Dimethyl dicarbonate

Dimethyl dicarbonate or DMDC is a colourless liquid with a sharp odour. Its primary use is as a beverage preservative or sterilant (INS No. 242), and acts by inhibiting the enzymes acetate kinase and L-glutamic acid decarboxylase [1]. It has also been proposed that methoxycarbonylation of the histidine part of the enzymes alcohol dehydrogenase and glyceraldehyde 3-phosphate dehydrogenase by DMDC inhibits these essential enzymes also [2]. Once it has been added to beverages, the efficacy of the chemical is provided by the following reactions:

• DMDC + H₂O → 2CH₃OH + 2CO₂
• DMDC + ROH → Ethyl methyl carbonate
• DMDC + NH₃ → Methyl carbamate
• DMDC + Amino acid → Derived carboxymethyl

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DMDC is sometimes used as a preservative in wine as a replacement to sulfur dioxide, inactivating wine spoilage yeasts such as Brettanomyces. In the U.S. the FDA approved its use in wines in 1998, with the maximum permitted level being set at 200mg/L, and only if there was less than 500 yeast cells/mL at time of dosage. Usage has also been approved in Germany (since 1978) and New Zealand. The application of DMDC is particularly useful when wine needs to be sterilised but cannot be sterile filtered, pasteurized, or sulfured.

DMDC has also been used to sterilise coffee, tea, cider, fruit wine and mead.