Phenolic Lab - Isolation of Phenolics from Fruit Juices by...

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Isolation of Phenolics from Fruit Juices by Adsorption Chromatography John Goodson Partner(s) : Jessica Highsmith Date Performed: 18 February 2010
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Abstract: The purpose of this study was to observe free-radical scavenging as well as the hydrophobic functions and determine the antioxidant activity in juices. This particular group focused its study on cranberry juice. Introduction: Antioxidants consumed in the diet are absorbed into the body and help to control oxidation of cells and avoid oxidative stress. Juices such as cranberry, pomegranate, and black cherry, for instance, contain large levels of phenolics, an important class of antioxidants in fruits and vegetables. Oxidation, where a loss of electrons by an atom or molecule occurs, can lead to deteriorative effects in quality and nutrition of foods. This reaction, once catalyzed by something such as light, heat, metal ions, hemoproteins and enzymes, becomes a chain reaction where the products of each oxidation reaction go on to cause another oxidation reaction. These products, known as free-radicals, can be inhibited or the reaction slowed by free- radical scavengers that can donate an electron or hydrogen atom. Free-radical scavenger compounds exhibit an antioxidant effect that can retard or inhibit oxidative chain reactions. In order to determine antioxidant activity, phenolic compounds in cranberry juice must first be isolated. A non-polar, amberlite XAD-16 resin column was used to adsorb to the polar aromatic compounds in the juice, including phenolic compounds, and the more polar non-phenolic compounds washed away with water. The adsorbed phenolic compounds were then eluted from the resin using 70% (v/v) methanol. The isolated fraction was then reacted with 1,1’-Diphenyl-2-picryl- hydrazyl (DPPH •) to form a change in conjugation visible as a colormetric change from purple to yellow and measurable by absorbance spectroscopy. Measurements from absorption via spectrophotometry then were used for calculation of the % inhibition of the DPPH • by the phenolics in the isolated juice fraction.
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Objective: To observe free-radical scavenging as well as the hydrophobic functions and determine the antioxidant activity in juices. Materials and Methods : Apparatus: Analytical Balance Spectrophotometer (GENESYS 20) = λ 517 nm Beakers Cuvette (1-cm) Test tubes Fumehood Volumetric flasks Pasteur Pipettes Vortex Spatula Stop Valve Erlenmeyer flasks Extension clamps Glass wool Graduated Pipettes
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This note was uploaded on 06/15/2010 for the course FDST 4080 taught by Professor Pegg during the Spring '10 term at University of Georgia Athens.

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Phenolic Lab - Isolation of Phenolics from Fruit Juices by...

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