[yso191]

What prompted the thought was looking at an ad for this fermentation vessel which is clear: https://craftabrew.com/pages/the-catalyst-fermentation-system

I'm curious about how much light it actually takes to skunk a beer.

So let's take an IPA which has lots of Alpha Acids available to twist into mercaptans by light.  How much exposure to light does it actually take to get above the taste threshold for skunkiness/lightstruck?

There is more than one organization on this site dedicated to experimentation which is why I posted the question rather than messaging someone.

[denny]

It's an interesting idea, but playing devil's advocate I see some problems....how do you quantify the amount of light hitting the fermenter?  What wavelength(s)/types of light do you use?  What type of beer?  Several different types?  Is the check for skunking simply tasting or do you get beers analyzed on some regular schedule?

As someone who sets up experiments, it's certainly one that would be great to see done.  But setting it up and analyzing it are where the details become important.

[Stevie]

Basic brewing did this, and I have experienced it myself. They put out some SNPA and it was skunked in <15 minutes. I've experienced it while BBQ'g outside.

[denny]

Basic brewing did this, and I have experienced it myself. They put out some SNPA and it was skunked in <15 minutes. I've experienced it while BBQ'g outside.

That kind of thing is easy...I've done it many times myself.  But as a quantifiable experiment there are hurdles.

[Stevie]

I guess it depends on how technical you need to be. I think it could be done low tech pretty easily.

[denny]

I guess it depends on how technical you need to be. I think it could be done low tech pretty easily.

It just depends on what you want to know....with what you propose, you can find that a hoppy beer will skunk in 5-10 minutes on bright direct sunlight.  But if you want to know how much sunlight, what wavelengths, how long it takes exactly you need to do more.  I got the impression that's what Steve was talking about.

[Stevie]

But I'm 1000% positive academic studies have already researched this and have data covering all of that. For the "We are homebrewers and academic research doesn't always apply to us" crowd, simply putting a beer of N IBUs outside in direct light for X minutes and tasting it in a triangle should suffice.

[dmtaylor]

In strong light, skunking happens very quickly.  Almost instantly.  The human nose is capable of detecting mercaptans in extremely low amounts (don't ask me for specific ppb's, I'm sure you can Google it).  In weak light, meh... I dunno.

I do wonder how much opacity, haze, and SRM would impact the reaction rate.  For instance, a brown bottle does protect the beer far better than a green or clear bottle.  But what about the beer itself, if added to a clear container, is a stout more protected than a pilsner?  Does the haze of a NEIPA provide more protection than a clear IPA?

In any case, I'm too lazy and uninterested to run experiments myself.  In fact, I dare say, I actually enjoy a barely detectable amount of skunk, especially in a German or Mexican lager.  Just seems okay to me for whatever reason.  Some people don't mind diacetyl or DMS.  I don't like those very much.  However I don't mind just the slightest hint of lightstruck.

So anywho... just mumbling to myself out loud probably.  Cheers.

[Lazy Ant Brewing]

I recently added daylight bulbs and lots of them to my kitchen where I bottle.  Now, I bottle with those lights off and less  light from a window with louvered blinds or a bit of light coming from a nearby utility room.

I mostly brew brown ales to black-as-the-ace-of-spades stouts.  Too date, I've had no skunking I could detect.
I would be very interested if there was some way to quantify the process.  How many lumens and how much time.

[yso191]

Ha ha!  Nothing is ever simple is it?  The bottom line for me is a practical application.  For those who use a transparent fermentation vessel, what is the maximum exposure to average (I know...) indoor light (where most fermenting & bottling occurs) without off-flavors occurring.

It seems this would be fairly easy.  Have brewers detail every bit of time the wort/beer is exposed to light, with some designated for specific periods of time (i.e.: 5 minutes, 10, 20, 30).  All one would have to do is open the cloth covering, open the door or whatever else is blocking the light.

I guess I am arguing for the middle of the road approach - something that would be indicative, but not worthy of publishing in a peer reviewed journal.

[denny]

Ha ha!  Nothing is ever simple is it?  The bottom line for me is a practical application.  For those who use a transparent fermentation vessel, what is the maximum exposure to average (I know...) indoor light (where most fermenting & bottling occurs) without off-flavors occurring.

It seems this would be fairly easy.  Have brewers detail every bit of time the wort/beer is exposed to light, with some designated for specific periods of time (i.e.: 5 minutes, 10, 20, 30).  All one would have to do is open the cloth covering, open the door or whatever else is blocking the light.

I guess I am arguing for the middle of the road approach - something that would be indicative, but not worthy of publishing in a peer reviewed journal.

Incandescent light, no worries.  Daylight and fluorescent is what you need to worry about.

[hopfenundmalz]

I have had a low SRM IPA skunk in about one minute on the rail of my deck in direct sunlight on crystal clear summer day.

Dark beers have some self protection due to the color, neverad that happen so fast on a porter or stout.

[Frankenbrew]

Ha ha!  Nothing is ever simple is it?  The bottom line for me is a practical application.  For those who use a transparent fermentation vessel, what is the maximum exposure to average (I know...) indoor light (where most fermenting & bottling occurs) without off-flavors occurring.

It seems this would be fairly easy.  Have brewers detail every bit of time the wort/beer is exposed to light, with some designated for specific periods of time (i.e.: 5 minutes, 10, 20, 30).  All one would have to do is open the cloth covering, open the door or whatever else is blocking the light.

I guess I am arguing for the middle of the road approach - something that would be indicative, but not worthy of publishing in a peer reviewed journal.

Incandescent light, no worries.  Daylight and fluorescent is what you need to worry about.

What about LCD lights? I'm thinking that many brewers, like me, have converted all their incandescent bulbs to LCD.

[pete b]

I just find it too easy to put a covering over my vessels. Why take a chance or experiment? Its too easy to simply cover up to not to.

[HoosierBrew]

I just find it too easy to put a covering over my vessels. Why take a chance or experiment? Its too easy to simply cover up to not to.

I agree, Pete. Each his own, though. As for being outside with a beer, I try to keep it out of the sun or just accept that it'll get lightstruck pretty quickly.