Chemically crosslinked magnetic sunflower pollen microgels achieve stable protein glutaminase immobilization to enhance deamidation and structural modification of sunflower seed protein.

Protease immobilization is often faced with enzyme activity loss and mass transfer resistance. Here, we developed a composite carrier with sunflower pollen microgel (SPMG) and NH2-Fe3O4@SiO2 to immobilize protein glutaminase (PGase) for controlled deamidation of sunflower seed protein (SSP). Under optimal conditions (35 mg NH2-Fe3O4@SiO2, 0.15% EDC/NHS), the immobilized PGase exhibited markedly improved thermal, pH, and storage stability relative to free PGase, probably because the hierarchical pores and covalent/hydrogen bonding between SPMG and NH2-Fe3O4@SiO2 stabilize the enzyme microenvironment. At appropriate deamidation degrees, the SSP solubility, emulsifying properties, and foaming properties were increased by about 1.32, 3.84, and 0.65 folds, respectively, accompanied by enhanced umami and sweetness. The structural, functional, and flavor changes in SSP were characterized by SDS-PAGE, particle size, zeta potential, spectral, and interfacial analyses. This study elucidates how the carrier properties influence the performance of immobilized enzymes and proposes a novel strategy for designing enzyme immobilization systems.