Sulfur dioxide (SO2) is an essential additive in winemaking. This chemical largely is used as a food and wine preservative for its antimicrobial and antioxidant properties. It inhibits, and in some cases kills, some yeast and bacteria. SO2 also protects grape must and wine from oxidation by enzymatic and chemical reactions, and therefore from browning and off-odors. With proper additions, SO2 aids in preserving aromas and provides protection against incidental oxygen and microbial exposure. It must be used in conjunction with sound winemaking practices, which include stringent cleaning and sanitation protocols and use of inert gases.