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Old 03-20-2013, 05:38 PM   #1
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Default skunking in the kettle?

I have never had this issue myself (because I usually brew under the roof of my porch) but I recently moved into a house with an uncovered patio.
While I was brewing today, the sun was nice and bright and I thought, "I wonder if my wort is getting skunked right now."
Any insight into that, it seems like it ought to be just as susceptible to skunking as any other time, more so perhaps because of the heat.
Is this the case or is there some other factor involved in skunking that I'm unaware of?
Thanks,
matt

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Old 03-20-2013, 06:01 PM   #2
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I could be wrong, but I believe beer has to be fermented before it can be skunked.

I always brew out in the open and have never had an issue with skunking.

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Old 03-20-2013, 07:20 PM   #3
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Hmmm,
Well let's hope so anyway.
Thanks!

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Old 03-20-2013, 07:30 PM   #4
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I thought it had to do with a reaction between UV and isomerized alpha acids from the hops, which doesn't seem like it would have to do with fermentation.

I've also heard that skunking can happen nearly instantly (like in the time it takes to walk a beer from the house to the shed) but I've never personally experience that and that seems a bit extreme to me. I brew outside all the time, never had an issue.

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Old 03-20-2013, 09:58 PM   #5
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Found this:
http://www.homebrewtalk.com/wiki/index.php/MBT
which says that the 'skunk molecule' if you will, is a thiol formed by the reaction of isohumulone (you were right on the isomerized alpha acid/UV part) with riboflavin, which I assume comes from the malt, in the presence of UV light.
So, it seems possible that wort could skunk in the kettle, but I've never heard anyone mention this and my brew today definitely didn't smell skunked, but I guess I'll know for sure when I rack it.

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Old 03-20-2013, 10:03 PM   #6
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Just occurred to me that MBT (skunk molecule) is likely pretty volatile since it is noticed as an off-aroma, meaning that during the boil, any MBT formed is probably vaporized like DMS...but maybe it's something altogether different.

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Old 03-20-2013, 10:37 PM   #7
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If brewing out in the sun skunked beer, there would be way more complaints about it in the threads. I brew outdoors in bright CO sun all the time, never had skunked wort.

I never have seen a perfect definition of why this doesn't happen, but experience strongly suggests wort won't skunk, only beer.

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Old 03-21-2013, 01:34 AM   #8
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Quote:
Originally Posted by Saccharomycetaceae View Post
Just occurred to me that MBT (skunk molecule) is likely pretty volatile since it is noticed as an off-aroma, meaning that during the boil, any MBT formed is probably vaporized like DMS...but maybe it's something altogether different.
Makes sense to me... Don't cool you're wort in the hot sun. I guess that is counter productive in its own right.
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Old 03-25-2013, 11:25 PM   #9
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Quote:
Originally Posted by Saccharomycetaceae View Post
Found this:
http://www.homebrewtalk.com/wiki/index.php/MBT
which says that the 'skunk molecule' if you will, is a thiol formed by the reaction of isohumulone (you were right on the isomerized alpha acid/UV part) with riboflavin, which I assume comes from the malt, in the presence of UV light.
So, it seems possible that wort could skunk in the kettle, but I've never heard anyone mention this and my brew today definitely didn't smell skunked, but I guess I'll know for sure when I rack it.
I got into a sorry pissing contest with some folks on here once in a thread that got closed down. If I remember right the generally accepted reason is bogus. The yeast eat the riboflavin. Someone claiming, and sounding like he knew what he was talking about, said it was actually another process but the thread got shutdown and. I don't remember the specifics now but I think I have the gist of that right. I could be wrong.
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Old 03-26-2013, 12:30 AM   #10
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I have wondered the same thing. I always attempt to shade my wort during the boil and cooling to avoid the skunk, but this is the first discussion I have seen addressing the issue. Given the number of brewers on this forum that brew outside, you would think someone would at least claim that their brew skunked during the boil. If not, it must not be an issue. Has anyone found a thread that blames sunlight on the brew kettle causing off flavors?

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