. Fäldt, P
    et al.
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    Spray-dried whey protein/lactose/soy-bean oil emulsions 2. Redispersability, wettability and particle structure1996In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 10, p. 431-439Article in journal (Refereed)
    Abstract [en]

    In the present paper redispersion and wettability experiments of spray-dried whey protein stabilized emulsions are presented. Emulsion droplet size after redispersion gives information about eventual coalescence between emulsion droplets in the powder matrix during drying or storage, resulting in an increase in emulsion droplet size after redispersion. Results from redispersion experiments are combined with previously presented knowledge about powder surface composition and particle structure to elucidate internal processes in the powder matrix and external processes on the powder surface during drying and storage of whey protein powder. The results show that with addition of lactose to whey protein stabilized emulsions, emulsion droplet structure remains intact in the powder matrix during drying since the emulsion droplet size in the redispersed spray dried emulsion is unchanged. In the absence of lactose there is a growth in emulsion droplet size after redispersion of the spray-dried whey protein stabilized emulsion showing that a coalescense of emulsion droplets occurs during the drying or redispersion process. Storage of the whey protein stabilized powders in humid atmosphere (relative humidity 75 %, 4 days) induces changes in some powders. When the powder contains a critical amount of lactose there is a remarkable increase in emulsion droplet size after redispersion of humid stored powders as compared to the emulsion before drying and compared to the redispersed dry-stored powder. In addition, there is a release of encapsulated fat after humid storage of lactose containing powders detected by ESCA. For powders which do not contain any lactose there is no increase in emulsion droplet size after storage in humid atmosphere as compared to the redispersed dry stored emulsion. Addition of only a small amount lactose prevents coalescence of emulsion droplets and the subsequent increase in droplet size during drying. If the lactose content is kept rather low there is neither an effect on the droplet size after storage under humid conditions nor a release of fat onto powder surfaces detected. Furthermore, wettability of the spray-dried whey-protein stabilized emulsions by water is presented. It is concluded that it is beneficial to wettability in water to have as high coverage of lactose on the powder surface as possible. In addition, a review of particle structure for powders with various composition is presented.

  • 7.
    Gómez-Heincke, Diana
    et al.
    University of Huelva, Spain.
    Martínez, Immaculada
    University of Huelva, Spain.
    Stading, Mats
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience. Chalmers University of Technology, Sweden.
    Gallegos, Crispulo
    University of Huelva, Spain.
    Partal, Perdro
    University of Huelva, Spain.
    Improvement of mechanical and water absorption properties of plant protein based bioplastics2017In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 73, p. 21-29Article in journal (Refereed)
    Abstract [en]

    Bioplastics deriving from plant proteins are becoming an increasingly popular source of raw material for plastic products since they are not only biodegradable but renewable resources. However, these bioplastics require improved mechanical and water absorption properties to be suitable for many applications, such as packaging. For this reason, this study considers potato and rice proteins as a new source for the manufacture of bioplastics. The proteins were mixed with different glycerol concentrations followed by thermomoulding at temperatures from 60 to 180 °C. The resulting bioplastic is characterized in terms of thermo-mechanical properties, water absorption and molecular weight distribution. Compared to well-known wheat gluten, these bioplastics required higher temperatures for their thermomoulding. However, both of them were more structured materials and exhibited less water absorption (e.g. as low as 9 wt.%) than those obtained for wheat gluten blend. Potato protein-based bioplastics showed complex modulus values comparable to synthetic polymers such as Low Density Polyethylene (LDPE).

  • 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.
    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.

  • 9.
    Hamberg, Lars
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Walkenström, Pernilla
    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.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Aggregation, viscosity measurements and direct observation of protein coated latex particles under shear2001In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 15, no 2, p. 139-151Article in journal (Refereed)
    Abstract [en]

    The aggregation under shear, of latex particles coated with whey protein isolate was monitored, in a continuous phase with a complex behaviour in relation to temperature dependence and shear thinning. The monitoring was done with viscosity measurements and microscopy. An aggregating dispersion of whey coated polystyrene latex particles, salt, sucrose and gelatine was sheared in a rheometer at shear rates between 0.05 and 5 s-1. The viscosity was monitored as a function of time during a temperature increase from 30 to 60°C. The viscosity curves were interpreted with the aid of additional information from light microscopy micrographs. The aggregation was clearly visible as an increase in viscosity. Aggregation was observed to initiate at a temperature between 40 and 50°C. Unbound protein, i.e. protein not a part of particle coating, was found to be essential for the aggregation of latex particles. After aggregation, a shear thinning behaviour was detected. This was due to two phenomena: structural changes of the aggregates and shear thinning behaviour of the dispersion. The build-up of the aggregates was followed by direct observation in a confocal laser scanning microscope. A sequence of micrographs was taken, in an unstopped 3-D flow field generated in a four-roll mill, which showed the evolution of the size of the aggregates. The micrographs were in good agreement with the viscosity measurements. This showed that the four-roll mill and a confocal laser scanning microscope is a useful tool for studying aggregation in an undisturbed 3-D flow. © 2001 Elsevier Science Ltd.

  • 10.
    Hamberg, Lars
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Wohlwend, M.
    Walkenström, Pernilla
    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.
    Shapes and shaping of biopolymer drops in a hyperbolic flow2003In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 17, no 5, p. 641-652Article in journal (Refereed)
    Abstract [en]

    The shaping of drops in a model system based on ? -carrageenan-emulsion drops in the millimetre range in silicon oil has been studied. The drops were shaped by exposing them to drag forces in a hyperbolic flow, while their shape was fixed simultaneously by introducing gel formation of the biopolymer in the drop. The shape and the shaping process were studied and evaluated with image analysis of macrograph sequences of the shaping. The effect of process conditions, flow speed and cooling temperature on the final shape and shape progress was investigated as well as the effect of different ?-carrageenan drop characteristics, such as drop viscosity and gel strength. Drop viscosity was altered by addition of locust bean gum, LBG, and the gel strength was altered by addition of ions. The ?-carrageenan solutions in the drop were characterised by rheological investigations. With the same type of flow, different shapes could be achieved with small process changes and with high reproducibility. The fixation of the characteristic drop features, perimeter, area, Feret's X and Y, does not occur at the same time and position. For the different process parameters investigated, a change in speed affected the process in a similar way to a change in the viscosity ratio. This applies if the viscosity ratio is changed at a constant temperature, but if the change in the viscosity ratio is temperature-induced, the effect is different. The final shape of the produced drops could be graded into three classes, correlated to the position in the flow field where the drops were fixed. A shape map of the different drop shapes obtained was presented. © 2003 Elsevier Science Ltd. All rights reserved.

  • 11. Holm, K.
    et al.
    Wendin, Karin
    SIK – Institutet för livsmedel och bioteknik.
    Hermansson, Ann-Marie
    SIK – Institutet för livsmedel och bioteknik.
    Sweetness and texture perceptions in structured gelatin gels with embedded sugar rich domains2009In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 23, no 8, p. 2388-2393Article in journal (Refereed)
    Abstract [en]

    Layered and homogeneous gelatin gels with controlled rheological properties were compared for their sensory characteristics, specifically sweetness, hardness, breakdown behaviour and frothing. All gels and layers had a gelatin/water concentration of 5%. The total sugar concentration was 9% in the layered samples and 0, 9, 15 or 22.5% in the homogeneous samples. These concentrations corresponded to the concentrations in the single layers. A seven-layered sample with different sugar concentrations in the layers gave a higher early sweetness intensity than a homogeneous gel with the same mean total sugar concentration. All layered gels were similar in hardness, breakdown behaviour and frothing; for the homogenous samples, sensory hardness was decreased in samples with much sugar. These gels also fell into smaller pieces than the sugarless sample. This study shows that it is possible by controlling the sugar distribution within a sample to produce sweeter gels while the sugar content is maintained. © 2009 Elsevier Ltd. All rights reserved.

