The Emulsifying Properties of Hydrolyzates of Whey Proteins

A commercial range of hydrolyzates of whey proteins with degrees of hydrolysis ranging from 8 to 45% was used to make emulsions with soybean oil (3% wt/wt); the range of the hydrolyzate concentrations used was 0.02 to 5% (wt/wt). The stability of these emulsions was measured by determining the average sizes of the emulsion droplets and their size distribution both immediately after formation and after storage. The effects of heating on the stability of the emulsions were also determined. As estimated by the particle sizes, the maximum emulsifying capacity was obtained from hydrolyzates with a 10 or 20% degree of hydrolysis. Higher hydrolysis resulted in peptides that were too short to act as effective emulsifiers, and, at lower proteolysis, the somewhat reduced solubility of the hydrolyzates slightly decreased their emulsifying power. All of the emulsions were unstable when they were subjected to heat treatment at high temperatures (122C for 15 min), but emulsions prepared from the less hydrolyzed peptide mixtures were stable to heat treatment at 90C for 30 min. To a limited extent, emulsion stability could be altered by mixing the different peptide preparations after an emulsion was formed using one of them.