In the present study the influence of plasmin hydrolysis of beta-casein (beta CN) on the foam and emulsion properties was tested. The hydrophilic, amphipathic and hydrophobic fractions produced by plasmin hydrolysis of beta CN and fractionation of the hydrolysate, show dear differences in emulsion, foam and surface-active properties. The hydrophilic peptide possessed poor functional properties. The hydrophobic peptides from beta CN showed interesting foam properties, especially at acidic pH. The amphipathic peptides exhibited improved emulsion-forming properties, compared to intact beta CN. It seemed that the presence of the hydrophilic N-terminus (i.e. fragment 1-28) in these amphipathic peptides was important for their stabilising properties. (C) 1999 Elsevier Science Ltd. All rights reserved.