Production of caseinophosphopeptides (CPPs) from sodium caseinate using a range of commercial protease preparations

Sodium caseinate hydrolysates were generated at laboratory-scale using 28 commercial protease preparations of bacterial, fungal, plant and animal origin. Caseinophosphopeptides (CPPs) were enriched from these hydrolysates by calcium chloride aggregation at pH 7.5 followed by ethanol precipitation of the aggregates. CPP yield ranged from 3.4 to 16.0% (w/w) of the original protein. The calcium binding and solubilising abilities of the enriched CPPs ranged from 0.40 to 0.61 and 7.4 to 24.0 mg Ca²⁺ mg^-1 CPP, respectively. Hydrolysis of sodium caseinate with Bioprotease N100L resulted in a 16.0% yield of CPPs which could solubilise 19.1 mg Ca²⁺ mg^-1 CPP. Significant differences in the gel permeation and reversed-phase chromatography profiles for the various enriched CPPs were evident. In general, no apparent relationship was observed between hydrolysate degree of hydrolysis (DH%), CPP yield, CPP calcium binding and solubilising abilities, and CPP apparent molecular mass distribution and hydrophobic peptide profiles.