"Skunking" -- Fact or Fiction?

[GHBWNY]

I've always heard it: bottled beer in anything but amber bottles goes bad.

Does anyone here on HBT have empirical evidence to support this phenomenon? It apparently can't be because of UV rays since even clear glass filters UV rays. Is it exposure to any light or does it have to be sunlight? If so, why? What exactly is supposed to happen when beer in a non-amber bottle is exposed to light? Why does it not happen with wine or liquor? And what about all those beers in green bottles? And Miller, for cryin' out loud!

Please! Enlighten me!

 

[fastengine]

I can't give you a bunch of scientific mumbo jumbo, facts or fiction.
I just know that ALL bottles will skunk if exposed to enough light, brown ones just take longer than clear ones.
The easy cure is keep all of your bottles in boxes or storage where they won't be exposed to excessive light. I have heard /read that it is UV light that causes skunkiness, and some breweries will expose there beer to UV light just to get that "special" flavor.
Forgot to add that it doesn't happen with wine or liquor because the hops are what go skunky in beer that is exposed to light.

 

[LLBeanJ]

It's the hop oils that cause beer to skunk when exposed to UV (sunlight and fluorescent) light, which is why it's not a problem with wine and other liquors. It does happen. I've had beers that I just poured from a keg be noticeably skunked within 10 minutes of sitting in direct sunlight.

 

[Jeffinn]

http://www.professorbeer.com/articles/skunked_beer.html

 

[paperairplane]

Get a Heineken mini keg and a 6 pack of bottles.

 

[IronBall]

http://www.professorbeer.com/articles/skunked_beer.html

That was pretty interesting. Thanks for posting

 

[GHBWNY]

http://www.professorbeer.com/articles/skunked_beer.html

Very interesting. Thanks.

 

[fastengine]

http://www.professorbeer.com/articles/skunked_beer.html

Pretty much just what I said....

 

[hunter_le five]

Pretty much just what I said....

Yeah, but do you have your own website? The other guy has a website. He must be an authority on the subject.

 

[JINKS]

Clear doesn't filter much UV. Brown is best.

 

[progmac]

i prefer clear bottles for my homebrew. it makes it easy to see what's inside. i have two cases of ez caps and maybe a case of standard cap clear bottles among about twice that many brown bottles. i have used the clear bottles hundreds of times and have never had any issues.

but here's my secret: i store my beer in the basement, not outside.

 

[UpstateMike]

I use brown. I use green. And I use clear. And I keep them in cardboard cases in the basement until they go in the fridge. No light, problem solved.

 

[fastengine]

I'd use invisable bottles if I could get my hands on some.. Like all of the wise brewers above said, Keep them in the dark...

 

[Dolomieu]

http://youtu.be/oZuHmglowJA

 

[orangehero]

Some people are more sensitive than others to 3-methyl-2-butene-1-thiol (3-MBT), the compound responsible for skunking. The reaction is catalyzed by riboflavin in response to certain light wavelengths (don't remember all, but UV being one of them).

 

[1977Brewer]

I can smell the skunk on a Corona as soon as I pop one. I tend a little bit of bar, for lighting buyers. I open a lot of Corona. Skunking is no myth.

 

[AdamBomb]

Is this compound in coffee? SWMBO always says that when I brew coffee that the house smells like skunk. I never notice it but of course I'm a trapper so I eat Violator-7 on crackers. Lol (predator lure with skunk essence) :rockin:

 

[biochemedic]

http://youtu.be/oZuHmglowJA

As soon as I saw this topic, this Basic Brewing Video episode is the one I was going to post if no one else got to it...

 

[amcclai7]

I am usually pretty sensitive to off flavors and have drank many, many an IPA outside in a clear glass and I've never noticed the beer slowly skunking. I'll have to try it with this in mind and see.

 

[BeerGRip]

The chemicals involved are pretty volatile and will evaporate quickly once the bottle is opened. Pour a skunked Corona into a glass and wait a bit. No more skunk.

 

[Black Island Brewer]

I've always heard it: bottled beer in anything but amber bottles goes bad.

Does anyone here on HBT have empirical evidence to support this phenomenon? It apparently can't be because of UV rays since even clear glass filters UV rays. Is it exposure to any light or does it have to be sunlight? If so, why? What exactly is supposed to happen when beer in a non-amber bottle is exposed to light? Why does it not happen with wine or liquor? And what about all those beers in green bottles? And Miller, for cryin' out loud!

Please! Enlighten me!

