Proteomic characterization of electrically stimulated and aged meat of heavy kids.

This work aimed to enlarge the knowledge about the chemical and physical modifications occurring on muscle myofibrils owing to some post-mortem (p.m.) treatments of carcass. Moreover, the protein identification was performed to increase knowledge on the goat proteome. The study was carried out on the Longissimus dorsi muscle of 6 male heavy kids ‘Derivata di Siria’ undergone 4 different post-mortem treatments: A (ageing for 48hrs, +4 °C), ES220v (220v applied 30’ p.m., sampled 8hrs p.m.), ES48vj (48v applied at the slaughtering, sampled 8hrs p.m.), ES48vs+A [48v applied at the slaughtering, sampled at the end of the ageing period (48hrs)]. The samples obtained from the 12 half-carcasses were analyzed using the common proteomic procedures (two-dimensional gel electrophoresis, image analysis of gels, protein identification through the Maldi-ToF mass spectrometer). The Maldi-ToF peptide mass fingerprinting allowed to identify with high expectation values a pool of 9 unspecific proteins: Actin (MW_39kD; Pi_5.2), Myosin light chain 2 fast (MLC2f) (a, b, c isoforms) (MW_17kD; Pi_4.6-4.9), Myosin light chain 2 slow (MLC2s) (MW_18.5kD; Pi_5.1), Myosin light chain 1 fast (MLC1f) (a, b isoforms) (MW_23kD; Pi_5.1-5.2), Heat shock protein 27 kDa (MW_25Kd; Pi_6.1), Spot n° 797 (MW_24Kd; Pi_5.8). The volume value of each one of them was computed from the relative spots on gels. The subsequent image analysis allowed to verify the relation between treatment of carcass and myofibrillar proteolysis degree (linked with the volume decrease of spots). The meat stimulated using a middle voltage (ES220v) and analyzed 8 hours p.m. presented proteolysis values similar to the meat aged for 48 hours (A), while the use of low voltage (ES48vj) produced the lowest values of proteolysis in comparison with the other treatments employed (P<0.001). However, this difference can be avoided with the supplementary employment of ageing on the low voltage electrically stimulated sides. Considering the level of muscular proteolysis, the middle voltage ES (220v) represents an useful technique in order to reduce the ageing time in cold store without compromising the proteolysis.