Aggregation-disaggregation cycling: A physical strategy for low-viscosity fish protein particles

The development of low-viscosity, high-concentration protein systems is hindered by shear-thickening behavior arising from intermolecular entanglement. We report a cyclical preheating-ultrasonication strategy that reconstitutes cod protein (CPs) into low-adhesion particles. Pre-heating (100 °C, 10 min) partially unfolds CPs to expose hydrophobic nucleation sites, followed by ultrasonication (400 W, 10 min) fragmenting aggregates into metastable subunits via cavitation shear while redistributing surface charges. Force curve analysis validated the adhesion force reduction (62.6%, 3.96 → 1.48 nN) and its direct correlation with significant viscosity reduction at high concentration. The modified CPs exhibit Newtonian fluid behavior at 6% w/v concentration, with the viscosity was reduced to approximately 0.1 Pa·s at a scanning frequency of nearly 1 s^-1. Small-angle X-ray scattering (SAXS) shows a structural shift from loose aggregates to dense molten spheres. This physical reprocessing approach provides a sustainable pathway to engineer high-density protein colloids for injectable formulations and 3D food printing.