Development of a database for total antioxidant capacity in foods: a preliminary study

摘要

For the first time, a database of the antioxidant capacities of both the lipophilic and hydrophilic components of foods has been developed using the modified oxygen radical absorbance capacity (ORAC(FL)) assay and a peroxyl radical generator. For lipophilic components, randomly methylated beta-cyclodextrin was used as a solubility enhancer. Four representative samples were extracted directly with the hydrophilic solvent (acetone: water: acetic acid, 70:29.5:0.5). Their ORACFL values were similar to that obtained for hydrophilic ORAC(FL) (H-ORAC(FL)) following lipophilic extraction with hexane:dichloromethane (1:1). Lipophilic ORAC values (L-ORAC(FL)) were relatively low compared to H-ORAC(FL), ranging from 0.11 +/- 0.06 to 154.70 +/- 3.58 mumol TE/g of fresh or dry weight, whereas H-ORAC(FL) ranged from 1.23 +/- 0.17 to 175.24 +/- 10.36 mumol TE/g of fresh or dry weight. Total antioxidant capacity (TAC) was calculated as the sum of the lipophlic and hydrophilic ORACFL values. L-ORAC(FL) as a percentage of TAC ranged from 0.27% to 63.70%. Sampling time during the year significantly influenced lipophilic and/or hydrophilic ORAC(FL) values in some food samples. In order to get an accurate total antioxidant capacity of a given food sample, both lipophilic and hydrophilic fractions need to be measured. Food processing, such as cooking or peeling, need to be considered as additional factors which can introduce variation in antioxidant capacity measurements of foods.