why don't we worry about hop skunking in glass carboys?

[twd000]

I understand that the greatest enemies of fresh beer are heat and light, and oxygen. We control temperatures and keep out oxygen during fermentation, but a lot of us use clear glass carboys. Why aren't we concerned about the beer getting prematurely skunked due to light?

 

[bob1852]

Because you cover them with a t-shirt or keep them in a dark place?

 

[twd000]

Because you cover them with a t-shirt or keep them in a dark place?

Starting today!

 

[veritas524]

because you cover them with a t-shirt or keep them in a dark place?

+1

 

[indigi]

I wrap mine in thin blankets or beach towels. I'm paranoid that some light will get through a t-shirt.

 

[bob1852]

I wrap mine in thin blankets or beach towels. I'm paranoid that some light will get through a t-shirt.

Of course - I meant those really expensive SPF80+ t-shirts that you can wear to the beach without getting sunburned

 

[Edcculus]

Oh but we do! Cover it, or keep it in a closet.

 

[ChshreCat]

I haven't heard anyone not worried about hop skunking in glass carboys. Get those suckers in a dark place!

 

[imasickboy]

Yup, I have 3 of 'em sitting in my dining room dressed nicely in my t-shirts, just waiting to be emptied.

 

[pkeeler]

I've always put my carboys in black garbage bags or cover them with something. Then I put them in a dark place. Double insurance.

 

[Ben_Persitz]

Because I keep mine in my temp controlled fridge where it is usually dark

 

[theonetrueruss]

dark towel and dark closet... and sitting in a plastic bin

 

[Revvy]

I think you missed the memo about keeping your carboy out of direct light, or at least covering them with t-shirts.

 

[vortexla]

dark closet works for me

 

[SwampassJ]

In a chest freezer, no one can hear you scream.

 

[kanzimonson]

Before someone jumps to the next conclusion, I wanted to add that you don't have to worry about skunking until you add yeast... so don't worry about the carboy sitting in the sun as you're draining from the boil kettle.

I'm gonna test out this screaming in a chest freezer thing...

 

[MikeRoBrew1]

Starting today!

DOH!! Thumbs up to you for asking

 

[Revvy]

In a chest freezer, no one can hear you scream.

I made this for a thread where a guy found a bunch of wine aging in the basement of an empty house.

 

[jerryalan]

I cover mine up with a cheap comforter. I'm quite paranoid about the light getting to the beer.

 

[mojotele]

Good lord that's a lot of wine! What, did your friend buy a house and that was left? Or was it just an empty house that your friend wandered in to?

And, to keep this thread on topic, you don't have to worry much about skunking in a glass carboy if you have a dark beer. Light can't penetrate a stout as much as it can penetrate a pilsner.

 

[Revvy]

Good lord that's a lot of wine! What, did your friend buy a house and that was left? Or was it just an empty house that your friend wandered in to?

And, to keep this thread on topic, you don't have to worry much about skunking in a glass carboy if you have a dark beer. Light can't penetrate a stout as much as it can penetrate a pilsner.

It's a thread on here from over a year ago, I can't remember the title, or the particulars.

 

[Hermit]

Before someone jumps to the next conclusion, I wanted to add that you don't have to worry about skunking until you add yeast...

Geez, and here I was thinking it was HOPS that skunked. So those hops I left too long in the hop bag after boil in the basement and started smelling like skunk must have been exposed to some wild yeast I guess? No, yeast have nothing to do with this.

 

[JohnnyO]

It's a thread on here from over a year ago, I can't remember the title, or the particulars.

I remember that!! (I don't remember much, or so SWMBO would have you believe).

I think the particulars were that he was some form of contractor going into a job with a new absentee owner and that was in the basement.

 

[Randar]

Anyone able to find a link to that thread. Totally intrigued now but my searches are failing to find it.

 

[Shooter]

I remember that!! (I don't remember much, or so SWMBO would have you believe).

I think the particulars were that he was some form of contractor going into a job with a new absentee owner and that was in the basement.

Something like this, I think the old guy who made the stuff might have still been around, but was a bit infirm, and his relatives might have had the OP doing something in the house. I do remember everyone telling him to try it. If I remember correctly, it had all gone to vinegar. I think it was twenty years old.

 

[ChshreCat]

Anyone able to find a link to that thread. Totally intrigued now but my searches are failing to find it.

https://www.homebrewtalk.com/f14/strange-find-135050/

 

[HerotBrewer]

And if you don't want to use a t-shirt, do what I do.
Every time you go to the grocery store (like when I buy spring water for brewing) get a couple of paper bags. Cut a hole in the top for the airlock to stick out of, and slide it over your carboy. Fits perfect, at least on Better Bottles.

 

[PVH]

Geez, and here I was thinking it was HOPS that skunked. So those hops I left too long in the hop bag after boil in the basement and started smelling like skunk must have been exposed to some wild yeast I guess? No, yeast have nothing to do with this.

Uh, the hops just rotted. You'd get equally terrible smells if you boil other vegetable matter and leave it sitting around.

 

[SwampassJ]

Geez, and here I was thinking it was HOPS that skunked. So those hops I left too long in the hop bag after boil in the basement and started smelling like skunk must have been exposed to some wild yeast I guess? No, yeast have nothing to do with this.

I wish I could be as much of a tool as you.

 

[kanzimonson]

Oh I love how wrong you are Hermit.

For a beer to get skunky, it requires all the ingredients in beer. Yes, the actual chemical comes from the hops, but it requires metabolic activity from the yeast's consumption of malt sugars. I don't know the science - just passing on something I heard from the BN.

Saying that skunkiness comes from light-struck hops is like simplying fermentation to "Sugar + Oxygen = Alcohol + CO2" Technically true but an extreme oversimplification. Sounds like Hermit's the kind of guy who needs that, though.

