Comprehensive comparison of egg yolk of three Korean native chicken varieties: Physicochemical quality, antioxidant activity, and flavor-related substances

The conservation of native chicken breeds is essential for promoting sustainable farming practice and preserving local genetic resources. Herein, we investigated the physicochemical quality, antioxidant activity, and flavor-related compounds of egg yolk from three Korean native chicken (KNC) breeds, namely blue-shelled egg (BSE), Woorimatdag No. 1 and 2 chicken egg (WRMD1E and WRMD2E), and commercial egg (CE). The physicochemical characteristics of chicken eggs, such as Haugh unit, yolk color, and eggshell characteristics, along with yolk traits including moisture, crude fat, pH, and cholesterol levels, were found to vary depending on the species (<italic>p</italic> &lt; 0.05). The yolk of WRMD2E and CE exhibited significantly higher levels of monounsaturated- and polyunsaturated fatty acids, respectively, compared to those of other groups. Umami-related free amino acids (Glu + Asp) were significantly higher in CE yolk than in KNC egg yolk. Multivariate analysis identified potential bio-volatile markers, including hexane, 3-ethyl-, hexadecane, and nonane, 2,5-dimethyl-, which could effectively differentiate between the yolk of various KNCs and CE. Notably, WRMD2E yolk exhibited substantial antioxidant power, as demonstrated by DPPH, ABTS, and ferric reducing antioxidant power assay. The overall results indicate that eggs from these native lines match the quality of a commercial egg product in many characteristics, with some superior traits, such as antioxidant capacity. The results of this study offer comprehensive insights into the egg yolk characteristics of KNC, particularly Woorimatdag chicken, providing fundamental data to enhance the utilization of KNC eggs in food applications while supporting efforts toward the conservation of native chicken biodiversity.