Hydro- and aerogels from ethanolic potato and whey protein solutions: Influence of temperature and ethanol concentration on viscoelastic properties, protein interactions, and microstructure

Denaturation, 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.