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United States Department of Agriculture

Agricultural Research Service

Research Project: VINEYARD MANAGEMENT PRACTICES AND THE QUALITY OF GRAPES AND GRAPE PRODUCTS IN THE PACIFIC NORTHWEST

Location: Horticultural Crops Research

Title: Understanding Micro-Oxygenation Technique and the Oxidation of Grape/Wine Polyphenolics: Year 3

Authors
item LEE, JUNGMIN
item TARARA, JULIE
item Ringer, Kerry -

Submitted to: Northwest Center for Small Fruit Research Proceedings
Publication Type: Proceedings
Publication Acceptance Date: December 15, 2009
Publication Date: December 15, 2009
Citation: Lee, J., Tarara, J.M., Ringer, K.L. 2009. Understanding micro-oxygenation technique and the oxidation of grape/wine polyphenolics: year 3. Northwest Center for Small Fruit Research Proceedings.

Interpretive Summary: Wine tannins and color are important red wine quality factors that can be manipulated by grape growing and winemaking practices. Tannin quality in wine is a high-interest research topic. Tannins stabilize wine color, enhance mouth-feel, and can impart characteristics that heighten the quality perception of red wines. This study examined the degradation of grape skin and grape seed tannin oxidation.

Technical Abstract: This study was initiated to better understand the evolution of polyphenolics (focus being proanthocyanidins, also known as tannins). Wine phenolics (tannins, anthocyanins, etc) are crucial factors of red wine that can be altered by grape growing conditions and winemaking practices. Proanthocyanidins play important roles in red wine by stabilizing color and enhancing mouth-feel, which are critiqued qualities of premium wines. By studying the changes that purified compounds undergo in a controlled system (i.e. model wine system, gas doses, etc), it is easier to identify and monitor their progression during winemaking. Controlled oxidation (by continuous oxygenation and UV light) of catechin, purified grape skin proanthocyanidin, and purified grape seed proanthocyanidin that had been dissolved in model wine solutions were compared and monitored. Absorbance was measured at three wavelengths and by phloroglucinolysis, followed by HPLC analysis. The presence of catechol increased the half-life of catechin (monomer), but the opposite was observed in both skin and seed proanthocyanidins (polymers). All monomer and polymer oxidations were dependant on initial solution concentration. As expected, monomer and polymer solutions showed a decrease in measureable phenolics.

Last Modified: 9/29/2014
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