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Extract and DMS

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In the process of making malt extract, wort goes through a boiling process (albeit a low temp, low pressure boil) to remove water from the wort and concentrate it into extract.  Does that process drive off DMS in the resulting extact?  In other words, does extract need to be boiled the same as all-grain wort in order to avoid DMS in the finished beer?

That's a great question, Gary!  I have no absolute knowledge or evidence, but a SWAG would be that extract manufacturing removes the SMM, which is the precursor to DMS.  It sure would be great to have some real evidence, though.

What I would be concerned with is the extend to which DMS-P or SMM is converted to DMS during the extract production. Once DMS is formed, it is quickly evaporated especially since extract production evaporates all or most of the water. The remaining DMS-P concentration is a function of initial concentration (determined by the malt that was used), temperature and time and while I'm not an extract manufacturer, if I were one my first goal would be to minimize the energy used to make the extract. Essentially this means that I would minimize the boiling that is necessary.

As a result I would expect that there is a need to boil extract to make sure the amount of DMS precursor in the wort at flame-out is sufficiently low that you won't get excessive DMS formation between then and cooling. The amount of boiling necessary should however be less than what you would need for a comparable AG batch.

So much for the theory. I have little practical experience with using extract.


Maybe we can ask the folks at Briess what the SMM level is in their pilsener extract (the lightest stuff I've found).
In my practical experience, I've found that an hour boil is fine (i.e. no DMS off-flavors) when I do extract batches.

I seem to remember a Jamil show where that topic was discussed and the advice was that for extract batches, an extended boil wasn't necessary to drive off the SMM.

No science here, but I went through three 50 pound bags of Briess Pilsen DME plus countless other little bags before I made the switch and never had an issue and never did more than a 60 minute boil.


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