Author: Marshall Schott

In beer evaluation, one of the most oft cited off-flavors is dimethyl sulfide (DMS), a sulfur compound commonly said to impart a creamed corn or cooked vegetable character in beer. Most brewers are well aware of methods purported to reduce the risk of DMS making it into their beer, for example extended boil lengths and making sure to keep the lid off the kettle. But what exactly is DMS and where does it come from?

The most prominent source of DMS originates from the decomposition of another compound, S-methylmethionine (SMM), which is created during the germination stage of the malting process. SMM being heat sensitive, it easily converts to DMS during the mash. Since roasting and kilning reduce the presence of SMM, brewers tend to be most concerned about DMS development when using larger amounts of very light malts such as Pilsner. For a more in-depth look at DMS, I highly recommend Scott Janish’s excellent article, How To Prevent DMS In Beer.

Undeniably, DMS is real and can impact beer character. Equally as true is the fact humans have some capacity to perceive it in relatively low amounts. I’m not here to question this. Rather, what I find curious is the sheer frequency people note detecting DMS when evaluating beers. Whether in sanctioned competitions or less formal homebrew shares, those three letters are almost certain to be uttered or written by someone, and while I’ve no solid evidence to back this up, my hunch is this collective knowledge of DMS stems primarily from descriptions provided by popular authors and podcast hosts. I know I’ve done it, many times, and I couldn’t help but wonder– how can we be so sure?

For this xBmt series, Brülosophy partnered with FlavorActiV, producers of various off-flavor capsules that brewers can use to help them become better overall sensory analysts.





| PURPOSE |

To evaluate the ability of blind tasters to distinguish between a pale lager dosed with DMS from an unadulterated sample of the same beer.

| METHODS |

I initially planned to use a batch of my own beer for this xBmt and actually brewed 10 gallons of what ended up being what I think is my best Vienna Lager to date. However, as I thought about how I wanted to approach this variable, I realized it’d be prudent not to use a homebrewed beer that could possess a certain level of DMS and instead go with a commercial example know for being clean and crisp. Lauded by my entire circle of brewing mates, Bitburger German Pilsner fit the bill perfectly, so I headed to my local Trader Joe’s to pick some up.

Without lab data, which I can’t find online, it’s hard to know what the actual level of DMS in Bitburger is, but in the years we’ve been enjoying it, that descriptor has not once been used.

FlavorActiV provided me with 6 DMS capsules, which based on conversations with a representative from the company, was enough to dose 32 fl. oz. of beer to above standard threshold levels.

I wanted to ensure the DMS crystals were well dissolved and equally distributed in the beer, so I decided to use the different colored Nalgene bottles I often use when traveling for data collecting, emptying the contents of the 6 capsules into one of them then filling each with 2 cans of Bitburger. I noticed the DMS dosed beer was slightly more foamy than the other, but that dissipated after the 1-2 minutes it took for the crystals to fully dissolve.

The filled and sealed bottles were placed in a small cooler with enough ice packs to keep them adequately chilled until data collection commenced about an hour later.

| RESULTS |

With 32 fl. oz. of beer in each bottle and a serving size of approximately 3 oz per sample per participant, my participant pool would be restricted compared to other xBmts. Even though experience may not effect perceptual abilities, given the variable being tested, it was important to me that most of the participants have at least some familiarity with DMS. In total, 11 people consisting of 4 BJCP Certified beer judges, 3 Cicerone Certified Beer Servers, 1 experienced homebrewer who now brews professionally, 2 craft beer fanatics, and my Miller Lite drinking neighbor participated in this xBmt. All participants were blind to the variable being tested as well as the fact the beer was a respected commercial German Pilsner. Each taster received 1 sample of the DMS dosed beer and 2 samples of the unadulterated beer in different colored opaque cups then were asked to identify the unique sample. In order to reach statistical significance at this sample size, 7 (P<0.05) tasters would have had to accurately identify the DMS dosed beer as being different. Ultimately, only 3 tasters (p=0.77) made the correct selection, meaning a beer dosed with DMS was not reliably distinguishable from a clean sample of the same beer among this panel of participants.

