What Is the ORAC Scale?

ORAC stands for Oxygen Radical Absorbance Capacity—a laboratory method used to compare the antioxidant capacity of foods.

ORAC is a laboratory assay used to measure the ability of compounds in a sample to inhibit oxidation induced by specific free radicals.1 Results are commonly expressed as µmol TE per 100 grams—meaning micromoles of Trolox Equivalents per 100 grams of food. Trolox, a vitamin E-like compound, is used as the laboratory reference standard.1

A note on this data's status: From 2007–2010, the USDA published an ORAC database compiled from numerous foods and published studies. In 2012, USDA withdrew this database from publication, citing "mounting evidence that the values indicating antioxidant capacity have no relevance to the effects of specific bioactive compounds, including polyphenols, on human health," and noting that ORAC values were frequently misused by food and supplement marketers to imply health benefits the data cannot support.2 We present the figures below as historical laboratory measurements only—useful for understanding relative antioxidant chemistry between foods, not as an indicator of health outcomes.

Representative Historical ORAC Comparison

FruitApproximate ORAC Value
Aronia / Black Chokeberry16,062
Wild Blueberry9,621
Cranberry9,090
Blackberry5,905
Raspberry5,065
Strawberry4,302
Blueberry4,669
Apple (with skin)3,049

Historical ORAC values expressed as µmol Trolox Equivalents per 100 g of raw fruit, from the USDA's discontinued ORAC Database for Selected Foods, Release 2 (2010).3Values from different studies and samples should be compared cautiously, as cultivar, maturity, growing conditions, storage, processing, extraction procedures, and analytical methods can all influence measured antioxidant capacity.

Aronia berries consistently measured among the highest ORAC values of any fruit tested in this database, a finding consistent with their unusually concentrated levels of anthocyanins and proanthocyanidins.4

Continue Exploring the Science

Learn more about antioxidants and free radicals, and how they relate to what ORAC actually measures.

AntioxidantsFree Radicals

References

  1. Prior, R.L., Wu, X., & Schaich, K. (2005). "Standardized Methods for the Determination of Antioxidant Capacity and Phenolics in Foods and Dietary Supplements." Journal of Agricultural and Food Chemistry, 53(10), 4290–4302.View source↩¹↩²
  2. U.S. Department of Agriculture, Agricultural Research Service. (2012). Statement on the removal of the USDA ORAC Database for Selected Foods.View source↩
  3. Haytowitz, D.B. & Bhagwat, S. (2010). USDA Database for the Oxygen Radical Absorbance Capacity (ORAC) of Selected Foods, Release 2. U.S. Department of Agriculture, Agricultural Research Service.↩
  4. Wu, X., Gu, L., Prior, R.L., & McKay, S. (2004). "Characterization of Anthocyanins and Proanthocyanidins in Some Cultivars of Ribes, Aronia, and Sambucus and Their Antioxidant Capacity." Journal of Agricultural and Food Chemistry, 52(26), 7846–7856.View source↩