ORAC Score and Antioxidants Explained

What is ORAC? ORAC stands for Oxygen Radical Absorption Capacity. It is an analysis that measures the antioxidant power of a substance. Specifically, it quantifies the amount of time it takes a substance to neutralize an oxidizing agent. And antioxidants are what neutralize these agents. Oxidizing agents, called Oxygen Radicals and Free Radicals are explained thoroughly in the article, Stop Free Radical Damage and Slow Your Aging. In short, they are terrorists to the body, damaging and destroying your body's cells.

The usual substances that are assessed include fruits, vegetables, beverages, and supplements. The ORAC analysis is an automated procedure carried out on COBAS FARA II spectrofluorometric centrifugal analyzer with fluorescent filters. This analyzer uses robotics to measure and transfer samples into reagent wells. These reagent wells are like test pools where the sample is then rotated at high speed, separating the materials of different densities, and incubated. (See Graph)

This procedure measures the protection ability of the sample against free radical attacks. The test uses a free radical source, producing the peroxl radical (most common in the body). B-PE (B-phycoerythrin) is employ as a target for the free radical attack. AAPH (2,2'-azobis-2-amidinopropane-dihydrochloride) is the free radical generator, and Trolox (a water-soluble vitamin E analogue) is the control standard.

Results are expressed in ORAC units, where 1 unit equals the net protection produced in 1 micron of the control standard, Trolox. The analyzer records the free radical target (B-PE) every 2 minutes after a release of free radicals from the free radical generator (AAPH).

As noted above, the ultimate value of an ORAC score measures the antioxidant capacity (and free radical neutralizing power) of a substance. This value represents the fast, medium, and slow acting antioxidants in the substance. Fast Antioxidants include ascorbate, thiols, uric acid, bioflavonoids and polyphenols. Medium Antioxidants include albumin and lipids. Over half the total ORAC value is from the protein and aqueous antioxidants, the other part is from lipid soluble antioxidants.

See the following chart showing various fruits and vegetables and their ORAC score.

FRUITS & VEGETABLES ORAC SCOREper 1 oz
Prunes 1649
Raisins 809
Blueberries 686
Blackberries 582
Kale 506
Strawberries 440
Spinach 350
Raspberries 349
Brussels Sprouts 280
Plums 271
Alfalfa 266
Broccoli 254
Beets 140
Oranges 214
Red Grapes 211
Red Bell Peppers 203
Cherries 191
Onions 129
Corn 114
Eggplant 111