• ✔ KILL WILD YEASTS AND BACTERIA. Potassium metabisulfite is the industry standard for preparing your juice for fermentation.
• ✔ PREVENT OXIDATION IN YOUR WINE. Potassium metabisulfite is the only tool to make sure your wine or cider does not become oxidized after fermentation.
• ✔ KEEP YOUR WINE FROM TURNING TO VINEGAR. Potassium metabisulfite at the right level and the exclusion of oxygen will ensure your wine stays fresh and does not turn acetic.

Potassium Metabisulfite (sulfite / SO2), has several uses in winemaking and cider making because of its antimicrobial and anti oxidant properties.
The most common use of potassium metabisulfite in the wine and cider industries is for killing natural yeast and spoilage bacteria in the juice before fermentation. Using the correct, pH dependent dose will help ensure that your fermentation gets off to a great start when pitching your cultured yeast.

Once fermentation is complete, wine and cider are at risk of oxidation during maturation. Adding potassium metabisulfite at this stage of the process will help to prevent oxidation and allow your vintages to make it to the bottle in their best state without getting brown and becoming flabby.

Exposure to oxygen and acetobacter will cause any wine to turn into vinegar. Prevent this from happening by maintaining adequate sulfite levels in your wine and cider at all times post fermentation. The last thing any winemaker needs is for a prize winning vintage to develop too much volatile acidity.

In addition to the use of sulfites in wine or cider, sanitizing equipment is a common use. By making a more concentrated solution than would be used for adding to wine or cider, equipment can be sanitized. In fact, many winemakers store tools, fittings and gaskets in SO2 solutions to prevent unwanted spoilage bacteria and wild yeast growth when not in use. 

It is important to store your potassium metabisulfite supply in a cool, dry area since exposure to moisture will reduce its efficacy and shelf life. Because of this we package our sulfite in a resealable foil pouch that is impervious to ambient humidity.

Note that the exact amount needed to effectively do the job is determined by the pH of the wine. In addition, it's important to keep in mind that free SO2 levels fall faster in wood cooperage than in glass or stainless.