When Good Beer Goes Bad

Skunked Beer

By Sara Hancock

The more you delve into the world of craft beer (i.e. the more you drink) the more familiar you become with the spectrum of styles and tastes out there in the beer world. Some tastes are good and some not so good and then every once in a while, when a blue moon rises, the magnetic poles reverse, and your house plants die, you get something a little …well …off. Not off in the way I sometimes feel like my hop heavy beers taste like lilac soap but off in the way that your beer smells and tastes like rotting vegetables or rubbing alcohol. Before I took my home brewing course I would have merely written off said ales as crappy beer I don’t like but now I realize that when things go wrong in the brewing process there a specific chemical changes that result in your beer tasting ‘off.’

Sampling beer

For those beer drinkers who have not yet transitioned into beer brewers (just you wait, you will get there soon enough) there exist off-flavour kits, which allow you to intentionally contaminate your brew. Yes, I know, I have officially reached Level 8 Beer Geek when I seek out spoiled brew but this can be an amazingly educational endeavour that actually enhances your overall beer drinking lifestyle. Ever send back a beer in a pub? Me neither, mostly because I could not really articulate what was wrong. Think this type of liquid insecurity ever happens to wine geeks with their uber-sophisticated terminology? No, it does not; they can send back a snifter with the best of them. So what are we afraid of beer geeks, get your geek on and learn to embrace the uglier side of beer.

Intentionally spiking samples with off-flavours can help with the recognition of their characteristics

This diatribe segues nicely into my recent participation at Legacy Liquor Store’s ‘Off-Flavour’ Beer Tasting (luckily not a beer pairing). Graham With from Parallel 49 Brewing was our instructor, and the ever insipid Coors Light was our unfortunate guinea pig. Opting to ease us in with samples of seven potential off-flavours, instead of the palate destroying twenty-one off-flavour kit, we got one control glass of Coors for comparison and then quickly work our way through the seven deadly beer sins.


Butter Diacetyl Buttery or oilyFlattens out the beer

Urine-like nose

Yeast begins to break down the diacetyl after the sugars ferment.
Green Apple Ethyl Acetate Unripe fruitPungent nose  
Banana Isoamyl Acetate BananasOther fruits A yeast by-product from too high fermentation temperatureDesired in certain white or wheat beers
Creamed Corn and Cabbages Dimethyl Sulphide (DMS) Canned vegetables (tin taste)Cabbage

Tomato juice

Skunky (Light Struck)   Rancid noseCorona flavour Left your beer in the sun too longClear bottles
Oxidized   CardboardLacquer


Infected   Band-Aid, plastic, medicinalSour


Acetic Acid

Poor sanitation at any stage of the brewing, bottling, tapping or serving

Sampling beer - it's a tough job, but someone's got to do it
Beer Flavour Wheel (from http://brewiki.org/BeerFlavours)I found this to be a really great opportunity to taste some of the things that can go wrong with beer. Some of the off-flavours were hard to pin point for me like the Diacetyl but generally it was pretty darn easy to tell when something was wrong. Most often the nose was a dead giveaway with some of the beers becoming so pungent you could barely drink them! Coors Light never tasted better than it did at the end of this evening. One thing that I wanted to ask about was visual changes produced through any of this chemical missteps but the set-up was not very conducive to getting any sense of dialogue going. I really wish this had taken place in a smaller venue where you could get a sense of what your table-mates were tasting/smelling as well. I also wish we had taken a bit more time to go over the different off-flavours, the whole tasting felt hurried. Another issue for me was how applicable this knowledge will be to craft beers, which generally differ significantly in flavour profile from Coors; could I discern green apple in a robust stout or a triple? Will the medicinal qualities of a double IPA negate any canned veg? Nonetheless, very worthwhile event and I think I may just purchase myself one of these kits and replicate the evening with a smaller group of dedicated (and brave) beer geeks.



Posted under Uncategorized

This post was written by Sara H. on September 20, 2012

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3 Comments so far

  1. Marty Nachel September 21, 2012 8:41 am

    Not to be a troll, but I couldn’t help noticing some questionable information -particularly in the grid section under the column labeled “Tasting Notes.”

    Diacetyl is universally registered as buttery or butterscotchy. I’ve never personally experienced –or heard anyone else’s experience, of a “urine-like nose.”

    Ethyl Acetate is an apple aroma and flavor that is often the result of unfinished or interrupted fermentations. It’s all about apple (usually green)- not any other fruit character.

    Dimethyl Sulfide is usually experienced as creamed corn or canned corn. It has absolutely nothing to do with the taste of tin; this would fall under a different descriptor: metallic.

    Lightstruck means that a beer has been damaged by light. The damage manifests itself as the smell of a skunk. I suppose that qualifies as “rancid”, but the only correct way to describe it is skunky. And this is most often an aroma, as opposed to a taste.

    Oxidation in beer is at first papery, then cardboardy. In well-aged, high ABV beers it can often be sherry-like. I’ve never experienced lacquer or woodiness in an oxidized beer.

    Infected –as it’s meant here– is soured and acidic/acetic. the other descriptors- “band aid”, “plastic” and “medicinal”, describe an entirely different type of off-aroma and flavor known as “phenolic.”

  2. Chezz September 21, 2012 12:23 pm

    Sara — Thanks for all that good info. The part that disappointed me is “Ever send back a beer in a pub? Me neither, mostly because I could not really articulate what was wrong.” Yes, I certainly have sent back beer in pubs (and returned beers to stores), and so have many other discerning drinkers, and so should you. You do not have to know exactly how to describe the flaw in chemical or poetic terms. Any pub is happy to replace your beer if there’s something wrong with it, just as a restaurant is happy to replace your meal. They need to know something is wrong with the beer. You are doing a public service, helping the pub and the other customers. Don’t be a wimp and sit there drinking a bad beer, please.

  3. Sara October 1, 2012 2:32 pm

    Hi Marty, Thanks for adding some clarity to the off-flavour descriptors. I should have mentioned that I included the terms being used by various tasters as we sampled the ‘off’ beers. While they may not have been accurate it was interesting to note that people had different interpretations of the aromas and flavours. I am sure it takes more practice and beer knowledge to correctly identify what went wrong. Since we were a group of newbies trying out an off-flavour kit I wanted to highlight our initial thoughts no matter how odd! Cheers.

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