Light struck/skunked ...

[lordnoise]

I left a few bottles (green Grolsch) of unremarkable homebrew (I brew quite a bit of that ) on a window sill for a month. I've just tasted one expecting something sulpherous to hit my buds but was left with a decidedly musty/mouldy flavour. Anyone come across the same ?
Further - do Skunks really smell like this?
I'd like to get to the bottom of this US 'skunky thang' - it appears in so many brewing articles as the light struck flavour but is completely lost on us Brits and neighbours.
Perhaps an American member (who has actually got up close and personal with one) can come up with something else that those of us on this side of the pond can latch on to ?

[mysterio]

Taste any green bottled beer in the shops and you'll taste it. Becks, grolsch, pilsner urquel all have it. Infact Becks is the light-struck beer par excellence. It's a difficult flavour to describe. Not sulphury at all though. Skunky doesnt really describe the flavour imo.

[adm]

That's a really difficult question to answer.....the real animal skunk kind of has a unique smell all of it's own.

I've smelled it in the US both close up (I used to trap animals for fur back in the mid 80s) and also diluted from far away when a skunk has been run over on a warm night.

It's one of those smells that you just don't know quite how to describe, then when someone tells you "It's Skunk", it makes sense.

I'd say that dilute skunk has an almost gassy, kind of chemical smell. Maybe with a bit of burnt plastic thrown in for good measure. Plus a lot of muskiness. So - musky, gassy, burnt chemically... dilute and on the wind, it's not that bad a smell.

Up close and personal though, it's just nasty retching, putridness - maybe like a month old dead body crossed with a million bottles of high intensity musk, with a load of rotten eggs chucked on then set on fire in a chemical works.

[lordnoise]

Up close and personal though, it's just nasty retching, putridness - maybe like a month old dead body crossed with a million bottles of high intensity musk, with a load of rotten eggs chucked on then set on fire in a chemical works.

Phew - thank God we only have their Grey Squirrels to contend with

Not sure if anything described so far fits in with my musty/mouldy flavours. The beer was only brewed 3 months ago and was fine to drink a month ago so I'm pretty sure oxidation isnt the issue.

Keep the descriptions coming please ...

[Aleman]

One thing we discovered at a recent meet up was that not everyone is sensitive to methyl mercaptan . . . We actually did a taste test and on opening the light struck bottle it was obvious to most members straight away, but a couple were blind to it . . . like me and diacetyl

[lordnoise]

Funny that Aleman - I'm known as a bit of a diacetyl hound at my local HB group ! The terrible thing about learning about flavour faults is that it can seriously mess with your drinking comfort zone - I didnt mind butterscotch in my beer until I discovered it was a flavour fault !

Still interested to know if anyone can come up with a nice neat Euro word or two way of summing up the flavour of skunked beer ...

[Aleman]

I really should stop killing of brain cells with alcohol . . . Or I would remember to go back to my references before making silly statements like that one above

Methylmercaptan is of course cooked cabbage . . . Skunking is of course 3-methyl-2-butene-1-thiol, which of course contains the sulphur in the thiol group, and is formed by light cleavage when iso alpha acids are exposed to light between 400 and 500 nm

my apologies for any confusion caused

[jamesb]

I've always thought it a bit like cat piss (and believe me, I know what that smells like)

[dcq1974]

Hi
I am a Flavour Chemist by Profession!!! And I can confirm to you all that the material in question that is responsible for the "sunstruck" flavour of beer is a chemical aroma compound called...........wait for it......

3-methyl-but-2-ene-thiol

This is really a typical smelling sulphur aroma chemical. Skunky is not a term I would use. I have played with this material in both solution and also have handled this chemical neat!!!! I think in it's dilute form (and you don't need much as the odour threshold of this material is mega low) this material smells like the stale beer odour you smell in a pub (or your own kitchen) the morning after! It's not unpleasant in the right amount, just stale beer!

Ooooppss I'VE JUST NOW READ ALEMANS EXPLAINATION TO THIS ABOVE AND HE HAS ALREADY PICKED THE CORRECT COMPOUND!!!
APOLOGIES CHAPS!

[paulcav]

and is formed by light cleavage when iso alpha acids are exposed to light between 400 and 500 nm

He said cleavage

[lordnoise]

Aaah - a fellow Carry On fan paulc !
Interesting paulb mentions cat pee - I've come across Tom Cat spray as a description before which fits in with the musky component often referred to.
dcq1974s contribution is a real headscratcher though as hes handled the stuff neat and can only come up with the rather vague "stale beer" - maybe hes one of those people who arent very receptive to the stuff

Any other contributions ?

[dcq1974]

Don't get me wrong - the lab stank of the stuff for days!!!!!!
I handle many smelly aroma chemicals and all I can say is that it isn't aggressively catty - more blackcurrant sulphur like. A similar material is Thiomenthone (p-Mentha-8-thiol-3-one or 8-Mercapto-p-menthane-3-one) which is used extensively as the catty note in blackcurrant flavours. This has also been known as "URINE DE CHAT" or litterally cat piss!

Maybe I'm less subseptible to the Skunk note as to me it is just another smelly sulphur chemical?

It is a very prominant aroma character in lager such as Heineken where you really can pick it out as a key odour compound! That's why we all drink Real Ale!


I've also never smelt a skunk!