Survey of conditioning indicators for pork loins: changes in myofibrils, proteins and peptides during postmortem conditioning of vacuum-packed pork loins for 30 days

This study was performed to examine the changes in myofibrils, proteins and peptides during postmortem conditioning of vacuum-packed pork loins at 4 °C for 30 days. The fragmentation of myofibrils has been observed during postmortem aging for 20 days and its ratio increased until 20 days. The 32 kDa component derived from troponin T increased during storage for 20 days, while a glyceraldehyde 3-phosphate dehydrogenase (GAPDH) among sarcoplasmic proteins was significantly degraded during storage for 15 days. Some oligopeptides increased during such storage, two peptides (peptides P1 and P2) significantly increasing during storage for 20 days. Their sequences were APPPPAEVHVHEEVH (P1) and VPTPNVSVVDLT (P2). Homology analysis showed that peptides P1 and P2 were derived from troponin T and GAPDH, respectively. It was concluded that the fragmentation of myofibrils, the increases in the 32 kDa component and peptides P1 and P2, and the decrease in GAPDH were useful as conditioning indicators of progressive degree during the storage of pork loins stored at 4 °C.