Preparation and Characterization of Casein–Soy Protein Hybrid Gels Cross-Linked by Transglutaminase

TL;DR

This study blends casein with soy protein using an enzyme to create stronger, more water-retaining gels with better structure.

Contribution

The novel approach uses transglutaminase to cross-link casein and soy protein, enhancing plant protein functionality.

Findings

A 1:1 casein-to-soy protein ratio produced the strongest gels with optimal water retention and structure.

Transglutaminase enabled covalent bonding, while hydrophobic and disulfide interactions stabilized the gel matrix.

Hybrid gels showed improved network uniformity and immobilized water effectively in a porous matrix.

Abstract

To enhance the gelling functionality of plant proteins, this study developed hybrid gels by blending casein with soy protein isolate (SPI) at various ratios using microbial transglutaminase (MTG) as a cross-linking catalyst. The gels were systematically characterized in terms of microstructure, water distribution, rheological and textural properties, secondary structure, and intermolecular interactions. Incorporation of casein significantly improved gel strength, water-holding capacity, and network uniformity. Notably, the 1:1 casein-to-SPI ratio yielded the highest performance, featuring extensive inter-protein cross-linking, an increased proportion of ordered secondary structures, and a finely porous matrix that effectively immobilized water. Mechanistically, MTG-catalyzed covalent bonding established the primary network scaffold, while hydrophobic interactions and disulfide bonds further stabilized the gel matrix. These findings demonstrate that MTG-induced Casein–SPI hybrid gels can enhance the functional properties of plant proteins and offer a viable strategy for designing sustainable protein-based food structures with tailored performance.

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