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Off Flavored Beer, Lessons from Scott at Blank Slate

Off Flavored Beer, Lessons from Scott at Blank Slate

Ever drink a beer and think to yourself, hm, there’s something wrong here? Maybe it was a beer you’ve had a hundred times, but this time, it just didn’t taste right. You couldn’t place what exactly it was that tasted off, but it was definitely off. Off flavored beer is an all too common occurrence, one which I have been trying my best to learn a lot more about in preparation for the cicerone exam (you know, that “beer sommelier” exam that you are all bored to tears of hearing me talk about).

Well luckily, a few weeks back, I was having a discussion with my friend Scott over at Blank Slate Brewing company all about my concerns, fears, and potential knowledge gaps for the upcoming exam, when Scott, who happens to be a certified cicerone himself, volunteered to host an off-flavor seminar for myself and a few other bloggers and homebrewers.

Scott is awesome. He first won my favor last year when he let me tour the brewery and answered all of my crazy beer and brewing questions without even knowing me (you can find that post by clicking here). Plus I don’t think I know anyone else who would take hours out of their crazy busy lives, on a Sunday, no less, to teach a few beer nerds about foul, off flavored beer. But, there we found ourselves, yesterday afternoon at Blank Slate, learning all about various beer afflictions.

In attendance were my dear friends and excellent homebrewers Sean and Becky (who I’ve mentioned before in the very popular Electric Brewery post), Ian Hoopes from Beerquest ABV, a great local beer blog, myself and hubby.

Mike took many of these photos since I was focusing on the learning aspect of the evening (thanks hubby!).

I came armed with bottled water and pretzels as palate cleanser. Scott kindly prepared an off flavor study guide and note sheet for us, which we reviewed before starting the tasting portion of the event, which we decided to do blind. I especially wanted to do the tasting blind to assess my baseline off-flavor recognizing skill, but it also made for an interesting game: “Name that Nasty Beer Cause,” if you will.

Alright, brace yourselves people, it’s about to get technical up in here.

The off-flavors that we focused on were the ones most relevant for the examination, and included: DMS, or Dimethyl Sulfide, Acetaldehyde, Diacetyl, Lightstruck (“skunked”), Acetic/Sour, Oxidation and finally, Fusel or Alcoholic.

Once Scott went through the off flavor overview, he disappeared into the cooler to mix up the first samples. A few minutes later, he emerged, tainted beer in hand. We all stuck our noses deep in the beer, and reluctantly took a sip, swirling and swishing to get every taste bud covered.

The first sample was pretty subtle. Not much on the nose to write home about, but after a good sip and swish, and especially in the immediate after taste, came a slight flavor of something fruity, apples!

Culprit: Acetaldehyde, a fairly common off flavor produced by yeast during fermentation. Scott explained that acetaldehyde can occur when yeast is overly stressed, usually because not enough yeast was originally pitched in the cooled wort, which means adding appropriate amounts of yeast is essential to preventing it. Acetaldehyde will typically turn itself into ethanol (alcohol) over time, so aging beer for long enough will help prevent this off-flavor as well. Interestingly, this was the only beer that Scott didn’t have to doctor – turns out Budlight Platinum is the perfect example of the acetyldehyde off flavor, which clearly is done on purpose since the flavor is consistent. Blech. I would not recommend anybody drink this nonsense, unless you too want to taste the flavor of acetaldehyde.

At first, none of us could identify what the off flavor of round two was. It just tasted like crappy beer. Scott ended up having to doctor a little more heavily, but after one more addition of the mystery substance, with just a whiff of the strong buttered popcorn aroma, it became clear what the beer “infection” was.

Culprit: Diacetyl, which is yet another byproduct of yeast during fermentation. Scott added imitation butter flavoring to the beer in order to obtain the diacetyl off flavor. In addition to buttery flavors, diacetyl can also create a slickness on the tongue and a “ropiness” in beer where you can visually see the beer in your glass bend in rope-like shapes. The causes of this off flavor vary, but it can sometimes be caused by under-oxygenating the yeast when you first pitch it (always avoid oxygen AFTER yeast is pitched). In lagers this will almost always be considered an off flavor, while a little bit of diacetyl in an ale can be appropriate. Some brewers will do a “diacetyl rest” where after a few days of fermentation they raise the temperature of the beer for a couple days then decrease back down to reduce the amount of diacetyl production. We have never tried this, but some folks swear by it. Another interesting fact about diacetyl is that some people are blind to it. In fact, three out of the five of us couldn’t smell or taste the butteriness at all. Luckily, I was not one of those people. Phew!

Sample number three tasted like old beer. Old, stale, crappy beer. Mmm.

Culprit: Oxidation. Probably one of the most common “off flavors” of beer. Oxidized beer can taste like wet paper or cardboard, and in some older and higher alcohol beers like sherry or wine. To prevent oxidation in homebrew, make sure to minimize any splashing during transfer from primary to secondary and secondary into bottles or kegs, which can cause oxygen to alter the flavor of the beer. In order to “create” this flavor, Scott poured beer into a new bottle about halfway full, allowing oxygen to fill the rest of the beer, re-capped it and stuck it somewhere warm for a week on its side.

