Phosphorproteome Changes of Myofibrillar Proteins at Early Post-mortem Time in Relation to Pork Quality As Affected by Season

The effect of season on phosphorylation of myofibrillar proteins and meat quality of pork <i>longissimus</i> muscles was investigated. Muscle samples were obtained from 40 pork carcasses (10 for each season) at 45 min and 3 and 9 h post-mortem. Myofibrillar proteins were extracted, separated by SDS-PAGE, quantified by phosphor-specific staining, and finally identified by LC-MS/MS. Muscle pH, glycogen, and ATP were measured, and pale, soft, and exudative (PSE) meat was identified by pH value at 45 min post-mortem. A total of 23 bands were detected on SDS-PAGE gels. The phosphorylation levels of bands did not differ between PSE and normal meat. However, the phosphorylation levels of 22 bands were significantly changed by season. Nine of them showed different changes from 45 min to 9 h post-mortem, which were identified to be involved in energy metabolism and sarcomere contraction. Correlation analysis indicated the regulatory progress of these proteins during rigor mortis. These observations contribute to a better understanding of the biochemical processes for the conversion of muscle to meat varying with season.