I think DMS is a brewing myth...

[BeaverBarber]

Like the leprechaun, autolysis, and secondary fermenters, I think that DMS is another brewing myth. I think the reason that so many people don't have problems with DMS is because it evaporates at 99 degrees F. (MSDS Dimethyl Sulfide http://www.gaylordchemical.com/index.php?page=msds-dms) So even a slowly cooling wort is still evaporating DMS, and if it's cooling all night long that's just more time to evaporate DMS as long as the wort stays warmer than 99 degrees. Maybe the DMS myth has been perpetuated because some bacteria may give off a flavor that tastes a lot like cooked corn. The main reason for boiling your wort is sterilization. However, it's not for water sterilization; it's for wort sterilization. Many grains obtain bacteria after milling, of particular concern is lactobacillus which can be difficult to kill and can survive the mashing process. (Quantitative and qualitative studies of the microflora of barley malt production http://onlinelibrary.wiley.com/doi/10.1 ... x/abstract) However, a temperature of 140 degrees for just a few minutes seems to be enough to kill Lactobacillus paracasei and Aspergillus niger in Pilsen beer. (http://www.sciencedirect.com/science/ar ... 7404001360). Lactobacillus is everywhere and likes growing at 99 degrees. Maybe it's not the slow cooling of wort causing DMS off-flavors, but the amount of time that a wort has between 99 and fermenting temperature causing a fantastic growth medium for bacteria that is a problem with slow wort cooling? Also some bacteria such as Pediococcus are rarely found in top fermenting breweries and are mostly found in bottom fermenting breweries. (Food Industries Manual. Search the book for lactobacillus: http://books.google.com/books?hl=en&lr= ... us&f=false) Perhaps, this can contribute to more off flavors in lagers? Whatever the case, the off flavors are not likely caused by DMS so we can all stop fearing the DMS boogie-man. Sincerely,

Professor Beaver Barber

[BDawg]

Interesting theory.

What about the claims that (low kilned) Pilsner malt is abundant in S-Methyl Methionine so therefore DMS is more prevalent in beers that use more pilsner malt. That may also support the claim that lagers suffer DMS more.

Thoughts?

[Stinkfist]

I have gotten DMS is a hoppy pilsner I made with 85% pilsner malt that was back when I was using a heat stick to boil my wort and the wort would boil but the max temp I would hit was 208F and I only boiled 60 mins..chilling was not a problem then and I had a fermentation chamber so that was not the issue...so I blame the lack of a strong boil and boil time..

This would be a simple test for you to do just do all the things they say cause DMS and see if you get it..

[BeaverBarber]

It seems from this chart in "Aroma of Beer, Wine and Distilled Alcoholic Beverages"
By L. Nykänen, H. Suomalainen at http://books.google.com/books?id=allg4X ... ne&f=false "search S-Methyl Methionine" that there is more DMS present in lagers than ales, but only in wheat beers does the amount traditionally exceed the flavor threshold of 50-60 micrograms per liter outlined in this book: http://books.google.com/books?id=juanNZ ... or&f=false Was your DMS flavor cooked corn or raw vegetables?

[BeaverBarber]

By the way, the reason I started looking this stuff up is because I just brewed a lager that I couldn't get to boil, what little boil I did get only went for 60 minutes, and it took 24 hours to cool all the way down to a 55 degree pitching temperature. If any beer in the history of time is going to taste like a can of corn, it's the beer that's in my refrigerator right now. I'll post the results of that tasting.

[brewinhard]

Some people have a very high threshold for tasting and percieving DMS while others are quite low. Don't be afraid to have a few others who are knowleadgeable taste your finished lager to see if they pick up any DMS as well. I for one, can only really smell or taste it when there are very high amounts of it in finished beers. Rarely in ales, but most commonly in pale lagers that either had poor boils (too short, or not vigorous enough) or sluggish fermentations.

[BeaverBarber]

I understand. However, much of what we read goes something like "DMS off-flavor: Use the juice from a can of corn and poor it into your light lager." I think anyone can pick that out flavor, but we're talking about something that's very difficult to detect by some and impossible to detect by others. The reason is because there's really only a very negligible amount of SMM left in malt after kilning and that includes lightly kilned malts; although there is more in lightly kilned malts. There are trace amounts of DMS in all beer, but it's negliglible. Most of our off-flavors are due to poor fermentation practices and poor sanitation. As homebrewers, we're not really scientists so we take the words of others who are not really scientists and spread the word like gospel. But we'll see. I have a beer fermenting now that should definitely taste like a can of corn. It might have problems, but I don't think one will be the taste of vegetables.

[BrewChemistinCO]

While I agree that most of the problems are a result of poor fermentation, I don't think you can say that SMM is negligible and therefore so is DMS without analyzing for it. Organoleptic analysis is unreliable at best due to palette variance.

If you look at the boiling points of SMM and DMS, I agree that your logic appears to be sound and that when you break down the SMM at 140F the DMS will evaporate off at temperatures above 100F.

However, when you heat in the presence of oxygen you will break down to both DMS and the oxidized form, DMSO. DMSO has a boiling point of 189F so it needs the boiling temperature to be broken down. From there, yeast have enzymes that will scavenge the oxygen and reduced DMSO down to DMS. (http://aem.asm.org/content/65/9/3915.full.pdf)

Your boil, above 190F, will drive off oxygen, DMSO, DMS and breakdown SMM. As long as you get a significant amount of the SMM, DMS and DMSO driven off in your boil, rapid cooling becomes less necessary. That assumes you have broken down most of the SMM. If that still remains, you will breakdown SMM during the whirlpool, which is oxygenating the wort, and you will produce DMSO. Completion of driving these components off, I would speculate is more a function of boil time than boil "strength." 4 degrees F, from a thermodynamic standpoint, is a minimal difference.

Furthermore, while most homebrewers aren't scientists, some are and so are researchers like Charlie Bamforth. I don't think you can just write off ideas that are part of many brewing texts. Brewing is one of the most widely researched processes in human history.