Glycerol improved film extensibility but reduced film puncture strength, elasticity, and water vapor barrier properties. The plasticizing effect of water was highly temperature dependent. During hydration of gluten film, a sharp decrease in puncture strength, elasticity, and an increase of extensibility and water vapor transmission rate were observed at 5, 30 and 5o'C for respective water contents of 30 (0,8 a,), 15 (0,7 a,) and 5% (0,4 a,). This was related to disruptive waterpolymer hydrogen bonding and glass-to-rubber transition.

An edible wheat gluten film was developed and effects of gluten concentration, ethanol concentration (ET) and pH of the film-forming solution on various film properties were evaluated using Response Surface Methodology. pH and ethanol concentration had strong interactive effects on film opacity, water solubility and water vapor permeability. A simultaneous variation of ethanol concentration and pH between 32.5% ET, pH 4 and 45% ET, pH 2 resulted in homogeneous and transparent film with relatively low water solubility. The lowest water vapor permeability would be expected with 20% ethanol concentration and pH 6. Mechanical properties were mainly affected by gluten concentration and pH. The most resistant film was obtained at high gluten concentration (12.5%) and pH 5.

Edible composite films comprised of wheat gluten as the structural matrix and various concentrations of different lipids as the moisture barrier component were tested for water vapour permeability, dispersion in water, opacity and mechanical properties. The effects of lipids on the functional properties of gluten-based composite films depended on the lipid characteristics and on the interactions between the lipid and the protein structural matrix. Beeswax, a solid and highly hydrophobic lipid, was the most effective lipid for improving moisture barrier properties of films; but these films were opaque, weak and disintegrated easily in water. Combining wheat gluten proteins with a diacetyl tartaric ester of monoglycerides reduced water vapour permeability, increased strength and maintained transparency.