Author Topic: Can sunlight affect wort?  (Read 2497 times)

Offline liquidbrewing

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Can sunlight affect wort?
« on: January 29, 2012, 02:14:20 PM »
So I had my latest batch of IPA  (all Falconer's Flight...looking forward to this one)  cooling in an ice bath, from this afternoon's brew day.  I had to leave for a couple hours and when I came home noticed the sun was ever so slightly peeking in on some of my wort.  Just a little sliver through a window.  Will this affect my wort??  Or is direct sunlight only bad for fermented beer?
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Offline Gribble

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Re: Can sunlight affect wort?
« Reply #1 on: January 29, 2012, 03:12:09 PM »
I dont think a little sliver of sunlight for a couple hours or less is gonna hurt your wort.  Not enough exposure.
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Offline denny

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Re: Can sunlight affect wort?
« Reply #2 on: January 29, 2012, 03:35:34 PM »
I dont think a little sliver of sunlight for a couple hours or less is gonna hurt your wort.  Not enough exposure.

While I generally agree, I've had hoppy IPAs skunk in less than 5 minutes when the glass was exposed to direct sunlight.
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Offline liquidbrewing

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Re: Can sunlight affect wort?
« Reply #3 on: January 29, 2012, 03:39:33 PM »
Ok, well I just pitched so I'll report back in a few weeks when the beer is drinkable and tell you if there were any off flavors.
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Offline morticaixavier

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Re: Can sunlight affect wort?
« Reply #4 on: January 29, 2012, 04:01:39 PM »
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.
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Offline jeffy

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Re: Can sunlight affect wort?
« Reply #5 on: January 29, 2012, 04:02:29 PM »
I've been searching the interweb for the actual article by Ray Daniels and can't find it, but memory tells me that beer needs to be fermented and contain riboflavin in order for skunking to take affect.  Unfermented wort is safe.
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Offline tom

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Re: Can sunlight affect wort?
« Reply #6 on: January 29, 2012, 04:43:51 PM »
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.
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Offline Joe Sr.

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Re: Can sunlight affect wort?
« Reply #7 on: January 29, 2012, 06:55:45 PM »
I dont think a little sliver of sunlight for a couple hours or less is gonna hurt your wort.  Not enough exposure.

While I generally agree, I've had hoppy IPAs skunk in less than 5 minutes when the glass was exposed to direct sunlight.

Denny - I've heard similar things before, but I also read an article about a study on this that seemed to say it needed significant exposure for detectable levels of "skunking."

I'll look for that article.  I can't recall where I read it, but it was interesting.  IIRC they did three tiers of exposure and were pretty methodical.

EDIT: There's too darn many post on-line for me to find that article ever again.  I guess if it tastes skunked to you, that's enough for me.


« Last Edit: January 29, 2012, 07:04:25 PM by Joe Sr. »
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Offline jeffy

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Re: Can sunlight affect wort?
« Reply #8 on: January 29, 2012, 07:07:49 PM »
I've had a pint of IPA start to smell bad within minutes of taking it out into bright sunlight.
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Offline hopfenundmalz

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Re: Can sunlight affect wort?
« Reply #9 on: January 29, 2012, 10:25:02 PM »
Light colored hoppy beers skunk in a minute or 1 in direct sunlight.  It has happened to me, even in the weak Michigan sun.

Riboflavin is the B vitamin required to make the skunking happen, and this is produced by the yest.

Wort in the sun is OK, beer is not.

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Offline denny

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Re: Can sunlight affect wort?
« Reply #10 on: January 30, 2012, 09:02:41 AM »
Denny - I've heard similar things before, but I also read an article about a study on this that seemed to say it needed significant exposure for detectable levels of "skunking."

I'll look for that article.  I can't recall where I read it, but it was interesting.  IIRC they did three tiers of exposure and were pretty methodical.

EDIT: There's too darn many post on-line for me to find that article ever again.  I guess if it tastes skunked to you, that's enough for me.




Yeah, it was very definitely skunked.  A very hoppy IPA and very bright direct sunlight.
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Re: Can sunlight affect wort?
« Reply #11 on: January 30, 2012, 09:08:19 AM »
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.

Good to know. I've always wondered why people can brew outside in direct sunlight with no problems. This explains that.
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Offline Joe Sr.

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Re: Can sunlight affect wort?
« Reply #12 on: January 30, 2012, 10:24:50 AM »
Denny - I've heard similar things before, but I also read an article about a study on this that seemed to say it needed significant exposure for detectable levels of "skunking."

I'll look for that article.  I can't recall where I read it, but it was interesting.  IIRC they did three tiers of exposure and were pretty methodical.

EDIT: There's too darn many post on-line for me to find that article ever again.  I guess if it tastes skunked to you, that's enough for me.




Yeah, it was very definitely skunked.  A very hoppy IPA and very bright direct sunlight.

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.
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Offline hubie

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Re: Can sunlight affect wort?
« Reply #13 on: February 05, 2012, 07:42:50 PM »
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.

Offline bonjour

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Re: Can sunlight affect wort?
« Reply #14 on: February 05, 2012, 08:17:45 PM »
fresh wort skunking -- never had it happen, but I always protect my wort from light.

Finished beer, I've routinely skunked beer in un-opened brown bottles (for class) and I have severely skunked a picture of APA in under a minute (direct sun, and for class)

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