Development and characterization of konjac glucomannan–agar hybrid hydrogels for peptide adsorption from casein hydrolysate

Abstract

A hybrid hydrogel composed of konjac glucomannan (KG) and agar (AG) was developed for the efficient adsorption of peptides derived from casein hydrolysate. Hydrogel matrix was formulated with different concentrations of KG and AG, and the optimal composition was determined on the basis of morphologies, structural properties, rheological behaviors, and mechanical characteristics. Among the tested formulations, the hydrogel containing 2.5 % KG and 1.5 % AG (2.5KG-1.5AG) exhibited significantly higher gel strength, gel content, swelling index, and hardness compared to the 3.0KG-1.0AG formulation. Moreover, 2.5KG-1.5AG exhibited more favorable surface characteristics, including a uniform porous structure, larger surface area, and enhanced peptide adsorption capacity. This formulation achived a maximum peptide adsorption capacity of 113.59 mg/g for peptides from a 150 mg/L casein hydrolysate solution. Adsorption kinetics followed a pseudo-second-order kinetics model, implying a chemisorption mechanism, while Freundlich isotherm suggested multilayer adsorption on a heterogeneous surface. In addition, 2.5KG-1.5AG showed excellent desorption properties (>93 %), suggesting its potential for reusability and operational stability. These findings confirm that the KG–AG hybrid hydrogel represents an effective and sustainable bio-based adsorbent for the selective separation of peptides. Its cost-efficiency, high adsorption capacity, and remarkable reusability support its applicability in food-grade bioactive peptide enrichment and purification systems. © 2025 Elsevier Ltd