compound
Dimethyl sulphide
A cooked-sweetcorn compound formed from a malt precursor, driven off by a vigorous open boil.
The full record
Dimethyl sulphide has its own catalogue entry with the detail this page summarises — mechanism, temperatures and what goes wrong.
DMS — A cooked-vegetable note from a malt precursor that a vigorous open boil should have driven off.
Pale, gently kilned malts — pilsner malt above all — retain more of the precursor S-methylmethionine, which converts to DMS during the boil. A vigorous uncovered boil evaporates it; a covered or short boil traps it.
A very low level is considered acceptable and even characteristic in some pale lagers. Anything obvious is a fault.