What constitutes skunked?

To add an example to Jack's point about Heineken being pre-skunked myth.

A few years back one of our neighbors had a pool party when one of the daughters graduated college. They have a kegerator and stocked both taps with Heinken for the guests. Since they expected there to be lots of folks there and lots of music they let us know in advance of the party. The day of the party shortly after they had tapped the "keg" one of them showed up at our front door with a full pitcher of nice fresh Heineken. Absolutely no sign of skunk.

 

My own first hand experience is that the skunk thiols scrub pretty easily, actually- at least if it's not at really obnoxious levels.

 

Perhaps a beer at 4 ng / l of 3-methyl-2-butene-1-thiol could dissipate in a short (1-2 minute) timeframe but a beer with 30 ng / l would take longer?

Maybe some brewing scientist has quantified this?

Cheers!

@Peter_Wolfe

 

Thanks for sharing that, interesting.

 

How does age affect the beer from a technical aspect? Is the diacetyl part of their brewing process or is it a batch variation? Some Urquell I’ve had I’d say we’re clean, others I didn’t like, I’ve noticed I’ve dislike the older beers in most cases. The taste I don’t like in some Urquell is also always present in Rolling Rock and at a much higher level, we’ve discussed this before. I don’t like that feature in any beer, I just never knew what it was or what to call it other than old beer.

 

Yeah, at a certain point there might not be enough CO2 to do the job .

But I just mean, on those occasions where I leave a beer outdoors in the sun, and come back to it with a whiff of skunk, just a little swirling seems to dissipate it.

 

Generally speaking beers get 'stale' with age with much of the staling being from oxidative chemical processes. In some beer style this can be considered to be a positive flavor change - for example development of sherry flavors in a Barleywine. So some beer styles staling can create honey-like sweetness or sometimes the flavor profile just develops into a muddied mess. For hoppy beers like IPAs the staling that folks hate if hop aroma/flavor fade.

Perceptible diacetyl is created in all beers during the primary fermentation but towards the end of fermentation the yeast 'cleans up' this compound (the diacetyl gets converted into other compounds like acetoin and 2,3-butanediol which have high taste thresholds). In Czech Lagers sometimes the diacetyl is not fully 'cleaned up' so it is perceptible. When brewing lagers some homebrewers conduct a "diacetyl rest' process towards the end of fermentation to aid the yeast to 'clean up' the diacetyl. I am uncertain what the brewers of PU do in this regard. I also do not know why sometimes the diacetyl if perceptible in PU and sometimes it isn't. Maybe just a function of amount of diacetyl per batch and the flavor threshold of each individual?

I believe you and I have already discussed Rolling Rock and the fact this beer has perceptible DMS (which tastes like creamed corn for my palate). I have never perceived DMS in any of the numerous times I have consumed PU.

I am not an 'expert' in drinking old PU since I only purchase this beer when it is fresh (a couple/few months from canning or bottling) so I have no idea how this specific beer 'evolves' with age.

Cheers!

 

You are more experienced here than I am. I take great pains to ensure that my beer does not get sun exposure. My wife makes fun of me when we go to the ballpark to watch the Phillies, I always make sure to 'shelter' my draft beer to make sure it does not get exposed to the sun.

Cheers!

 

Same... if I'm out by the pool I always make sure to set my glass under the chair or in the shade somewhere.

 

Why tempt fate and ruin a perfectly good beer by not using shade here?

Cheers!

 

Hah! Yeah, but sometimes it's not really possible. Thankfully it's the age of the can lately, and I hardly have that problem anymore because I'll just forgo the cup when we're out playing bocce or frisbee or whatever.

 

John Kimmich would applaud you here!

Cheers!

 

If the precursor to Diacetyl is in the beer, O2 ingress through the caps will turn it into Diacetyl.

 

If it airs out and becomes pleasant I would not consider it skunked.
Cheers

 

Innis & Gunn (which at the time was still using clear glass) claimed it could by "stirring up the esters" by pouring it into another glass, in an old blog post in 2011. (No longer online but it can be found via the Wayback Machine here - not sure if their URL's are permanent).

Describing an "experiment" exposing both their lower ibu (18) beer with a "100+ ibu IPA" to sunlight in clear glasses their conclusion was:

http://www.innisandgunnnews.com/2011/august.html

Of course, they did change to brown glass eventually. Seems like a lot of work to justify using packaging that, rather than help preserve the beer, was chosen because "...the different colors of the different beers in the Innis & Gunn range appeal to consumers and provide some clear message about the different tastes of each beer" according to their brewer. I don't know, maybe they hoped to sell more beer to "experimenters" (it does seem to be a popular pastime for some).

 

I suppose there are degrees of skunkiness? Some have been tolerable, others, not so much (beer style might play a role).

 

Beer style, for sure, but also in a related way, the amount of IBUs. The skunk comes when ultraviolet light reacts with the isomerized alpha acids from the hops.

 

So they're saying that it does get scrubbed. Then again, there's good stuff getting scrubbed, too, so that's not exactly a virtue .

 

Take a 6 pack of beer leave it in your hot car a couple of hours, chill it and then drink it. You'll know what skunked tastes like.

 

Age and storing conditions also play a part