This study investigated the influences of Ca lactate precipitation, lactic acid coagulation and renneting of proteins in skimmed milk on the physicochemical properties of milk protein powders. Scanning electron micrographs indicated that milk curd from Ca lactate precipitation had the densest network with the smallest protein particles compared with others. It also had the lowest antioxidant capacity: i.e., 0.27 and 0.05 µmol Trolox equivalent (TE)/mg protein, as measured by oxygen radical absorbance capacity–fluorescein (ORACFL) and Trolox equivalent antioxidant capacity (TEAC) assays, respectively (P < 0.05). Nevertheless, tryptic hydrolysis for 30 min increased the antioxidant capacity of all milk protein products to 0.85–1.11 and 1.17–1.19 µmol TE/mg protein in ORACFL and TEAC assays, respectively, regardless of the coagulants used (P ≥ 0.05). Although milk protein hydrolysate obtained from Ca lactate milk protein had the lowest ζ-potential, its antioxidant capacity remained unaffected by self-association of peptides into large-sized aggregates (P ≥ 0.05).