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While not as common as skunky beer or diacetyl off-flavors, dimethyl sulfide is another beer off flavor you’ll likely experience. Dimethyl sulfide, or DMS for short, is an organic sulfur compound that occurs naturally in germinated barley. Of course, germinated barley is is a major component of beer.
DMS is often perceived as a vegetable flavor, like creamed corn or cooked tomatoes, but it can taste like many other foods. Here’s a list of of thing we’ve heard it described as:
- sweet or creamed corn
- tomato sauce or cooked tomatoes
- cooked asparagus
- cooked cabbage
- seafood
Tasty, eh?
That’s because DMS is a common element in the aroma of foods like cooked vegetables, ketchup and seafood. It can be detected by smell without even tasting the beer. Most people are able to detect DMS easily, unlike some off flavors which are harder for the average person to detect without sensory training. DMS comes from 2 sources: naturally occurring in barley and beer spoiling bacteria.
Low levels of DMS can get in any beer. That’s because the DMS from malted barley gets into the beer during wort production. However, most is removed during brewing. Fortunately, the boiling point of DMS is about 99 degrees, so a vigorous, thorough boil of the wort can remove it. DMS is also the result of bacteria that spoil the beer. If the beer is infected, levels of DMS result that are much higher than the DMS the barley contributes. High levels of DMS indicate bacterial contamination during fermentation. This infection can be reduced by quickly cooling the beer before fermenting and by thorough cleaning and sanitation practices by the brewers.
DMS is an off flavor undesirable in most beers, but may be appropriate in some pale lagers and ales, usually German lagers.
Here’s to flawless beer, cheers!