The substance DMDC (also DMPC = dimethyl pyrocarbonate or pyrocarbonic acid dimethyl ester) is an ester of pyrocarbonic acid. The artificially produced substance is approved within the EU as food preservative E 242 (one of the best known brands is Velcorin). It is mainly used in fruit juices and soft drinks as a declaration-free cold sterilant. Dimethyldicarbonate kills harmful beverage pests such as fermentation yeasts by carbomethoxylation of proteins. After addition to the beverage, the agent decomposes completely into the smallest quantities of methanol and carbon dioxide within a few hours, depending on the temperature, and is no longer detectable after this.
According to the EU regulation, dimethyldicarbonate is permitted in wine making for grape must, wine (all quality levels), sparkling wine, semi-sparkling wine and liqueur wine. A maximum of 200 mg/l may be added; the substance must not be detectable in the finished product. Since 2012, the use of this substance is only permitted for semi-dry, sweet and semi-sweet wines (until then it was permitted up to a residual sugar content of 5 g/l). In Austria, however, DMDC may only be used for the lowest quality class of wine. In red wines, it is mainly used as a protection against mice and horse sweat, because it prevents the excessive occurrence of the yeast species Brettanomyces bruxellensis, which causes these wine faults.