Structural transitions and molecular interactions of zein induced by ethanol and extrusion

Ethanol improves the zein network in gluten-free dough, but the molecular mechanisms underlying this improvement remain incompletely elucidated. This study investigated ethanol plasticization (0-50 %, <i>v</i>/v) on commercial zein (C-zein) and extrusion-modified zein (E-zein, 140 °C). Both self-assembled into spherical microparticles merging into membranes at 50 % ethanol. Ethanol increased the porous structure and reduced the glass transition temperature (<i>T</i> _g) of zein, whereas extrusion showed the opposite trend. Analysis showed ethanol bonded to zein primarily through hydrophobic interactions, hydrogen bonds, and van der Waals forces. This binding induced the partial unfolding of zein molecules, thereby exposing additional hydrophobic residues and hydrogen-bonding sites, facilitating the formation of zein networks predominantly driven by non-covalent forces. Plasticization with 10 % ethanol above 40 °C is recommended to optimize E-zein functionality. These findings provide molecular-level insights into the interactions (hydrophobic, hydrogen-bonding, and van der Waals) between zein and ethanol and guide strategies for improving gluten-free zein foods.