Colloidal mineral diminished and casein dissociation reached maximum at pH 5.6–5.4. Released casein existed as loose particle that finally aggregated into gel network. Micelle lost surface heterogeneity and became more homogeneous with decreasing pH. A 3-phase model for micellar size evolution was proposed based on various changes. Changes were qualitatively similar but quantitatively different for GDL and HCl.