Freeze-thaw treatment assists isolation of IgY from chicken egg yolk

In this study, the effect of freeze-thaw treatment on isolation of IgY was investigated, with macrograph, protein concentration, solid content, and transmittance evaluated. The results showed that higher refrigeration power (at -18 °C for more than 4 h and -40 °C for more than 2 h) caused yolk gelation and was helpful for removing heteroproteins. To reveal the mechanism of freeze-induced gelation assisting isolation of IgY, the properties of yolk frozen at -5°C, -18 °C and -40 °C for 8 h were determined, with SDS-PAGE, rheology property, low field NMR and interactions between proteins evaluated. As the results showed, the purity of separated IgY increased obviously (frozen at -18 °C and -40 °C), corresponding to the removal of LDL which aggregated during freezing. LDL aggregation may be triggered by hydrophobic interaction during boundary water crystallization. Therefore, freeze-induced yolk gelation is beneficial for IgY isolation by keeping LDL in dense gel structure while releasing IgY to the supernatant.