  • 12.
    Homer, Stephen
    et al.
    CSIRO, Australia ; University of Melbourne, Australia.
    Lundin, Leif
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Dunstan, Dave E.
    University of Melbourne, Australia.
    A detailed investigation of whey protein isolate solutions and gels reveals a number of novel characteristics2018In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 77, p. 566-576Article in journal (Refereed)
    Abstract [en]

    The structure and rheology of whey proteins at a concentration of 10 % has been investigated as a function of pH. The turbidity of whey protein isolate (WPI) solutions was measured and DSC thermograms were run on samples at 0.2 pH unit intervals. The structure of heat-set gels prepared from these solutions was investigated by confocal laser scanning microscopy and gel strengths and fracture behaviour was also examined. From the DSC studies the maximum denaturation onset temperature of β-lg under these conditions was found to be 3.4 ± 0.2. A number of pH regions were identified where significant physical changes were found. Differences between the two transition regions between fine-stranded and spherical aggregates have been discussed and potential reason put forward. General trends were identified and an anomalous region at pH 6.2 (possibly related to the Tanford transition) was found in all of the properties of the solutions and gels investigated. This work provides a more detailed investigation into a range of structural and behavioural features of WPI gels over the acidic pH range than is currently available in the literature.

  • 13.
    Homer, Stephen
    et al.
    CSIRO Commonwealth Scientific and Industrial Research Organisation, Australia.
    Lundin, Leif
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Food and Bioscience.
    Dunstan, Dave E.
    University of Melbourne, Australia.
    Modifying the microstructure and mechanical properties of whey protein isolate gels using large deformation oscillatory strain2016In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 61, p. 672-677Article in journal (Refereed)
    Abstract [en]

    The effect of oscillatory shear during heat-induced gelation of whey protein isolate has been investigated. For each gel sample, a single oscillating strain was applied during the gelation process from within the range of 0-1.0. A strain sweep was then used to evaluate the linear viscoelastic region as well as the fracturing properties of each gel. The application of strains lower than ∼0.01 during gelation did not affect the storage modulus while larger strains resulted in lower storage moduli in the linear viscoelastic region. Furthermore, gels produced under small (<0.01) strain amplitudes showed a single fracture point, while gels produced under high (>0.01) amplitude strain were characterised by a two-step fracture pattern. Between the fracture steps, strain hardening behaviour was observed. Confocal laser scanning microscopy was used to identify structural differences between the gels. Greater inhomogeneity was found in gels produced under large amplitude compared to small amplitude strain. It is suggested that localised redistribution of aggregates due to shear during gelation increases the average pore size and possibly creates two distinct types of aggregate structure with differing moduli. The combined effect of heating rate and oscillatory strain was also investigated. We postulate that the mechanism underlying our observations is generic to many gel systems.

  • 14. Landström, K
    et al.
    Alsins, J
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    Competitive protein adsorption between bovine serum albumin ß-lactoglobulin during spray-drying2000In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 14, p. 75-82Article in journal (Refereed)
  • 15. Landström, K
    et al.
    Arnebrant, T
    Alsins, J
    Bergenståhl, B
    YKI – Ytkemiska institutet.
    Competitive protein adsorption between ß-casein and ß-lactoglobulin during spray-drying: effect of calcium induced association2003In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 17, p. 103-116Article in journal (Refereed)
    Abstract [en]

    Competitive adsorption between ß-casein and ß-lactoglobulin (ß-Lg) during spray-drying was studied by the new surface sensitive technique using fluorescence quenching of pyrene labelled protein at the powder surface. The difference in competitiveness of -casein when present as monomers and as associated into micellar like structures were studied. Results were compared with the adsorption of single proteins at the powder surface. The adsorption of monomeric ß-casein alone gave an apparent surface load of ≈1 mg/m2 at a protein concentration of 0.3% dry weight and then remained constant with an increasing protein concentration. In the presence of Ca2+, associated ß-casein gave a lower affinity adsorption than monomeric ß-casein and did not reach a plateau value, instead it continued to increase with an increasing protein concentration. ß-Lg showed a low-affinity adsorption during spray-drying compared to monomeric ß-casein, although not as low as associated ß-casein. Competitive adsorption between monomeric ß-casein and ß-Lg resulted in a higher apparent surface load of ß-casein than ß-Lg at both protein concentrations studied (total 0.3 and 3.3% dry weight). However, in an associated form ß-casein was less competitive than ß-Lg. At a low bulk protein concentration (0.3% dry weight) ß-Lg dominated the powder surface, whereas at a higher concentration (3.3% dry weight) there was little difference between the proteins. The results indicate that the competitiveness of a protein during spray-drying is highly influenced by the ability of the protein to attach and rearrange at the droplet's air–water interface during the spray-drying process

  • 16.
    Langton, Maud
    et al.
    SIK – Institutet för livsmedelsforskning.
    Hermansson, Ann-Marie
    SIK – Institutet för livsmedelsforskning.
    Image analysis of particulate whey protein gels1996In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 10, no 2, p. 179-191Article in journal (Refereed)
    Abstract [en]

    Two different methods of image analysis have been used to characterize particulate gel networks quantitatively. The methods have been used to analyse the effect of different preparation conditions on the microstructure of whey protein gels. The microstructure has been characterized at different structural levels by light microscopy, transmission electron microscopy and scanning electron microscopy. The structural parameters have been quantified by digital image analysis and by using a group of experienced microscopists evaluating SEM-micrographs. A stereological approach was used to quantify pore size, particle size and amount of threads within the pores in volume weighted mean volumes. The mode of aggregation was determined by the expert microstructural panel. A 2-level fully factorial experimental design has been used, with heating rate (1-5°C/min), pH (4.6-5.4) and salt addition (0-0.1 mol/dm3) as design parameters. The results showed that the heating rate and the pH had main effects on both the particle size and the pore size. The faster heating rate produced both pores and particles of smaller volume. The mean volume of the particles varied between 0.3 and 1.4 ?3, which could be compared to diameters between 0.8 and 1.4 ?3 if a spherical shape is assumed. The size of pores and particles increased by an increase in pH. Pore volume was found to be affected by an interaction between heating rate and pH. The change in pH had a pronounced effect when the slower heating rate was used. If the voids were approximated with a spherical shape, the diameters varied between 10 and 40 ?, compared with the volumes between 1200 and 29 100 ?3. The interaction effects showed that the heating rate influenced the mode of aggregation at the higher pH 5.4, whereas the salt addition affected the mode of aggregation at the lower pH 4.6. © Oxford University Press.

