Characterization of oil-in-water emulsions stabilized by hen's egg yolk granule

Egg yolk granule proteins at pH 4.0, 7.0 and 9.0 were used to stabilize oil-in-water emulsions containing pure triolein. Average particle size of the emulsified droplets decreased with increase in protein concentration. Concentration of protein at the interface was greater for emulsions made at pH 4.0 than at pH 7.0 and 9.0, a result attributed to formation of lipoprotein dimers at pH 4.0. On the other hand, storage of the emulsions for 7 days at 4 degrees C showed that stability was higher at pH 7.0 and 9.0 with smaller increases in particle size than at pH 4.0 which had large increase in particle size. Electrophoretic analysis of the emulsified droplets revealed formation of higher molecular weight proteins at the interface than were present in the granule. At pH 4.0, more protein was dissociated from the interface after treatment of the emulsion with urea than at pH 7.0 and 9.0. Increase in protein concentration resulted in a higher phosphatidyl-choline (PC) to phosphatidyl-ethanolamine (PE) ratio for emulsions made at pH 4.0 and pH 7.0. However, at pH 9.0 the PC to PE ratio was decreased as the protein concentration in the emulsions increased. (C) 1998 Elsevier Science Ltd. All rights reserved.