What is ORAC?
Oxygen Radical Absorbance Capacity (ORAC) is a laboratory analysis that provides an overall measure of a food’s antioxidant activity. The test works by challenging a food product with an oxidizing agent, and then measuring the overall capacity of that food to resist oxidation. The higher the ORAC score, the greater is the food’s antioxidant capacity. Several such measures of “total” antioxidant activity have been developed. None are definitive, but ORAC has gained the widest acceptance in commercial circles.
ORAC tests are often used to compare the antioxidant activities of different foods (fruits, vegetables, juices, wines, etc.). Such comparisons can be valuable, but they do carry limitations. First, ORAC analyses are not extremely precise. When a given food product is tested multiple times in a given laboratory, variation in ORAC score from one sample to the next is often on the order of 10-15%. Second, different laboratories conduct ORAC testing in different ways, and often produce markedly different results. Third, different orange juices, for example, that were manufactured and diluted in different ways and stored under different conditions, can actually have very different antioxidant activities such that it is difficult to assign a meaningful ORAC score to orange juice in general.
Nevertheless, comparisons based on ORAC testing can be meaningful when similar products are compared, when all ORAC analyses are conducted in a single, qualified laboratory using the same analytical methods, and importantly when the ORAC values reported pertain to equal amounts of product (for example, all the ORAC values are presented on a per ounce or per 100 gram basis). Under these circumstances, large differences in ORAC score (particularly differences on the order of 3-10 fold) can indicate meaningful differences in true antioxidant activity.