  • 17.
    Langton, Maud
    et al.
    SIK – Institutet för livsmedel och bioteknik.
    Jordansson, E.
    Altskär, Annika
    SIK – Institutet för livsmedel och bioteknik.
    Sorensen, C.
    Hermansson, Ann-Marie
    SIK – Institutet för livsmedel och bioteknik.
    Microstructure and image analysis of mayonnaises1999In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 13, no 2, p. 113-125Article in journal (Refereed)
    Abstract [en]

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

  • 18.
    Langton, Maud
    et al.
    SIK – Institutet för livsmedel och bioteknik.
    Åström, Annika
    SIK – Institutet för livsmedel och bioteknik.
    Hermansson, Ann-Marie
    SIK – Institutet för livsmedel och bioteknik.
    Influence of the microstructure on the sensory quality of whey protein gels1997In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 11, no 2, p. 217-230Article in journal (Refereed)
    Abstract [en]

    A full two-level factorial experimental design was used to study particulate whey protein gels. The processing conditions, pH, heating rate and the addition of salt were used as design factors. The results were evaluated by using a response surface model, and analysis of variance, M(ANOVA), was performed. The microstructure of particulate whey protein gels has been characterized previously, and the two-dimensional images from light microscopy and transmission electron microscopy were quantified by a stereological approach, while the more three-dimensional scanning electron micrographs were quantified by an expert panel of microscopists. In this study the texture of the same gels was analysed by a sensory panel. Correlations were made between the microstructure and sensory descriptors, and the panellists were able to detect differences between very small particles <1 ?m3 in volume. The sensory descriptors grainy appearance, gritty texture, creamy texture and tendency to fall apart had a logarithmic dependence on the microstructural parameters, particle size, and size of small and large pores. Multivariate techniques were used to create models to describe groups of the sensory descriptors by some of the microstructural parameters. A model with good correlation (r ? 0.8-0.9) was found for grainy appearance, gritty texture, creamy texture and falling apart. They were all dependent on the star volume of particles and small and large pores. The soft and springy textures were influenced by combinations of microstructural parameters, where the formation of strands into strings of beads or in clusters and conglomerates seemed to play an important role. The sticky texture was negatively correlated to the proportion of threads within the pores. © Oxford University Press.

  • 19. Lofgren, C.
    et al.
    Hermansson, Ann-Marie
    SIK – Institutet för livsmedel och bioteknik.
    Synergistic rheological behaviour of mixed HM/LM pectin gels2007In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 21, no 3, p. 480-486Article in journal (Refereed)
    Abstract [en]

    The objective of this study was to investigate the rheological behaviour of mixed gels of high methoxyl (HM) and low methoxyl (LM) pectins with the purpose of designing gels with reduced sucrose content but unaltered rheological properties. The gelation behaviour of mixed HM/LM pectin gels was compared to that of HM and LM pectin gels in the presence of 30%, 45% and 60% sucrose. The gels were investigated in the presence of 0.1% CaCl2·2H2O and pH 3.5, conditions that favour the gel formation of both HM and LM pectins. Strong synergistic effects occurred in the rheological behaviour for three mixed 0.8% HM/0.4% LM pectin gels under conditions where LM pectin formed microgels instead of coherent gels. The addition of LM pectin strongly increased the storage modulus in mixed HM/LM pectin gels based on 60% and 45% sucrose compared to HM pectin gels of the same sucrose concentration. The kinetic behaviour of the mixed HM/LM pectin gels during gel formation varied depending on the kinetic behaviour of the HM pectins differing in degrees of blockiness. Transmission electron microscopy (TEM) showed that the gel microstructure of the mixed gel with 60% sucrose was inhomogeneous. The addition of HM pectin in mixed gels with only 30% sucrose increased the storage modulus two to five times compared to that of 0.4% LM pectin gels under the same conditions. The phase angle for the mixed gel with 30% sucrose was also higher than for the corresponding 0.4% LM pectin gel. © 2006 Elsevier Ltd. All rights reserved.

  • 20.
    Lopez-Sanchez, Patricia
    et al.
    Maurten AB, Sweden.
    Fredriksson, Nils
    Maurten AB, Sweden.
    Larsson, Anette
    Chalmers University of Technology, Sweden.
    Altskär, Annika
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience. Chalmers University of Technology, Sweden.
    Ström, Anna
    Chalmers University of Technology, Sweden.
    High sugar content impacts microstructure, mechanics and release of calcium-alginate gels2018In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 84, p. 26-33Article in journal (Refereed)
    Abstract [en]

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

  • 21.
    Lopez-Sanchez, Patricia
    et al.
    University of Queensland, Australia.
    Martinez-Sanz, M.
    University of Queensland, Australia; Australian Nuclear Science and Technology Organisation, Australia.
    Bonilla, M. R.
    University of Queensland, Australia.
    Sonni, F.
    University of Queensland, Australia.
    Gilbert, E. P.
    Australian Nuclear Science and Technology Organisation, Australia; University of Queensland, Australia.
    Gidley, M. J.
    University of Queensland, Australia.
    Nanostructure and poroviscoelasticity in cell wall materials from onion, carrot and apple: Roles of pectin2020In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 98, article id 105253Article in journal (Refereed)
    Abstract [en]

    The hierarchical organisation of polysaccharides in primary plant cell walls is responsible for their unique mechanical properties, and in turn for the textural and rheological properties of plant-based foods and ingredients. It is expected that at the nano scale, the mechanical properties of cell wall materials arise from a combination of structural deformation of the polysaccharide networks and hydraulic properties of the continuous water phase, as has been shown for other cellulose-based composites. Pectin plays a key role in the load bearing properties of (bacterial) cellulose-pectin composites due to its contribution to both hydration structure and the dynamics of water movement. To investigate whether these features are also important in plant cell wall materials we have used a set of advanced characterisation techniques to elucidate cell wall structural features at different length scales (X-ray diffraction and small angle X-ray and neutron scattering) in cell walls from two dicotyledons (apple and carrot) and a non-commelinid monocotyledon (onion). The strength of isolated cell walls was measured under compression and fitted to a poroviscoelastic mechanical model, demonstrating that the mechanical properties of the isolated cell wall materials are directly linked to both polysaccharide networks and fluid flow through the networks. Our results show how pectin polysaccharides influence the viscoelastic behaviour of these materials and contribute to the texture of plant-derived food systems. 

  • 22.
    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.

  • 23.
    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.

  • 24. 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.

  • 25.
    Lundin, Leif
    et al.
    SIK – Institutet för livsmedel och bioteknik.
    Hermansson, Ann-Marie
    SIK – Institutet för livsmedel och bioteknik.
    Multivariate analysis of the influences of locust bean gum, ?s-casein, ?-casein on viscoelastic properties of Na-?-carrageenan gels1998In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 12, no 2, p. 175-187Article in journal (Refereed)
    Abstract [en]

    A full factorial experimental design, with five design variables, was used to study the viscoelastic effects of ?s-casein, ?-casein and locust bean gums with two different mannose to galactose ratios on Na-?-carrageenan gels in 0.25 M NaCl. Dynamic viscoelastic measurements were performed during cooling, 1 h storage at 15°C and re-heating. This study demonstrates the potential of using multivariate methods when evaluating the effect of different constituents on the viscoelastic properties of a multicomponent biopolymer mixture. Partial least square regression shows that it is possible to obtain a relation between the storage modulus (G?) and the concentration of the polymers in the mixture. Evaluation of the models obtained during the course of gelation, storage and melting shows that the G? of the ?-carrageenan system is predominantly influenced by locust bean gum with a high mannose to galactose ratio. Significant co-operative concentration effects were observed for ?-carrageenan in combination with the locust bean gums. No co-operative concentration effects were observed between the caseins and the locust bean gums, which suggests that the effects of these can be evaluated separately. ?s-Casein influences the G? in the initial state of gelation, whilst ?-casein shows effects after gel formation. The gelation and melting temperatures of the ?-carrageenan system, measured by rheology, were influenced by addition of locust bean gum, ?s-casein and ?-casein. Measured thermal hysteresis was increased and shifted to higher temperatures. © 1998 Published by Elsevier Science Ltd. All rights reserved.