Once all the data was collected, I revealed to tasters that this was an xBmt focused on off-flavors and that at least one of the samples they were tasting had been dosed with a commonly cited off-flavor. After going back through for sniffs and sips, I asked each taster what off-flavor they believed was used for the xBmt, only one person identified DMS, and he happened to be one of the few who was accurate on the triangle test.

My Impressions: I love Bitburger… and I’m pretty sure I hate DMS. From pouring the beers into the Nalgene bottles to cleaning them out the next morning, I was easily able to detect the dosed sample. To me, it absolutely did not have creamed corn character, which I quite enjoy, but rather smelled of overly boiled cabbage slathered in cheap ketchup. Curious if what I was detecting was a function of knowing which sample had the DMS or if I was truly smelling the compound, I participated in multiple “blind” triangles served to me by others. On my first attempt, my buddy asked me to close my eyes then handed me separate cups one by one, lo and behold, I couldn’t pick out the sample with DMS, which I interpreted as confirmation my brain had been playing tricks on me. But then, before opening my eyes, my buddy handed me one more cup and, sure enough, I detected that horrible smell… he’d initially tried to fool me by serving me 3 of the same non-dosed samples.

| DISCUSSION |

Humans are interesting. I don’t fancy myself an expert on our species and cringe a bit when others claim to be. If I’ve learned anything in my 15 years in this profession (psychology), it’s that human beings do weird things for weird reasons, often outside of our awareness. When it comes to the evaluation of beer, I can’t help but believe there’s far more going on than we’re aware of, that our perceptual idiosyncrasies, personal preferences, and past experiences all play a role in what we often think to be objective.

As I observed taster after trusted taster making the wrong selection in the triangle test, my mind began to wonder what could be going on here. After all, I was immediately able to identify the DMS dosed beer in multiple triangle tests, regardless of whether the beer was cold or warm. This was a very unique experience for me, as I almost always perform as well as if not worse than the participants. I was quite befuddled and naturally considered some some potential explanations.

I suppose it’s possible the concentration of DMS in the beer wasn’t high enough, but that seems like such an easy excuse, and I’m personally compelled to trust the manufacturer’s recommendation is sound. The odds seem awfully slim the intentionally dosed beer would contain less DMS than a non-dosed homebrewed beer, and the fact those who did detect the DMS beer seemed to do so rather easily suggests to me it was at least beyond standard threshold levels. Maybe certain people have a sensitivity to DMS, as was posited by a couple of my friends, both BJCP judges who I rely on for honest feedback, and both who were wrong on the triangle test. This being the case, those with the sensitivity should have been able to consistently identify the dosed beer over a series of multiple attempts, which is exactly what happened for 2 of the 3 correct tasters and myself. In the end, there’s really no telling why the results were the way they were, my guess is as good anyone else’s.

Personally, I’m far more interested in the implications that can be drawn from the fact a group of arguably qualified beer tasters were not only unable to identify the presence of DMS in a beer, but couldn’t tell it apart from clean samples. I’ve always assumed this compound was rather easily identifiable, and now I’m left shamefully aware that past DMS comments I’ve made have probably been wrong, that the “creamed corn” character I noticed after intentionally digging so hard for it may have been an acceptable component of the style imparted by ingredients… that my use of regurgitated jargon was likely motivated by my own desire to feel adequate.

I’ve found the extent of my rambling tends to correspond with my level of bewilderment, and while I could pontificate much more about this stuff, I’ll put the brakes on. For the sake of brevity, I won’t address the various contentions I’m presuming some will make against these results. But for those inclined to rely on the shitty palates argument to reconcile the dissonance experienced as a result of these findings, particularly if your only experience with DMS is what you believe you’ve tasted in beer, please consider getting some flavor standards and trying this out for yourself. You might be surprised.

If you’ve ever experienced a DMS dosed beer or even if you think you’ve had a beer with noticeable amounts of DMS, please share your thoughts in the comments section below!

Support for this xBmt comes from FlavorActiV who provide GMP Quality Flavour Standards, sensory panel taster training, and the world’s biggest beverage sensory proficiency schemes.

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