Changes

'''Dimethyl sulfide (or DMSfor short)''', sometimes spelled "dimethyl sulphide" <ref name="pubchem"></ref>, is the simplest type of [https://en.wikipedia.org/wiki/Thioether thioether] <ref name="Scheuren2016">[http://onlinelibrary.wiley.com/doi/10.1002/jib.301/full Evaporation behaviour of DMS in an aqueous solution at infinite dilution – a review. H. Scheuren, M. Baldus, F.-J. Methner and M. Dillenburger. 2016]</ref>, which are sulfur-containing oils that are generally considered off-putting 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 and C. W. Bamforth. 1982.]</ref>. The flavor and aroma of DMS have been characterized as being like cooked sweetcorn, tomato sauce, celery, or sauerkraut. In beer, it is sometimes confused with methyl thiocetate, ethanethiol, and dimethyl trisulphide. DMS in beer originates from the malt-derived precursors, S-methyl methionine (SMM) and dimethyl sulphoxide (DMSO). SMM is converted to DMS during boiling wort, and to a lesser extent DMS can be formed from DMSO 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>. Small amounts of DMS have also been found in hops, which is volatilized during boiling <ref name="Scheuren2014">[http://onlinelibrary.wiley.com/doi/10.1002/jib.156/abstract Decomposition kinetics of dimethyl sulfide. H. Scheuren, J. Tippmann, F.-J. Methner, and, K. Sommer. 2014.]</ref>. The flavor threshold of DMS is 30-50 µg/liter. Low levels above threshold 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), and maybe some traditional farmhouse ales that are not boiled (see [[Dimethyl_Sulfide#Considerations_for_Historical_Examples_of_Raw_Ale|Considerations for Historical Examples of Raw Ale]]). However, amounts above 100 µg/liter are generally considered offensive for any beer. Ales typically have below the flavor threshold of DMS <ref name="Anness"></ref>. The basis of the understanding of DMS and it's creation in beer was uncovered 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, helping the navigation of seabirds, and is found in many foods such as corn, cabbage, parsley, asparagus, potatoes, beef, Camembert cheese, fish (carp), tea, cocoa, milk, wine, rum, beetroot, black truffles, and seafood <ref name="Scheuren2016"></ref><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>. DMS can be [https://beersensoryscience.wordpress.com/2011/06/02/corn/ confused with a malt-based compound called 2-acetylpyridine (2AP)] which is formed during Maillard reactions and is described as tasting like "corn tortilla"; 2AP has also been confused with [[Tetrahydropyridine#Similar_Compounds|tetrahydropyridines]].

Anecdotal reports of no issues with DMS in these types of beers seem to far outweigh the reports of DMS problems <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/2655174547844076/ Multple MTF members. Milk The Funk Facebook group thread on experiences with DMS in np-boil beer. 05/09/2019.]</ref><ref>[http://brulosophy.com/2015/10/08/update-lab-data-on-pils-malt-boil-length-exbeeriment/ "Update: Lab Data on Pils Malt Boil Length Exbeeriment" on Brulosophy. Retrieved 03/08/2016.]</ref><ref>[http://beerandwinejournal.com/30-min-boil/ "All Grain Pale Ale 30-Minute Boil Experiments" by James Spencer on Beer & Wine Journal. 06/24/2015. Retrieved 03/08/2016.]</ref><ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1243791188982426/ Discussion on MTF regarding DMS in raw ale/no boil/short boils. 03/01/2016.]</ref><ref name="larsblog"></ref>. The specific nature of (or lack of) DMS detection in no-boil/raw ale has not been widely explored by science. There are, however, some explanations that have been proposed. For example, when boiling smaller volumes of wort such as on the homebrew scale there is a larger surface area to volume ratio. This larger surface area to volume ratio allows for more evaporation and volatilization of DMS to occur <ref name="beersmith">[https://www.youtube.com/watch?v=YDBKUCkg8cM Boiling Home Brewed Beer with Dr Charlie Bamforth - BeerSmith Podcast #121.]</ref> (~30 minutes in). Smaller fermenters would also benefit from a larger surface area to volume ratio since CO² from fermentation volatilize DMS. This may account for the general lack of DMS reported in homebrewed and small-scale farmhouse beer.

* Use more highly kilned malts such as 2 row pale malt instead of pilsner malt.* If the pH must be lowered, for example , when [[Sour_WortingWort_Souring#How_to_Pre-Acidify|pre-acidifying the wort before kettle souring]], lower the pH near the end of the boil but before the cooling or whirlpooling process. A higher pH will increase the rate that SMM converts to DMS during the boil, and lowering the pH after the boil but before cooling will slow the rate at which SMM converts to DMS <ref>[http://onlinelibrary.wiley.com/doi/10.1002/jib.49/full#jib49-sec-0018 125th Anniversary Review: Bacteria in brewing: The good, the bad and the ugly. Frank Vriesekoop, Moritz Krahl, Barry Hucker and Garry Menz. 2013.] </ref>.

! Temp°C !! SMM half-life at ph 3.4 (min - minutes; may not be reflect reality) !! SMM half-life at ph 5.2 (minminutes) !! SMM half-life at ph 5.5 (minminutes) <ref name="bamforth"></ref>

* [[Sour WortingWort Souring]]