  • 26.
    Lundin, Leif
    et al.
    SIK – Institutet för livsmedel och bioteknik.
    Stenlof, B.
    Hermansson, Ann-Marie
    SIK – Institutet för livsmedel och bioteknik.
    NIR spectra in relation to viscoelastic properties of mixtures of Na-?-Carrageenan, locust bean gum and casein1998In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 12, no 2, p. 189-193Article in journal (Refereed)
    Abstract [en]

    Near-infrared spectral data were correlated with the viscoelastic property storage modulus, G?, for mixtures of five biopolymers using multivariate analysis. Gels containing Na-?-carrageenan (0.5-1.0%) mixed with locust bean gums with two different mannose to galactose ratios, ?-casein and/or ?-casein (0-0.5%, polymer concentration) in 0.25 M NaCl were studied. Forty-two experiments based on a multivariate, central composite circumscribed design (CCC) were performed. Partial least square (PLS) regression was used to find a model relation between NIR transmittance spectra, recorded at 15°C in the wavelength interval 400-2500 nm, and the G? for the biopolymer gels at 15°C. Depending on sample composition, the G? varies between 0 and 3500Pa. Cross-validation using a designed data set led to a model based on 11 principal components with a correlation coefficient of 0.85 and a root mean square error of prediction of 540 Pa. © 1998 Published by Elsevier Science Ltd. All rights reserved.

  • 27.
    Millqvist-Fureby, A
    et al.
    YKI – Ytkemiska institutet.
    Smith, P
    YKI – Ytkemiska institutet.
    In-situ lecithination of dairy powders in spray-drying for confectionery applications2007In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 21, p. 920-927Article in journal (Refereed)
    Abstract [en]

    Powders are essential ingredients of chocolate. In particular for milk chocolate milk and whey powders are important, together with sucrose, lactose and cocoa solids. During processing to maintain a good flow of the molten chocolate mass, particles with hydrophilic surfaces, such as dairy powders and sugars, are coated with a surface-active compound. Only lecithin and polyglycerol polyricinoleate (PGPR) (at a limited level) are allowed in chocolate, and as these are expensive as little as possible is added, whilst maintaining rheological properties. Conventionally, lecithin is added during conching, and through the intense kneading of the chocolate mass it is distributed throughout the mass. Usually about 0.5% is added, although the level depends upon the composition of the chocolate. Here we present a new approach to lecithination of spray-dried milk and lactose powders, which we call in-situ lecithination. It has been found that the surface of a spray-dried powder is dominated by any surface-active species, and in a competitive situation, the most rapidly adsorbing species dominates. This behaviour is utilised when lecithin is added to the spray-dryer feed, and through the competitive adsorption of surface-active agents during the drying process, it dominates the powder surface composition as measured by X-ray photoelectron spectroscopy (XPS). This is also seen in differences in sedimentation rate when the powders are mixed with cocoa butter to assess the rheological properties of the powder dispersions. The effect was large for lactose powders, but smaller for skim milk powder and whey powder.

  • 28.
    Millqvist-Fureby, A
    et al.
    YKI – Ytkemiska institutet.
    Smith, P
    YKI – Ytkemiska institutet.
    In-situ lecithination of dairy powders in spray-drying for confectionery applications2007In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 21, p. 920-927Article in journal (Refereed)
    Abstract [en]

    A newly developed acoustic emission on-line monitoring technique (Voltaire J. et al. 2004) provides insight into the dynamic interactions occurring between paper, inkfount emulsion, and rubber blanket in offset printing. The technique uses a microphone placed in the vicinity of the exit of the paper-blanket nip. Through digital signal processing of the measured sound pressure it is possible to distinguish between machinery sound and that caused by the tacky ink splitting. In this study, printing of coldset inks on newsprint was carried out on a two-unit sheet-fed offset press. In line with earlier results, an increase in print density was found to correspond to increased sound pressure at the nip exit for higher frequencies (above 15 kHz). Depending on the status of the press at startup, i.e. ink and fount condition and temperature, an increase or decrease towards a more stable value of the sound pressure was detected during the early running of the press, and in both cases this correlated well with the evolution in print density to its target value. This and related results can prove useful for monitoring, and adjusting by feedback, the initial press equilibration before the print-ready stage. Moreover, the acoustic emission can directly reveal destabilised conditions at longer running times that by other means would not be detected until later

  • 29. Naushad, Emmambux
    et al.
    Stading, Mats
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    In situ tensile deformation of zein films with plasticizers and filler materials2007In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 21, no 8, p. 1245-1255Article in journal (Refereed)
    Abstract [en]

    Material deformation is a dynamic process. Visualisation of this deformation can help to understand the local deformation and fracture behaviour. Zein (the prolamin protein from maize) films with different amount of plasticizers (0-25%) and different filler materials (maize oil, Dimodan®, Vestosint®, at 25% (w/w) to protein) were deformed under tension and observed at micron scale in real time by a confocal laser scanning microscope (CLSM). The addition of plasticizers increased strain and decreased stress of zein films. At low level of plasticizers (6.25% and 12%), zein films deformed and fracture through micro-crack formation and propagation normal the tensile axis. At high Plasticization, only micro-pores were observed during tensile deformation. The filler material oil and Dimodan® increased, but Vestosint® decreased tensile strain in comparison to the control. This shows that the fracture dynamic is affected by the filler materials and is indeed observed by the CLSM. Analysis of local strain by Fluospheres® as particle tracking showed a good linear correlation with the tensile strain of the plasticized zein films. The local strains of filler materials and zein matrix in the films were different from the overall tensile strain. The combination of CLSM with a fluospheres® as particle tracking is a good method to study local deformation in biomaterials to understand the deformation and fracture behaviour of biomaterials. © 2006 Elsevier Ltd. All rights reserved.

  • 30. Olsson, C.
    et al.
    Langton, Maud
    SIK – Institutet för livsmedel och bioteknik.
    Hermansson, Ann-Marie
    SIK – Institutet för livsmedel och bioteknik.
    Dynamic measurements of ?-lactoglobulin structures during aggregation, gel formation and gel break-up in mixed biopolymer systems2002In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 16, no 5, p. 477-488Article in journal (Refereed)
    Abstract [en]

    The kinetics of aggregation and gelation of ?-lactoglobulin/amylopectin microstructures have been studied by using confocal laser scanning microscopy (CLSM) equipped with a temperature stage, transmission electron microscopy (TEM) and dynamic mechanical analysis in shear. The behaviour of the final gels was studied during fracture deformations using a tensile stage adapted to the CLSM. The different types of particulate ?-lactoglobulin (?-1g) network structures were generated by adding non-gelling amylopectin of varying concentration and viscosity. The results showed that the higher the concentration and the higher the viscosity of the amylopectin, the lower the temperature required for ?-1g to aggregate into particle aggregates and clusters visible in the CLSM. The gelling temperature of the ?-1g, determined by small deformation rheological measurements, was also found to decrease with increase in amylopectin concentration. However, although an increased concentration of amylopectin accelerated the particle aggregation of ?-1g, amylopectin with a higher viscosity was found to restrict the aggregated protein aggregates and clusters to form a connected protein network. The result of the difference in connectivity was shown when the gel structures were studied during fracture deformations in tension. In the weaker gel type, where the continued aggregation to a connected network had been obstructed, the fracture was extended more deeply inside the structure than in the stronger gel type with good connectivity, when exposed to the same deformation. The distribution of the protein and the amylopectin in the aggregated structure was visualized by TEM. Amylopectin was found inside the ?-1g aggregates in the gels containing a lower viscosity of the amylopectin. In gels containing amylopectin with higher viscosity, the amylopectin was found in the pores between the protein networks, separated from the protein phase. © 2002 Elsevier Science Ltd. All rights reserved.

