Factors Influencing Black Circle Formation and Changes in Proteins in Yolks of Cooked Salted Eggs
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Abstract:
To investigate the factors influencing the formation of dark circles in vacuum-packed cooked salted egg yolks and the changes in protein patterns. First, the role of egg white and yolk on black circle formation in salted eggs was determined; second, the changes in the physicochemical properties of the egg white, external yolk, internal yolk proteins, and phosvitin (Pv) in the yolks of fresh duck eggs, raw salted eggs, cooked salted eggs, and cooked salted eggs with black circles in the yolks were assessed. The results showed that black circle formation in salted egg yolks occurred gradually during storage after sterilization because of the combined actions of factors in the egg white and yolk. Ovalbumin degraded after the fresh duck eggs were salted. The total sulfhydryl content in the egg white in cooked salted eggs decreased by 31.62 μmol/g compared to that of fresh duck eggs. Additionally, the spatial structure of the egg white changed. Furthermore, the Pv content of the external yolk of salted eggs decreased from 2.21 to 0.11 mg/g, and the iron-reducing capacity increased from 0.20 to 0.51. The metal chelating capacity of Pv in the external yolk in cooked salted eggs with black circles decreased from 79.64% to 71.26%. The Pv structure in the external yolk gradually formed a stable β-structure. These results indicate that the salting and cooking processes are key stages in black circle formation in vacuum-packed cooked salted eggs, providing a theoretical basis for reducing black circle formation in yolks in salted eggs by controlling the salting and cooking conditions.
