Thermal transitions and dynamic gelling properties of oxidatively modified myosin, β-lactoglobulin, soy 7S globulin and their mixtures

Oxidative effects on myosin, β-lactoglobulin and soy 7S globulin as well as their composites were studied by differential scanning calorimetry and dynamic rheological analysis. Myosin, oxidised with a free radical-generating system (FeCl₃/H₂O₂/ascorbate), was destabilised, showing a marked decrease (>50%) in storage modulus during thermal gelation. On the other hand, oxidised β-lactoglobulin and 7S globulin exhibited only minor changes in their thermal stability and gelation properties. In the non-oxidised myosin/β-lactoglobulin composite, β-lactoglobulin affected the thermal denaturation and gelation properties of myosin through non-covalent interactions. The nature and extent of the interactions were altered by oxidation. 7S globulin did not change the thermal stability but slightly enhanced the rheological properties of myosin, regardless of oxidative conditions. Hence, in muscle foods that contain whey or soy protein ingredients, all the protein components can be oxidatively modified, and the extent of the functionality changes in myosin will be influenced by the presence of the non-muscle proteins. (C) 2000 Society of Chemical Industry.