Novel composite gels of gelatin and soluble dietary fiber from black bean coats with interpenetrating polymer networks

The soluble dietary fiber (SDF) extracted from black bean coats was used to produce a novel composite gel with gelatin by forming an interpenetrating polymer network (IPN). The gel prepared by the cross-linking of transglutaminase (TG) and Ca2+ was called IPN gel, and the gel prepared only by TG or Ca2+ was named as G-semi-IPN and F-semi-IPN, respectively. The rheology and micro-morphology were observed to confirm the formation of semi-IPN and IPN. The thermodynamic, mechanical and hydration properties of gelatin-SDF composite gels with different cross-linking conditions were determined. It was found that the IPN gel had enhanced mechanical properties, better freeze-thaw stability and lower swelling capacity. Bile acid binding assays showed that both semi-IPNs and IPN had certain ability of binding bile acids. These studies on gelatin-SDF composite gels suggested a new strategy to increase the gelling ability of dietary fibers. In addition, it could improve the utilization of bean coats during the food processing.