Denaturation and covalent network formation of wheat gluten, globular proteins and mixtures thereof in aqueous ethanol and water

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Food processing often includes heating and/or exposure to solvents as unit operations. Here, the impact of heating at 100 °C in water or aqueous ethanol [10 or 50% (v/v)] on denaturation and covalent network formation of three model proteins [bovine serum albumin (BSA), soy glycinin and wheat gliadin] was examined. Already at room temperature 50% (v/v) ethanol induced disulfide cross-linking between BSA proteins. Increased ethanol concentrations reduced heat-induced polymerization of soy glycinin and wheat gliadin. The use of aqueous ethanol limited the extent of β-elimination, sulfhydryl-disulfide exchange reactions and sulfhydryl oxidation. Gliadin and soy glycinin had higher colloidal stability in 50% (v/v) ethanol than in water. The conformation of BSA and soy glycinin already changed at lower temperatures in 50% (v/v) ethanol than in water. In all media, different proteins influenced each other's denaturation and/or polymerization. During heating in water but not in 50% (v/v) ethanol, gliadin-BSA and gliadin-soy glycinin mixtures polymerized more than expected than the isolated proteins. Thus, phase-separation of proteins did not limit intermolecular disulfide formation. Pretreatment of proteins with aqueous ethanol did not substantially influence their subsequent polymerization during prolonged heating in water. However, ethanol pretreatment of gluten impacted heat-induced polymerization of BSA in gluten-BSA mixtures.