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November 2016 WINES&VINES 109 WINE EAST WINEMAKING most wines, particularly white wines. Since red wines contain high levels of polyphenols (color and astringency), some beneficial chemical re- actions may develop with small amounts of dissolved oxygen. The main substrates for wine oxidation are phenolic compounds. These molecules are connected with two mechanisms of wine oxidation: enzymatic and nonenzymatic (chemical). Enzymatic oxidation occurs very fast and early in the winemaking operation. During crushing and pressing, polyphenolic oxidase activity leads to brown coloration. Also, the resulting wine may have less vari- etal character. Winemakers often prevent enzymatic oxi- dation by using inert gases such as nitrogen and carbon dioxide, adding sulfur dioxide and settling the juice prior to alcoholic fermenta- tion. Studies have indicated that enzyme ac- tivity decreased some 90% with the addition of 50 ppm SO 2 . Since enzyme activity is inhibited, the most important oxidation mechanism is non- enzymatic, chemical oxidation in wines. Along with ascorbic and tartaric acids, phe- nolic molecules are substrates for this un- wanted oxidation process, a slow reaction. Through a series of several pathways and reactions, chemical oxidation leads to the formation of several compounds including quinones, acetaldehyde and hydrogen per- oxide (H 2 O 2 ), a strong oxidizing agent. Often, the aroma and flavor of an oxidized wine are described as being caramel, sherry- like, bruised banana and rancid, to name a few descriptors. To control dissolved oxygen (DO), wine- makers frequently minimize oxygen pickup during vinification and prevent its oxidizing effect by adding appropriate amounts of sulfur dioxide. For the latter, attention is given to specific winemaking operations that include racking, pumping, filtration, tartrate stabiliza- tion and bottling. Studies indicate that bottle filling is a main source of oxygen exposure, with DO levels from 0.2 ppm to 7.0 ppm, and may be responsible for a 70% increase. Other steps potentially contributing oxygen are pro- cesses such as racking, which can have an up- take of as much as 5 ppm oxygen, and filtration, with an uptake of as much as 7 ppm. Besides the above unit operations, two other aspects also influence oxygen enrich- ment: wine temperature and volume. Tempera- ture has an important effect on the O 2 level in wines. It is well known that decreasing wine temperature accelerates oxygen uptake. To illustrate, the solubility of O 2 in water at 50 o F is 15.4 ppm, while at a higher temperature of 68 o F, O 2 solubility is 9.1 ppm. This relationship is decisive in tartrate stabilization, where low temperatures approach 32 o F and DO levels may reach 2.7 ppm or higher in wine. Sources of DO: bottling For wine volumes during bottling, oxygen up- 251 Gambee Road, Geneva, NY 14456 Phone: 315-759-2118 Toll free: 888-234-6752 Fax: 315-789-1848 Email: cjennings@vancemetal.com Website: www.vancemetal.com Quality Rugged 12 gauge, Custom & Stock Stainless Tanks Catwalk Systems • Pump Over Carts • Custom Hoppers, Chutes & Bins PROUDLY MADE IN THE USA KEY POINTS Wines exposed to high levels of oxygen can de- velop undesirable changes in color, fruitiness and flavors. Winemakers often add sulfur dioxide during vinification operations such as racking, pumping, filtration and tartrate stabilization to control oxygen pickup. A second critical time for oxygen exposure is during bottling, especially at the beginning and end of a bottling run. The holding tank should receive special attention, especially for estab- lishing the proper temperature level, using inert gas during wine transfer and avoiding turbulence. The closure type dictates the amount of head- space volume, but headspace oxygen is critical to the dissolved oxygen level in the bottled wine. The oxygen transfer rate also varies by closure type. Adding appropriate amounts of SO 2 can prevent unwelcome oxidation processes as well as browning of the wine. Wine Packaging by Packaging Designed & Manufactured by a Wine Maker, for a Wine Maker 4138 Vineyard Road Stewartstown, PA 17363 Tel: 800-292-3370 Fax: 717-993-9460 Phone: 717-993-2431 Naylor Wine Cellars is a lifetime member of Wine America, Pennsylvania Wine Assoc, Ohio Wine Producers and NY Wine & Grape Foundation WPN is a premier supplier to over 2,000 wineries and wine & spirits shops. 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