Abstract: Abstracts: In this study, the changes in autophagy and its relationship with beef quality during 14 days of postmortem aging were investigated. In terms of meat color, the L* value increased with aging time, and the a* and b* values increased first and then decreased; the tenderness increased, while the shear force and the expression of desmin decreased (P < 0.05). The water-holding capacity decreased during postmortem aging, while the purge loss and cooking loss increased (P < 0.05). Further studies on autophagy-related proteins showed that the expression of Beclin-1 and microtubule associated protein 1 light chain 3 (LC3), as the markers of autophagy, increased first and then decreased, reaching the maximum at 12 h. AMP-activated protein kinase (AMPK)-mammalian target of rapamycin (mTOR)-yeast Atg1 homolog unc-51 like kinase 1 (ULK1), as an important energy metabolic pathway, activated autophagy in an ischemia and hypoxia environment. During postmortem aging, the protein expressions of AMPK, p-AMPKThr172, and ULK1 all initially increased and subsequently decreased, reaching the maximum at 12 h. The expression of mTOR continuously decreased (P < 0.05), suggesting that autophagy was up-regulated from 0 to 12 h postmortem aging. Pearson correlation analysis showed that the expression levels of autophagy-related proteins were negatively correlated with meat color, but positively correlated with water-holding capacity and shear force during postmortem aging process (P < 0.05). In summary, autophagy could be activated through the AMPK-mTOR-ULK1 signaling pathway during the 336 h postmortem aging process, thereby regulating beef quality.

Key words: beef; postmortem aging; autophagy; quality