The fourth beer was our control: Genuine Budweiser, which was used as the base for most of the other tainted beers. We ultimately guessed that it was the control after eliminating all the options, though we all agreed that whether it was intentionally tainted or not, the beer was terrible.

Beer sample number 5 had more of a smell than a taste, a strong whiff of overcooked vegetables.

Culprit: DMS (Dimethyl sulfide), which is produced when beer wort is boiled. Technically, SMM or s-methyl methionine is created during grain malting, which is then converted to DMS during the boil. SMM is especially common in lighter malts like pilsner – darker malts are kilned longer which drives away the SMM. Thus, lighter beers are more prone to smells and flavors of DMS which can exhibit themselves as creamed corn, cabbage or stewed tomatoes. A vigorous boil for at least 60 minutes will prevent DMS from being trapped in the beer wort. You should also never cover your boil kettle and cool as quickly as possible in order to make sure any DMS lingering doesn’t become re-absorbed in the wort.

I didn’t even have to taste skunky sample number 6, which was the primary culprit for the disgusted look on everyone’s face in the pictures above.

Culprit: Lightstruck. Chances are, you’ve had a skunky lightstruck beer before. Skunkiness is created when the chemicals in hops are exposed to light, which is especially likely in clear or green bottled beers like Corona or Heineken. Ian forced himself to taste the beer just so he knew exactly what the lightstruck skunked beer tasted like. Blech. His face is priceless though. You’re a brave man Ian!


Sample number 7 was narrowed down to two options.

At first we all had a hard time with this one and all the samples needed to be re-doctored. Subsequently, the beer had a “heat” sensation that could only be explained by one thing.

Culprit: Alcohol (fusel), which is most often caused by a too warm fermentation, or in a higher ABV beer that is not left to age long enough such as a young barleywine. The flavor of the beer tastes of alcohol in an unpleasant way, tasting sharp, hot, or acetone-like. In order to mimic this, Scott dumped a shot of Everclear into the beer before splitting up the sample for each of us.

Last but not least!

Sour, vinegary flavored Budweiser – yum!

Culprit: Acetic off flavors, usually produced by bacteria which infect the beer. This is a common cause of “crap tap” or beer infected from tap lines that are not cleaned often enough. Beer lines should be cleaned at least every two weeks, though many places will not do this. I am 99% sure I had a soured beer at a bar locally and I am PISSED that I didn’t say anything to the bartender. I knew the beer was bad, and should’ve said something. Let’s just say that when a beer you are drinking tastes sour, and isn’t a traditionally sour beer such as a lambic, geuze or otherwise wild fermented or sour beer, the beer is infected. In order to replicate this off flavor, Scott added a bit of vinegar to our beers. Interestingly, some of us thought the vinegar actually improved the beer. Oh Budweiser, you are gross.

To wash all that foul beer out of our mouths, Scott very graciously provided us with a glass of a new, small batch collaboration beer called “Flagship City Mild,” a nice easy drinking Oktoberfest style beer.

Blank Slate Brewing Company Beer

Again, I can’t thank Scott enough for his dedication to beer and beer education, and for being an all around nice guy. And seriously, his beer is EXCELLENT. You can find Blank Slate beer on draft at better beer establishments around Cincinnati.

So now I’m curious, what’s your experience with off flavored beer?


9 thoughts on “Off Flavored Beer, Lessons from Scott at Blank Slate”

  • Awesome post! It’s one thing to taste a beer and think it tastes off, but it’s great to have the knowledge of knowing what isn’t right about it and what caused it.

    I hope there are education events like this held for the public! I just recently found out about the even Scott had done at Whole Foods, unfortunately it was a day late. I wish there was more information about their “beer school” events.

    • Thanks! Totally agree. I wish there were more opportunities for the general public to learn about beer. I haven’t attended any of the beer school events, but am curious.

      Perhaps when I get cicerone certified I could actually collaborate with local business to do some education! There is so much people don’t know about beer, it would be fun to help the cause. Cheers!

  • Love this! I think we’ve all experienced the classic “skunked” beer… Chris and I had some sour-hinted beer at a little brew pub down here. We later figured it must have been the yeast – even the porter was sour. But now I think it was their tap lines! Wow! Also – I did experience a mislabeled keg a few years ago. The Hefeweizen I had ordered arrived a clear, copper color. I instantly said to the bartender that this wasn’t what I had ordered. He was a little wet behind the ears and he checked the tap which he said was right. So I still pushed, explaining that this should be a hazy yellow color. Finally he got the manager and because the keg was mislabeled they both *insisted* that this was the Hefeweizen. I finally convinced them that perhaps they were wrong and had a mislabeled keg when I showed them the brewer’s website with photos of the hefe and their amber. They weren’t rude about it but they certainly should have noticed it immediately (considering the establishment claims to “know beer.”)

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