Guidelines for antioxidant assays for food components

Abstract Recently, research on antioxidants has become increasingly active in various fields. Antioxidants react through free radical or molecular oxygen quenching, being capable to either delay or inhibit the oxidation processes that occur under the influence of molecular oxygen or reactive oxygen species. Accordingly, assays developed to evaluate the antioxidant activity of food constituents vary. Therefore, to investigate the antioxidant activity of chemical(s), choosing an adequate assay based on the properties of chemical(s) is critical. Antioxidant assays may be broadly classified as electron transfer (ET)‐based assays and hydrogen atom transfer (HAT)‐based assays. ET‐based assays include ABTS assay, DPPH assay, ferrous oxidation‐xylenol orange assay, ferric thiocyanate assay, ferric reducing/antioxidant power assay, potassium ferricyanide reducing power assay, and cupric reducing antioxidant power assay. HAT‐based assays include oxygen radical absorbance capacity assay, total peroxyl radical‐trapping antioxidant parameter assay, thiobarbituric acid assay, β‐carotene bleaching assay, and cellular antioxidant activity assay. In this guideline, assays used recently were selected for extended discussion, including the mechanisms underlying each assay as well as the practice of antioxidant capacity assessment.