Light damage

[Cass]

Just wondering how much damage light does to beer in the secondary. Just noticed that mine was getting some sunlight in the very early morning for about half an hour a day. It has been there a week. I moved it today when I noticed. Will it really harm my beer a great deal?

 

[boo boo]

It will skunk your beer. Throw a dark towel over it or otherwise keep the sun off it.
My beer is brewed in my basement and I put a black trash bag with a hole cut in the top over it.

 

[Denny's Evil Concoctions]

Light reacts with hop oils to produce the same oil that skunks use, though a teeny but, but enough to "skunk" beer.

Only wayo see is to try a sample form the secondary. Was it direct sunlight?

 

[ColoradoXJ13]

I usually just throw a dark colored t-shirt over all my carboys that have hops in em'.

 

[BierMuncher]

I doubt your beer was tanslucent (sp) enough to allow much penetration.

 

[RichBrewer]

At this point all you can do is relax. I'm betting that you will end up with a good batch of beer.
As already stated. Throw a black T-shirt over your carboys and you won't have to worry about light.

 

[david_42]

Check a sample. Beer will skunk is less than an hour in full sun. But, I suspect the light was passing through several layers of glass, which will block some of the UV (not all). If the beer is skunked, it will be obvious. Unfortunately for homebrewers, the more hops, the easier it is to skunk. And the chemical involved is detectable in the parts per billion range.

If it isn't skunked and you keep it out of the sun, it won't get worse.

 

[Nexus555]

What I don't understand is how New Castle and Heineken (just to name a few) get away with clear and green bottles. How is this so?

 

[New Brew]

^^^^
They don't. I don't drink a lot of Newcastle, but I know Heineken is often skunked by the time you buy it. It's gotten to the point where some think it's a valid flavor in beer, and some breweries let it happen intentionally now it seems.

 

[Nexus555]

New Castle is in a clear bottle and where I buy it (Wal Mart) it's right under the flourescent lights. I've read flourescent lights produce the same skunk that sunlight does. I drink this beer every now and then and love it. There are absolutely no "skunk" flavors in New Castle. Is there perhaps a secret perservative they put into these?

 

[Buford]

Miller uses an isomerized hop extract that won't skunk in UV light, which is how they get away with bottling MGD and High Life in clear glass. Newcastle might be the same way.

 

[BierMuncher]

^^^^
They don't. I don't drink a lot of Newcastle, but I know Heineken is often skunked by the time you buy it. It's gotten to the point where some think it's a valid flavor in beer, and some breweries let it happen intentionally now it seems.

St. Pauli Girl.

Pure skunk heaven.

 

[Nexus555]

Miller uses an isomerized hop extract that won't skunk in UV light, which is how they get away with bottling MGD and High Life in clear glass. Newcastle might be the same way.

Ahh that explains things. Is there any way for normal people to do this to their hops? Or does it require special machines? Thanks.

 

[brewt00l]

Reduced iso-humulones and hydroisohumulones

It has long been known that iso-alpha acids in the presence of sunlight undergo transformations to forms which produce a "skunky" or "light struck" flavor in beer. This is why beer is packaged in light proof bottles. Research on the chemical transformation of iso-alpha acids (isohumulones) revealed that upon reduction to dihydro (rho) isohumulones the capacity to produce skunkiness is lost and the potential to produce light resistant beer using reduced isohumulones was recognized.

Hydrogenation of the dihydroisohumulones produces the tetrahydroisohumulones and further reduction generates the hexahydroisohumulones. These two forms of isohumulone are also light resistant.

Brewing experience with the different forms of reduced isohumulones show that they differ in their relative bitterness and in their capacity to contribute foam stability. A summary of the effects relative to standard isohumulones is given in Table VII together with the other details of these products.

Using various chemical procedures it is also possible to prepare the hydroisohumulones from the beta acids (lupulones) of the hop resins.

Today a number of the world's main brewing groups produce beer in clear glass bottles. Some of these are not known to use light stable bitterness but to rely on packaging and distribution to eliminate light struck flavor. Others do use reduced isohumlones and/or hydroisohumulones to produce a completely light resistant beer.


http://www.hopunion.com/hop-use-products.shtml

 

[britishbloke]

So, Im still wondering... Will regular light bulbs still affect beer?

My roomate is known for leaving the light on in the beer room....

 

[brewt00l]

So, Im still wondering... Will regular light bulbs still affect beer?

My roomate is known for leaving the light on in the beer room....

From what I have read in the past, it takes several days worth of direct florescent exposure to cause lightstruck beer. I haven't tried any experiments to see exactly how long.

 

[Ó Flannagáin]

I'll agree with you Nexus, about Newcastle. I like that beer, a lot, and when I get it, its been sitting in a fluorescent lit gas station shelf. I don't understand it, makes me doubt that its as easy to skunk as some say. Maybe direct sunlight is different though.

 

[Brewsmith]

Regular incandesant bulbs are fine. Flourescent bulbs produce a little UV.

 

[muph]

Apparently any light regardless of source "visible light" can cause the beer to become lightstruck whether it is UV light or not..

Beer bottle - Lightstruck Beer