Practical Winery
65 Mitchell Blvd, San Rafael, CA 94903
phone: 415-453-9700 ext 102
email: Office@practicalwinery.com
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JANUARY/FEBRUARY 2009
WINEMAKING
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 at a level that are cause for concern however winemakers are exposed to higher 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 PMBS, first mix the powder in a small amount of cold wate (about 50 g per Liter, [7oz per gal]), then after the PMBS 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 PMBS 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 PMBS.
Summary
Sulfur dioxide is one of the most effective tools that a winemaker has to protect wine and influence what it will taste like.Decidingwhen and howmuch 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 PMBS 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. This allows you to use sulfur dioxide not only as a preservative but also as a tool to influence your wine style.
The Ripper method works much betterwithwhitewines 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 Va and Vb. The blue color of the endpoint in the reaction is much more difficult to determine in deeply colored red wines as seen in Figures Vc and Vd. 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 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.