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During mashing, little DMS is produced, and what is produced is volatilized by the mash temperatures, and then by the early stages of boiling. SMM from the malt, however, is easily dissolved into the wort during mashing. Very little of it is broken down into DMS at mash infusion temperatures, although slightly more amounts can be converted into DMS during decoction mashing <ref name="Anness"></ref>.
Boiling has and cooling have the most effect on levels of DMS in beer. At boiling temperatures, SMM is reduced to DMS. Wilson & Booer showed that SMM's [https://en.wikipedia.org/wiki/Half-life half-life] is about 35 minutes at a pH of 5.4, meaning that it takes ~35 minutes to reduce half of the SMM present into DMS <ref name="Anness"></ref>. pH plays a role in the reduction of SMM to DMS, with a higher pH reducing the half-life of SMM. Dickenson showed that at a pH of 5.2 and in 1.060 gravity wort, SMM had a half-life of 38 minutes, but at a pH of 5.5 the SMM has a half-life of 32.5 minutes <ref>[http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1979.tb03914.x/abstract THE RELATIONSHIP OF DIMETHYL SULPHIDE LEVELS IN MALT, WORT AND BEER. C. J. Dickenson. 1979.]</ref>. The half-life of SMM doubles for every 6°C cooler, meaning that at 95°C the half-life is ~70 minutes(see the table below). During the boil, the converted DMS is evaporated off due to its low boiling temperature of 37.3°C <ref name="pubchem">[https://pubchem.ncbi.nlm.nih.gov/compound/dimethyl_sulfide#section=Odor Dimethyl Sulfide. PubChem. Retrieved 03/02/2016.]</ref> and the convection currents of the boil. However The largest contribution of DMS from SMM is after boiling the wort, and during the chilling process. SMM continues to breakdown into DMS after boiling and before the wort is completely chilled. DMS formed during this time is mostly retained in the wortdue to the wort being still, especially in a closed cooling system where evaporation is prevented completely. Once the wort reaches a temperature of 80-85°C, the decomposition of SMM into DMS is greatly reduced <ref name="Anness"></ref>. It has been shown that a longer boil will help decompose the SMM and drive off DMS <ref>[http://onlinelibrary.wiley.com/doi/10.1002/j.2050-0416.1979.tb06845.x/abstract CONTROL OF THE DIMETHYL SULPHIDE CONTENT OF BEER BY REGULATION OF THE COPPER BOIL. R. J. H. Wilson andC. D. Booer. 1979.]</ref>, however if the level of SMM in the malt is high (3-8 µg DMS equivalents/g malt) and more than 50 µg DMS equivalents/liter of SMM survives the boil, then reducing the time in the whirlpool where the wort sits above 80°C can help reduce the amount of DMS in the finished beer. SMM that is not decomposed into DMS during the boil/whirlpool and survives going into the fermenter is not metabolized by yeast, but is also not decomposed into DMS (most brewery typical brewing conditions result in little SMM going into the fermenter) <ref name="Anness"></ref><ref name="bamforth"></ref>. {| class="wikitable"|-! Temp°C !! SMM half-life at ph 5.2 (min) !! SMM half-life at ph 5.5 (min) <ref name="bamforth"></ref>|-| 100 || 38 || 32.5|-| 94 || 72 || 65|- | 88 || 152 || 130|-| 82 || 304 || 260|-| 76 || 608 || 520|-| 70 || 1,216 || 1,040|-| 64 || 2,432 || 2,080|-|}
===DMSO Precursor and Effects of Fermentation===
[http://www.garshol.priv.no/blog/331.html Raw ale], also referred to as "no-boil", is a method of wort production that involves not boiling the wort, or perhaps by some definitions, very short boils <ref name="larsblog">[http://www.garshol.priv.no/blog/331.html Raw ale. Lars Marius Garshol. Larsblog. 06/05/2016. Retrieved 03/02/2016.]</ref>. Although mainly a historical method of brewing, this style of brewing has recently become popular in the production of [[Berliner Weissbier]] and other styles of beer using [[Sour_Worting|sour worting or kettle souring]] methods. Many recipes for these styles of beer call for pilsner malts to be used, which can contain higher amounts of SMM precursor. An often asked question about no-boil/raw ales and wort boiled for 15 minutes or less is: are there concerns about DMS production?
Anecdotal reports of no issues with DMS in these types of beers seem to far outweigh the reports of DMS problems <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 helps to volatilize DMS. This may account for the general lack of DMS reported in homebrewed and small-scale farmhouse beer.
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.
===DMS Prediction Models===
Equations have been established for estimating how much DMS will be converted from SMM during boiling, and how much SMM will be converted to DMS during cooling the wort after the boil. These equations are well explained in [http://www.amazon.com/Principles-Brewing-Science-Serious-Issues/dp/0937381748 "Principles of Brewing Science: A Study of Serious Brewing Issues", by George Fix, 1999, Pgs 89-93]. One thing to keep in mind is that the equations assume "typical" brewing practices, which include boiling the wort at some point. Because of this, the equation for how much SMM is converted to DMS during cooling may not reflect no-boil wort accurately. Let's look at some examples of the equations from "Principles of Brewing Science: A Study of Serious Brewing Issues": First let's look at an example that should accurately predict how much SMM is in a given batch of wort, and how much of that SMM is converted during an 82°C no-boil pasteurization rest at 15 minutes. Assuming a given pilsner malt has 6 µg of SMM per gram, and the malt concentration is 200 g/L, the SMM content can be calculated: <code>Total SMM = 5 µg/g x 200 g/L = 1,000 µg/L</code> The half-life of SMM at 100°C is ~40 minutes, but since we are not boiling then the half-life of SMM at 82°C is ~300 <ref name="bamforth"></ref>. Time also has to be considered, but since the heating up time period would make the equation unwieldy, it is suggested to add the heating up time to the "boil" time (To door for us, "pasteurization" time)<ref name="zinder"></ref>. If it takes 20 minutes to heat up the wort, and it is held at 82°C for 15 minutes, then that gives us 35 minutes. With the time and half-life values, we can predict how much SMM will survive the heat pasteurization and how much will be converted to DMS: <code>SMM left over = 1,000 µg/L x 2<sup>-(35 min/300 min)</sup> = 1,000 x 2<sup>-0.12</sup> = 1,000 x 0.92 = 920 µg/L </code> and <code>DMS created = 1,000 µg/L - 920 µg/L = 80 µg/L </code> As expected, a high amount of SMM survives (920 µg/L) the 82°C heat pasteurization, and a relatively low amount of DMS is created (80 µg/L). The example in "Principles of Brewing Science: A Study of Serious Brewing Issues" uses the same SMM value in the malt, but with a 90 minute boil 210 µg/L of SMM is left over after the boil, and 790 µg/L of DMS is created during the boil. During boiling the created DMS is evaporated off, but during heat pasteurization the DMS is retained in the wort. The next equation determines how much SMM is converted to DMS during cooling, and this amount is considered more important because it is mostly not evaporated off (especially in a closed cooling system). This equation, however, uses an average between the boiling temperature and the final chilling temperature. This model has proven to work well assuming normal brewing procedures which assume the wort is boiled, but cannot be used for wort that is not boiled. This is because the half-life of SSM is doubled for every 6°C cooler:
===Considerations for Historical Examples of Raw Ale===