ORAC stands for Oxygen Radical Absorbance Capacity. In this assay the ability of a substance to subdue oxygen free radicals in vitro or “total antioxidant capacity” is determined. The method is spectrofluorometric, performed by an outside lab (automated), and it is based on the time-dependent decrease in the fluorescence of the beta-PE indicator protein with the following parameters:
– Free-radical generating system: AAPH
– Sensitive target of the free radical attack: B- or R-PE
– Quantification: area under the curve (combines both inhibition percentage and the length of inhibition time of free radical action by an antioxidant into a single quantity)
Trolox (water-soluble analog of vitamin E) is used as a standard. This method is more common in the U.S. than in Europe and more customers are requesting this data.
We had samples analyzed for ORAC values by Brunswick Laboratories (Wareham, MA). They have a fairly detailed web site that explains ORAC as well.