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108 WINES&VINES November 2016 WINEMAKING WINE EAST O xygen is an important element that can alter the chemical and sensory properties of a wine through oxidation. All wineries need to understand both the impact that oxygen can have on a wine and the criti- cal points in the winemaking process where excess oxygen poses a serious concern or threat. This article, part one in a series, describes oxygen and its effects while looking at the sources of oxygen exposure for wine during the vinification process, bottling and, fi- nally, at the influence of the type of closure on the dis- solved oxygen in wine. The second part of this series will look at a study done by the The Ohio State University's Ohio Agricultural Research and Development Center to determine the dissolved oxygen status in commercial wines at bottling from 14 Ohio wineries. A total of 12 bottles of wine from the 2014 vintage were collected from each participating winery during the middle of the bottling process. Using a NomaSense oxygen analyzer, dissolved oxygen (DO) and headspace oxygen (HSO) were measured at several storage times ending at 126 days after bottling. In addition, the free and total sulfur dioxide and pH were analyzed in triplicate and compared with the DO and total package oxygen (TPO) levels over time. As will be seen in the results of the study at the end of part two, sig- nificant improvements need to be made in reducing wine oxygen levels at the bottling tank and throughout the bottling process for the participating wineries. Sources of DO: vinification The amount of oxygen that a wine acquires during winemak- ing has an impact on its sensory quality. Wines exposed to high levels of oxygen often lose fruitiness and freshness, and develop a brown color. These responses are unwanted in Oxygen Status at Bottling Identifying winery sources for oxidation in Ohio wines By J.F. Gallander, T.E. Steiner, P.L. Pierquet and L. R. Robbins Bottling is a main source of oxygen exposure during the winemaking process.