Abstract
This study aims at investigating the effect of ethanol (EtOH) on the textural properties of whey protein and egg white protein hydrogels. The hydrogels were produced by thermally induced gel formation of aqueous protein solutions. The water contained in the gel network was subsequently exchanged by EtOH to assess structural changes upon exposure of hydrogels to ethanolic aqueous phases. The textural properties of the hydrogel and alcogel samples were analyzed by uniaxial compression tests. For both protein sources, the hardness increased exponentially when pH and EtOH concentration were increased. This increase correlated with a shrinkage of the gel samples. The gel texture was found to be elastic at low EtOH concentrations and became stiff and hard at higher EtOH concentrations. It was found that the solvent exchange influences the ion concentration within the gels and, therefore, the interactions between molecules in the gel structure. Non-covalent bonds were identified as substantially responsible for the gel structure.
Highlights
The effect of ethanol (EtOH) on proteins in solution as well as on resulting protein or polysaccharide gels has been studied by various works for several reasons
This study aims at investigating the effect of ethanol (EtOH) on the textural properties of whey protein and egg white protein hydrogels
A constant EtOH weight fraction in the surrounding solution was taken as an indicator for a completed solvent exchange
Summary
The effect of ethanol (EtOH) on proteins in solution as well as on resulting protein or polysaccharide gels has been studied by various works for several reasons. Protein gels may be used itself as semi-solid food containing alcohol or as a carrier system for microorganisms in fermentation processes producing EtOH, where a change of the gel structure induced by variable. A protein hydrogel can be described as a porous matrix and networked structure completely soaked with water as a gel solvent. Before hydrogels can be converted into an aerogel, exchanging the contained water entirely by CO2 -soluble EtOH is necessary [6]. The gel is postulated to undergo structural changes during the solvent exchange step of the water with a Molecules 2020, 25, 4417; doi:10.3390/molecules25194417 www.mdpi.com/journal/molecules
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