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ARS Home » Northeast Area » Wyndmoor, Pennsylvania » Eastern Regional Research Center » Residue Chemistry and Predictive Microbiology Research » Research » Publications at this Location » Publication #258429

Title: Determination of the total phenolic anti-oxidants in superfoods and beverages by a new chemical method

Author
item Medina, Marjorie

Submitted to: Journal of Functional Foods
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/28/2011
Publication Date: 3/29/2011
Citation: Medina, M.B. 2011. Determination of the total phenolic anti-oxidants in superfoods and beverages by a new chemical method. Journal of Functional Foods. 3:79-87.

Interpretive Summary: Phenolic compounds in plant-derived foods have preventive and disease fighting properties and are important in the maintenance of human health. Polyphenols contribute to antioxidant properties of foods and beverages, and are essential in the human diet. Food and beverages containing high anti-oxidant properties are popular today but the consumer is often mis-informed on the phenolic anti-oxidant content of the products on the store shelf. The standard method for measuring “total phenolics” by the Folin-Ciocalteu (FC) test is not an accurate measurement for total phenolics in foods or beverages where the phenolics are measured indirectly. There is a need for a direct and accurate detection of total phenolic anti-oxidants in foods that is simple, rapid and inexpensive. We have developed a novel method to detect and quantify phenolic antioxidants in beverages and foods. The method consisted of mixing a specific chemical with the samples containing phenolic compounds. In this research, we measured the total phenolic content of “super foods” and compared the results with the FC standard method. The results showed that our novel method resulted in higher phenolic values than the standard method. The novel method is simple, rapid and inexpensive costing less than a penny per test, and can be used to rapidly measure the phenolic anti-oxidants in foods and beverages before, during or after processing. Results from this method can be used for labeling purposes.

Technical Abstract: An accurate chemical method for detection of phenolics in foods and beverages is needed. The current standard method (Folin-Ciocalteu) indirectly measures the total phenolics. A novel method was developed to quantify polyphenols or phenolic compounds through direct interactions with Fast Blue BB azo dye in an alkaline medium. measured the absorbance at 420 nm after 90 min. The interactions with gallic acid (0 – 500 ug.mL) resulted in R = 0.9979 (+/- 0.0006 SD) linear correlation with limits of detection of <10 and limits of quantification of 10 ug/mL in 12 trials. Total phenolics (gallic acid equivalent, GAE) in beverage samples had mg GAE /100 mL of 168–1868 with FBBB assay and 70-1390 with F-C assay in juices and juice mixes; and 84–660 (FBBB) and 26-207 (F-C) in fermented grape juice. Solid samples were extracted with 70% ethanol and the GAE values (mg/100g) in fresh fruits were 37–1291 (FBBB) and 21–315 (F-C); and 337–595 (FBBB) and 399-1036 (F-C) in dry fruits. The freeze-dried acai powder had 10,000 and 3000 mg GAE/100g by FBBB and F-C, respectively. The FBBB:FC ratios ranged from <1- 4.8. The novel method is simple and inexpensive and can be used to rapidly measure the polyphenolic content of foods and beverages prior to, during,or after processing.