Browsing by Subject "Rheology"

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  • Mikkonen, Kirsi Susanna; Merger, Dimitri; Kilpeläinen, Petri; Murtomäki, Lasse; Schmidt, Ulrike S.; Wilhelm, Manfred (2016)
    Materials manufacturing industries seek efficient, economic, and sustainable compounds for stabilizing dispersed systems such as emulsions. In this study, novel, abundant biobased hydrocolloids spruce galactoglucomannans (GGM) and birch glucuronoxylans (GX) were obtained from a forestry biorefining process and characterized as versatile stabilizers of rapeseed oil-in-water emulsions. For the first time, GGM and GX isolated by pressurized hot water extraction (PHWE) of spruce and birch saw meal, respectively, were studied in emulsions. The PHWE wood hemicelluloses—polysaccharides with relatively low molar mass—facilitated the formation of emulsions with small average droplet size and efficiently prevented droplet coalescence. GGM and GX lowered the surface tension of emulsions’ oil–water interface and increased the viscosity of the continuous phase. However, viscosity of the wood hemicellulose-based systems was low compared to that of commercial polymeric stabilizers. GGMstabilized emulsions with varying oil volume fractions were characterized in terms of their rheological properties, including large amplitude oscillation shear (LAOS) measurements, and compared to emulsions prepared with a classical small-molecular surfactant, Tween20. The physical emulsion stabilization mechanisms of GGM and GX are suggested as steric repulsion assisted by Pickering-type stabilization. Wood hemicelluloses have potential as highly promising future bioproducts for versatile industrial applications involving colloidal systems and soft materials.
  • Wang, Yaqin; Sorvali, Päivi; Laitila, Arja; Maina, Ndegwa Henry; Coda, Rossana; Katina, Kati (2018)
    The incorporation of faba bean flour into wheat-based products is a sustainable way to obtain protein-enriched food items. However, developing breads with a higher content of faba bean flour is challenging due to the poor textural/sensory properties of the final product. A potential solution is to use hydrocolloids as structuring agents to increase the viscoelastic properties of the composite bread. Microbial dextran is a natural hydrocolloid which can be used as a bread texture improver either as a pure food ingredient or by in situ production during sourdough fermentation. The aim of this study was to compare the influence of dextran produced in situ by Weissella confusa VTT E-143403 (E3403) and Leuconostoc pseudomesenteroides DSM 20193 in faba bean sourdoughs on the quality of wheat bread supplemented with 43% faba bean sourdough. The impact of dextran on the rheological properties of dough and textural properties of the final bread were evaluated. Dextran formed by W. confusa and L. pseudomesenteroides reached a level of 5.2 and 3.6% (flour basis), respectively. Incorporation of faba bean sourdough containing dextran synthesized by W. confusa improved the dough viscoelastic properties, and also increased the specific volume (similar to 21%) and reduced crumb hardness (similar to 12%) of the final bread, compared to control breads. Similar positive effects were not obtained with sourdough containing dextran from L. pseudomesenteroides, probably due to its higher acidity. Dextran synthesized in situ by W. confusa is a promising clean label hydrocolloid option to improve the quality of wheat bread enriched with faba bean flour.
  • Xu, Yan; Coda, Rossana; Holopainen-Mantila, Ulla; Laitila, Arja; Katina, Kati; Tenkanen, Maija (2019)
    The aim of this study was to investigate the impact of in situ produced exopolysaccharides (EPS) on the rheological and textural properties of fava bean protein concentrate (FPC). EPS (dextrans) were produced from sucrose by two lactic acid bacteria (LAB). The acidification, rheology, and texture of FPC pastes fermented with Leuconostoc pseudomesenteroides DSM 20193 and Weissella confusa VTT E-143403 (E3403) were compared. A clear improvement in rheological and textural parameters was observed in sucrose-added pastes after fermentation, especially with W. confusa VTT E3403. Only moderate proteolysis of fava bean protein during fermentation was observed. The microstructure of the protein in FPC pastes, as observed by confocal laser scanning microscopy, revealed a less continuous and denser structure in EPS-abundant pastes. The beneficial structure formed during EPS-producing fermentation could not be mimicked by simply mixing FPC, isolated dextran, lactic acid, and acetic acid with water. These results emphasize the benefits of in situ produced EPS in connection with the LAB fermentation of legume protein-rich foods. Fermentation with EPS-producing LAB is a cost-effective and clean-labeled technology to obtain tailored textures, and it can further enhance the usability of legumes in novel foods.
  • Wang, Hang; Luo, Yongkang; Ertbjerg, Per (2017)
    Minced beef was stored for 8 days and myofibrillar protein (MP) was extracted to investigate the effect of oxygen concentration (0, 20, 40, 60, and 80%) in modified atmosphere packaging (MAP) on heat-induced gel properties. Compression force of gels was lower when prepared from beef packaged in 0% oxygen, intermediate in 20 to 60% oxygen and greater in 80% oxygen. Total water loss of gels prepared from beef packaged with oxygen (20-80%) was higher and rheology measurements presented higher G' and G '' values. Additionally, gels from beef packaged without oxygen exhibited higher J (t) values during creep and recovery tests, demonstrating that oxygen exposure of meat during storage in MAP affect MP in such a way that heat-induced protein gels alter their characteristics. Generally, storage with oxygen in MAP resulted in stronger and more elastic MP gels, which was observed already at a relative low oxygen concentration of 20%. (C) 2017 Elsevier Ltd. All rights reserved.
