Chemical, physical, and gel-forming properties of oxidized myofibrils and whey- and soy-protein isolates

Myofibrils, oxidized with FeCl3/H2O2/ascorbate, exhibited an increase in carbonyls and amines, SH-->SS conversion, peptide scission, myosin polymerization, and a decrease in thermal stability and gel-formation ability. Amino-acid side chains of whey-protein isolates (WPI) and soy-protein isolates (SPI) were also modified during oxidation, but the thermal stability of WPI or SPI was not significantly altered. Oxidation increased elasticity of SPI gel but not that of WPI gel. Similarly, oxidation promoted interactions of myofibrils with SPI but not with WPI, resulting in > 30% increases in elasticity of the myofibril/SPI composite gel over its nonoxidized control. Hence, in processed meats where oxidation occurs, the presence of soy proteins may enhance the functionality of myofibrillar proteins.