Plasmin Hydrolysis of β-Casein: Foaming and Emulsifying Properties of the Fractionated Hydrolysate

Bovine β-casein (βCN) 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 βCN sequence, possessed improved foam-forming and -stabilizing properties compared to those of intact βCN, especially at pH 4.0. Soluble peptide fractions, containing a variety of peptides from the “middle” part of the βCN sequence in different proportions, possessed improved emulsion-forming capacity at pH 6.7, compared to that of intact βCN, and showed large variations in emulsion stability. The fraction containing the hydrophilic N-terminal part of βCN 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.