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Simple water dilution was employed for the separation of water-soluble plasma proteins from egg yolk granules. An optimum recovery of immunoglobulin Y (IgY, 93-96%) in water-soluble fraction was obtained by sixfold water dilution at pH between 5.042 with incubation time of 6 hr at 4°C. Among the factors studied, pH was found lo be the most important factor affecting IgY recovery. Active IgY of high purity with good recovery was obtained by a combination of several techniques including salt precipitation, alcohol precipitation, ultrafiltration, gel filtration and ion exchange chromatography. Salt precipitation, ultrafiltration, and get filtration is the recommended sequence. Over 100 mg of electrophoretically pure IgY was routinely obtained from one egg.

8-Lactoglobulin was chemically modified by attaching different levels of stearic acid, and the effect on hydrophobic@, emulsifying and foaming properties was investigated. Incorporation of the hydrophobic ligands led to increased hydrophobic interactions, resulting in a decreasing solubility with extent of incorporation. Surface hydrophobicity measurements showed that the two fluorescence probes 8 anilinonaphthalene-1-sulfonate (ANS) and cis-parinaric acid (CPA) used were not equivalent. Some improvement of emulsifying and foaming properties was observed at low and medium levels of incorporation which decreased as the extent of fatty acid attachment further increased. High solubility and ANS surface hydrophobicity were both needed for the best emulsifying properties.

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Chicken egg yolk phosvitin showed a remarkable antibacterial effect against Escherichia coli under thermal stress at 50 degrees C. E. coli cells (10(6)/mL) completely disappeared in 1 mL of L-broth coexisting with 0.l mg/mL phosvitin when incubated at 50 degrees C for 20 min, whereas a considerable amount of cells (10(5)/mL) survived at the same thermal stress without phosvitin. Blocking of the chelating effect of phosvitin by the addition of Ca(2+) ion displayed a protective effect against the bactericidal activity at 50 degrees C. In addition, the antibacterial activity of phosvitin was dramatically reduced by treatment with alpha-chymotrypsin, although the chelating effect remained. The surface properties, such as interfacial tension and emulsifying properties of phosvitin, which are an index of the affinity with the outer membrane, were greatly reduced by the alpha-chymotrypsin digestion. This indicates that the alpha-chymotrypsin-digested membrane-penetrating hydrophobic domains at the N- and C-terminal regions play an important role in antibacterial activity. These results suggest that a significant part of the bactericidal activity of phosvitin against E. coli resides in the synergistic effect of the high metal-chelating ability and the high surface activity under the influence of thermal stress.