Effect of plasticizer and zein subunit on rheology and texture of zein network

Zein can form viscoelastic network, similar to gluten network, to support the weak structure of gluten-free dough caused by the lack of gluten, which greatly improves the textural quality of gluten-free foods. The effect of plasticizer and zein subunit on viscoelasticity of zein network was studied. In this study, total zein (comprising α-, β- and γ-subunits) or α-zein (comprising mainly α-subunit) were used to prepare network with two plasticizer, ethanol or acetic acid, at room temperature, and the glass transition temperature, rheological properties, textural properties, protein secondary structure, and microstructure of the networks were analyzed. The glass transition temperature of total zein was higher than that of α-zein due to β- and γ-zein. The zein network with acetic acid could maintain its viscoelasticity consistently, while the zein network with ethanol hardened gradually. The zein network with acetic acid had a larger yield strain, higher cohesive force, and stronger resistance to external stress than the zein network with ethanol. The existence of β- and γ-zein in total zein could increase the yield strain and cohesive force of zein network. After zein transformed from solid particle to viscoelastic network, its ordered secondary structures decreased, and disordered secondary structures increased. The more plasticized zein was, the more uniform and ordered zein network was. It is concluded that rheological and textural properties of zein network were both subunit and plasticizer-dependent, and these properties of total zein network with acetic acid was the closest to those of gluten network.