Proteomic and metabolomic profiling of aged pork loin chops reveals molecular phenotypes linked to pork tenderness.

The ability to predict fresh pork tenderness and quality is hindered by an incomplete understanding of molecular factors that influence these complex traits. It is hypothesized that a comprehensive description of the metabolomic and proteomic phenotypes associated with variation in pork tenderness and quality will enhance the understanding and inform the development of rapid and nondestructive methods to measure pork quality. The objective of this investigation was to examine the proteomic and metabolomic profiles of ~2-wk aged pork chops categorized across instrumental tenderness groups. One hundred pork loin chops from a larger sample (N = 120) were assigned to one of the four categories (n = 25) based on instrumental star probe value (Category A, x¯ =4.23  kg, 3.43-4.55 kg; Category B, x¯ =4.79  kg, 4.66-5.00 kg; Category C, x¯ =5.43  kg, 5.20-5.64 kg; and Category D, x¯ =6.21  kg, 5.70-7.41 kg). Soluble protein from ~2 wk aged pork loin was prepared using a low-ionic-strength buffer. Proteins were digested with trypsin, labeled with 11-plex isobaric tandem mass tag reagents, and identified and quantified using a Q-Exactive Mass Spectrometer. Metabolites were extracted in 80% methanol from lyophilized and homogenized tissue samples. Derivatized metabolites were identified and quantified using gas chromatography-mass spectrometry. Between Categories A and D, 84 proteins and 22 metabolites were differentially abundant (adjusted P < 0.05). Fewer differences were detected in comparison between categories with less divergent tenderness measures. The molecular phenotype of the more tender (Category A) aged chops is consistent with a slower and less extended pH decline and markedly less abundance of glycolytic metabolites. The presence and greater abundance of proteins in the low-ionic-strength extract, including desmin, filamin C, calsequestrin, and fumarate hydratase, indicates a greater disruption of sarcoplasmic reticulum and mitochondrial membranes and the degradation and release of structural proteins from the continuous connections of myofibrils and the sarcolemma.