THE EMULSIFYING PROPERTIES OF HYDROLYZATES OF WHEY PROTEINS

A commercial range of hydrolyzates of whey proteins with degrees of hy drolysis 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 d etermining the average sizes of the emulsion droplets and their size d istribution both immediately after formation and after storage. The ef fects of heating on the stability of the emulsions were also determine d. As estimated by the particle sizes, the maximum emulsifying capacit y 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 reduce d 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 (122 degrees C for 15 min), but em ulsions prepared from the less hydrolyzed peptide mixtures were stable to heat treatment at 90 degrees C for 30 min. To a limited extent, em ulsion stability could be altered by mixing the different peptide prep arations after an emulsion was formed using one of them.