Infection/Quality Problems: what we should know

Nope. That's why skunking is also called "light struck". The video and the link above have excellent info regarding the phenomenon.

 

Exactly. This is something those enamored by IBUs tend to not attend to when it comes to perceived bitterness in in different beers.

Your training course sounds as though it was well conducted and a great learning experience.

 

For sure. Most people understandably assume the beer in front of them is not flawed and aren't looking for flaws. There's a learning curve for tasting, as you're aware from your sensory training. The most obvious example of public ignorance of beer flaws is probably light-struck/skunk. There are people who believe skunk is a characteristic feature of imported Euro lagers. You can find evidence for this by looking through the beer reviews on this website, despite members here tending to be more aware/educated about beer than the average person. Also, I think I remember @jesskidden saying that when Pilsner-Urquell (SAB-Miller) switched to brown bottles from green there a bunch of complaints from people who said the beer didn't taste right anymore, but all they changed was the bottle color...people were accustomed to the flaw.

I'm not picking on you I swear... beer skunk literally smells like a skunk, but slightly more bearable... like skunk from 100 yards away. Try this test... The next sunny day (preferably around midday) grab a hoppy IPA or APA you're familiar with. Stay inside or in the shade and pour the beer into a glass. Drink about half the glass while taking note of hop aromas. Then expose the beer to direct sunlight for about 5 minutes and smell it. Note the difference.... that's skunk. A hoppy pilsner (like Victory Prima) would be a good test subject too.

 

The worst offender was a St Pauli Girl many years ago. Popped the top and my house smelled like a cabbage farm. Just awful. Infected beers that are tart like cherries are palatable. Being a heretic it's one reason why I didn't love BC Cherry Rye, that sour cherry taste was imbedded.

 

And you're sure that cabbage smell was not dimethyl sulfide (DMS)? DMS is usually described as having a creamed corn aroma/flavor, but this website says, "....When caused by bacterial infection, DMS has a more rancid character, more liked cooked cabbage than corn." I can imagine other vegetables could come to people's minds too.

More DMS info: https://beerandbrewing.com/off-flavor-of-the-week-dms/

FYI, Rolling Rock is purposely brewed with some moderate levels of DMS as part of it's flavor profile.

 

Not to butt in but is there perhaps some confusion being created by people conflating "edible" cabbage and skunk cabbage?

The swamp behind my house is full of the damn stuff so I might be more inclined to jump to that conclusion than is warranted

 

Guess I was thinking more along improper storage of a keg from vendor to distro to tap.

 

Mostly that would lead to premature aging rather than infection.

 

My thing I've come across lately is flat kegs. For instance. I've had Lexington College Heights twice now. First time the beer was rather mild for an IPA, but carbonation with the hops delivered a nice effect. Second time I kept wondering what was wrong. Didn't even have any real head to it either. Both times were from different bars as well.

 

That might be it. @nc41 ? I am not that familiar with skunk cabbage....

 

Well, lack of carbonation isn't really going to be a problem caused by infection. One of the signs of a possible infection can be over carbonation. It sort of sounds like both the bars where you've had it were either not properly caring for or connecting their kegs to the taps or maybe the bartenders weren't giving it a proper pour. I've had well carbonated beers that were served with a 1/4" or less head (some places prefer to maximize the liquid). Also I don't think we can rule out the fill procedures used at the brewery for getting the beer into the kegs in the first place. (But not sure.)

 

Perhaps 2015 BCBS was an exercise by AB/InBev to educate the public regarding infected beer

 

Edible cabbage tastes good to me, but it's a bit oderiffus. Probably not a real word. But skunk cabbage , just stinks. When I popped that St Pauli Girl the room just exploded in stink, literally a full room was enveloped by the smell. I've had skunked beers before the luck of German beers in the day, but stank is stank.

 

the legal limit for abv on bourbon barrel entry is 125 proof. right?

look up the proof on most releases of Booker's, all of Elijah Craig Barrel Proof, George T. Stagg & others. explain how they began at 125° but wind 126°- 145° by the time they're bottled? the water contents is escaping faster than the alcohol contents (even though alcohol evaporates faster).

 

A fella opened a Peroni the other day at Old Chicago. Several seats away. Similar air permeation of the light struck smell.

 

The most embarrassing thing is I still drank some of that beer. It smelled far worse than it tasted. Today I'd have brought it back to Total Wine and want a refund. Would have loved to pop one in front of the manager, take that. Clearing out the front end of the store in the process.

 

Hahaha. Good one.

The microbe responsible for that infection is pretty interesting, fwiw.

 

Well, water molecules are certainly smaller than ethanol molecules, so it's possible that might be the mechanism, even though the boiling and evaporation points of ethanol are lower than that of water. What it comes down to is that the molecules need to escape the semi-permeable environment of the barrel when they are in the gas (not liquid) phase, so more of a smaller molecule would probably be able to escape than a larger one, even though the larger molecule evaporates more quickly.

A quick look reveals that this is, in fact, the science on this, if anyone cares.

 

fwiw, the science you linked, is almost word for word what i'd been told by multiple well established Master Distillers. that's where i got the whole water *molecule* vs alcohol molecule data-point.

 

This goes in my "learn something new everyday" folder. Thanks, man!