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'''Dimethyl sulfide (DMS)''', sometimes spelled "dimethyl sulphide" <ref name="pubchem"></ref>, is a type of [https://en.wikipedia.org/wiki/Thioether thioether], which are sulfur containing oils with that are generally considered off-putting aromas and flavors in beer <ref>[https://en.wikipedia.org/wiki/Thioether Wikipedia. Thioether. Retrieved 03/01/2016.]</ref><ref name="Anness">[http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1982.tb04101.x/abstract DIMETHYL SULPHIDE—A REVIEW. B. J. Anness andC. W. Bamforth. 1982.]</ref>. The flavor and aroma of DMS have been characterized as being like cooked sweetcorn or tomato sauce. In beer, it is sometimes confused with methyl thiocetate, ethanethiol, and dimethyl trisulphide. DMS in beer originates from malt-derived precursors, S-methyl methionine (SMM) and dimethyl sulphoxide (DMSO), and to a lesser extent can be formed during fermentation by certain microbes <ref name="aroxa">[http://www.aroxa.com/beer/beer-flavour-standard/dimethyl-sulphide/ Aroxa. Dimethyl sulphide. Retrieved 03/01/2016.]</ref>. The flavor threshold of DMS is 30-50 µg/liter. Low levels between 30-100 µg/liter are considered acceptable and even beneficial to some lagers in the United Kingdom (but not in Germany) <ref name="beersmith"></ref> (~25 minutes in), however amounts above 100 µg/liter in lagers are considered offensive even for UK brewers. Ales typically have below the flavor threshold of DMS <ref name="Anness"></ref>. The majority of scientific publication on DMS in beer was done in the late 70's and early 80's. DMS is a common compound found throughout nature, including having an importance in cycling sulfur in ecosystems involving algae and other microbes, hypothesized navigation of seabirds, and is found in many foods such as corn, cabbage, tea, cocoa, milk, wine, rum, beetroot, and seafood <ref name="bamforth">[http://www.asbcnet.org/publications/journal/vol/abstracts/ASBCJ-2014-0610-01.htm Dimethyl Sulfide – Significance, Origins, and Control. Charles W. Bamforth. 2014.]</ref>.
==Production from Malt==
In sour beer, there might be other compounds that make the detection of DMS more difficult. For example, 2-phenylethanol and phenethyl acetate mask the perception of DMS in beer <ref name="bamforth"></ref>. Additionally, some tasters might be genetically predisposed to perceive the flavor of DMS more easily than others.
===Considerations for Raw Ale===
In the case of raw ale, and particularly [http://www.garshol.priv.no/blog/331.html Norwegian/Latvian/Lithuanian traditional farmhouse ales, Finish "sahti", and Estonian "koduõlu"], there is some debate as to whether or not DMS should even be considered an off-flavor. Traditionally these beers were made with lightly kilned malts that were malted by the brewers themselves (up until about 20 years ago), and these malts may have had high levels of SMM precursor. [http://www.garshol.priv.no/blog/304.html Lars Marius Garshol offers his philosophy] on off-flavors in beer in general, which is inspired by writings of Michael Jackson, and makes an argument that DMS may have been considered desirable or acceptable in farmhouse raw ales brewed in certain regions of Europe <ref>Private correspondence with Lars Marius Garshol by Dan Pixley regarding whether DMS should be considered an off-flavor in farmhouse raw ales. 03/10/2016.</ref>.