Physicochemical properties and issues associated with trypsin hydrolyses of bovine casein-dominant protein ingredients

Abstract

Milk protein concentrate (MPC) and sodium caseinate (NaCas) were hydrolysed using the enzyme trypsin and the subsequent physical properties of the two ingredients were examined. Trypsin hydrolysis was carried out at pH 7 and at 45 °C on 11.1% (w/w) protein solutions. Heat inactivation of trypsin was carried out when the degree of hydrolysis reached either 10 or 15%. Size-exclusion chromatography and electrophoresis confirmed a significant reduction in protein molecular weight in both ingredients. However, whey proteins in MPC were more resistant to trypsin hydrolysis than casein. Oil-in-water emulsions were prepared using intact or hydrolysed protein, maltodextrin, and sunflower oil. Protein hydrolysis had a negative effect on the subsequent physical properties of emulsions, compared with non-hydrolysed proteins, with a larger particle size (only for NaCas stabilised emulsions), faster creaming rate, lower heat stability, and increased sedimentation observed in hydrolysed protein emulsions.