talking DMS in DME

Terrytate · Mar 16, 2014

Hey all. Been reading the forums for a while but never posted. I saw lots of conflict on this issue (especially regarding starters) and had a thought, so figured I might help clear it up. Here is why I think pilsner DME, or any DME for that matter, doesn't have DMS in it. As for my background, I am a Ph.D. Graduate student (5th year) at Boston University in synthetic organic chemistry.

Per Wikipedia (which I use all the time for the characteristics, such as boiling point, melting point, etc, of small molecules):
Dimethyl sulfide is a water-insoluble flammable liquid that boils at 37 °C (99
°F).
This can also be found at Sigma-Aldrich, the walmart of organic chemistry.http://www.sigmaaldrich.com/catalog/product/sial/274380?lang=en&region=US

Simply put, DME has no liquid, DMS is a liquid, therfore DME has no DMS. Common sense tells us that if DMS evaporates at 38 degrees and they are removing water which evoporates at 100 degrees then they also removed DMS.

The same arguement doesn't apply to LME, since it actually is liquid so I can't say there isn't a liquid in it, but if they are removing huge amounts of water which has a boiling point of 100 degrees, then they no doubt distilled off all of the DMS in the process.

I don't see any issues in the arguement, but let me know if you guys see something I'm missing.

-Terry

Beernik · Mar 16, 2014

I agree with your conclusion. However, water evaporates at a lot of temperatures. Vapor pressure = atmospheric pressure at the boiling temperature of the liquid.

DME is is pumped to the top of a tower and atomized by a sprayer into a high temperature dryer (120 - 205C). This causes the water to vaporize almost instantly and the DME drops to the bottom as dust.

Terrytate · Mar 16, 2014

Hey Beernik,
Good to see you agree. I made a starter with pilsen DME with the lid on and started to freak out after I had pitched it.
And that is cool how they make the DME. They probably put that tower under vacuum to lower the boiling points of everything. Then they spray through a nebulizer and the DME is solid by the time it hits the bottom. At least that is how they make on the ton scale all the solid chemicals that we buy in lab. Never thought about it for DME, but I guess it is the same thing, removing solvent to get a powder.
But back to DMS, if they lower the boiling point of water through vacuum then it also lowers the boiling point of DMS. If water is being evaporated, then the DMS is also. And significantly faster than the water since its boiling point is a whopping 60 degrees less. 39 celsius is 102F, which means DMS would evaporate on a hot Texas day.

brdb · Mar 17, 2014

According to Beersmith, evaporating off DMS seems to be more related to its half life versus its boiling point.
"The half-life for DMS is 40 minutes, so half of the DMS will be boiled off in a 40 minute vigorous boil. So if we do the math, a 60 minute boil gets rid of 64.7% of the DMS and a 90 minute boil rids us of 79% of the DMS."
If you use that logic, then that means not all of the DMS is removed simply because it has a lower boiling point than water. However, there is still the issue you brought up about DME having no water content and DMS being a liquid.

Beernik · Mar 17, 2014

DMS is more a problem for all grain than for LME or DME. For LME they use a vacuum environment for evaporating the water at a lower temperature. Both involve an evaporation process so they have low levels of DMS when you add them to your wort.

I don't think you would have much to worry about with a cup full of DME in a starter.

With all grain, both DMS and the precursors for forming DMS are in the malt and made soluble during the mash. So while DMS is boiled off during the boil, it can be recreated in the wort if it isn't cooled fast enough after the boil.

There is a good wiki on it here

DSorenson · Mar 17, 2014

Solid reasoning beernik. Spot on and absolutely why no one has to worry about DMS when working with DME. Concerning the P V T question and your most excellent response: we just covered this topic in thermo and I am stoked to see the principles used for something I am so passionate about.