Evaluation of the antioxidant capacity of food samples: a chemical examination of the oxygen radical absorbance capacity assay

Abstract

This chapter describes, from a critical point of view, the main in vitro methodologies employed to assess the antioxidant capacity (AC) of food samples. Considering the wide use of the oxygen radical absorbance capacity (ORAC) assay, it presents a chemical examination of this methodology. The methods for AC evaluation are based on different strategies; these include the use of colored and stable free radicals, evaluation of the capacity of antioxidants to reduce cupric or ferric ions, estimation of the ability of phenolic compounds (PC) to protect a target molecule exposed to a free radical source, and evaluation of the capacity of PC to form nanoparticles. When the antioxidant activity of a particular sample is evaluated, it is recommended to know the meanings and limitations of the assays being employed. In the case of the ORAC assay, the nature of the free radicals generated during the thermolysis of AAPH should also be considered.