Effect of peroxyl radicals on the structure and gel properties of isolated rabbit meat myofibrillar proteins

We investigated the effect of peroxyl radicals (ROO center dot), which are products of lipid peroxidation, on the structure and gel properties of myofibrillar proteins (MPs) isolated from rabbit meat. 2,2 '-Azobis(2-amidinopropane) dihydrochloride (AAPH) was heated to stably derive ROO center dot. As the AAPH concentration increased, the protein carbonyl compounds significantly accumulated (P < 0.05), and the total sulfhydryl content was significantly lost (P < 0.05). Circular dichroism spectra, UV absorption spectra, intrinsic fluorescence spectra and surface hydrophobicity revealed that ROO center dot caused protein unfolding and conformational changes in MPs. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) analysis indicated that moderate (0-3 mm) and relatively high (5 and 10 mm) AAPH concentrations could lead to protein crosslinking and protein aggregation, respectively. These changes in protein structure could influence the gelling properties of MPs. Low-level protein oxidation could increase gel strength and water holding capacity, whereas high-level protein oxidation could reduce gel properties.