The addition of antioxidants is one of the best ways to prevent the oxidative deterioration of foods. Therefore, the development of effective antioxidants, both artificial and natural, has been underway in recent years. However, these antioxidants are not always as effective when used in actual food products. Of the many possible reasons for this, one is that foods are complex systems consisting of various ingredients. For example, effect varies in of emulsion-based foods depending on whether the antioxidant is in the aqueous or oil phase, as well as its presence at the interface, which can explain the so-called polar paradox phenomenon. The coexistence of antioxidants is known to affect the total antioxidant capacity. The antioxidant effects of coexisting substances have been reported to add up in effects, however, synergistic and antagonistic effects have also been observed. To better understand the function of antioxidants, an analysis is necessary, assuming the influence of other components in food. If the resulting synergistic effects could enhance the function of existing antioxidants, technologies could in turn be developed to prevent the oxidative degradation of foods more effectively and for longer with the addition of smaller amounts.