Properties of Cysteine-Added Soy Protein-Wheat Gluten Films

Soy and wheat proteins as film ingredients are advantageous due to relative abundance, biodegradability, and their renewable nature. Research objectives were to evaluate effectiveness of gluten and cysteine addition in improving properties of soy protein-based films. Thickness, mechanical, and barrier properties were evaluated. Gluten addition and pH 3.0 lowered water vapor permeability and thickness. Mechanical properties were enhanced at pH 7.0 with cysteine addition. Cysteine increased tensile strength of some treatments due to increase in disulfide bond formation. Best compromise between barrier and mechanical properties was observed for the cysteine-added soy:gluten (4:1) film at pH 7.0. These films could find application as primary packaging for low moisture foods.