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The changes in lipid properties of duck egg yolks during processing may affect the quality of egg yolks. In this paper, various physicochemical and instrumental methods were used to study the changes of lipid characteristics of duck egg yolks under extreme processing conditions such as high salt, high salt-heat synergy and strong alkali. The results showed that both the high salt and high salt-heat treatments resulted in the decrease of the moisture content and the increase of the oil exudation of egg yolks. The iodine value of the lipid extracted from salted egg yolks with or without heat treatment decreased. However, strong alkali treatment increased the moisture content of egg yolks, and the oil exudation increased at first and then decreased. The iodine value of the lipid obtained from preserved egg yolks showed an overall trend with first increase and then decrease, and the saponification value of the lipid got from preserved egg yolks was lower than the lipid got from the raw salted egg yolks. According to the conjugated diene acid value and thiobarbituric acid value, the lipid of egg yolks was oxidized to different degrees under the three processing conditions. At the end of pickling, the fatty acid content of the lipid acquired from egg yolks all increased. Therefore, all three extreme treatments significantly changed the lipid properties of duck egg yolks.

This study aimed to investigatethe mechanism of stewing with tea polyphenols (TP) on the properties of boiled egg white gel (BEWG). The results indicated that, during the stewing process, soluble protein and hardness showed an overall increasing trend, while surface hydrophobicity showed a decreasing trend with blue‐shift. The free sulfhydryl group showed that TP could promote the formation of disulfide bonds, and the position of immobilized water at T2 showed a decreasing trend. Environmental scanning electron microscopy and SDS‐PAGE showed that the protein gel aggregation degree increased. Moreover, Fourier transform infrared spectrometry showed that protein polarity increased and that α‐helices, β‐turn, intramolecular β‐sheets, as well as intermolecular antiparallel β‐sheets showed an increasing trend. Generally, TP strengthened protein aggregation by promoting the formation of disulfide and hydrogen bonds, thus enhancing the gel strength of BEWG. Moreover, the secondary structure of proteins became more stable under the action of TP, and the higher the concentration of TP, the greater the effect on BEWG. Practical Application TP, an ideal, cheap, and safe natural food additive, can be applied to the processing of egg products because the addition of TP can significantly improve the gel strength of egg white.