  • Paukkonen, Heli; Kunnari, Mikko; Lauren, Patrick; Hakkarainen, Tiina; Auvinen, Vili-Veli; Oksanen, Timo; Koivuniemi, Raili; Yliperttula, Marjo; Laaksonen, Timo (2017)
    Concentrated 3% and 6.5% anionic nanofibrillar cellulose (ANFC) hydrogels were introduced as matrix reservoirs for controlled delivery applications of small molecules and proteins. A further aim was to study how the freeze-drying and subsequent rehydration of ANFC hydrogel affects the rheological properties and drug release of selected model compounds from the reconstructed hydrogels. It was demonstrated that the 3% and 6.5% ANFC hydrogels can be freeze-dried with suitable excipients into highly porous aerogel structures and redispersed back into the hydrogel form without significant change in the rheological properties. Freeze-drying did not affect the drug release properties from redispersed ANFC hydrogels, indicating that these systems could be stored in the dry form and only redispersed when needed. For large molecules, the diffusion coefficients were significantly smaller when higher ANFC fiber content was used, indicating that the amount of ANFC fibers in the hydrogel can be used to control the release rate. The release of small molecules was controlled with the ANFC fiber content only to a moderate extent. The results indicate that ANFC hydrogel can be used for controlled delivery of several types of molecules and that the hydrogel can be successfully freeze-dried and redispersed.
  • Koivunotko, Elle; Merivaara, Arto; Valkonen, Sami; Chinello, Lisa; Salmaso, Stefano; Korhonen, Ossi (Helsingin yliopisto, 2020)
    Biomimetic native nanofibrillated cellulose (NFC) hydrogel has recently proven its efficacy, safety and diversity at the site of pharmaceutical industry. Yet, properties for the long-term storage in dry condition at room temperature and feasible transportation needs to be developed for NFC hydrogel before it is suitable for freeze-dried biomedical applications. Our aim was to optimize freeze-drying cycle for NFC hydrogel formulation with suitable lyoprotective biomolecules and preserve its properties after freeze-drying process and reconstitution. NFC hydrogel formulations with different combinations of chosen biomolecules were freeze-dried, and physicochemical properties and rheological features were characterized. In addition, morphology of the freeze-dried cakes was studied. The effects of the biomolecules on the water contents in NFC systems were simulated for both of the crystal and amorphous ones. All the results of the characteristics were compared with the non-freeze-dried NFC hydrogel formulations. NFC hydrogel formulation, which had the most optimal preservation properties after freeze-drying and reconstitution, was optimized. We hypothesized that without any chemical modifications native NFC hydrogel can be successfully freeze-dried and subsequently reconstituted with the proper biomolecules only by using biological and natural materials, which are human and xenon-free for the further use in biomedical applications of the native NFC hydrogel.
  • Oleyaei, Seyed Amir; Razavi, Seyed Mohammad Ali; Mikkonen, Kirsi S. (2018)
    Sage seed gum (SSG) is a promising biopolymer candidate for utilization and substitution prevalent galactomannan gels of interest in soft biomaterial applications. Herein, physicochemical and rheo-mechanical properties of SSG matrix reinforced by various titanium dioxide (TiO2) nanoparticles loading (0-25wt%) were monitored. Particle size and density of the nanocomposite increased with raising TiO2 content, due to the creation of more compact agglomerated and aggregated microstructure. Increasing the particle size resulted in lower electrophoretic mobility of SSG-TiO2 systems upon nanoparticles addition, confirmed the adsorption of TiO2 on the SSG macromolecule. Mechanical spectra of the SSG-based nanocomposites demonstrated a more solid-like behavior by lower frequency-dependent viscoelastic moduli, suggested a structural decoration of the nanohybrid gels discussed in terms of polymer bridging effect and formation of percolated matrix-particle superstructure. Crucial textural parameters improved with increasing TiO2 until a critical level (15 wt%), after which further increments in filler resulted in a reduction of hardness, adhesiveness and apparent modulus of elasticity. Deformation of rod-like junction zones acting as physical crosslinks in the system and fracture theory were used to explain the strain-stiffening and adhesive behavior of SSG-based gels, respectively. The nanocomposite gels with tunable functional properties might be ideal candidates for biomaterial industry. (C) 2018 Elsevier B.V. All rights reserved.
  • Bhattarai, Mamata; Penttilä, Paavo; Barba, Luisa; Macias-Rodriguez, Braulio; Hietala, Sami; Mikkonen, Kirsi S.; Valoppi, Fabio (2022)
    Oleogels are a class of solid-fat mimetics that contain a large fraction of oil. Most of these materials have low stiffness and poor oil-binding capacity at commercially viable concentrations, which limits their application in the food and cosmetic industries. To improve their mechanical behavior, we exploited the concepts of particulate-filled materials by developing oil-continuous monoglyceride composites reinforced with crystalline cellulose of various sizes. Cellulose was used as the reinforcing filler material due to its strength, biodegradability, and abundance. The composites gradually stiffened and became more brittle with a progressive increase of the cellulose weight fraction as the maximum packing fraction of fillers approached. This was manifested as an increase in the viscoelastic moduli and yield stress, consistent with the size of the filler. Based on differential scanning calorimetry, X-ray diffraction, X-ray scattering analyses, and microscopic analyses, the inert surface of crystalline celluloses provided a solid substrate for the crystallization of monoglycerides, favoring the lamellar stacking of monoglyceride molecules during the composite oleogel formation regardless of the cellulose size. The present study suggests that cellulose is a suitable bio-based filler material to obtain mechanically strong oleogels suitable for high-shear applications e.g., in food and pharmaceutical industries.