Abstract: The dynamic evolution of lipid metabolism in intramuscular fat of Ningxia Tan sheep during chilled storage for 12 days was investigated by combined use of gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-mass spectrometry (LC-MS) with the OmicsBean cloud platform. The results showed that the types of metabolism pathways increased at the beginning of storage, and then decreased. The metabolism pathways related to the flavor precursors oleic acid, palmitic acid and stearic acid were not different from day 0 to day 4, while the fatty acid biosynthesis pathways (P = 6.65 × 10-3 < 0.05) and the gonadotropin-releasing hormone (GnRH) signaling pathway (P = 4.67 × 10-2 < 0.05) were significantly different from day 4 to day 8; the biosynthesis pathways of unsaturated fatty acids pathway significantly differed from day 4 to day 8 (P = 5.87 × 10-5) but not from day 0 to day 4 (P = 3.24 × 10-1). From day 8 onward, the fatty acid biosynthesis pathways and the GnRH signaling pathway were not different, and the biosynthesis pathways of unsaturated fatty acids were not significantly different (P = 1.57 × 10-1). At the early stage of storage, no difference in the biosynthesis pathways of fatty acids was observed, but the relative contents of short carbon chain compounds as precursors for the biosynthesis of palmitic acid such as 3-hydroxybutyric acid and 3-oxohexadecanoic acid. Their relative contents were significantly different from day 0 to day 4; from day 4 to day 8, the palmitic acid decomposition and fatty acid β oxidation pathways were activated, and consequently, the relative content of palmitic acid decreased significantly. The initiation of the fatty acid biosynthesis pathways could be ascribed to the activation of a variety of oxoylases, fatty acid synthases and acetyl-CoA. These enzymes catalyzed the formation of 3-hydroxybutyrate and 3-oxohexadecanoic acid as precursors for the formation of palmitic acid during the first 4 days of storage at 0–4 ℃. Therefore, it seems that metabolism does not stop immediately postmortem despite oxygen deficiency, and cells are still able to maintain their normal energy level. As the chilled storage time prolongs, the energy metabolism pathways in the body alternately work for energy supply. During the metabolic process, the relative contents of flavor precursors such as oleic acid, stearic acid, and palmitic acid change accordingly.

Key words: Tan sheep, postmortem, fat, metabolic pathway, pathway conversion