Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 7, 2011
Publication Date: February 10, 2011
Citation: Medina, M.B. 2011. A simple and rapid method for the analysis of phenolic compounds in beverages and grains. Journal of Agricultural and Food Chemistry. 59:1565-1571. Interpretive Summary: Phenolic compounds in plant derived foods have various preventive and disease fighting properties and are important in the maintenance of human health. These compounds contribute to anti-oxidant 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 “total phenolics” of food or beverages are measured indirectly by the standard Folin-Ciocalteau method. There is a need for a direct and accurate detection of total phenolic anti-oxidants in foods that is simple, rapid and inexpensive. A novel method was developed and optimized to detect and quantify phenolic anti-oxidants in beverages and foods. The method consisted of mixing a specific chemical with the samples containing phenolic compounds. In this research, we analyzed different juices, juice drinks, ready to drink teas and fresh fruits. The total phenolic anti-oxidants were measured with the standard method and the novel chemical method. The results showed that the 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 during or after processing. The method can also be used for labeling purposes.
Technical Abstract: A simple, rapid and direct method for detection of phenolics in foods and beverages is needed. The current standard method (Folin-Ciocalteau) indirectly measures the “total phenolics” through the reducing capacity of components of food or beverages. A novel method was developed to quantify polyphenols or phenolic compounds through direct interactions with diazonium salts. This method was improved for detection of phenolics in beverages and fresh fruits. The azo dye was mixed with the samples followed by addition of an alkali. The absorbance was measured at 60 and 90 min at the optimum wavelength of 420 nm. The interactions with gallic acid achieved linearity (R2 = 0.9958 +/- 0.0006 SD) at 90 min. Total phenolics in 45 beverages and 11 fresh fruits were analyzed with the azo dye method and the gallic acid values were compared with Folin-Ciocalteau method. The novel method is simple and inexpensive and can be used to rapidly assess the polyphenolic contents of foods and beverages.