Effect of Different Protease Treatments on the Solubility of Milk Protein Concentrate

Milk protein concentrate (MPC) is a high-quality ingredient for food formulations, but the reduction of MPC solubility during storage can seriously affect its use in foods. This study explored the effects of enzymatic hydrolysis with different proteases, an exoprotease (Flavourzyme 500MG (F500)), endoproteases (Alcalase 2.4L FG (A2.4L), Formea CTL 300BG (F300) and Neutrase 5.0 BG (N5.0)) and proteases with both exoproteolytic and endoproteolytic activities (Protamex 1.6 (P1.6), ProteAXH (AXH) and Protease A 2SD (A2SD)), on MPC aggregates and solubility. The results showed that hydrolysis by different proteases improved MPC solubility differently. The solubility of all hydrolysates was higher than that of MPC (54%). The endoproteases were the most effective; the solubility of MPC hydrolyzed by A2.4L, F300 and N5.0 under optimal conditions was 88.93%, 91.91% and 62.39%, respectively. The exoprotease was the least effective; the solubility of MPC hydrolyzed by F500 was 59.98% and a large amount of protein precipitated after hydrolysis. The solubility of samples hydrolyzed by P1.6 and F500 firstly increased and then decreased with increasing hydrolysis time.