Wheat gluten protein-based biodegradable or edible films are produced using aqueous, essentially alcohol-free casting dispersions containing modified wheat protein and a plasticizer. The modified wheat protein is prepared by treating purified naturally occurring wheat protein with a reducing agent (e.g., sodium metabisulfite) in order to reduce the average molecular weight of the wheat protein and to cleave disulfide bonds therein. Such modified wheat gluten protein lowers the viscosity and allows increased solid contents in the casting dispersions, allowing fabrication of improved films.