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Methods for Calculating SO2 WineEast and bottling. The use of SO2 I n the first part of this article about the use of SO2 the functions that SO2 and looked at the use of SO2 , we reviewed performs in the process of making wine before and after fermentation. This article covers ways to monitor and adjust SO2 during aging ment are a pH meter and some method of determining SO2 are two primary groupings of equipment for the analysis of SO2 content as well. The two most important pieces of lab equipment for SO2 manage- . There : wet chemistry and instrumental, and there are two analytical procedures to determine the SO2 Probably the most common analytical procedure used in small wineries to determine SO2 is the Ripper method. The wet chemistry method uses simple glassware and relatively common reagents. The procedure can be found in any winery lab manual. Its greatest shortcoming is in finding an endpoint in red wines. In dark red wines, the wet chemistry method is virtually useless. It also suffers from interference from other naturally occurring wine components (phenols) and additives (ascorbic acid, copper), so your reading will be artificially high. The instrumental analysis for the Ripper methodology is per- formed by a mini-titrator. Using simple laboratory equipment, you add the same reagents as the Ripper method, but instead of determining the endpoint with your eye, the onboard calcula- tor measures the endpoint determined by an ORP electrode (Oxidation/Reduction Probe). This considerably reduces the EasternWineLab_Mar09.qxp 1/22/09 9:47 AM Page 1 EASTERN WINE LABS Serving the Analytical needs of East Coast Wineries WWW.EASTERNWINELABS.COM Ph 609-859-4302 Cell 609-668-2854 chemist@easternwinelabs.com AOAC Member endpoint confusion of the manual method. The cost is several hundred dollars. Another way to analyze for SO2 is to use reflectance spectros- copy and various test strips. The initial cash outlay is higher than wet chemistry but about the same cost as the mini-titrator on a per-test basis. The equipment can be used for a wide variety of analysis including malate. The biggest limitation is obtaining fresh analytical strips and the need for refrigeration to store them. Aeration-oxidation is another affordable wet chemistry alterna- tive. Unlike Ripper, it avoids the interference of ascorbic acid, copper and phenols. Since the SO2 is volatilized out of the wine sample into a clear trapping solution, titration endpoints are easy to see even with red wines. Cost per test is minimal and takes about 15 minutes. The A/O method is the gold standard for SO2 analysis. Whether you like this method or can tolerate the Ripper method with the mini-titrator, you are still tied to your procedure or your instrument for 15 minutes per test. A slightly more expensive option is a more upscale titrator, which will perform many other titration-based analyses. These can save hours per day if you are running numerous tests, and they can directly transfer the data to a PC. These titrators sell for between $5,000 and $10,000. After the reagents are added, the instrument determines the end- point and then records the data in a data file. These instruments can also run the titration portion of the A/O method. In the long term they may reduce the cost per analysis due to lower reagent costs. Another popular tool for SO2 vacuum tube that utilizes a reverse titration. The instruments are fast, handy and easy to use, but they lack precision and are of marginal utility for red wines. Whichever laboratory procedure you select, you will learn to factor its particular idiosyncrasies into your operation. 66 Wines & Vines JUne 2011 during aging Wine East HIGHLIGHTS: • A winemaker in new York's Finger Lakes region explains how to measure and adjust sO2 well as before and after bottling. • in wine during aging as Methods discussed include the Ripper method with wet chemistry and mini-titrator, the aeration-oxidation method, reflectance spectroscopy and upscale titrators. • The article explains how to correlate molecular sO2 free sO2 and discusses their important relationship to pH. and Winemaking Part 2 of a two-part series covers sulfur dioxide additions during aging and pre-bottling By Chris Stamp determination is a small, single-use