13,602
edits
Changes
no edit summary
====Mashing and Boiling====
During mashing, little small spikes of DMS have been reported. This has been proposed to be due to the volatility of DMS is producedexisting in the malt rather than being converted from SMM. When mashing in a closed system, evaporated DMS condenses and what falls back into the mash. The small amount of DMS that is produced during the mash is volatilized by the early stages of boiling. Decoction mashing also introduces DMS due to the boiling of the mash temperatures, and then by the early stages resulting conversion of boilingSMM into DMS. SMM from the malt, however, is easily dissolved into the wort during mashing <ref>[http://onlinelibrary.wiley.com/doi/10.1002/jib.234/abstract Explanation for the increase in free dimethyl sulphide during mashing. Very little of it is broken down into DMS at mash infusion temperaturesH. Scheuren, K. Sommer and, although slightly more amounts can be converted into DMS during decoction mashing Dillenburger. 2015.]</ref><ref name="Anness"></ref>.
Boiling 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.