I teach a Homebrewing class, and to demonstrate a skunked beer, I bottle one beer in a Samuel Smith's bottle. The clear glass, which does NOT block UV, allows the chemical reaction with the hops to take place. I leave it outside in the light for a week. Florescent light would work, but it takes longer. As soon as I pop the top, the smell quickly spreads, and I have not yet had any student confused about what skunking is like.
As for Miller, they use a stabilized hop product, does not react with UV.

 

[GHBWNY]

OK, here's what's been inferred so far by the above explanations: "alpha acids are isomerized by UV light and thus it turns the beer skunky". Do we all agree that skunkiness is an aroma characteristic? OK, consider that hops are also isomerized during the boil. The longer the boil, the greater the isomerization = more bitterness in the beer. At the same time, a longer boil results in loss of aroma and flavor. So, if aroma (skunkiness) is lost by a greater amount of isomerization, then why does isomerization by UV light supposedly result in GREATER aroma/skunkiness)?

Are dry-hopped beers potentially skunkier beers? It would be an interesting to see if a lightly-hopped beer would skunk-out at the same rate and/or intensity as a heavily-hopped/dry-hopped beer.

 

[orangehero]

No, they aren't isomerized (actually they already are from the boil), they are converted to 3MBT through light exposure and light activated riboflavin.

Also, aroma isn't lost due to isomerization, it is lost because of the boil causing those aromatic compounds to evaporate.

The skunk comes from isomerized acids, so dry hop rate should have little effect. In fact it would probably help to mask the skunkiness.

The stabilized hop products do still react with light, they just don't produce 3MBT.

Here's a good read if you want to know the gritty details as well as a quick lesson in organic chemistry nomenclature:
https://beersensoryscience.wordpress.com/2011/03/17/lightstruck/

 

[govner1]

It's not just UV but all visible light that causes "skunking" (400-760nm).

 

[JonM]

I have found that skunking is especially noticeable in light-flavored beers. I left a cream ale on the patio table for a couple minutes while messing with the grill, and it skunked immediately. Last summer, I got a New Glarus "Totally Naked" at our State Fair's craft brewing tent. It was in a clear glass. Drank a few sips in the tent, and it was perfect. Walked out into the sun, and it got noticeably skunked in just a couple minutes.

EDIT: If you want empirical evidence, take a bottle of beer, pour 6 oz into two clear glasses, and wrap one in aluminum foil. Leave both in the sunshine for 5-10 minutes, then take them both inside and taste them side-by-side. SECOND EDIT: Better yet, have someone else taste them - someone who doesn't know which one was covered - and see if that person can taste the difference.

 

[uncleleon]

I think sulphury and skunky overlap on my pallet. I've tasted it in my lagers and kolsches from time to time. It's something I used to crave. (St. Paulie girl / hieniken) Now not so much. Just saying once you get into the realm of personal taste it's all up in the air.
It's reminds me of the story of acetaldehyde being the characteristic flavor of Budweiser. Byproducts aren't always flaws, it depends on who likes what.

 

[GHBWNY]

No, they aren't isomerized (actually they already are from the boil), they are converted to 3MBT through light exposure and light activated riboflavin.

Also, aroma isn't lost due to isomerization, it is lost because of the boil causing those aromatic compounds to evaporate.

The skunk comes from isomerized acids, so dry hop rate should have little effect. In fact it would probably help to mask the skunkiness.

The stabilized hop products do still react with light, they just don't produce 3MBT.

Here's a good read if you want to know the gritty details as well as a quick lesson in organic chemistry nomenclature:
https://beersensoryscience.wordpress.com/2011/03/17/lightstruck/

Thank you for that article. No more questions, Your Honor.

 

[GHBWNY]

I have found that skunking is especially noticeable in light-flavored beers. I left a cream ale on the patio table for a couple minutes while messing with the grill, and it skunked immediately. Last summer, I got a New Glarus "Totally Naked" at our State Fair's craft brewing tent. It was in a clear glass. Drank a few sips in the tent, and it was perfect. Walked out into the sun, and it got noticeably skunked in just a couple minutes.

EDIT: If you want empirical evidence, take a bottle of beer, pour 6 oz into two clear glasses, and wrap one in aluminum foil. Leave both in the sunshine for 5-10 minutes, then take them both inside and taste them side-by-side. SECOND EDIT: Better yet, have someone else taste them - someone who doesn't know which one was covered - and see if that person can taste the difference.

I will do this --- if we ever get sun here in the northeast!

 

[Hello]