Where does DMS (dimethyl sulfide) originate in the brewing process?

Dimethyl sulfide (DMS) primarily originates from heated S-methyl methionine (SMM) present in malt during the brewing process. SMM is a compound found in certain malts, particularly pale malts, and is formed during the malting process from the breakdown of proteins. When the malted grain is subjected to heat during the mashing and boiling stages, SMM is converted to DMS.

This conversion typically occurs when malt is boiled or otherwise heated, making it essential for brewers to understand the implications of their boiling techniques. If the wort is not boiled vigorously or if it is cooled too slowly, DMS can persist in the final beer, leading to off-flavors that are often characterized as cooked corn or vegetal notes.

Malt that has been improperly processed or not boiled adequately can result in higher levels of DMS, which can ultimately affect the beer's aroma and flavor profile. Therefore, controlling the temperature and the duration of boiling is crucial for minimizing DMS levels in the final product.