Sunlight?

[eddy401]

Hey everyone,

this might seem like a stupid question, but everyone says to keep your beer out of the sun as it damages the beer - does this mean you should keep the bottles in complete darkness or just not in direct sunlight? what about during fermentation - i keep my fermenter out of the sun but its not in the dark. what kind of off flavours does this cause? my guess is its the UV light that causes the problem, and that the more dark the storage the better, is there a time period to it like after a few weeks in the bottle the beer wont be very badly affected?

thanks :icon_cheers:

 

[hsb]

Hey everyone,

this might seem like a stupid question, but everyone says to keep your beer out of the sun as it damages the beer - does this mean you should keep the bottles in complete darkness or just not in direct sunlight? what about during fermentation - i keep my fermenter out of the sun but its not in the dark. what kind of off flavours does this cause? my guess is its the UV light that causes the problem, and that the more dark the storage the better, is there a time period to it like after a few weeks in the bottle the beer wont be very badly affected?

thanks :icon_cheers:

AFAIK, from fermentation through to drinking you'll be wanting to keep your beer out of sunlight. Hops don't like UV light - see 'skunkiness':
http://www.washingtonpost.com/wp-dyn/conte...7022700312.html

Dark storage/fermentation is best. Indirect sunlight is still UV light. Brown bottles are the way to go and prevent UV light getting to the beer, though whether that is absolute, I don't know?

 

[keifer33]

Brown bottles block out more uv but u wouldn't want to leave them in the sun as direct light will have more of an effect than ambient light in a room or shed. If u can see inside the bottle, light obviously has to get in thus a portion of uv can. As far as how much uv ruins beer I've gotno idea.

 

[Brewing_Brad]

Here in North America (US & Canada) they call the chemical reaction that occurs between hops and sunlight "skunking" because apparently it produces the same chemical that a skunk produces. Now, I don't know if you've ever smelt a sunk in real life but SWEET JESUS! You DO NOT want that in your beer!

Actually, the guys who do that Basic Brewing video did an experiment to see what happens when you leave the beer out in the sun in a clear glass - not so great apparently - I'll try to dig up a link.

Cheers
Brad

--UPDATE--
The link to the video is here.

 

[muckey]

I beleive that the UV light causes a reaction with the isomerised hops which causes the "skunking"

There is no time frame after which it wont happen

brown bottles are better than green and far better than clear but as previously stated - dont keep you beer in direct sunlight.

beers that are bittered with iso hop dont seem to skunk quite as readily as beers that are bittered with hops added to a boil. I beleive that the alpha acids are somehow stablised during manufacture of iso hop.

thats about as far as my understanding extends these days - hopefully one of the gurus on the forum will ad some detail here

:icon_cheers:

 

[DaKing]

The industry call it Light-Strike
According to the local CSIRO, green bottle aren't much better then clear bottles at protecting the hops from souring due to exposure to different types of light. (UV mostly I believe)

http://www.csiro.au/solutions/Sunscreen-For-Bottles.html
http://www.solve.csiro.au/0205/article11.htm

I've actually been using green plastic bottles for years (silly me used to think Green was as good as brown). In my experience, about 20mins of direct sunlight will start to have a noticeable effect.

 

[the_yobbo]

UV rays are bad for hops, but how about yeast.
I'm sure I've read that you can use UV rays to sterilise bottles (not that a homebrewer would have the equipment). So, if UV kills yeast then it could lead to autolysis = bad flavours? ... Or is it nothing in comparison to the UV + Hops combination?

 

[Hatchy]

As far as I'm aware it's hops that suffer from light strike. I happily bottle cider & ginger beer in clear & plastic bottles.