EMULSIFYING PROPERTY OF WHEY PEPTIDE FRACTIONS AS A FUNCTION OF PH AND IONIC-STRENGTH

Solubility and emulsifying properties of whey protein concentrate (WPC), heat-treated WPC (90-degrees-C, pH 2.5, 10 min), and their tryptic or chymotryptic peptide fractions obtained by ultrafiltration were measured from pH 3 to 9 at two ionic strengths (mu=0 and 0.6). There was no correlation between solubility and emulsifying capacity (EC). Heat treatment induced some conformational changes in WPC, resulting in better EC. Some peptide fractions had better EC than proteins at pH 7 and 9. Treatments resulting in more hydrophobic peptides or a higher content of larger peptides produced fractions with better emulsifying properties. pH and ionic strength affected conformation and emulsifying properties of proteins and peptides.