During vinification, SO2 has historically represented one important tool used by winemakers to control microbiological growth. Due to health concerns (Yang and Purchase, 1985), some wineries have reduced usage dramatically, with a possible increased risk of microbial spoilage.
Acidulated SO2 may be used as an effective sanitizing agent especially for hoses. Because the antimicrobial activity of SO2 is pH dependent (Section 5.2.1), the sanitizing agent (100 mg/L SO2 or 200 mg/L potassium metabisulfite) is usually made up in acidulated solution by inclusion of 3 g/L citric acid. Due to volatility and corrosive properties, SO2 solutions should only be used in a well-ventilated area away from metal surfaces. For the same reasons, employees should be cautioned to avoid direct contact or inhalation of SO2. Although wineries commonly prepare this sanitizer in acidulated, hot water (60°C/140°F), this practice serves to increase the volatility of SO2 as well as to increase safety risks. When not in use, SO2 solutions should be sealed to minimize volatilization.
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