 

[mojotele]

The compounds in question that cause skunking are primarily riboflavin (from the yeast) and isohumulone (from the hops). Here's a good source.

Riboflavin, a yeast chemical, absorbs light energy with wavelengths of 350 to 500 nanometers (nm). This energy makes the iso-alpha acids release free radicals that combine with sulfur chemicals produced by the yeast, resulting the stinky thiol (sic)

 

[Hermit]

You are telling me my used hops didn't smell like skunk because there was no yeast? I know what I smelled. Sorry.

 

[Shooter]

I bet they smelled skunky, like cousin skunky. Maybe that's different than light struck skunky.

 

[Hermit]

The compounds in question that cause skunking are primarily riboflavin (from the yeast) and isohumulone (from the hops). Here's a good source.

Here is one that says the compounds are created in the boil, which is my experience.


https://www.homebrewtalk.com/wiki/index.php/Can_light_skunk_hops%3F


Dave Wills of Freshops answered this question on the June 1, 2006 episode of Basic Brewing Radio. He confirmed that skunking is the result of light interacting with isomerized alpha acids, which do not exist in the raw hop products (including hop pellets and hop plugs), but are created in the boil.

Nothing about yeast here. Again, my personal experience, listed in my first post, leads me to believe the latter.

What you site appears to be someone that has studied beer after bottling and is talking about one possible path to skunking based on that. Let's face it, probably not too many actual studies are done on wort that is allowed to sit around in the sun since this just isn't done in commercial breweries. Sulfur and other compounds involved can be in the wort without the need for yeast to release it.

 

[mojotele]

Isohumulone is an isomerized alpha acid. So your source just agrees with mine. I made no mention of how the isohumulone was produced. Indeed, it is produced when humulone from hops becomes isomerized during the boil.

Skunk flavor in beer comes from riboflavin absorbing light and causing a chemical reaction in isomerized alpha acids, particularly isohumulone. Here's another source, and another, and another.

This isn't really a matter of belief or opinion. It is fact. Your used hops likely smelled skunky because leftover sugars on the hops were being fermented by wild yeast. Hence, riboflavin was present as well as isohumulone. Add light and you get MBT.

 

[Hermit]

Uh, the hops just rotted. You'd get equally terrible smells if you boil other vegetable matter and leave it sitting around.

You are telling me I can leave just any vegetable matter laying about and it will eventually smell like skunk?

 

[Hermit]

Oh I love how wrong you are Hermit.

For a beer to get skunky, it requires all the ingredients in beer. Yes, the actual chemical comes from the hops, but it requires metabolic activity from the yeast's consumption of malt sugars. I don't know the science - just passing on something I heard from the BN.

Saying that skunkiness comes from light-struck hops is like simplying fermentation to "Sugar + Oxygen = Alcohol + CO2" Technically true but an extreme oversimplification. Sounds like Hermit's the kind of guy who needs that, though.

Before calling me wrong please at least attempt to quote a source and not just say one exists. Again, I'm going from personal experience so your source is going to have to be pretty damned good to make me change what I have experienced first hand.

 

[Hermit]

Isohumulone is an isomerized alpha acid. So your source just agrees with mine. I made no mention of how the isohumulone was produced. Indeed, it is produced when humulone from hops becomes isomerized during the boil.

Skunk flavor in beer comes from riboflavin absorbing light and causing a chemical reaction in isomerized alpha acids, particularly isohumulone. Here's another source, and another, and another.

This isn't really a matter of belief or opinion. It is fact. Your used hops likely smelled skunky because leftover sugars on the hops were being fermented by wild yeast. Hence, riboflavin was present as well as isohumulone. Add light and you get MBT.

You are assuming only one path is available to release the compounds formed in the hops based on what was probably experiments involving bottled beer on a commercial level. This isn't a hard experiment to do though in my area I'd have to wait till next spring to get enough light. Just take my hydro sample outside and let it sit.

Also, your very first source says: "MBT can be prevented by avoiding exposing wort or beer to the relevant wavelengths of light after the completion of the boil."

And: "MBT is the abbreviation for 3-methyl-2-butene-1-thiol, a compound formed by the reaction of isomerized alpha acids, specifically isohumulone, with riboflavin in the presence of certain wavelengths of light."

Are you saying no yeast, no riboflavin?

Second source says the same thing. Again, the isohumulone and riboflavin.

Third source, same story: isohunulone and riboflavin.

 

[Hermit]

I wish I could be as much of a tool as you.

Sounds like you just passed me. Congratulations. :rockin:

 

[Hermit]

http://www.franklinbrew.org/brewinfo/lightstruck.html

Conclusions

Photochemistry undoubtedly deteriorates the quality of beer and protection against light is absolutely necessary. Isohumulones, the main beer bitter compounds derived from hops, undergo light-induced decomposition either on direct illumination with UV-A light, or via a photoredox reaction involving excitation of a visible-light absorber such as riboflavin.

Please notice riboflavin is NOT necessary: undergo light-induced decomposition either on direct illumination with UV-A light, or

I can't find a breakdown for malted barley but since we find riboflavin in malted barley flour, can we assume that it is in the original? Note also "such as riboflavin"in the research. (Actually riboflavin is usually in the germ so much is lost in the milling process so the link figure is probably much lower in riboflavin than the malted barley we use.)

http://nutritiondata.self.com/facts/cereal-grains-and-pasta/5788/2

We now have both bases covered. Neither require yeast. I think someone reading the research decided yeast played a key role since they produce riboflavin and someone else "ass-u-me"d that yeast were therefore needed. Then one web page quotes another until you have all sorts of circular references backing each other up.

I think it is safe to add this to another busted brewing myth at this point.