High-elongation zein films for flexible packaging by synergistic plasticization: Preparation, structure and properties

Abstract To obtain high-elongation flexible packaging, glycerol (GLY) and a series of polyethers (PEs), i.e. poly (ethylene glycol) (PEG), poly (propylene glycol) (PPG), poly (tetramethylene glycol) (PTMG), were chosen as model plasticizers to soften zein films. Different characterizations were conducted to investigate the structure and properties of films in detail. The results indicated that when using a suitable ratio of GLY and PEs, i.e. 1:1 in mass, the plasticized zein films showed excellent elongation at break of 245–350% at 0.45 g plasticizer/g zein. The synergistic plasticizing effects on films were discussed and attributed to the structural change of zein molecules, i.e. the disruption of inter- α -helix packing and the increase of β -sheet content, then the plasticization mechanism was proposed. Films plasticized by GLY and PTMG had higher water vapor permeability because of their unique porous structure. All zein films exhibited excellent UV barrier properties, and PEG improved the transmittance of zein film.