DMS formation and evaporation.

[BrewStooge]

Hi all, quick ? on the DMS and any posibly any ther formed-in-the-boil compounds.

The short version: if heating a pot covered and then boiling uncovered is there any reason that DMS shouldn't evaporate off as normal (ie: would it bind somehow when heating by being covered)?

The long version/reason, I recently picked up a 8 gallon SS kettle to do full boils, but still use the stove inside by putting it on 2 burners at once. Now I'm working out the making of a pale lager next weekend or two, so it wouldn't kick out as much during primary as a fast moving ale from what I know. With this kettle being used as it is it takes a good hour or more to really get boiling when left open so I was considering leaving the top on to get it up to temp and removing to work from there once it was. I haven't had any corn beer yet, but thought I'd put this out before doing this batch to keep it that way.

 

[Edcculus]

If you are using a significant amount of pils malt in your recipe, just make sure you account for a 90 min boil. Leaving the lid on while heating shouldn't be a problem. DMS has a half life of something like 40 min, so 90-100 min boil gets it down to very insignificant levels.

Also, FYI, DMS is not formed during fermentation, so the ale/lager thing doesn't matter. DMS is formed because malt, primarily lightly kilned (IE Pilsner) malts contain a substance called SMM. SMM is a precursor to DMS. Under heat, SMM will break down into DMS. Since DMS is very volatile, a good rolling open boil will get rid of it all. Finally, chilling quickly to under 140 is another key to keeping DMS levels down. When you take the wort off the boil, it is still hot enough to break SMM down into DMS. The problem is that you are no longer driving the DMS off with a hard boil.

 

[BrewStooge]

Good deal, no pils in the brew but heating w/the cover would certainly make it a bit easyer at this point. Actually the wording was a bit off re reading the post too. I was reffering to the primary ferm getting rid of some of it with the co2 flowing rather than forming it but since lagers are a bit less active it's not as likley to cause any real reduction. Thanks.