  • 31. Olsson, C.
    et al.
    Langton, Maud
    SIK – Institutet för livsmedel och bioteknik.
    Hermansson, Ann-Marie
    SIK – Institutet för livsmedel och bioteknik.
    Microstructures of ?-lactoglobulin/amylopectin gels on different length scales and their significance for rheological properties2002In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 16, no 2, p. 111-126Article in journal (Refereed)
    Abstract [en]

    Different microstructures of ?-lactoglobulin gels, generated by adding non-gelling potato amylopectin of varying concentrations and rheological behaviour, were characterised by microscopic techniques on several length scales. The overall network microstructure of the ?-lactoglobulin gels was analysed by using light microscopy (LM) and confocal laser scanning microscopy (CLSM), while the construction of the separate strands was investigated by using transmission electron microscopy (TEM). At an overall level of structure, increased concentration of amylopectin resulted in a more open network with larger pores and coarser clusters of aggregated protein. Examination of the microstructure of one cluster showed that increased concentration of amylopectin resulted in a more close-packed structure of aggregated protein particles. Thus, the results of the studies on different length scales showed that gels with an open protein network structure at an overall level were constructed of close-packed clusters, while gels which were dense at an overall level of structure were constructed of open and porous clusters. By using TEM at high magnifications it was possible to observe the particles forming the aggregates building up the clusters. The particles had about the same diameter, perceived to be 100-200 nm in all the types of gels studied. By studying thick sections of the microstructure in the light microscope, differences in connectivity of the protein network strands were possible to detect. The results from the microstructural investigations were analysed together with the rheological properties of the gels. It was found that the cluster size and the pore size between the strands of clusters were related to storage modulus and stress at fracture as long as the connectivity of the network strands was good. © 2002 Elsevier Science Ltd. All rights reserved.

  • 32. Olsson, C.
    et al.
    Stading, Mats
    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.
    Rheological influence of non-gelling amylopectins on ?-lactoglobulin gel structures2000In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 14, no 5, p. 473-483Article in journal (Refereed)
    Abstract [en]

    The effect of non-gelling potato amylopectin on the gel properties of a particulate ?-lactoglobulin gel was studied by small and large deformation rheology and by light microscopy. Two different techniques using small deformations, one measuring the modulus in shear and the other measuring the modulus in compression, have been compared. The fracture tests of the gels were performed in tension. The concentration of ?-lactoglobulin was kept constant at 6 wt%, and the amount of potato amylopectin was varied from 0 to 2 wt%. Two preparations of potato amylopectin, with different rheological behaviour, were used. The results illustrate the importance of a full theological characterisation, since small and large deformation tests responded different to the structure. Both the viscoelastic and the failure properties of ?-lactoglobulin gels changed on addition of potato amylopectin even at low concentrations. The effect of the potato amylopectin concentration on the rheological properties of the mixed system varied with the properties of the potato amylopectin. The higher viscosity (HV) potato amylopectin had a shear-thinning behaviour and a small yield stress, while the lower viscosity (LV) potato amylopectin had a lower viscosity with a Newtonian behaviour. The gels containing the LV potato amylopectin increased in the modulus of small deformations with increasing potato amylopectin concentration, while the stress at fracture was constant up to a concentration of 0.5 wt% potato amylopectin and then increased with increasing potato amylopectin concentration. For the gels containing the HV potato amylopectin the modulus of small deformations reached a maximum at 0.25 wt% potato amylopectin and then decreased with increasing potato amylopectin concentration. The stress at fracture was constant up to 0.5 wt% potato amylopectin and decreased at higher concentrations. The state of aggregation of ?-lactoglobulin was influenced both by concentration and properties of potato amylopectin. The higher the potato amylopectin concentration the larger the pores in the ?-lactoglobulin gel. (C) 2000 Elsevier Science Ltd.

  • 33. Partanen, R
    et al.
    Forssell, P
    Mackie, A
    Blomberg, Eva
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Kemi Material och Ytor.
    Interfacial cross-linking of β-casein changes the structure of the adsorbed layer2013In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 32, no 2, p. 271-277Article in journal (Refereed)
    Abstract [en]

    The mechanism of transglutaminase-induced cross-linking of interfacial β-casein layer was investigated in tetradecane/buffer system. Monolayer studies were carried out in a Langmuir trough, where incubation with the enzyme mostly affected the compression of the film through adsorption of transglutaminase to the interface. Interfacial shear rheology was used to follow the kinetics of formation of a visco-elastic film upon cross-linking. Substrate concentration affected the rate of the interfacial cross-linking, when enzyme was dosed per protein concentration. This was most likely due to the saturated substrate layer at the interface in all cases. SDS-PAGE revealed that most of the β-casein at the interface was not cross-linked by intermolecular links, but rather, intramolecular links were formed. Finally, studies of adsorbed β-casein layers on polystyrene beads revealed that cross-linking reduced the thickness of the adsorption layer from 11-12 nm to 8-9 nm. These results suggest that it may be mainly intra-molecular cross-linking which modifies the physical interactions of β-caseins at the interface resulting in a higher layer density and thus, formation of a visco-elastic network.

  • 34. Petersson, M.
    et al.
    Hagstrom, J.
    Nilsson, Katarina
    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.
    Kinetics of release from kafirin films2007In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 21, no 8, p. 1256-1264Article in journal (Refereed)
    Abstract [en]

    Two separate studies were performed. The first studied release of two different preservatives (lactic acid and calcium propionate) from a biopolymer film to a model food with a water activity of aw=0.95. The second investigated the release of four sugars (fructose, maltose, raffinose and stachyose) with different molecular weights from a biopolymer film to a model food with water activities ranging from 0.85 to 0.95. In both studies, the biopolymer films containing the release components were made from kafirin and placed on the model food, consisting of a gel made of gelatine, sucrose and water with well defined water activity. The amount of preservatives and sugars released from the film to the gel were monitored over time using HPLC at different depths in the model food. The release of preservatives was rapid in both cases, and a gradient of released substances had already formed after 2 h in the model food. The gradients levelled out with time. Calcium propionate had a somewhat faster release than lactic acid. The water activity of the model food had a large impact on the release of sugars. A slow release was observed in the model food with aw=0.85, while a much more rapid release occurred in the model food with aw=0.95. There was a limited diffusion depth in the model food with aw=0.85, probably owing to a limited trial time, while the sugars in the model food with aw=0.95 diffused deeper into the model food until the film was depleted of available sugars. © 2006 Elsevier Ltd. All rights reserved.

