Sodium Dodecyl Sulfate and Agar Improve Physical Properties of Plastic Films Made with Soy Curd Residue Protein

Soy curd waste, okara of Japanese soy curd industry, was once an important daily food, but modernization in life style has reduced its status to a normal industrial waste. The waste protein content is still high. Using the waste to produce biodegradable films substituting the petroleum plastics means adding high economic value to it. Since the waste contains few amino acids, it was experienced that more glycerol was needed for it to reach an acceptable elasticity. Tensile strength and elongation of this protein film were weaker than those of soy protein film. However, the physical properties of okara protein film can be improved to those of a commercial polyethylene film made with CaCO3 if sodium dodecyl sulfate were added. However, the addition oppressed tensile strength and makes the produced film too elastic. This deformation could be adjusted by the addition of agar.