Evaluation of The Antioxidant Capacity of Food Products: Methods, Applications and Limitations

Abstract

Assays of total antioxidant capacity (TAC) are popular in the analysis of food products. This review presents the most popular assays of TAC and their limitations, databases of TAC of food products, their application in clinical studies, and the effect of processing on the TAC of food. The importance of sample preparation for TAC assays and striking effects of digestion in the gastrointestinal tract on the TAC of food are discussed. Critical opinions on the validity of food TAC assays are considered. It is concluded that TAC methods can be useful as screening assays for food quality control and as low-cost, high-throughput tools used to discover potential antioxidant sources and follow changes in the content of antioxidants during food processing. However, effects revealed by TAC assays should be followed and explained using more specific methods.

Investigating the Antioxidant and Color Properties of Bee Pollens of Various Plant Sources

“…The FRAP assay resulted in antioxidant capacities between 2.22 and 10.59 mg AAE/g dw (5.98 mg AAE/g dw on average), while results of the CUPRAC assay ranged between 7.90 and 44.89 mg TE/g dw (25.58 mg TE/g dw on average). Differences may be attributed to the limited ability of the FRAP assay to measure lipophilic antioxidants, thiol‐type antioxidants and slow‐reacting phenolic compounds [3,33,34] . Results of the ABTS⋅ + and DPPH⋅ assays fell within a comparable range (between 3 and 20 mg TE/g dw), but the ABTS⋅ + assay resulted in higher values for most of the samples, probably due to the fact that the DPPH⋅ assay is less sensitive to the hydrophilic and highly pigmented antioxidants [36,37] .…”

“…The color change can be monitored spectrophotometrically at 593 nm [32] . As the Fe III ‐TPTZ complex has higher affinity toward the aqueous phase than towards organic solvents, the determination of lipophilic antioxidants is limited [33] . This method is unable to accurately detect the antioxidant activity of slow reacting polyphenols, such as caffeic acid, tannic acid, ferulic acid and quercetin [30] .…”

“…The CUPRAC assay is based on the increase in absorbance of bis(neocuproine)copper(II) containing solution upon the reduction of Cu II to Cu I at 450 nm. The reaction takes place at a neutral pH, so it better simulates the physiological action of antioxidants compared to the FRAP assay [33] . The CUPRAC chromophore is soluble in both aqueous and organic solvents, enabling the determination of hydrophilic and lipophilic antioxidants as well [35] .…”

“…The ORAC assay is based on the inhibition of the oxidation of a fluorescent substrate by peroxyl radicals. This assay can be adapted to detect both hydrophilic and hydrophobic antioxidants [33] …”

“…[32] As the Fe III -TPTZ complex has higher affinity toward the aqueous phase than towards organic solvents, the determination of lipophilic antioxidants is limited. [33] This method is unable to accurately detect the antioxidant activity of slow reacting polyphenols, such as caffeic acid, tannic acid, ferulic acid and quercetin. [30] Furthermore, the FRAP assay is not sensitive to thiol-type antioxidants, such as glutathione and proteins.…”