gluten protein - based biodegradable or edible films are produced using aqueous , essentially alcohol - free casting dispersions containing modified protein and a plasticizer . the modified protein is prepared by treating purified naturally occurring wheat protein with a reducing agent 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 using continuous casting techniques and without use of organic solvents .