Oxygen radical absorbance capacity 2832162 216939795 2008-06-03T22:16:41Z Paul144 1676299 /* Comparisons of ORAC values */ '''Oxygen Radical Absorbance Capacity''' ([[ORAC]]) is a method of measuring [[antioxidant]] capacities of different foods.<ref>{{cite journal |author=Cao G, Alessio H, Cutler R |title=Oxygen-radical absorbance capacity assay for antioxidants |journal=Free Radic Biol Med |volume=14 |issue=3 |pages=303–11 |year=1993 |pmid=8458588 |doi=10.1016/0891-5849(93)90027-R}}</ref><ref>{{cite journal |author=Ou B, Hampsch-Woodill M, Prior R |title=Development and validation of an improved oxygen radical absorbance capacity assay using fluorescein as the fluorescent probe |journal=J Agric Food Chem |volume=49 |issue=10 |pages=4619–26 |year=2001 |pmid=11599998 |doi=10.1021/jf010586o}}</ref> It was developed by the scientists at the [[National Institute on Aging]] in the [[National Institutes of Health]] ([[NIH]]) in [[Baltimore, Maryland]], but it does not mean that this method is approved by NIH. Recently, US Department of Agriculture [[USDA]] listed a database of the ORAC value in its home page (www.usda.gov) without evaluation. A wide variety of foods have been tested using this methodology, with certain [[spice]]s, [[berries]] and [[legume]]s rated very highly<ref>[http://www.ars.usda.gov/SP2UserFiles/Place/12354500/Data/ORAC/ORAC07.pdf] Oxygen Radical Absorbance Capacity of Selected Foods - 2007; Nutrient Data Laboratory, Agricultural Research Service, ''United States Department of Agriculture'', November 2007</ref>. 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 original idea of the ORAC assay is based on Glazer's study. The assay measures the oxidative degradation of the fluorescent molecule (either beta-phicoerythrin or [[fluorescein]]) after being mixed with free radical generators such as azo-initiator compounds. Azo-initiators are considered to produce [[peroxyl]] [[free 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. As a fluoresent probe, fluorescein is mostly used these days. 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 recorded for typically 35 minutes after the addition of the azo-initiator (free radical generator). The degeneration (or decomposition) of fluorescein that is measured as the fluorescence delay becomes less prominent by the presence of antioxidants. Decay curves (fluorescence intensity vs. time) are recorded and the area between 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.<ref>{{cite journal |author=Huang D, Ou B, Prior R |title=The chemistry behind antioxidant capacity assays |journal=J. Agric. Food Chem. |volume=53 |issue=6 |pages=1841–56 |year=2005 |pmid=15769103 |doi=10.1021/jf030723c}}</ref> One benefit of using the ORAC method to evaluate substance's 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)free radicals which damage fluorescein molecule are not identified; 2)the nature of the damaging reaction is not characterized; and 3) there is no evidence that free radical is involved in this reaction. Moreover, the relationship between ORAC values and the health benefit has not been established. ==Food Sources== In 2007, scientists with the [[United States Department of Agriculture]] published an updated list of ORAC values for 277 foods commonly consumed by the U.S. population (fruits, vegetables, nuts, seeds, spices, grains, etc.).<ref>Nutrient Data Laboratory, Agriculture Research Service, US Department of Agriculture, Oxygen radical absorbance capacity (ORAC) of Selected Foods - 2007.[http://www.ars.usda.gov/SP2UserFiles/Place/12354500/Data/ORAC/ORAC07.pdf]</ref> Values were reported as micromoles of [[Trolox]] equivalents (TE, vitamin E derivative) per 100 grams both for lipid-soluble ("[[lipophilic]]" as for [[carotenoids]]) and water-soluble ("[[hydrophilic]]" as for [[phenolics]]) antioxidant chemicals in foods, thus were a sum of lipophilic and hydrophilic values or ''total'' ORAC. These values are considered to be more accurate than previously published ORAC numbers because lipophilic values were being included for the first time. These data showed that all plants have variable amounts of both lipophilic and hydrophilic phytochemicals that contribute to total ORAC. {| class="wikitable" |+USDA data on foods with high levels of antioxidant [[phytochemical]]s |- ! Food !! Serving size !! Antioxidant capacity per serving size<ref>Units are Total Antioxidant Capacity per serving in units of micromoles of Trolox equivalents.