Multi-dimensional analysis of rennet-induced micellar casein gels after ultrasound

Multi-dimensional analyses (pH, particle size, zeta potential, surface hydrophobicity, protein structure, microstructure of gels, free sulphydryl content, and fluorescence intensity) were performed to determine the structural changes and gel properties of micellar casein concentrate (MCC) at different protein concentrations (8%, 12%, 16%) treated with ultrasound (40 kHz, 500 W, 0–60 min). The gel strength and water holding capacity were improved with the increase in ultrasound treatment time and protein concentration. A denser gel network with smaller pore size was formed. For gels made from MCC after ultrasound treatment for 60 min, the gel properties were especially improved. The particle size decreased, zeta potential and hydrophobicity increased after ultrasound treatment. Ultrasound treatment influenced the secondary structure of MCC while no change in the molecular weight of the protein was detected.