  • 35. Petersson, M.
    et al.
    Stading, Mats
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Water vapour permeability and mechanical properties of mixed starch-monoglyceride films and effect of film forming conditions2005In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 19, no 1, p. 123-132Article in journal (Refereed)
    Abstract [en]

    The effect on water vapour permeability (WVP) and mechanical properties of an addition of various amounts of an acetylated monoglyceride (Acetem) to native potato starch (NPS) films was studied. Phase separation was also evaluated by drying the films at different temperatures, since phase separation between starch and Acetem is affected by temperature. Films were gel-cast from a heated solution of NPS (3%). Five different concentrations (0-10%) of Acetem based on NPS were added to the solution and the films were dried at three different temperatures (23, 35 and 50°C). The film properties were evaluated by measuring thickness, moisture content (MC), WVP and mechanical properties and the results were then evaluated with multivariate analysis. The MC was slightly reduced in the films dried in higher temperatures, despite reconditioned samples, and the film thickness increased with an increasing amount of Acetem. The WVP of a pure NPS film was decreased by 27 and 37% with addition of 10% Acetem or high drying temperature, respectively. The mechanical properties were affected mainly by changes in Acetem concentration. A greater amount of Acetem decreased Young's modulus, stress at break and strain at break. Micrographs showed extensive phase separation in the films, but pure bilayer films were not formed. © 2004 Elsevier Ltd. All rights reserved.

  • 36. Richardson, G.
    et al.
    Bergenstahl, B.
    Langton, Maud
    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.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    The function of ?-crystalline emulsifiers on expanding foam surfaces2004In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 18, no 4, p. 655-663Article in journal (Refereed)
    Abstract [en]

    The expanding capacity and the stabilizing function of an ?-crystalline emulsifier on the bubble surfaces during and after expansion of a sugar foam were examined by volume measurements, confocal laser scanning microscopy (CLSM), freeze-etching and transmission electron microscopy (TEM) and oscillatory rheological measurements. 0.2-10% (w/w) emulsifier, either a polyglycerol ester mixed with monoglycerides (PGE/MG) in ?-gel form or sodium oleate in micellar form, was mixed into a 65% sucrose solution in a specially designed vessel at a pressure of 1-5 bar. The foam produced was expanded to ambient pressure before measurements were made. The total volume of the foam was shown to increase proportionally to the expansion with both emulsifiers. With PGE/MG, small bubbles were produced (1-4 ?m). With oleate, the bubbles became much larger (5-25 ?m) and more coalescence could be observed. The storage modulus of the foam was shown to depend on the bubble sizes, the volume fraction of air and also the emulsifier. The foam stabilized with PGE/MG was stiff at a high concentration of emulsifier, while the micelle forming emulsifier remained more liquid-like. A possible explanation was that the ?-crystalline PGE/MG emulsifier formed aggregates and caused an attractive bridging interaction between the bubbles, which resulted in a higher storage modulus. The micellar oleate did not cause any bubble bridging. © 2003 Elsevier Ltd. All rights reserved.

  • 37.
    Schuster, Erich
    et al.
    RISE - Research Institutes of Sweden, Bioscience and Materials, Agrifood and Bioscience.
    Wallin, P.
    Chalmers University of Technology, Sweden.
    Klose, F. P.
    Chalmers University of Technology, Sweden.
    Gold, J.
    Chalmers University of Technology, Sweden.
    Ström, A.
    Chalmers University of Technology, Sweden.
    Correlating network structure with functional properties of capillary alginate gels for muscle fiber formation2017In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 72, p. 210-218Article in journal (Refereed)
    Abstract [en]

    Capillary alginate gels have the potential to be used as scaffold for the growth of muscle cells for cultured meat owing to the formation of aligned skeletal muscle cells along the length of self-assembled micro-capillaries within the calcium alginate gel. The functional properties (mechanical and permeability) of the gels were determined and correlated to the nano-lengthscale of the gel network using small-angle X-ray scattering. Calcium ions were let to diffuse into the alginate solution in order to obtain spontaneously formed capillaries. We show that the resulting calcium alginate network is isotropic in the plane perpendicular to the inflow of cross linking ions while anisotropic in the parallel plane. The structural anisotropicity is reflected in the mechanical properties (measured via uniaxial stress relaxation) of the gel, where a larger force is required to compress the gel in the isotropic plane than in the anisotropic plane. The findings suggest that the network is layered, or composed of “sheets” with denser regions of alginate, sheets that are weakly attached to each other, similar to the structure of bacterial cellulose. Such structure would further explain the increased permeability of labeled dextran (as determined using fluorescence recovery after photo-bleaching) that we observed in the alginate gels used in this study, as compared to internally set calcium alginate gel.

  • 38. Walkenström, Pernilla
    et al.
    Hermansson, Ann-Marie
    SIK – Institutet för livsmedel och bioteknik.
    Effects of shear on pure and mixed gels of gelatin and particulate whey protein1998In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 12, no 1, p. 77-87Article in journal (Refereed)
    Abstract [en]

    Microstructural and rheological effects of shear on pure whey protein (WPC) gels and on mixed gels of gelatin and WPC have been investigated at pH 5.4. The shear was performed just before the gel formation of the WPC, using shear rates of up to 300/s for times of up to 600 s. The microstructure was investigated by light microscopy (LM) and quantified by image analysis. The behaviour of the storage modulus (G?) upon shear was analysed according to fully factorial experimental designs, where the shear rate and time were used as design variables. Pure WPC suspensions, sheared at ~2/s for ~20 s, formed gels which showed an extremum in G?. In the vicinity of the extremum, the G? showed a value twice that for a gel formed from an unsheared suspension. Image analysis on LM micrographs at different magnifications revealed that an inhomogeneous WPC network was formed from the suspensions sheared at ~2/s for ~20 s. Heavily sheared WPC suspensions (92/s for 240 s) formed gels which showed a weaker G? than the gels formed from unsheared suspensions. The behaviour of G? of mixed gels upon shear was similar to that of the pure WPC gels. The G? for the mixed gels proved to be less sensitive to variations in the shear conditions than the pure WPC gels. During cooling after the gel point of both pure and mixed gels, the loss modulus (G?) showed a pronounced peak for samples sheared in the vicinity of the extremum. Mixed suspensions sheared in the vicinity of the extremum formed inhomogeneous WPC networks with large domains of gelatin. The mean pore size of the WPC network, estimated by image analysis, increased from 40 000 ?m3, for the unsheared mixed sample, to 120 000 ?m3 for the sheared mixed sample. Results from image analysis at different magnifications further confirmed that suspensions sheared in the vicinity of the extremum formed an inhomogeneous WPC network. © 1998 Elsevier Science Ltd. All rights reserved.

  • 39.
    Walkenström, Pernilla
    et al.
    SIK – Institutet för livsmedelsforskning.
    Hermansson, Ann-Marie
    SIK – Institutet för livsmedelsforskning.
    Fine-stranded mixed gels of whey proteins and gelatin1996In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 10, no 1, p. 51-62Article in journal (Refereed)
    Abstract [en]

    Rheological properties of mixed and pure gels of gelatin and whey protein concentrate (WPC) have been investigated by means of tensile tests and dynamic oscillatory measurements. The microstructure of the system has been evaluated by transmission electron microscopy. The pH values chosen are within the range where the WPC forms a fine-stranded network structure, i.e. pH 7.5 and 3.0. When the ratio between the polymers was varied at pH 7.5, a shift in rheological properties was observed. The shift took place around 10% WPC addition to 3% gelatin. Below the shift, the mixed gels followed the behaviour of gelatin, and above, they followed the behaviour of WPC. Gel formation studies showed that the components gel individually, suggesting a phase-separation of the polymers. The gel formation of the WPC was independent of the presence of gelatin, while that of gelatin was shown to be dependent on the presence of WPC. At concentrations below the shift the mixed gels were remeltable and the system was interpreted as gelatin-continuous. At concentrations above the shift, the microstructure of the mixed gels suggested that a phase-separated, bicontinuous system was formed. The WPC network structure seemed to be unchanged in the presence of gelatin. No microstructural phase inversion took place. At pH 3.0 the gel formation of the WPC was strongly affected by the presence of gelatin, i.e. a stronger gel with an earlier gel point was formed. The microstructure of the system showed that an inhomogeneous, aggregated mixed gel, containing large pores, was formed. © Oxford University Press.

