Inclusion of konjac glucomannan in pea protein hydrogels improved the rheological and in vitro release properties of the composite hydrogels

In this study, a composite hydrogel consisting of pea protein and konjac glucomannan (KG) was fabricated using three approaches, namely neutral, salt-set, and alkaline gelation. Hydrogels made from pea protein were brittle and weak. The addition of KG improved the elasticity and water holding capacity of the pea protein hydrogels. Concomitantly, a decrease in syneresis rate and swelling of the composite hydrogels was observed. The alkaline-set hydrogels exhibited the highest resilience to strain. Thixotropicity was found to be less pronounced for salt-set hydrogels. Sulphate had a greater positive effect on the structural recovery and negative effect on hysteresis area than chloride due to the greater salting-out effect of the sulphates. The addition of KG facilitated the formation of an interconnected structure with limited mobility of biopolymer chains. A sharp increase in G' and G" during the temperature ramp indicated the predominance of hydrophobic interactions towards the aggregation of biopolymers. The infrared spectra of the hydrogels revealed a change in secondary structure of proteins on addition of KG. A controlled in vitro release of riboflavin was observed in neutral and salt-set hydrogels. The alkaline-set hydrogels exhibited a prolonged gastric retention time, thereby establishing in vitro antacid activity in the gastric environment.