Functionality of Bacillus proteinase hydrolysates of sodium caseinate

Sodium caseinate (NaCN) was digested with Protamex, a Bacillus proteinase, at 40°C and pH 7.0 to degree of hydrolysis (DH) values of 2.7%, 5.3% and 13.3%. The solubility, emulsifying, foaming and viscosity properties of the hydrolysates were investigated between pH 2.0 and 10.0. Foam expansion of >1300% was observed for the 5.3% DH hydrolysate at pH 4.0, compared to 670% for unheated NaCN. Significantly improved foam expansion properties (P<0.005) were observed over the entire pH range examined for the 13.3% DH hydrolysate compared to unheated or heat-treated NaCN. Hydrolysis resulted in significantly improved solubility (P<0.005) around the isoelectric point and significant improvements in the emulsifying activity and stability (P<0.005) at alkaline pH compared to unheated NaCN. Hydrolysis with Protamex increased the apparent viscosity of NaCN at the isoelectric point. Reversed-phase HPLC profiles showed that high DH samples contained high levels of hydrophilic peptides.