Sunday, September 30, 2018

Sensory Evaluation Session: Off Flavors

As much as I really enjoy living in my little town on the Eastern Shore, I do miss the beer culture of a city. It's not that there aren't great cities with great beer cultures nearby, but most of the things I'm interested in--mostly homebrewing club meetings, seem to take place on a weekday night when a three hour round trip won't really work for me.  So I was THRILLED when I saw a guy post a sensory evaluation session on a WEEKEND when I didn't have any real plans. I dropped the guy a line a few weeks ahead of time, got a seat, and was ready for a road trip today.

If you're not familiar with a sensory evaluation, it's a bit of a tune up for your palate. When you taste a beer, it's almost always an amalgam of flavors, yeast, hops, malt, process all mixed up and hard to untangle. So a sensory evaluation is a series of concentrated flavors added to nearly-flavorless beer (miller high life light, in this case) that highlights the flavor in question. You get the flavor by itself, in isolation, and writ very large. That way, you're better able to recognize the flavor in a more complex beer. It's a bit like hearing a symphony and being told there's a oboe involved, but you don't know what an oboe is so you can't pick it out. But then you hear the oboe solo, and you can't help but hear the oboe for the rest of the piece.  It's been more than six years since I've done a sensory evaluation, so it was about time for a tune-up. 

Unfortunately, it's especially useful for off-flavors...flavors that aren't supposed to be in the beer in the first place, often because they are awful. Some of those flavors are appropriate in some beers, but some are inappropriate in any situation except black-site interrogations that shouldn't be allowed at all.

Being a huge dork, I brought a notebook, and thought I'd expand on the entries while it's still fresh.  One interesting thing to me is that some flavors are highly objectionable to some people, while other people barely notice it, or even enjoy it.

Grainy - This is essentially excess tannins, usually from oversparging.  There's not really an aroma, or even a flavor, component to this, but you do end up with the drying sensation you get from overbrewed tea on your tongue and the inside of your cheeks. I have definitely had this in a few beers, most notably in some beers I've made with second runnings off the mash from a high-gravity beer.  I remember this over-brewed tea character made those beers seem drier than they would have been, and thinking it wasn't totally unpleasant.  This was very different from my reaction to....

Papery - This is the wet-cardboard flavor from an oxidized/stale beer.  For me, nothing was worse than this flavor. According to our flavor guide, this was supposed to be similar to grainy, but I had diametrically-opposed reactions.  My stomach did a backflip just smelling this one, something that didn't even happen for the infamous baby-vomit (see below).

Earthy - You ever get some garden soil in your mouth? That's pretty much what this tasted like.  No real aroma here, but the flavor is soil, worm castings, beets, fresh bag of compost, etc.  I can see this being an attribute to some beer, but not at this concentration. Usually the result of overly mineral brewing water.

Metallic - About what it sounds like and usually resulting from too much iron in your water, not passivating your stainless brewing gear, and other situations where you've basically managed to get rust in your beer.  On tasting, my thought was to decide whether this reminded me more of drinking blood or licking a nail...not my favorite flavor.

Lactic Acid  - This was pretty straight forward. Lactic acid is produced by a number  of bacteria, known as LAB (get it?) and, interestingly, by certain yeast strains (previously a controversial statement, but now pretty much confirmed?).  In any event, at first it's not bad--like lemon juice, but there's a sour milk flavor that I find really unpleasant in this situation. That's interesting to me because 1) I actually like a number of beers produced with LAB and 2) I drink buttermilk straight.  Clearly, I don't usually mind lactic acid, but there was an afternote here that turned my stomach.

Acetaldehyde - The classic "green" beer, apple jolly rancher flavor of a fermentation that hasn't been allowed to complete and/or stressed yeast.  I feel like I taste this in Budweiser. Not the most objectionable flavor here, but unpleasant and, apparently, a potent carcinogen.  Wish I'd heard that last bit before drinking most of my sample.

Dimethyl Sulfide (DMS) - The product of beers made from low-kilned malt that have either 1) not been boiled properly or 2) not been cooled quickly enough.  Lots has been written about how it's produced and how to avoid it, but the interesting thing to me is that I don't experience the creamed/canned corn flavor that a lot of folks got. To me, it tasted like the air in a house where cabbage was cooked the day before, or a beer made with a portion of water from cooked cabbage. 

Diacetyl - Accent on the "ass." This is the buttery compound that's important, in small amounts, to some style, but was extremely unpleasant at this concentration.  Several yeasts/processes result in the yeast dropping out before they can process this, and so the way to cure is to raise the temperature at the end of such fermentations for a few days to keep the yeast active until the beer is clear.  At one point, early in my brewing career, I was in the habit of brewing stouts and porters without this step, and I actually enjoy a bit of buttery in the nose. But, again, it wasn't fun at this concentration.

Combined lactic acid with Diacetyl  - I think of this flavor as "there's nothing wrong with our tap lines, dude."  Gross. 

Spicy - This was a subtle, palate cleanser of a flavor. Described as clovey, I thought of it as one of the main components of some saison yeasts. This is definitely one of those off-flavor-in-some-but-not-in-others flavors. Things got worse from here.

Cheesy - This is the flavor of old, degraded hops.  Smelled like a ripe cheese.  Not the end of the world on a cracker, but unpleasant in Miller High Life.

Light Struck - Skunk. And strong, too.  This is the reason beer bottles are brown (or should be). But, it's also the flavor a hoppy lager gets pretty much the moment you take it out to sit in a sunny biergarden (or your back yard).  This one is bad in a beer out of the tap, but I can't help but have positive feelings about it, as it reminds me so much of days when I had the time and money to hang out in the sun with a beer.

Butyric Acid - Awful.  Baby vomit. Breast milk, digested for 20 minutes, and then projectile-vomited across the room by an infant with a fever.  Enteric bacteria, inappropriate in most styles, but an important precursor compound to some fruity esters in lambics, apparently. You learn something every day.  Only Papery was worse than this, though.

Mercaptan - Another infection flavor. This one smells like the end of a shift working at a dive bar as a prep cook. The smell of trash liners and the juice at the bottom of the cans.  Still not as bad as baby vomit or Papery, but pretty bad. 


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