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Oxygen Radical Absorbance Capacity (ORAC) is a method of measuring antioxidant capacities in biological samples. A wide variety of foods have been tested using this methodology, with certain spices, berries and legumes rated very highly. Correlation between the high antioxidant capacity of fruits and vegetables, and the positive impact of diets high in fruits and vegetables, is believed to play an important role in the free-radical theory of aging.

Method

The assay measures the oxidative degradation of the fluorescent molecule (either beta-phycoerythrin or fluorescein) after being mixed with free radical generators such as azo-initiator compounds. Azo-initiators are considered to produce the peroxyl radical by heating, which damages the fluorescent molecule, resulting in the loss of fluorescence. Antioxidant is able to protect the fluorescent molecule from the oxidative degeneration. The degree of protection will be quantified using a fluorometer. Fluorescein is currently used most as a fluorescent probe. Equipment that can automatically measure and calculate the capacity is commercially available (Biotek, Roche Diagnostics).

The fluorescent intensity decreases as the oxidative degeneration proceeds, and this intensity is typically recorded for 35 minutes after the addition of the azo-initiator (free radical generator). The degeneration (or decomposition) of fluorescein is measured as the presence of the antioxidant slows the fluorescence decay. Decay curves (fluorescence intensity vs. time) are recorded and the area between the two decay curves (with or without antioxidant) is calculated. Subsequently, the degree of antioxidant-mediated protection is quantified using the antioxidant trolox (a vitamin E analogue) as a standard. Different concentrations of trolox are used to make a standard curve, and test samples are compared to this. Results for test samples (foods) have been published as “trolox equivalents” or TE.

One benefit of using the ORAC method to evaluate substances’ antioxidant capacity is that it takes into account samples with and without lag phases of their antioxidant capacities. This is especially beneficial when measuring foods and supplements that contain complex ingredients with various slow and fast acting antioxidants, as well as ingredients with combined effects that cannot be pre-calculated.

Drawbacks of this method are: 1) only antioxidant activity against particular (probably mainly peroxyl) radicals is measured; 2) the nature of the damaging reaction is not characterized; and 3) there is no evidence that free radicals are involved in this reaction. Moreover, the relationship between ORAC values and the health benefit has not been established.

When comparing ORAC data, care must be taken to ensure that the units and food being compared are similar. Some evaluations will compare ORAC units per grams dry weight, others will evaluate ORAC units wet weight and still others will look at ORAC units/serving. Under each evaluation, different foods can appear to have higher ORAC values. Although a raisin has no more antioxidant potential than the grape from which it was dried, raisins will appear to have a much higher ORAC value per gram wet weight than grapes due to their reduced water content. Likewise, watermelons large water content can make it appear as though they are very low in antioxidants. Similarly, the typical quantity used culinarily should be considered; herbs and spices can be nutritionally dense but are used in much smaller quantities than other foods. Additionally, considering the ORAC value per calorie could be of some utility, as understanding just how much antioxidizing potential one could incorporate from a product into one’s diet would determine the real utility of the product.

Comparisons of ORAC values

Recently, a number of health food companies have capitalized on the ORAC rating, with dozens selling concentrated supplements that they claim to be “the number one ORAC product”. Most of these values have never been published in the scientific literature so are difficult to evaluate. It is not known whether such values are accurate or how absorbable and functional these concentrated antioxidants are in the human body.

Sources

• ORAC levels of various foods These are “old” data from the ORAC assay used before 2004 and should be viewed only as qualitative rankings. A revised ORAC assay used since 2004 provides quantitative values several times higher than these measurements. See an abstract of the reference report at this link from PubMed .
• Availability of food-based natural antioxidants
• Database of ORAC values based on 2007 USDA study, sortable alphabetically or by ORAC level
• Food Orac List Your Key To Slow Down The Aging Process
• Effect of soaking, boiling, and steaming on total phenolic content and antioxidant activities of cool season food legumes, Feb 2, 2008.

Tags: Brunswick Labs, Euforia, euforia score, orac, orac score

This entry was posted on Wednesday, February 17th, 2010 at 10:40 pm and is filed under Antioxidents, Euforia, Ingredients. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.