The skeletal muscle type has a significant impact on postmortem aging. Skeletal muscle tissue is fabricated with a hierarchical myofiber bundle structure. Myofibers are classified into two major types, fast and slow, based on their contractile and metabolic properties with specific markers, such as myosin heavy chain (MYH) isoforms . This reflects the differential expression of genes and proteins between different types of myofiber cells . Accordingly, fast-and slow-type muscles with varying compositions of fast-and slow-type myofibers exert distinct physiological functions. Previous studies based on gene and protein expression have suggested that metabolite composition is considerably different between physiologically different types of muscles or myofibers, which also suggests intermuscular differences in postmortem metabolism during aging. Indeed, differences in metabolite distribution were observed between different muscle types: an abundance of AAs (Ala, Gly, Gln, and His) and glutathione in porcine VI muscle (a slow-type muscle) and abundance of γaminobutylate, nucleotide sugars, and anserine in LL muscle (a fast-type muscle) immediately after slaughter . The essential postmortem metabolism, such as glycolysis, purine metabolism, and AA degradation, differ in the rate and extent in relevant pathways between fast-and slow-type muscles.