The impact of bifunctional molecules on the gluten network during mixing

The protein network in gluten was either cross-linked or functionalized by using chain extenders to afford novel bio-based materials. These chain extenders consist on di- or tri- ethylene glycol oligomers functionalized at both end with maleimide or maleate groups and also with commercially available vinyl ether. These bi-functional additives are incorporated into standard gluten/glycerol blends during batch mixing. The gluten polymerization proceeds by thiol/disulfide exchanges during mixing and was assessed by the loss of the soluble fraction of protein in SDS. Modifications of protein size distribution revealed a cross-linking between chain extender and gluten, depending on the reactivity of the terminal functions of the used extender. Maleimide end-groups induced a high gluten polymerization whereas maleate ones lead to a complete depolymerization. Depending on their reactivity, bi-functional additives can thus act either as non-reducible chain extender or, thanks to the grafting of one of the additives-end onto the gluten thiol groups, as functionalizing agent: in this last case, one of the end-groups remained free and thus available for further reaction.