PHYSICO-CHEMICAL STUDIES ON GELATION OF HENS EGG YOLK - SEPARATION OF GELLING PROTEINS COMPONENTS FROM YOLK PLASMA

A study of the component(s) in egg yolk responsible for gelation of yolk on freezingand thawing has shown that granule-free yolk plasma, obtained by high-speed centrifugation of yolk, has the capacity to gel. As with the whole yolk, gelation of yolk plasma on freezing and thawing could be inhibited by additives such as sugars, sodium chloride, proteolytic enzymes, and phospholipase-A. Phospholipase-C, which induces gelation of whole yolk at room temperature,has a similar effect on yolk plasma. Yolk plasma has been separated into aggregating(gelling) and soluble fractions by delipidation, using formic acid. Each of these fractions consists of three or four protein components, as observed by gel filtration,ultracentrifugation, and agar electrophoresis. The proteins are glycoproteins and contain bound hexoses, hexosamine, and sialic acid. The gelation of yolk has been attributed to the interactions between proteinmolecules following disruption of lipidprotein bonds. © 1969, American Chemical Society. All rights reserved.