Aging of Meat

Unshortened muscle at rigor has a basal level of tenderness that is enhanced by subsequent aging of the muscle. Severely cold-shortened meat does not age to any degree (Fig. 5) (27). Aging involves the breakdown of the muscle proteins (eg, troponin T, troponin I, tropomyosin, C-protein, and M-protein and cytoskeletal proteins, titin, nebulin, and desmin), by endogenous enzymes, termed cal-pains (37-39), although minimally involving the major proteins actin and myosin. Calpains are members of the cysteine class of proteases and are inhibited by calpasta-tins. They exert their effect by altering structural integrity at the junction of the A-I band, as well as fragmentation of the Z-lines. Calpains exist in two forms, ¡x- and m-calpains, that differ in their calcium requirements, ju-Calpain requires 1—30 ,umol of calcium, and m-calpain requires 270 to 750 //mol of calcium for half-maximal activity. Binding of calcium also induces the autolysis of the calpains that results in loss of activity. In the presence of calcium sufficient to activate calpains, calpastatin complexes with calpains to inhibit activity; thus, the way calpain exerts its effects is still unclear. Even so, among the enzymes involved, the calpains seem to be the best candidates to tenderize meat, and the inhibitor calpastatin prevents their activity in normal tissues (40-43). Indeed there is more than enough calpastatin in any muscle to inactivate the calpains. A synergistic contribution by lysosomal (ca-thepsins) and calcium-dependent proteinases (calpains) has been proposed (44), with no direct relationship between aging rate and protease content of muscles found. The aging rate of meat increases dramatically as the temperature rises and has a temperature coefficient of 2.4, and aging even takes place during cooking but ceases dramatically at a temperature of 66°C (Fig. 6) (45).

As aging is temperature dependent and carcasses are in a cooling environment, processes such as electrical stimulation that produce an early rigor while the carcasses are still relatively warm ensure maximum aging in the shortest possible time (apart from also avoiding the effects

Sleeping Sanctuary

Sleeping Sanctuary

Salvation For The Sleep Deprived The Ultimate Guide To Sleeping, Napping, Resting And  Restoring Your Energy. Of the many things that we do just instinctively and do not give much  of a thought to, sleep is probably the most prominent one. Most of us sleep only because we have to. We sleep because we cannot stay awake all 24 hours in the day.

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