Abstract: In order to investigate the nutritional value and small molecule metabolite composition of Taihe silky chicken eggs, this study comparatively analyzed the appearance, egg quality and hydrolyzed amino acid content of Taihe silky chicken eggs and Mahuang chicken from the same production batch. A global non-targeted metabolomics approach was applied to comprehensively characterize the metabolites in Taihe silky chicken egg white and yolk and to select the marker metabolites of Taihe silky chicken eggs. The results showed that Taihe silky chicken eggs were smaller in size than Mahuang chicken eggs, with the small end being more pointed, and black spots were deposited on most of the surface of Taihe silky chicken eggshells. The total mass, yolk color, yolk mass, and yolk ratio of Taihe silky chicken eggs were significantly lower (P < 0.05), whereas the egg shape index and Haugh unit were significantly higher than those of Mahuang chicken eggs (P < 0.05). Taihe silky chicken eggs contained 17 hydrolyzed amino acids, and the difference in hydrolyzed amino acid content compared with that of Mahuang chicken eggs was small, with only histidine content being significantly higher in Taihe silky chicken eggs (P < 0.05). Metabolomics identified 51 differential metabolites (P < 0.05, variable importance in the projection (VIP) > 1) in Taihe silky versus Mahuang chicken egg white. The relative contents of 32 differential metabolites were higher, while those of the remaining 19 were lower in Taihe silky than Mahuang chicken egg white. The differential metabolites were mainly enriched in amino acid metabolism, having the most significant enrichment in the metabolic pathways of alanine, aspartic acid, and glutamate with the greatest influential factors. Qctadecanamide, arachidic acid, L-lysine, and L-aspartic acid, whose contents in egg white significantly differed between Taihe silky and Mahuang chicken, could be used as potential marker metabolites to discriminate between eggs from the two species. In total 33 differential metabolites were identified between Taihe silky and Mahuang chicken egg yolk, whose class distribution was scattered. The contents of 3-amino-4-methylpentanoic acid, iminoarginine and D-glucose in egg yolk significantly differed between Taihe silky and Mahuang chicken, which could be used as potential marker metabolites to discriminate between eggs from the two species. The results of this study provide basic data support for the promotion and food development of Taihe silky chicken eggs.

Key words: Taihe silky chicken eggs; egg quality; hydrolyzed amino acids; global untargeted metabolomics