Relationship Between Weakening of Z‐disks and Liberation of Phospholipids During Postmortem Aging of Pork and Beef

The liberation of phospholipids from Z‐disks was investigated to elucidate the cause of the structural weakening of Z‐disks, which contributes to the tenderization of meat during postmortem aging. The amounts of lipids in Z‐disks were 2.2 g per 100 g of myofibrillar proteins in porcine and 2.7 g in bovine semitendinosus muscles. Phospholipids were the major component of the lipids. The postmortem liberation of phospholipids correlated well with Z‐disk weakening, though a‐actinin, the major protein of Z‐disks, remained unchanged even after prolonged aging of pork and beef. We therefore concluded that Z‐disks are weakened by liberation of phospholipids during postmortem aging of pork and beef.