Deamidation-enabled fabrication of tough, stretchable, and transparent plant protein hydrogels

Plant protein hydrogels are promising for food structuring and nutrient delivery, yet conventional soybean protein systems suffer from weak mechanical strength due to particulate aggregation. Enzymatic deamidation can dissociate dense aggregates and improve homogeneity, but limited intermolecular connectivity still restricts mechanical performance of soybean protein hydrogels. Here, a sequential strategy involving protein-glutaminase (PG)-induced deamidation and transglutaminase (TGase)-mediated crosslinking was developed. PG promoted protein unfolding and aggregate reorganization, generating a transparent and designable network precursor, while TGase enhanced intermolecular connectivity via ε-(γ-glutamyl)lysine bonds. This led to denser, more homogeneous and ordered gel networks without compromising transparency. Multiscale analyses revealed increased network compactness, stronger protein-water interactions, and more uniform water distribution. Consequently, the hydrogels exhibited improved viscoelasticity, elasticity, deformation resistance and cyclic stability, with optimal performance at moderate TGase levels. This study provides a feasible and sustainable approach for fabricating tough and transparent soybean protein hydrogels for food and bioactive delivery applications.