Abstract: In order to study the mechanism of gel formation and color change during the processing of Sansui featured yellow preserved eggs, produced by leadless curing, the dynamic changes of free alkalinity, microstructure, protein secondary structure, intermolecular forces, texture, color difference, reducing sugar content and free amino acid contents in egg white were measured and analyzed. The results showed that during the curing process (from day 0 to 18), the free alkalinity increased continuously, and ionic bond interactions increased first and then decreased, while hydrogen bonding interactions, hydrophobic interactions and disulfide bonding interactions increased gradually. The protein structure was transformed from disordered macroporous to ordered three-dimensional reticular. On the 12th day, the texture properties of the gel were the highest, and β-sheet and β-turn were the major secondary structure components. From day 12 to day 18, the structure of the gel was destroyed due to the high alkalinity, showing larger holes, and ionic bonding interactions and texture properties exhibited a downward trend. After the completion of curing (18 days), the free alkalinity decreased gradually and then became stable, and the texture properties increased at first and then tended to be stable; the gel structure could be self-repaired, becoming tight and stable. The main forces responsible for maintaining the gel structure were ionic bonding and disulfide bonding, and the major protein secondary structures were β-sheet and β-turn. In the process of color formation, carbonyl ammonia reaction and protein decomposition occurred at the same time; the content of reducing sugar in egg white decreased, and the content of free amino acids decreased at first and then increased; the redness-greenness value (a) and yellowness-blueness value (b) of egg white gradually increased, and the color gradually became yellow and dark. After the completion of curing, there was no significant change in any of the color values of egg white, indicating the formation of a stable golden yellow color. Finally, it is concluded that the curing stage from day 6 to day 12 could be the key to controlling the quality of yellow preserved eggs. After curing, the gel property of egg white was slightly improved, the color was stable, and the product quality was better when stored at room temperature for 6 days.

Key words: preserved egg; curing; processing; egg white gel; egg white color