Lipophilic and Hydrophilic Antioxidant Capacities of Common Foods in the United States

Both lipophilic and hydrophilic antioxidant capacities were determined using the oxygen radical absorbance capacity (ORACFL) assay with fluorescein as the fluorescent probe and 2,2'-azobis(2-amidinopropane) dihydrochloride as a peroxyl radical generator on over 100 different kinds of foods, including fruits, vegetables, nuts, dried fruits, spices, cereals, infant, and other foods. Most of the foods were collected from four different regions and during two different seasons in U.S. markets. Total phenolics of each sample were also measured using the Folin−Ciocalteu reagent. Hydrophilic ORACFL values (H-ORACFL) ranged from 0.87 to 2641 μmol of Trolox equivalents (TE)/g among all of the foods, whereas lipophilic ORACFL values (L-ORACFL) ranged from 0.07 to 1611 μmol of TE/g. Generally, L-ORACFL values were <10% of the H-ORACFL values except for a very few samples. Total antioxidant capacity was calculated by combining L-ORACFL and H-ORACFL. Differences of ORACFL values in fruits and vegetables from different seasons and regions were relatively large for some foods but could not be analyzed in detail because of the sampling scheme. Two different processing methods, cooking and peeling, were used on selected foods to evaluate the impact of processing on ORACFL. The data demonstrated that processing can have significant effects on ORACFL. Considering all of the foods analyzed, the relationship between TP and H-ORACFL showed a very weak correlation. Total hydrophilic and lipophilic antioxidant capacity intakes were calculated to be 5558 and 166 μmol of TE/day, respectively, on the basis of data from the USDA Continuing Survey of Food Intakes by Individuals (1994−1996). Keywords: Antioxidants; hydrophilic; lipophilic; ORACFL; total phenolics; fruits; vegetables; nuts; dried fruits; spices; baby foods; chocolate; cereal