Synergistic effects of ultrasonication and alkaline treatment on curcumin-induced cross-linking and gelation of casein-soy protein isolate hybrids

The development of hybrid protein gels through the partial replacement of animal proteins with plant-based proteins represents a promising strategy for sustainable food production. This study investigated whether ultrasonication-generated free radicals, alone or combined with alkaline treatment, could induce curcumin to act as a cross-linker between casein and soy protein isolate. Gels were prepared under different pretreatments (alkali, ultrasound, or their combination) and characterized using rheology, spectroscopy, solubility assays, and microscopy. Results demonstrated that only ultrasound and combined treatments induced stable gel formation, with the synergistic treatment exhibiting the strongest gel network, highest cross-linking density, and most ordered protein structure. The enhanced gel properties were attributed to the dual effect of radical-mediated and alkali-driven covalent conjugation. This study provides a novel, enzyme-free approach for constructing hybrid protein gels, offering a sustainable strategy to tailor the texture of plant-protein-enriched foods.