Protein Modifications in Cooked Pork Products

Abstract Heat treatment induces protein modifications in both cooked whole cuts of meat and in products such as emulsion sausages. Cooking results in shrinkage and water loss with the main proteins changing through conformational rearrangements, oxidation of amino acid residues, and polymeric aggregation (as supramolecular structures). The proteomes of whole-cut meats (e.g., Parma and “Praga” cooked hams) and comminuted pork (e.g., mortadella and wurstel) products have been compared to raw pork using traditional proteomics approaches employing two-dimensional gel electrophoresis (2-DE) coupled to image analysis and mass spectrometry (MS). These studies revealed that other than heat-induced breakdown of part of the myosin heavy chains, the 2-DE pattern of cooked ham was highly similar to that of raw pork. However, MS-based analysis showed protein modifications, including extensive oxidation of methionines. In contrast, likely due to emulsification, comminuted sausages were characterized by an abundant insoluble protein fraction. Interestingly, in comminuted sausages, tropomyosin and myosin light chains were exclusively found in the insoluble protein fraction, whereas actin was found in each supramolecular structure. Experimental evidence showed that the protein aggregation systems of cooked hams and emulsion sausages reflected the processing conditions and were definitely different, the former being characterized mainly by disulfide bridges and the latter by additional covalent interprotein links.