Physical Properties of Biodegradable Films of Soy Protein Concentrate/Gelling Agent Blends

Soy protein concentrate (SPC) is modified by blending with gelling agents such as agar, Agargel, and Phytagel and the properties of the blended films are characterized. Gelling agent addition significantly improves the mechanical properties, thermal stability, and moisture resistance. SPC blended with 30% PG show over 180% increase in the tensile stress and Young's modulus and the moisture regain decreases from 17.9 to 13.9%. The glass transition temperature of the SPC films increases from 132 to 148 degrees C after blending with Agargel and Phytagel. IPN-like structure formation after adding gelling agents is responsible for the improvements. The results also suggest that the gelling agent chemistry determines the amount of gelling agent required to form IPN-like structures.