Gelling, rheological, and structural modification of myofibrillar proteins using sonication and protease treatments

This study examines the effects of ultrasound (U; 50 W, 0, 10 or 20 min) and Alcalase at low (AL; 3 × 10^-7 U/g) and high (AH; 3 × 10^-4 U/g) doses on the structural and functional attributes of MPs. Ultrasound alone modestly reduced particle size and increased DH, whereas enzyme addition strongly increased DH and shifted number-weighted size distributions toward small particles. The combined treatments produced the largest structural shifts. While AL samples (ALU0, ALU10, ALU20) exhibited the highest WHC and gel strength and the most continuous, compact microstructures, AH samples (AHU0, AHU10, AHU20) produced fragile, porous networks. Across frequency, all samples were elastic-dominant (G' > G″), but AL samples showed higher a'/a″ and lower b'/b″, indicating strong, frequency-stable networks; temperature sweeps revealed delayed weakening and greater final G' for AL samples, while AH samples shifted transitions to lower temperatures. Collectively, ultrasound increased accessibility, and limited proteolysis edited chain length to a mid-range that percolated during heating via hydrophobic association and disulfide exchange, whereas over-hydrolysis fragmented the matrix and disturbed network formation.