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Posttranslational N-glycosylation of food proteins plays a critical role in their structure and function. However, the N-glycoproteome of chicken egg yolk (CEY) has not been studied yet. Glycopeptides hydrolyzed from CEY proteins were enriched, with deglycosylation occurring using PNGase F, and then were identified using a shotgun glycoproteomics strategy. A total of 217 N-glycosylation sites and 86 glycoproteins were identified in CEY, and these glycoproteins are mainly involved in the binding, biological regulation, catalytic activity, and metabolic processes. Among the identified CEY glycoproteins, 22 were recognized as proteases and protease inhibitors, suggesting that a proteinase/inhibitor regulation system exists in CEY; further, 15 were members of the complement and immune systems, which provide protection against potential threats during hatching.The study provides important structural information about CEY glycoproteins and aids in the understanding of the underlying mechanism of embryo development as well as changes in CEY functional characteristics during storage and processing.

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In addition to small amounts of minerals and carbohydrates, most of the dry matter of chicken egg white is protein, making egg white an ideal resource for obtaining food proteins. Ovalbumin (OVA), which accounts for more than 50% of the total egg white protein, is one of the most widely studied food proteins due to its multiple functional properties, and it has also been used as a model protein molecule in many research fields. The objective of this study was to develop a simple and rapid method for the purification of OVA from egg whites on large scale. First, OVA was separated from ovomucin, ovotransferrin, and ovomucoid by polyethylene glycol (PEG) concentration, using the following optimal parameters: the PEG concentration was 15%, the pH was 6.5, the salt concentration was 100 mmol/L, and the operating temperature was 10°C. The OVA-rich supernatant obtained from PEG precipitation was further purified by isoelectric precipitation at a pI of 4.5 and a temperature of 4°C, and the purified OVA was obtained with at a purity of 95.1% by HPLC, with a yield of 46.4%. After the extraction of OVA, the PEG solution was vacuum dried and then utilized cyclically in the PEG precipitation steps. The whole purification process could be finished within 2 to 3 h at a scale of several kilograms of egg white. This method has the advantages of rapidity, simplicity, low cost, and ease of scalability.

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