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.