Measurement of Antioxidant Activity in Food and Biological Systems

Abstract

The importance of lipid oxidation and antioxidants in biological systems and foodstuff has been widely recognized. Oxidative changes involving free radicals in membrane lipids are thought to have destructive cellular effects in vivo; whereas oxidative processes in foods result in flavor and nutritional quality deterioration that may also affect their safety and wholesomeness. Antioxidants protect cells and foods against oxidative stress. Many methods have been developed for evaluating the activity of antioxidants; these may be classified into two categories. The first category measures the ability of antioxidants in inhibiting oxidation reaction in a model system by monitoring the associated changes using physical, chemical or instrumental means. Radical scavenging assays include methods based on hydrogen atom transfer (HAT) or electron transfer (ET) mechanisms. Oxygen radical absorbance capacity (ORAC), total radical trapping antioxidant parameter (TRAP) and crocin bleaching assays are the major methods that measure HAT while Trolox equivalent antioxidant capacity (TEAC), ferric reducing antioxidant power (FRAP), and DPPH assays represent ET-based methods. An overview of relevant methods for evaluating antioxidant activity with emphasis on the chemistry, basic principles involved as well as advantages and disadvantages of each assay is provided.