IMPROVED EMULSIFYING PROPERTIES OF BETA-BARREL DOMAIN PEPTIDES OBTAINED BY MEMBRANE-FRACTIONATION OF A LIMITED TRYPTIC HYDROLYSATE OF BETA-LACTOGLOBULIN

Fragments of the beta-barrel domain of beta-lactoglobulin were obtaine d by membrane fractionation of a limited proteolysate prepared with an immobilized trypsin bioreactor. Analysis of this fraction by size-exc lusion chromatography under physiological conditions indicated that th e fraction contained a predominant peptide (50%) with a size of 8400 D a and several other peptides with sizes ranging from 2000 to 30700 Da. Analysis of reductively denatured peptides by sodium dodecyl sulfate polyacrylamide gel electrophoresis in the presence of 2-mercaptoethano l indicated the presence of a major peptide with a size of 6400 Da, su ggesting that a small peptide was linked to the 8400-Da peptide by a d isulfide bond. Comparison of the surface and emulsifying properties of the peptide fraction with those of intact beta-lactoglobulin indicate d that the domain peptides have a lower surface hydrophobicity and a s lightly higher surface and interfacial tension. Furthermore, the emuls ifying activity index for the domain peptides was twofold larger than that of the intact protein. Examination of the emulsion by scanning el ectron microscopy revealed that the oil droplets formed with the domai n peptides were smaller than those formed with intact protein.