  • 40.
    Walkenström, Pernilla
    et al.
    SIK – Institutet för livsmedel och bioteknik.
    Hermansson, Ann-Marie
    SIK – Institutet för livsmedel och bioteknik.
    High-pressure treated mixed gels of gelatin and whey proteins1997In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 11, no 2, p. 195-208Article in journal (Refereed)
    Abstract [en]

    Microstructural and rheological properties of high-pressure treated mixed and pure gels of gelatin and whey protein concentrate (WPC) were studied at pH 7.5 and 5.4. The microstructure was studied using light microscopy and transmission electron microscopy, and the rheological properties using dynamic oscillatory measurements and tensile tests. The results showed that the high-pressure treatment induced a higher degree of aggregation for the pure WPC gels, compared with a conventional heat-treatment, showing a network that consisted of larger aggregates and pores, leading to a weaker gel strength. The pure gelatin networks were unaffected by the high-pressure treatment. Differences in rheological properties were, however, found between pressurized and unpressurized gelatin gels. At pH 5.4, the high-pressure treated mixed gels formed a phase-separated network with a gelatin continuous phase and a discontinuous WPC phase. The rheological properties of the mixed gels followed those of pure gelatin independently of the WPC concentration. At pH 7.5, the rheological properties of the high-pressure treated mixed gels indicated a higher degree of gelatin continuity compared with the heat-treated mixed gels. The microstructural studies showed a dense network in which neither the gelatin nor the WPC network could be identified. © Oxford University Press.

  • 41.
    Walkenström, Pernilla
    et al.
    SIK – Institutet för livsmedel och bioteknik.
    Hermansson, Ann-Marie
    SIK – Institutet för livsmedel och bioteknik.
    Mixed gels of gelatin and whey proteins, formed by combining temperature and high pressure1997In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 11, no 4, p. 457-470Article in journal (Refereed)
    Abstract [en]

    Mixed and pure gels of gelatin and whey protein concentrate ( WPC) were formed by using temperature and high pressure simultaneously. Combining these gel formation methods enables the two polymer networks to set at the same time. The microstructure of the gels was studied by means of light microscopy and transmission electron microscopy, and the rheological properties by means of dynamic oscillatory measurements and tensile tests. The pH values investigated were 5.4, 6.8 and 7.5. The isoelectric point of the WPC is around pH 5.2 and that of gelatin between pH 7.5 and 9. At pH 5.4, the mixed gel formed a phase-separated system, with a gelatin continuous network and spherical inclusions of the WPC. The storage modulus (G) of the mixed gel was similar to that of a pure gelatin gel. At pH 6.8, the mixed gel formed a phase-separated system, composed of an aggregated network and a phase with fine strands. The aggregated network proved to be made up of both gelatin and WPC, and the fine strands were formed of gelatin. The mixed gel at pH 6.8 showed a high G compared with the pure gels, which decreased significantly when the gelatin phase melted. At pH 7.5 the mixed gel was composed of one single aggregated network, in which gelatin and WPC were homogeneously distributed. It was impossible to distinguish the gelatin from the WPC in the mixed network. The mixed gel at pH 7.5 showed a significantly higher G than the pure gels. As the gelatin phase was melted out for the mixed gel, a large decreasein G was observed. The pure gelatin gels, formed by a temperature decrease under high pressure, proved to be pH-dependent, showing an increase in aggregation as the pH increased from 5.4 to 7.5. A fine-stranded, transparent gelatin gel was formed at pH 5.4, while an aggregated, opaque gel was formed at pH 7.5. The stress at fracture for the gelatin gels decreased as the aggregation, and consequently the pore size, increased. © Oxford University Press.

  • 42.
    Walkenström, Pernilla
    et al.
    SIK – Institutet för livsmedel och bioteknik.
    Kidman, Siw
    SIK – Institutet för livsmedel och bioteknik.
    Hermansson, Ann-Marie
    SIK – Institutet för livsmedel och bioteknik.
    Rasmussen, P.B.
    Hoegh, L.
    Microstructure and rheological behaviour of alginate/pectin mixed gels2003In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 17, no 5, p. 593-603Article in journal (Refereed)
    Abstract [en]

    The synergistic interaction between alginate and pectin was systematically investigated using samples of different chemical compositions. Pectin samples with high and low degrees of esterification (DE) and amidated pectin (LA) were mixed with alginate of high and low M/G (mannuronic acid/guluronic acid) ratio. The microstructure of the gels was characterised by TEM (transmission electron microscopy) and the rheological properties by dynamic oscillatory measurements. The TEM images of the mixed gels revealed a coarse, strand-like network with pores in the range of microns, independent of the ratio and the composition of the samples. A comparison with the microstructure of a pure pectin gel showed that the pectin network was composed of thinner strands and smaller pore sizes than the mixed network. The strongest synergism was found between alginate with low M/G ratio and pectin with a high DE. These gels show the highest G? (storage modulus) and the fastest kinetics of gel formation. Lower G? and slower kinetics were found for gels based on alginate with a high M/G ratio and pectin with a low DE, or LA pectin. The nature of the pectin sample affected the network density and the strand characteristics. In contrast, no influence was found of the alginate sample. Gels based on pectin with a high DE showed a dense network composed of highly branched strands, whereas the LA-pectin based gels showed a sparse, open network, composed of long, straight strands. A relation close to 1:1 for low-G alginate and pectin with a high DE resulted in gels with the highest G?. In contrast, for LA-pectin based gels, the highest G? was found for mixtures of alginate dominant ratios. For the overall network properties, the homogeneity in the microstructure decreased with alginate content, independent of the pectin sample. © 2003 Elsevier Science Ltd. All rights reserved.

  • 43.
    Walkenström, Pernilla
    et al.
    SIK – Institutet för livsmedel och bioteknik.
    Panighetti, N.
    Windhab, E.
    Hermansson, Ann-Marie
    SIK – Institutet för livsmedel och bioteknik.
    Effects of fluid shear and temperature on whey protein gels, pure or mixed with xanthan1998In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 12, no 4, p. 469-479Article in journal (Refereed)
    Abstract [en]

    The effects of shear on whey protein isolate (WPI) gels, pure or mixed with xanthan, have been investigated at pH 5.4 by dynamic oscillatory measurements and light microscopy (LM). The shear was performed on the suspensions under a constant stress of between 0.04 and 2.1Pa. Various temperature conditions were chosen in order to describe the effects of shear at the different states of aggregation of the WPI. Shear-sensitive aggregation phenomena were already found around 40°C for the pure WPI samples. Continuous shearing during heating from 20 to 40°C, prior to heat treatment at 90°C, resulted in a gel with a storage modulus (G?) half that of the unsheared gel, independent of the shear stress. Continuous shearing during heating from 20 to 76°C resulted in a further decrease in G?. Inhomogeneities arose in networks formed from continuously sheared suspensions during heating from 20 to 50°C and above. Depending on the shear stress and on the heating range of the shear, the networks showed areas of varied compactness and different classes of pores, ranging from 10 to 200?m. A higher G?, compared to that for the unsheared gel, was found for gels subjected to shear for short periods in the vicinity of the gel point. The presence of xanthan inhibited the aggregation and demixing of the WPI, described as a sterical phenomenon. Under static conditions, the presence of xanthan resulted in a more homogeneous WPI network. Exposing the mixed suspensions to shear generally increased the inhomogeneity of the network structure. Short periods of shearing in the vicinity of the gel point affected the kinetics of the gel formation and resulted in gels with higher G? values than the unsheared gel. Continuous shearing under stresses below 0.09Pa, during heating from 20 to 60°C and above, also resulted in gels with an increased G?. Continuous shear under stresses above 0.9Pa resulted in gels with a decreased G?.

