Identification of the components responsible for the gelation of egg yolk during freezing.

The aggregates in gelled yolk were isolated by gel filtration with a Sepharose 4B column, after suspension in 1 m NaCl, and then they were identified by chemical analysis and sodium dodecyl sulfate polyacrylamide gel electrophoresis.No significant difference was found in lipid and protein composition between the aggregates and the low density lipoprotein in plasma (LDLP).It was concluded that the aggregates in gelled yolk were composed only of LDLPwhich suggested that the other yolk components (i.e.lipovitellins, livetins and phosvitin) might not directly participate in yolk gelation.However, the possibility that low deensity lipoprotein in granule (LDLG) might be partly responsible for gelation can not be excluded, because the lipid and protein composition of LDLGand LDLPwere almost the same and LDLGalso aggregated during the freezing as well as LDLP.The freezing and thawing of yolk induces an irreversible increase in viscosity and a decrease in solubility.This phenomenonhas been termed gelation.Although it has been generally accepted that the components which is mainly responsible for yolk gelation is low density