Label-free proteomic strategy to compare the proteome differences between longissimus lumborum and psoas major muscles during early postmortem periods.

Beef M. longissimus lumborum (LL) and M. psoas major (PM) muscles showed significant differences in various meat quality attributes (such as pH, lipid oxidation, and color stability). To better understand the underlying molecular variations between LL and PM, the proteome changes at early postmortem periods were investigated by comparative proteomic approach. A total of 504, 519, and 487 mutual proteins of each comparison (LL vs. PM at 1 h, 12 h, and 24 h, respectively) were successfully identified. Among these proteins, 238 proteins were differentially expressed in LL samples compared to PM ones. Proteins involved in glycolysis and with functions of protection and repair were overabundant in LL, whereas those participating in tricarboxylic acid (TCA) cycle, oxidative phosphorylation, and fatty acid β-oxidation were overabundant in PM. Furthermore, the bioinformatics analyses provided insightful information for explaining the differences in meat quality traits between LL and PM, and for further metabolomics studies.