  • 44.
    Walkenström, Pernilla
    et al.
    SIK – Institutet för livsmedel och bioteknik.
    Windhab, E.
    Hermansson, Ann-Marie
    SIK – Institutet för livsmedel och bioteknik.
    Shear-induced structuring of particulate whey protein gels1998In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 12, no 4, p. 459-468Article in journal (Refereed)
    Abstract [en]

    The effects of steady shear on particulate whey protein isolate (WPI) gels, at pH 5.4, have been investigated by light microscopy (LM) and dynamic oscillatory measurements. The steady shear was performed on suspensions at constant rates between 0.5 and 126/s. The gel point under static conditions (Tg) was around 78°C and the shearing was performed during heating from 20 to 76 or to 82°C. The gel point was postponed by the shear up to 82°C. Steady shear up to 76°C, at rates less than ~6/s, resulted in a weaker storage modulus (G?), less frequency dependence and a higher stress at fracture compared to the unsheared gel. Steady shear up to 82°C, at rates below ~6/s, resulted in the formation of two different types of network structure. One structure was similar in appearance to the unsheared network, showing pores in the range of 50?m. The other structure was dense, composed of smaller particles than the unsheared network and with pores in the range of 10?m. The gels composed of two structures showed a lower G? and stress at fracture compared to the unsheared gel. A shear rate above 24/s up to 76°C resulted in irregular networks, which were composed of two different types of structures. One was loose and open, similar in appearance to the unsheared network structure. The other structure was dense and compact, and was present as individual aggregates. These gels also showed a weaker G? than the unsheared gel. A shearing up to 82°C at rates above 24/s resulted in a coarse, inhomogeneous network structure. The gels showed a weak G?, indicating aggregate break-up during the steady shear.

  • 45.
    Walther, Bernhard
    et al.
    SIK – Institutet för livsmedel och bioteknik.
    Walkenström, Pernilla
    SIK – Institutet för livsmedel och bioteknik.
    Hermansson, Ann-Marie
    SIK – Institutet för livsmedel och bioteknik.
    Fischer, P.
    Windhab, E.J.
    Flow processing and gel formation: A promising combination for the design of the shape of gelatin drops2002In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 16, no 6, p. 633-643Article in journal (Refereed)
    Abstract [en]

    This investigation is a model study on how drops can be structured by a combination of flow processing and gel formation. Different drop shapes were created by subjecting gelatin drops to various flow conditions. At the same time, temperature induced gel formation of the drops fixed the shape. Elongated drops and drops of complex form were created. The flow to shape the gelatin drops was generated in a 4-Roll Mill (4RM) and silicon oil was used as the continuous phase. During processing in the 4RM, the drops were allowed to follow two different streamlines and thereby being subjected to purely elongational and a mixture of shear and elongational flow. The drop size varied between 1.5 and 2.8 mm. The gelatin drops were temperature conditioned before the experiment to 60 °C and the silicon oil to 5 °C. The drops were cooled via the cold oil phase during the flow process, and gel formation was induced. A gel strength strong enough to resist further deformation was achieved at different fixation zones in the 4RM, and this depended on the process parameters of flow type, flow rate, drop size and gelatin concentration. The shape created was directly related to the fixation zone. There was a broad freedom to combine different parameter values to fix a drop in a certain fixation zone. The mechanism behind the various drop shapes is explained in terms of elongation, relaxation, pinching and gel formation in relation to flow pattern and time in the 4RM. Elongation is a major contribution to the mechanism in the case of elongated shapes, while elongation followed by relaxation and pinching are the dominant determinants in the creation of complex shapes. © 2002 Elsevier Science Ltd. All rights reserved.

  • 46.
    Wassen, Sofia
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Rondeau, E.
    Sott, K.
    Loren, Niklas
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Fischer, P.
    Hermansson, Ann-Marie
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Microfluidic production of monodisperse biopolymer particles with reproducible morphology by kinetic control2012In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 28, no 1, p. 20-27Article in journal (Refereed)
    Abstract [en]

    Microdroplets of phase separating and gelling gelatin-maltodextrin mixtures were produced by a microfluidic technique. The microstructures observed inside the gelled particles were highly reproducible. This resulted from both the controlled production of monodisperse droplets in a microfluidic device and the tuning of gelation and phase separation kinetics.We showed that the internal particle microstructure can be tailored by varying the cooling rate (90 °C/min, 55 °C/min, 5 °C/min), the biopolymer composition (4% gelatin and 6%-7.3% maltodextrin) and the gelatin type (lime hide, pig skin). The particles were analyzed using confocal scanning laser microscopy and image analysis. Microstructures with smaller domain sizes were formed at the fastest cooling rate (90 °C/min), and microstructures with large domain sizes were obtained at the slowest cooling rate (5 °C/min). Furthermore, differences in particle morphology were observed at this slowest cooling rate. In particles containing pig skin gelatin, maltodextrin was located in the core, whereas gelatin was present at the water-oil interface. The opposite was observed for particles consisting of lime hide gelatin where the maltodextrin was found toward the oil phase. The results also showed that a higher concentration of maltodextrin formed larger bicontinuous microstructures compared to the ones obtained with lower concentrations. © 2011 Elsevier Ltd.

  • 47.
    Wendin, K
    et al.
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, SIK – Institutet för livsmedel och bioteknik.
    Aaby, K
    Edris, A
    Risberg Ellekjaer, M
    Albin, R
    Bergenståhl, B
    RISE, SP – Sveriges Tekniska Forskningsinstitut, SP Sveriges tekniska forskningsinstitut, YKI – Ytkemiska institutet.
    Low-fat mayonnaise: influences of fat content, aroma compounds and thickeners1997In: Food Hydrocolloids, ISSN 0268-005X, E-ISSN 1873-7137, Vol. 11, p. 87-99Article in journal (Refereed)
    Abstract [en]

    The effects of fat content and thickeners, propylene glycol alginate (PGA; 1.40%) and guar gum (1.55%), on sensory and instrumental quality descriptors on reduced mayonnaises (15 and 30% fat) with and without added aroma compounds, citral (semi-polar) and oyroligneous acid (polar), were investigated. One mayonnaise, 82% fat, without added thickener or aroma compounds, was used as reference. Sensory evaluation (quantitive descriptive analysis; QDA), rheological analysis (yield stress, maximum viscosity, G' and G"), measurements of particle size and headspace GC-MS analyses were carried out. Correlations between the results were developed. Perceived and instrumental texture, and perceived smell and flavour, changed differently in magnitude and direction due to fat content and type of thickener.

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