Electrophoretic pattern, thermal denaturation, and in vitro digestibility of oxidized myosin

Physicochemical changes and in vitro digestibility of chicken breast myosin oxidized with a nonenzymic free-radical-generating system (FeCl3/H2O2/ascorbate) were studied by SDS-PAGE, differential scanning calorimetry, and o-phthaldialdehyde assay. Oxidation caused fragmentation and polymerization of myosin. Myosin polymers were cross-linked mainly through disulfide bonds. Hydroxyl radicals destabilized myosin, lowering its denaturation temperature by up to 4 degrees C. Oxidized myosin also produced a new thermal transition in the 60-80 degrees C temperature range, which could be attributed to the formation of disulfide-stabilized polymers. The proteolytic susceptibility of myosin to pepsin, trypsin, and chymotrypsin was increased by oxidation. Under nonreducing conditions, however, oxidized myosin showed decreased digestibility, The results may help explain variations in the functionality and nutritional quality of muscle foods in meat processing in which oxidation is involved.