Dimethyl dicarbonate
DMDC, Velcorin
A cold sterilant that kills yeast at bottling and then breaks down.
Typical dose
Up to about 200 mg/L, which is also the US limit. Needs metered dosing equipment.
When to add it
At bottling, into filtered wine.
Legal limit
United States limit 200 mg/L (TTB).
Vegan
Not a fining question for this one; nothing animal-derived is involved in a normal addition.
In practice
Sterilises a sweet wine at the filler without heat, hydrolysing within hours into methanol and CO2 at levels well below concern. It is hazardous to handle undiluted and needs a dosing pump, so it is a commercial tool rather than a home one; it is here because a sweet wine's stability is otherwise a sulphite-and-sorbate problem.
Linked faults are the ones this addition either treats or, used wrongly, causes. The fault page says which, and whether it can be undone.
Others in sulphite, sorbate and antioxidants
Potassium metabisulphite
The antioxidant and antimicrobial the whole cellar leans on, and the usual source of SO2.
Sodium metabisulphite
An SO2 source like the potassium salt, but one that leaves sodium in the wine.
Potassium sorbate
Stops surviving yeast refermenting a sweetened wine. A preventer, not a killer.
Ascorbic acid
A fast oxygen scavenger for whites, used only alongside sulphite.