The effects of temperature, ionic strength, and enzymatic hydrolysis on the average hydrodynamic radius (Rh) of casein micelles in phosphate buffer were studied by using dynamic light scattering. The results showed that the average Rh value of casein micelles decreased irreversibly during the heating, decreased with the increase of ionic strength in lower ionic strength solution (less than 0.05 mol/L), but opposite in higher ionic strength solution (above 0.1 mol/L). The Rh value of casein increased rapidly during the process of enzymatic hydrolysis, and the structural model of casein micelles in the enzymatic hydrolysis process was also proposed, i.e. the casein micelle changed from compact sphere into unfolded and regularly flocky peptides.
