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Item type:Publication, Access status: without files , Hydro- and aerogels from ethanolic potato and whey protein solutions: Influence of temperature and ethanol concentration on viscoelastic properties, protein interactions, and microstructureDenaturation, aggregation, and gelation of protein solutions can be induced through increased temperatures and the presence of organic solvents. Depending on the molecular features of the involved proteins, the denaturation conditions lead to very different gel properties. However, it is poorly understood how organic solvents in combination with heat treatments can be used to modify the textural properties of protein gels. In this study, the combined effects of heat and ethanol (EtOH) treatment on hydrogel formation by whey (WPI) and potato protein isolates (PPI) were investigated. The different protein hydrogels were subjected to a complete solvent exchange with EtOH and dried with supercritical CO2 to obtain aerogels with a high inner surface area. Increasing EtOH concentration during thermally induced hydrogel formation reduced the temperature of unfolding up to a point where denaturation occurred at room temperature. WPI and PPI formed very different gels in the presence of EtOH. WPI gels with an EtOH content below 10% (w/w) were elastic and mainly linked through disulfide bonds. Higher EtOH content led to weak gels, mainly linked through electrostatic and hydrogen bonds. For PPI gels, increasing EtOH content did not influence the protein interactions within the gels, and textural properties were very similar. The textural properties of the resulting aerogels were dependent on the type of protein interactions created in the hydrogels. This work provides insights into the way food proteins form gel networks and how these interactions can be manipulated to produce gels with tailor-made properties.Publicationtype: Journal Article121 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Microstructures of potato protein hydrogels and aerogels produced by thermal crosslinking and supercritical dryingAerogels are highly porous structures created from hydrogels by solvent exchange and supercritical CO2 drying. They can be produced from proteins and used for encapsulation of active ingredients. In this work, the structural relationship between various protein based hydrogels and aerogels was investigated. We compare egg white protein (EWP) and patatin rich potato protein isolates (PPI) in terms of gel and aerogel production thereof. Thereby, aerogels were produced for the first time from patatin-rich potato protein isolates. Both protein sources can form strong hydrogels, but they differ in their molecular properties, especially regarding the presence of reactive groups available for covalent crosslinking. Therefore, we studied the rheological profiles of hydrogels of both protein groups and applied the ratio of elastic modulus at gel formation temperature (G'hot) and after cooling to ambient temperature (G'cool) as criterion for comparing gel formation capacities produced from structurally different proteins. The ratio G'cool/G'hot was also identified as an indicator of the relation of non-covalent bonds to covalent and/or hydrophobic interactions and for characterizing aerogel structural properties. PPI hydrogels were found to be dominated by hydrophobic interactions, while covalent disulfide bonds determine EWP hydrogel stabilization. Nevertheless, PPI and EWP hydrogel and aerogels showed similar stabilities. More than the protein source, the pH during hydrogel formation was found to decisively influence the protein interaction potential and gel/aerogel characteristics. Irrespective of the protein source low pH led to brittle aerogels with high specific surface areas and low G'cool/G'hot ratios. At a pH close to the isoelectric point (IEP) brittle gels with low specific surface areas and high G'cool/G'hot ratios were measured. At alkaline pH gels were most stable, the specific surface area and G'cool/G'hot ratios were intermediate. Overall, the results help to control the structural properties of gels and aerogels towards potential applications in food systems.Publicationtype: Journal Article249