Structural and morphological optimization of low-salt myofibrillar proteins aggregates by ultrasound treatment:...

Excessive sodium intake increases cardiovascular risks, driving demand for low-sodium meat products. Yet low-salt conditions (0.2 M NaCl) weaken the solubility and gelation capacity of pork myofibrillar proteins (MPs). This study investigated the mechanism by which ultrasound treatment (500 W, 20 kHz, 60 % amplitude) modulated the thermal aggregation behavior of low-salt pork MPs to enhance their gel properties. Changes in the secondary and tertiary structures of the modified MPs, along with their thermal aggregation behavior, were systematically characterized and comprehensively analyzed. Results showed that ultrasound treatment (500 W, 20 kHz, 60 % amplitude) significantly (p < 0.05) improved the gel properties of low-salt MPs by effectively regulating their thermal aggregation. Specifically, 9 min ultrasound treatment induced disordering of the secondary structure, reduced particle size to 133.70 nm, increased free sulfhydryl group content to 7.21 × 10^-5 mol/g and elevated surface hydrophobicity to 81.49 %, thereby suppressing aggregate nucleation. At 50 °C, ordered aggregates formed through hydrophobic domains. Subsequently, at 80 °C, the gel network transitioned from a predominantly salt-bridge structure to one stabilized by covalent bonds, as confirmed by scanning electron microscopy. This approach provides an efficient strategy for developing low-salt pork products (e.g., sausages, hams) and facilitates the industrial production of healthier meat alternatives.