Proteomic analysis of water soluble and myofibrillar protein changes occurring in dry cured hams

The myofibrillar fraction of raw ham muscles and dry-cured hams with different ripening times was extracted in denaturing andreducing conditions and subjected to two-dimensional gel electrophoresis. The two-dimensional maps gave overall pictures of thealready noted progressive disappearance of actin, tropomyosin and myosin light chains during ripening. In addition, two fragmentsfrom Myosin Heavy Chain proteolysis, marked as myosin chain fragments MCF1 and MCF2, were identified by immunodetectionand matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS). Furthermore, a new form ofactin on two-dimensional gel was identified by MALDI-TOF peptide mapping. In 12-month-old dry-cured ham, most myofibrillarproteins were completely hydrolyzed. At this stage of ripening, in fact, in some Parma and S. Daniele dry-cured ham samples, myosinheavy chain fragments and other unidentified neo-formed spots were found. Some of the sarcoplasmic proteins in water extractsfrom pork meat markedly decreased in amount or disappeared totally, during ripening. Surprisingly, two-dimensional gel electrophoresismaps of the water soluble protein fraction from dry-cured ham showed the presence of two spots identified as tropomyosina- and b-chain. This result suggests that some of the saline soluble myofibrillar proteins can disappear from this fraction because ofsalt solubilization and not due to complete enzyme action. Two-dimensional gel electrophoresis (2-DGE) has proved a powerful toolto evaluate the enzymatic susceptibility of meat proteins and the evolution of protein map fragmentation throughout ripening processas well as a means of obtaining a standard fingerprinting map characterizing the final product.