From the HBD Archive
From: polstra!larryba@uunet.UU.NET (Larry Barello)
Subject: Re: DMS and counter flow chillers.
Date: 1992-06-29 16:43:59 GMT

Russ Gelinas writes:
> I've got some question that pertain to chillers, hopping, and all
>this sort of stuff we've been talking about. Isn't it a good idea to
>allow the steam from the hot wort to escape to disperse DMS (dimethtyl
>sulfide, the cooked vegetable smell)? If so, do you counterflow-chiller
>users wait a while before you start chillin'? How long is "long enough"?
Per George Fix, in "The Principles of Brewing Science", DMS precursors
have a 45 minute half life at boiling temperatures. DMS is volatile and
is quickly removed in the vapors of your boiling wort. A typical American
2 row malt will have the precursors reduced below the sensory threshold
after 2 or three half lifes. I guess that is why a 90 minute boil is
a good thing. Anyway, the conversion of precursors to DMS halts when
the wort is chilled. So all that is needed is to have the hot wort vented
until chilled.

In my case, I put the lid on my wort until ready to chill (about 10 minutes
waiting for the swirling to stop) and I had a pretty consistent DMS
problem. Since leavign the top off my kettle, I have not had a problem.

- Larry Barello

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