What off-flavor is associated with Dimethyl Sulphide (DMS)?

Dimethyl Sulphide (DMS) is a compound that can impart a distinctive flavor to beer, often described as reminiscent of sweetcorn or cooked corn. This off-flavor typically comes from the thermal degradation of a precursor molecule, S-methylmethionine, which is formed during the malting process. If not adequately boiled, DMS can escape from the wort, leading to its presence in the finished beer.

The characteristic sweetcorn flavor is usually most evident in lagers and can overshadow the intended flavor profile if not managed properly. This is why understanding DMS and its effects on beer flavor is crucial for brewers, particularly in styles that are meant to be clean and crisp, such as pilsners. The presence of DMS is often discouraged, as it indicates a lack of proper boiling or inadequate fermentation conditions, which can lead to off-flavors that detract from the overall quality of the beer.