Muscle postmortem changes

Figure 21.1. Scheme summarising early postmortem changes in muscle and its influence on water binding. Reprodueed with permission from Toldra (2002). 

Inside the muscle fiber there is also a cytoskeleton — the protein structures assuring the integrity of muscle cells. Cytoskeletal proteins such as titin and nebulin are located in myofibrils and anchored in the Z line. Desmin is made up of costamers, which connect the myofibrils vinculin connects myofibrils and sarcolemma. Postmortem changes in cytoskeletal proteins probably play a role in the improvement of meat functional properties, especially its tenderness and water-holding capacity. 

Before the influence of freezing was studied, it was necessary to determine whether postmortem (p.m.) storage of muscle at temperatures above freezing (+4°C) influenced the subcellular distribution of the enzymes investigated. As is well known, storage of muscle p.m. results in drastic changes such as development of rigor mortis and a decline in pH from above 7 to about 5.5. 

In general, in beef muscle free catheptic activity reaches its maximum between four and six days postmortem (81, 92). At the same time major textural properties of meat show large changes between four and 13 days postmortem (33). Lysosomal enzymes have been implicated in the tenderization of meats by a number of workers. 

Raw muscle in a specific postmortem physiological stage and/or stored under proper temperature conditions has been strictly selected and used as the raw material for some specific IM meat products due to the eventual physical properties of the finished items (Chang et al, 1991). Examples include Zousoon and cooked-dried pork pieces or cubes (Leistner, 1987 ... 

Meat taste is one of the most inportant factors responsible for its palatability as described previously. It is mainly caused by chemoreception of water-soluble (non-volatile) conqjounds. The improvement of meat taste during postmortem aging is caused by changes in chemical components, which are catalyzed by several biochemical reactions in the muscle in the absence of oxygen after death. 

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