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 steriliser. Dimethyldicarbonate kills harmful beverage pests such as fermentation yeasts by carbomethoxylating proteins. After being added to the beverage, the agent completely decomposes into minute amounts of methanol and carbon dioxide within a few hours, depending on the temperature, and is then no longer detectable.
According to the EU regulation, dimethyldicarbonate is permitted in winemaking for grape must, wine (all quality levels), sparkling wine, sparkling wine and liqueur wine. A maximum of 200 mg/l may be added; the substance may no longer be detectable in the finished product. Since 2012, its use has only been permitted for semi-dry, sweet and 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. Above all, it serves as protection against mice and horse sweat in red wines, because it prevents excessive occurrence of the yeast species Brettanomyces bruxellensis, which causes these wine defects. See also a list under Agents in winemaking.