Developing an Environmentally Friendly Sequential Separation and Purification Process of Six Functional Components From Egg Yolk.

Egg yolk contains multiple high-value bioactive components, yet most existing technologies only achieve single/dual-component extraction and suffer from low comprehensive utilization efficiency. This study established an integrated sequential separation and purification process of six functional components, which was rationally designed based on the inherent differences in solubility, isoelectric precipitation pH, and salt tolerance of yolk fractions. Egg yolk was diluted with nine volumes of water, adjusted to pH 5.2 and centrifuged to separate supernatant (SUP) and precipitate (PPT). Livetins-rich fraction was harvested from SUP by ultrafiltration, while 1% NaCl and centrifugation produced low-density lipoprotein (LDL)-rich SUP and granules. Note that 20% (NH4)2SO4 + 10% NaCl was selected to separated immunoglobulin Y (IgY) and IgY-free livetins (IgY-free). Phospholipids (PLs) were extracted from granules with ethanol. The post-extraction residues were homogenized in 10% NaCl (pH 10.5), adjusted pH to 4.0 and centrifuged to obtain phosvitin (PV) and phosvitin-free fraction (PV-free). Experiments were conducted in three replicates, employing 60 eggs per replicate. The yields of IgY, IgY-free livetins, LDL, PLs, PV, and PV-free fraction were 0.73%, 1.41%, 31.82%, 1.16%, 0.96%, and 6.75%, respectively. Total yield of the six components reached (86.06 ± 1.34%), with the two key components, IgY and PV, exhibiting purity of 81.86% and 97.23%. PRACTICAL APPLICATIONS: This process realizes full-value graded utilization of egg yolk by fully recovering six distinct functional fractions, avoiding resource waste caused by partial component extraction. Benefiting from accessible and scalable separation techniques, it delivers reliable technical backing for the scaled-up production and practical commercialization of egg yolk-derived bioactive substances within the food and pharmaceutical sectors.