Author Topic: Can sunlight affect wort?  (Read 2970 times)

Offline liquidbrewing

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Re: Can sunlight affect wort?
« Reply #15 on: February 10, 2012, 04:35:45 PM »
I just sampled this stuff yesterday...and man!  The aroma from the Falconer's Flight is amazing.  I should have bittered more, but it's a great IPA.  I'm gonna start dry hopping and keg it in a few days.  Apparently no damage from the little sunlight that hit it.  Thanks for all the replies.
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Offline tubercle

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Re: Can sunlight affect wort?
« Reply #16 on: February 10, 2012, 05:22:05 PM »
I'm sort of embarrassed to admit it, but when I have beers outside I typically have them in a red Solo cup.  Racking leaves, painting windows, and what not.

Plus, I try to put them in the shade so they don't get warm.

Maybe that helps.

 Dang Joe?!?!

 How long does it take for you to drink a beer?
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Offline Joe Sr.

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Re: Can sunlight affect wort?
« Reply #17 on: February 11, 2012, 11:04:26 AM »
When I'm painting windows and sipping an old ale, I take my time and enjoy it.

This ain't Miller I'm drinking!

Plus, I was painting in 90+ temps this summer.
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Offline liquidbrewing

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Re: Can sunlight affect wort?
« Reply #18 on: February 12, 2012, 11:34:09 AM »
When I'm painting windows and sipping an old ale, I take my time and enjoy it.

This ain't Miller I'm drinking!

Plus, I was painting in 90+ temps this summer.

Painting and drinking at the same time?  Who's ever heard of such a thing! ;D
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Offline tom

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Re: Can sunlight affect wort?
« Reply #19 on: February 13, 2012, 09:38:20 AM »
I thought the UV light/hops/yeast(riboflavin) reaction was the major cause.  http://onlinelibrary.wiley.com/doi/10.1002/1521-3765(20011105)7:21%3C4553::AID-CHEM4553%3E3.0.CO;2-0/abstract
Can you point me towards you sources?
The skunking compounds are not present until fermentation. It's a combination of certain compounds in the hop oils and B vitamins produced by the yeast that cause the skunking from light. wort is safe.
+1, if your wort hadn't been pitched, then there is no chance of skunking.

As I understand the chemistry, that is not true.  The skunking comes from interactions with the isomerized alpha acids.  Riboflavin (vitamin B) is one mechanism that contributes to this through a series of chemical reactions, but the iso-acids are also broken up by direct UV exposure.  I believe the energetics are such that direct light exposure requires energies approaching the UV range, while the chemistry involving riboflavin is caused by light with a broader band of wavelengths out to as long as 500 nm (green light).  Though you get riboflavin from yeast, it is also present in malt.

The skunking compound is part of the thiol family which has a ridiculous detection threshold, something like a few nano-grams per liter.  Because of the very low detection threshold and the general unpleasant odor, thiols are put in things like natural gas to make it easy to detect.

As you'd expect, there are all sorts of factors involved that will determine how much it skunks and how easy it is to detect (hop level, beer color, pH, etc.).  However, the worst light you can exposure your beer to is green (bad) to blue (worse) to UV (even worse).  It is funny because I am writing this as I watch the Superbowl ads for Bud Light Platinum which appears to be packaged in blue bottles.  For their sake I hope they are using those special lightstruck-resistent hop extracts for that.
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Offline kramerog

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Re: Can sunlight affect wort?
« Reply #20 on: February 13, 2012, 11:09:58 AM »
As I understand the chemistry, that is not true.  The skunking comes from interactions with the isomerized alpha acids.  Riboflavin (vitamin B) is one mechanism that contributes to this through a series of chemical reactions, but the iso-acids are also broken up by direct UV exposure.  I believe the energetics are such that direct light exposure requires energies approaching the UV range, while the chemistry involving riboflavin is caused by light with a broader band of wavelengths out to as long as 500 nm (green light).  Though you get riboflavin from yeast, it is also present in malt.

The skunking compound is part of the thiol family which has a ridiculous detection threshold, something like a few nano-grams per liter.  Because of the very low detection threshold and the general unpleasant odor, thiols are put in things like natural gas to make it easy to detect.

As you'd expect, there are all sorts of factors involved that will determine how much it skunks and how easy it is to detect (hop level, beer color, pH, etc.).  However, the worst light you can exposure your beer to is green (bad) to blue (worse) to UV (even worse).  It is funny because I am writing this as I watch the Superbowl ads for Bud Light Platinum which appears to be packaged in blue bottles.  For their sake I hope they are using those special lightstruck-resistent hop extracts for that.

Possibly people don't detect skunking of the wort in the finished beer because fermentation scrubs out the thiols and because the yeast reduces thiols to H2S which is scrubbed out too during fermentation.
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