13,591
edits
Changes
no edit summary
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 wort due 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 (typical brewing conditions result in little SMM going into the fermenter) <ref name="Anness"></ref><ref name="bamforth"></ref>.
DMS is very volatile, and evaporates easily at temperatures below boiling (80°C, for example), and assuming the wort is not in a closed system, will eventually evaporate off even if the wort is not boiling. Scheuren et al. (2016) determined that there is not a significant difference in DMS evaporation in water versus wort, and came up with equations for determining the evaporation of DMS in water using laws of thermodynamics. They also established that the volatility of DMS is the same regardless of the concentration of DMS, and that it is effected by temperature and atmospheric pressure . A larger surface area will allow for faster evaporation of the total DMS present in the wort, but the total DMS present in the wort would eventually be evaporated off despite surface area <ref name="Scheuren2016"></ref>.
{| class="wikitable"