SO2 Addition DetailsWhy adjust SO2?
It will keep your wine from turning into vinegar. A winery is not usually a sanitary environment (barrels being a good example), but it's not a problem if you use modest amounts of SO2. The low pH and high alcohol in wine will do most of the heavy lifting involved in keeping things from living in the wine, but there are still some nasties that can ruin wine if the SO2 is not managed effectively.
To fully understand what levels of SO2 you should have in your wine, you'll need to know your wine's pH as well to figure out the molecular SO2.