Factors and mechanisms responsible for meat ageing

Although the increase in meat tenderness during the storage of animal carcasses at refrigeration temperatures (ageing) is known since the beginning of the last century, the factors and mechanisms involved in the process remain controversial. In fact, meat ageing is a very complex multifactorial process, dependent on many ante-mortem and post-mortem factors, which can explain in part this difficulty. However, many causes and mechanisms have been suggested as responsible for meat ageing. In this work, we reviewed these possible factors and the proposed structural and biochemical mechanisms involved. These factors are of physico-chemical nature and of endopeptidasic (EC 3.4.21-24,99) nature. The physica-chemical factors include the calcium ions, the osmotic pressure and the oxidative processes. The suggested endopeptidases, acting individually or in association, are: cathepsin B (EC 3.4.22.1), cathepsin L (EC 3.4.22.15), cathepsin H (EC 3.4.22.16), cathepsin D (EC 3.4.23.5), mu-calpain (EC 3.4.22.17), m-calpain (EC 3.4.22.17), 20 S proteasome (EC 3.4.99.46), interstitial collagenase (EC 3.4.24.7) and unknown endopeptidases (EC 3.4.99). However, the relative contribution of these factors to the meat tenderisation during ageing remains unknown. Nevertheless, most of researchers have suggested a major role for calpains, cathepsins, or both in association, mediated by the degradation of myofibrillar proteins and structures.