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- Lopez-Sanchez, Patricia, 1977, et al.
(author)
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Impact of Glucose on the Nanostructure and Mechanical Properties of Calcium-Alginate Hydrogels
- 2022
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In: Gels. - : MDPI AG. - 2310-2861. ; 8:2
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Journal article (peer-reviewed)abstract
- Alginate is a polysaccharide obtained from brown seaweed that is widely used in food, pharmaceutical, and biotechnological applications due to its versatility as a viscosifier and gelling agent. Here, we investigated the influence of the addition of glucose on the structure and mechanical properties of alginate solutions and calcium-alginate hydrogels produced by internal gelation through crosslinking with Ca2+ . Using1H low-field nuclear magnetic resonance (NMR) and small angle neutron scattering (SANS), we showed that alginate solutions at 1 wt % present structural hetero-geneities at local scale whose size increases with glucose concentration (15–45 wt %). Remarkably, the molecular conformation of alginate in the gels obtained from internal gelation by Ca2+ crosslinking is similar to that found in solution. The mechanical properties of the gels evidence an increase in gel strength and elasticity upon the addition of glucose. The fitting of mechanical properties to a poroelastic model shows that structural changes within solutions prior to gelation and the increase in solvent viscosity contribute to the gel strength. The nanostructure of the gels (at local scale, i.e., up to few hundreds of Å) remains unaltered by the presence of glucose up to 30 wt %. At 45 wt %, the permeability obtained by the poroelastic model decreases, and the Young’s modulus increases. We suggest that macro (rather than micro) structural changes lead to this behavior due to the creation of a network of denser zones of chains at 45 wt % glucose. Our study paves the way for the design of calcium-alginate hydrogels with controlled structure for food and pharmaceutical applications in which interactions with glucose are of relevance.
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| 2. |
- Maire Du Poset, Aline, et al.
(author)
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Controlled Loading and Release of Beta-Lactoglobulin in Calcium-Polygalacturonate Hydrogels
- 2020
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In: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 21:4, s. 1417-1426
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Journal article (peer-reviewed)abstract
- We show here how the structure of polygalacturonate (polyGalA) hydrogels cross-linked by Ca2+ cations via external gelation controls the loading and release rate of beta-lactoglobulin (BLG), a globular protein. Hydrogels prepared from a polyGalA/BLG solution are found to be similar to those obtained from a polyGalA solution in our previous study (Maire du Poset et al. Biomacromolecules 2019, 20 (7), 2864-2872): they exhibit similar transparencies and gradients of mechanical properties and polyGalA concentrations. The nominal BLG/polyGalA ratio of the mixtures is almost recovered within the whole mixed hydrogel despite such strong concentration gradients, except in the part of the hydrogels with the largest mesh size, where more BLG proteins are present. This gradient enables one to tune the amount of protein loaded within the hydrogel. At a local scale, the proteins are distributed evenly within the hydrogel network, as shown by small-angle neutron scattering (SANS). The release of proteins from hydrogels is driven by Fickian diffusion, and the release rate increases with the mesh size of the network, with a characteristic time of a few hours. The specific structure of these polysaccharide-based hydrogels allows for control of both the dosage and the release rate of the loaded protein and makes them good candidates for use as oral controlled-delivery systems.
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| 3. |
- Martínez-Sanz, Marta, et al.
(author)
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Nano-/microstructure of extruded Spirulina/starch foams in relation to their textural properties
- 2020
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In: Food Hydrocolloids. - : Elsevier B.V.. - 0268-005X .- 1873-7137. ; 103
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Journal article (peer-reviewed)abstract
- This work reports on an in-depth characterization of the nano- and microstructure of extruded starch foams loaded with the microalga Spirulina (1, 5 and 10 wt%), as well as the implications of Spirulina incorporation on the textural properties of the foams. Due to the gelatinization process occurring during extrusion, the crystalline and lamellar structures originally present in the starch granule were disrupted, resulting in very amorphous foams. Moreover, the crystalline structure of the fatty acids present in the raw microalga was lost during processing. The presence of Spirulina intracellular components induced the formation of more thermally-stable V-type crystallites through complexation with amylose, hence producing slightly more crystalline foams (XC~5–9%) than the pure extruded starch (XC ~3%). This affected the microstructure of the hybrid foams, which showed more densely packed and well-connected porous structures. Microstructural changes had an impact on the texture of the foams, which became harder with greater Spirulina loadings. The foams underwent very limited re-crystallization upon storage, which was further reduced by the presence of Spirulina. Interestingly, the free fatty acids from Spirulina re-crystallized and the resistant starch content in the 10% Spirulina foam increased, which could potentially be interesting from a nutritional perspective. These results show the potential of extrusion cooking to produce healthier snack foods and highlight the suitability of advanced characterization tools such as neutron tomography and small angle X-ray scattering to investigate food structure.
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