Abstract: The objective of this study was to understand the mechanism of changes in flavor precursors in Tan sheep meat during post-mortem ageing. The proteomic analysis of Tan sheep meat at different times (0, 4 and 8 days) of post-mortem ageing was conducted by isobaric tags for relative and absolute quantification (iTRAQ) combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS). The results showed that the differentially expressed proteins during postmortem aging mainly included metabolic enzymes, structural proteins and stress proteins. The activity of triose phosphate isomerase, enolase 3, L-lactate dehydrogenase, phosphoglucose mutase 1 and pyruvate kinase rose obviously from Day 0 to Day 4, while the expression of troponin C1, troponin T3, myosin light chain 2, myosin light chain 1, myosin 3 and heat shock protein 70 were up-regulated from Day 0 to Day 4 but significantly down-regulated from Day 4 to Day 8. The relative gene expression of differentially expressed proteins at the transcription level was evaluated using quantitative real-time polymerase chain reaction (qPCR). It turned out that for four differentially expressed proteins, namely two metabolic enzymes (L-lactate dehydrogenase and triose phosphate isomerase) and two structural proteins (myosin light chain 2 and actin α1), the mRNA and protein expression patterns between Day 0 and Day 4 as well as between Day 4 and Day 8 were consistent with each other. Therefore, the modulation of metabolic enzymes, the degradation of structural proteins, and the protective effect of stress proteins on the stability of myofibrillar protein could together regulate the changes of flavor precursors in Tan sheep meat during post-mortem ageing.

Key words: ageing; Tan sheep meat; proteomics; flavour precursor; change mechanism