Methods were presented in this study for preparing protein films from wheat gluten, corn zein, soy protein isolate, and egg white. Film properties, as related to various processing factors, were evaluated. The oxygen permeability of corn zein, wheat gluten, and wheat gluten/soy protein isolate (2.1:0.9) films was determined at 7, 15, 25, and 35\sp\circC under 0% relative humidity. Data for all three films showed good agreement with the Arrhenius activation energy model. Equations were presented for correcting water vapor transmission data of hydrophilic films, such as protein films. Corn zein and methyl cellulose films were used for validation of the corrective equations. Tensile strength of corn zein and wheat gluten films was found to decrease with relative humidity (23-75%) and to increase with temperature (5-45\sp\circC). Properties of wheat gluten and soy protein isolate films were significantly affected by the pH of film-forming solutions. Wheat gluten and soy protein isolate films of higher tensile strength were obtained under alkaline, rather than acidic, conditions. Glass transition, mechanical, and water vapor barrier properties of wheat gluten films containing glycerin, sucrose, glycerin-sucrose, or glycerin-sorbitol were studied. Glycerin and sucrose were immiscible and the gluten film containing both solutes showed two separate glass transitions (−58\sp\circC and −5\sp\circC). The glass transition temperature of films showed low correlation with water vapor barrier and mechanical properties. Gluten:glycerin:sorbitol films (15:3:3 w/w) showed a single effective glass transition temperature (−42\sp\circC). Soy protein isolate films heated at 80 or 95\sp\circC for 2, 6, 14, and 24 h had increased tensile strength and +b (yellowness) Hunter color values and reduced elongation at break, water solubility, and water vapor permeability. Film properties were affected more by heating at 95\sp\circC than 80\sp\circC. Films were cast from aqueous alkaline solutions of dried egg white. At equal concentrations, polyethylene glycol-plasticized films had greater tensile strength and elongation at break than glycerin- or sorbitol-plasticized films. Partial substitution of egg white with dried yolk solids decreased film tensile strength and elongation at break and increased −a (greenness) and +b (yellowness) Hunter color values
