Issue link: http://winesandvines.uberflip.com/i/235959
w i inneeGM A K IN GG w R O WIN Measuring sulfur dioxide The exact amount of both free and total sulfur dioxide in a wine or must can only be determined by chemical analysis. Two primary methods that are used are known as the Ripper method and the Aeration-Oxidation method. Both methods have limitations and require an investment in laboratory equipment and chemicals and a degree of expertise in laboratory practices. The Ripper method works much better with white wines than it does for red wines. At the endpoint of the ripper reaction, the indicator goes from colorless to indigo blue as seen in a white wine in Figures V-a and V-b. The blue color of the endpoint in the reaction is much more difficult to determine in deeply colored red wines as seen in Figures V-c and V-d. In the Aeration-Oxidation method the endpoint of the titration is not affected by a wine's color and goes from purple to light green, as seen in Figures V-e and V-f. For this reason, the Aeration-Oxidation method is preferred for red wines. If the Ripper method is the only method available, red wines can be diluted 50% before analysis to lower the intensity of the color. Just be sure to double the COOL-FIT® Plus Systems! Your pre-insulated piping solution for glycol installations. results to make up for the dilution. Additionally for red wines, the free sulfur dioxide by ripper usually runs slightly higher than the actual amount. After adding sulfur dioxide, wait 24 hours before performing analysis to allow the free SO2 to stabilize. Working with sulfur dioxide Working with the powdered forms of sulfur dioxide is not a dangerous activity but there are certain precautions that should be taken. Sulfur dioxide at the levels that are found in wine are not high enough to cause for concern however winemakers are exposed to greater levels when they are working with sulfur dioxide solutions. Fumes of sulfur dioxide gas can irritate the throat and eyes so it is always best to work in a well-ventilated place and to use a respirator when mixing sulfur dioxide solutions. When adding KMB, first mix the powder in a small amount of cold water (about 50 g per Liter, [7 ounce per gal]), then after it has dissolved, mix the solution into the wine. Additionally, under highly acidic conditions, the concentration of the more volatile molecular form SO2 is higher, so you should never mix both acid and sulfites together in the same container when they are being added to wine. A better method is when adding both acid and KMB is to first mix and add the acid to the wine and then add sulfur dioxide. A very small portion of the population can have an intense asthmatic reaction when exposed to the fumes of sulfur dioxide, so extra care should be taken for anyone with a history of asthma when working with sulfites. Summary www.cool-fit.georgfischer.com The Unified Wine & 329 Grape Symposium it us VisBooth at www.cool-fit.georgfischer.com 2882 Dow Avenue, Tustin, CA 92780-7258 • Phone (714) 731-8800, Toll Free (800) 854-4090 e-mail: us.ps@georgfischer.com • www.gfpiping.com 60 p racti c al w i ne ry & v i n e yard JANUARY 20 14 Sulfur dioxide is one of the most effective tools that a winemaker has to protect a wine's quality and influence what it will taste like. Deciding when and how much sulfur dioxide to add depends on what stage of winemaking the wine is in and what you are trying to accomplish with the addition. Furthermore, to determine the proper quantity of potassium metabisulfite to use for the addition, you need to know the pH and free and total sulfur of the wine. With any technique used by a winemaker, it is important to have knowledge of the science behind the skill. By understanding the chemistry of sulfur dioxide and what reactions that occur when it is added to wine, you can make decisions that are based on your goals for what you want the wine to ultimately taste like rather than just following a "one size fits all" recipe. PWV