Proteomic study of muscle sarcoplasmic proteins using AUT-PAGE/SDS-PAGE as two-dimensional gel electrophoresis

The conversion of muscle to meat in pig involves mainly proteolysis of myofibrillar proteins, which undergo notable changes since early stage of rigor mortis, even after 48 h post mortem. The tenderness of meat has been thoroughly investigated to understand the biochemical mechanisms, which influence texture and flavour development as well as the technological parameters and hence meat quality. Cytoplasmic proteolytic calcium dependent enzymes, named -and m-calpains, which act in the early stages of rigor mortis, significantly contribute to tenderization weakening myofibrils. These enzymes, however, act for fewdays because they are specifically inhibited by calpastatin and by pH lowering. However, when pH falls to about 5.0, proteolytic activity on muscle proteins is continued by longer acting lysosomal proteinase, cathepsins [3,7–9]. Post mortem proteolysis also causes relevant changes in sarcoplamic protein fraction, which represent the water soluble fraction (quantitatively about 30–35%) of meat total protein, and the involved proteins has already been identified by proteomic-based studies. Recent investigations have demonstrated that the most commonly found Lactobacillus species in dry fermented meats are able to hydrolyse myofibrillar and sarcoplasmic muscle proteins in vitro.The most abundant sarcoplasmic proteins, as mixture of basic polypeptides with a narrow spread range of molecular masses, represented an excellent model to test our analytical technique and to delineate its capabilities. In the present study, we compared 2D AUT-PAGE/SDSPAGE maps of water-soluble proteins extracted from fresh meat and from dry-cured ham, a non fermented product, from “Naples-type” salami, a microbiologically fermented product, and from “Coppa”, a typical semi-fermented product. Electrophoretically separated proteins have been identified by MALDI-ToF mass fingerprinting.