</ref> |- ! [[Cinnamon]], ground || 100&nbsp;grams || 267,536 |- ! Aronia black [[chokeberry]] (''Aronia melanocarpa'') || 100&nbsp;grams || 16062 |- ! Small Red Bean || ½&nbsp;cup dried beans || 13727 |- ! Wild [[blueberry]] || 1&nbsp;cup || 13427 |- ! Red [[kidney bean]] || ½&nbsp;cup dried beans || 13259 |- ! [[Pinto bean]] || ½&nbsp;cup || 11864 |- ! [[Blueberry]] || 1&nbsp;cup (cultivated berries) || 9019 |- ! [[Cranberry]] || 1&nbsp;cup (whole berries) || 8983 |- ! [[Artichoke heart]]s || 1&nbsp;cup, cooked || 7904 |- ! [[Blackberry]] || 1&nbsp;cup (cultivated berries) || 7701 |- ! [[Prune]] || ½&nbsp;cup || 7291 |- ! [[Raspberry]] || 1&nbsp;cup || 6058 |- ! [[Strawberry]] || 1&nbsp;cup || 5938 |- ! [[Red Delicious]] [[apple]] || 1&nbsp;apple || 5900 |- ! [[Granny Smith]] apple || 1&nbsp;apple || 5381 |- ! [[Pecan]] || 1&nbsp;[[ounce|oz]] || 5095 |- ! [[Wild Cherry|Sweet cherry]] || 1&nbsp;cup || 4873 |- ! Black [[plum]] || 1&nbsp;plum || 4844 |- ! [[Russet Burbank potato|Russet potato]] || 1, cooked || 4649 |- ! [[Black bean]] || ½&nbsp;cup dried beans || 4181 |- ! Plum || 1&nbsp;plum || 4118 |- ! [[Gala (apple)|Gala apple]] || 1&nbsp;apple || 3903 |} The values for other spices and high-ORAC fruits such as black [[elderberry]] (''Sambucus nigra'') have not been included in the chart which, according to the new data published in 2007, have among the highest values yet recorded for common North American foods.<ref>Oxygen Radical Absorbance Capacity of Selected Foods - 2007; Nutrient Data Laboratory, Agricultural Research Service, United States Department of Agriculture, November 2007.[http://www.ars.usda.gov/SP2UserFiles/Place/12354500/Data/ORAC/ORAC07.pdf]</ref> ==Comparisons of ORAC values== 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. To say then that chocolate has "more antioxidant" potential than blueberries is tenuous at best. While ounce per ounce chocolate may have a higher ORAC value, on the comparison of dry weight, we see blueberries have a higher ORAC value. 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. The range of ORAC for common fruits was around 1.40 micromoles TE per gram ([[watermelon]]) to 95 ([[cranberry]]). Lowbush blueberry (wild [[blueberry]]) was also very high at 92.6 µmol/g. For vegetables or [[legumes]], it was 1.15 ([[cucumber]]) to 149 small red (red kidney [[bean]]); for nuts, 7.19 ([[cashew]]) to 179.4 ([[pecan]]); and for dried fruits, 23.87 (medjool dates) to 85.78 ([[prune (fruit)|prune]]). By comparison, different species of [[apples]] had ORAC values of 22.10 to 42.75 micromoles TE per gram, white [[potato]] was under 11, [[peanut]] was 31.66 and [[tomato]] about 4.00 [[Spices]] ([[clove]], [[cinnamon]]) showed the highest ORAC values (>2500, converted to micromoles TE per gram). [[Cocoa]] has a high ORAC value, giving baking chocolate a value of 1032 and milk chocolate an average of 71.30. A recent paper by Schauss and colleagues reported an extremely high total ORAC value of 1027 micromoles TE per gram for a ''freeze-dried'' fruit pulp and skin powder from the [[açaí]] berry (''Euterpe oleracea'').<ref>{{cite journal |author=Schauss A, Wu X, Prior R, Ou B, Huang D, Owens J, Agarwal A, Jensen G, Hart A, Shanbrom E |title=Antioxidant capacity and other bioactivities of the freeze-dried Amazonian palm berry, Euterpe oleraceae mart. (açaí) |journal=J. Agric. Food Chem. |volume=54 |issue=22 |pages=8604–10 |year=2006 |pmid=17061840 |doi=10.1021/jf0609779}}</ref> This is the highest ORAC value ever reported for a fruit or vegetable to this date, after converting values of fresh food weights to dry weights. This includes a hydrophilic ORAC antioxidant capacity of 997 micromoles TE per gram, and a lipophilic ORAC antioxidant capacity of 30 micromoles TE per gram. ORAC data comparisons of açaí with other berries and plant foods, however, are difficult because most other ORAC data were not derived from freeze-dried specimens, but rather fresh or air-dried samples were used. Indeed, if açaí is spray-dried or simply frozen rather than freeze-dried, the measured total ORAC score is only about 50 micromoles TE per gram.<ref>Schauss AG, Açaí: An Extraordinary Antioxidant-rich Palm Fruit from the Amazon, Biosocial Publications, Tacoma, WA, 2008, p 86, ISBN 978-0-9814906-3-2</ref> 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. There have been some efforts to raise the credibility of ORAC values. [[ORACWATCH]] (www.oracwatch.org) is issuing a seal showing that the claimed ORAC value has been evaluated by their facility. ==References== {{reflist}} * Commercial ORAC assays and antioxidant information, Brunswick Laboratories Inc., [http://brunswicklabs.com/about.shtml] ==See also== *[[Polyphenol antioxidant]]s *[[Reduction potential]] *[[List of antioxidants in food]] ==External links== *[http://www.oracwatch.org/ Certification of ORAC values by ORACWATCH] *[http://optimalhealth.cia.com.au/OracLevels.htm 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 [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=15186133&query_hl=2&itool=pubmed_docsum]. *[http://naturalantioxidants.org Availability of food-based natural antioxidants] *[http://oracvalues.com Database of ORAC values based on 2007 USDA study, sortable alphabetically or by ORAC level] *[http://www.antioxidants-guide.com/orac_list.html Food Orac List Your Key To Slow Down The Aging Process] [[Category:Nutrition]] [[fr:ORAC (indice)]] [[ja:ORAC]]