The solubility of sodium coprecipitate in water and in salt solution of the composition corresponding to simulated milk ultrafiltrate was studied at 3000, 8000, 19000 and 110000 g. The molecular state of protein determining its solubility was defined together with the contribution of Ca, Mg, P, K and Na to the formation of this state. The (Ca+Mg)/(Na+K) weight ratio in the protein aggregates insoluble in the salt solution decreased with an increase in gravity. The constant (Ca+Mg)/N weight ratio and protein composition of the protein aggregates insoluble in the salt solution in the gravity ranging from 3000 to 110000 g suggested increased contributions of hydrophobic interactions and covalent bondings in the integration of protein particles as their size increased.