Plasmin hydrolysis of beta-casein: Foaming and emulsifying properties of the fractionated hydrolysate

Bovine beta-casein (beta CN) was hydrolyzed by plasmin. The hydrolysate was fractionated by ultrafiltration and selective precipitation, which resulted in several peptide fractions of which the peptide composition was monitored by reversed-phase high-performance liquid chromatography. Poorly soluble, hydrophobic peptide fractions, containing peptides from the C-terminal half of the beta CN sequence, possessed improved foam-forming and -stabilizing properties compared to those of intact beta CN, especially at pH 4.0. Soluble peptide fractions, containing a variety of peptides from the ''middle'' part of the beta CN sequence in different proportions, possessed improved emulsion-forming capacity at pH 6.7, compared to that of intact beta CN, and showed large variations in emulsion stability. The fraction containing the hydrophilic N-terminal part of beta CN showed inferior foam, emulsion, and surface-active properties, especially at pH 6.7. The differences in functionality found between the various peptide fractions may be attributed either to synergistic effects between peptides or to a specific functionality of some individual peptides.