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LOW BOOKLET SO2 TECHNICAL Reducing SO2 levels: control of indigenous populations in musts and wines
In France, the permitted total dose of SO2 has Not only because consumers are looking for steadily decreased since 1907, falling from 450 more natural products with fewer inputs, but mg/L to 350 mg/L in 1926. In 1999, European also because of the allergenic effects of this regulation 1493/1999 drastically reduced the preservative. maximum dose to 160 mg/L for red wines and 210 At the present time, no single process or substance mg/L for dry whites and rosés. In 2009 these values can completely replace the use of SO2. were again revised downwards by 10 mg/L. Although their use remains highly controversial, Today, the use of sulfites lies at the centre of sulfites have many advantages that make their use technical concerns. in winemaking indispensable. antiseptic actionofmolecular SO provide novel solutionsto supplement the of sulfites, it clearly appearsnecessary to and thecurrent tendency to reduce theuse Bearing inmindalltheabove observations especially inthecaseofBrettanomyces . appear to have developed resistance, for several years now, somemicroorganisms since theuseofsulfites hasbeenwidespread and wines over the past few years. Moreover, led to aconstant increase inthepHofmusts Global warming andclimate change have the lesssignificantisitsantisepticaction. activity. Thus, thehigherpHofwine, molecular form of SO dominant atthepHofwine. However, itisthe As Figure 2 shows, the bisulfite ion is largely term ‘SO The SO As aresult, inorder to reduce dosesof a majoradvantage. are easyto use, whiletheirlow costis antiseptic properties. Inaddition, they antioxidant, anti-oxidasic and spectrum ofaction. They combine Sulfites have broad a particularly SULFITES The relative abundanceofeach oftheseforms dependsonthepH(Figure 2). dioxide (Figure 1). wines isrequired. interaction withmicroorganisms inmusts and of itsoxidation mechanisms aswell asits To do this, a thorough understanding other. undesirable microorganisms onthe on theonehand, andagainst protective effects: againstoxidation The bisulfite ion When dissolved inwater, ityieldssulfurous acid Molecular 2 , to itisnecessary actonbothits “SO 2 2 ”: refers to several forms ofsulfurdioxide ’ actuallyrefers to several forms ofsulfur H2 HSO S O 2 that exhibits antiseptic that exhibits antiseptic SO 3 3 - +H +H 2 +H 2 2 O 1HSO O 1SO 2 O 1H 2 . 3 2 2 3 - +H SO - +H 3 3 3 O+ O+
MolecularSO pKa pKa