Diacetyl in Beer

It's a flaw depending also to style. Sometimes amounts of it are expected or considered ok as "to style" for some beers such as English Bitter...

also depends on how you define "infection"

but here's the thing and it sort of makes a bit of your questions harder to answer.

People have different levels of tolerance for diacetyl, some easily pick it up making it very unpleasant for them, others like myself only notice it when it's very obvious, and some people never detect it...

Therefore, diacetyl sometimes depending on the person isn't always a problem.

For me personally it smells more like artificial movie theatre popcorn, and can sometimes be very slick on the palate almost like an olive oil finish.

 

tasting beer by Randy Mosher is the book to read.

also Off tasting kits will help you learn if your interested.

http://cicerone.org/off-flavor

 

I have a friend who is super sensitive to it, and I have low sensitivity to it. I can recognize it more easily in aroma, but in taste it has to be pretty evident for it to bother me.

It is a natural product of fermentation and occurs early in the ferment. As far as cleaning up, in fermenting it can certainly be cleaned up with a proper rest. Lager yeast, and also ale yeast brewed at lower temps, need to have the temp increased for a couple days when nearing terminal gravity. Ale yeast brewed at higher temps and left to condition for proper time naturally take care of diacetyl (most of the time, some exceptions are bacterial infection, or underpitching yeast)

Not sure about the increase or decrease in bottle conditioning beers over time.

 

Some of the experienced homebrewers could comment more on this in their forum and probably have.
We worry about diacetyl from underpitching yeast. Depending on the original gravity of your beer, a certain number (billiions) of cells of yeast need to be pitched. If you do not pitch enough yeast, alcohol will still be made, and you will have beer. However, the yeast will not properly "clean up" after themselves, and that leads to diacetyl.

My guess as to the BA beers you had is that they are very high ABV. There is a chance not enough yeast was pitched to account for the higher alcohol content. That would lead to diacetyl. I don't think infection or the barrels themselves have much to do with it.

 

I found this video on the subject a few months ago, hope it helps. I learned a few things, but sadly got bored part way through, so my memory retention is now pretty much fail because I really didn't pay attention.

 

It's 32 minutes on diacetyl. I think the beer Gods will give you a pass this time.

 

The last time I had anything really "diacetyl like" in my experience was the following:

Minor: Popcorn Pilsner Sun King - could be argued to style based on what they were achieving, cask Wings of Armageddon and mango and peppers, gave a pint to someone who is very sensitive and he detected it right away, I didn't even notice it.
Medium: Silva Stout 3 (there is a well known thread on this and in the review section ) real slick, but I found it tolerable and almost kind of interesting component to it, but it certainly didn't come off as what the brewery had in mind for the flavor profile
Pushing it: Bigger Better Bolder Faster Bruery/Dogfish collaboration. Bought this when it came out and loved the idea but the diacetyl was really noticeable and not that pleasant, and overtook everything the beers intended flavors were probably trying to achieve. Interestingly enough I went to a tasting many years later with someone who brought a bottle that was obviously years aged and the diacetyl character while still there was much more toned down and tolerable. Interesting.
Overboard: Great Lakes Holy Moses on tap at a local bar : This was literally like drinking liquid butter and castor oil. It felt like liquid grease going down my throat it was shockingly awful. Very surprised that this happened from a keg, and more so from Great Lakes because they are one of my favorite and well consistent breweries, I love much of their beers a good solid go to, but it has put me off from ever thinking of trying this beer again unfortunately

So that's my diacetyl experience to date which as you can see is luckily very little over the many brews I've had

 

There's a difference between free diacetyl and total diacetyl. Free diacetyl in beer is what is perceived - which is due to taking the beer off of the yeast too soon or due to an infection. Total diacetyl is made up of free diacetyl and the conversion of alpha-acetolactate into diacetyl. You do this conversion by heating up a sample of beer and adding some oxygen to it. This is why sometimes if you get a fresh beer you detect no free diacetyl, but if you taste the same beer later on as it's aged then you'll taste the butter.

Micro organisms like pediococcus throw diacetyl as well, so sometimes it's due to an infection. If you ever had a butter bomb at a bar, usually it's due to poor draft line cleaning than a flaw with the beer itself.

Some english style ales allow a small amount of diacetyl and don't consider it a flaw. Pretty much all lagers and american style ales consider diacetyl an off flavor.

Yeast will clean up diacetyl if it's healthy. The yeast forces alpha-acetolactate out of the cell due to its toxic nature to the yeast. The alpha-acetolactate will convert into diacetyl, which the yeast will then break down into 2,3 butanediol, which is nearly flavorless. This is all for the synthesis of certain amino acids.

 

I'm freakishly sensitive to it. I can smell beers with it from a few feet away and will drain-pour or at the very least refuse anything that has much of it. I consider it a major flaw in just about anything and find that brewers love to call something English or Czech style to cover for a beer that didn't turn out right.

One thing I have noticed is that when lots of native (purchased in the country) German beers get old, they seem to become buttery. That's even when it was totally absent in a fresh bottle. I've always wondered how/why that happens.

 

I find that diacetyl takes the optimism out of drinking the beer. Even if the taste and smell is mild that beer is less than fun to drink as compared to when diacetyl is not present. Sometimes when people say I just don't like that beer it's because of diacetyl. Movie theater popcorn, popcorny, buttery, fake butter or just a mild slickness on the palate can all be diacetyl. In some beers it's expected and part of the flavor in others it is not. I can literally consume mass qantities of lager all day because it's clean.

 

The O2 in the package, and the O2 that diffuses in through the cap liner combine with the precursor to form Diacetyl.

 

Good thread, I think its possible I've strangely become more aware of the buttery popcorn or slickness as of late. Very recently visiting two local new-ish breweries I could only pick up that sensation/flavor from thier IPA's.
I assumed it was related to diacetyl but wasnt sure, I defintely did not care for it.

 

Many of the questions posed by the OP have been addressed.

Some of my 2 cents:

During fermentation yeast will create a lot of diacetyl but if the fermentation is permitted to complete in a healthy fashion the yeast should ‘clean up’ the diacetyl by converting it into differing compounds.

I am pretty sensitive and my palate perceives diacetyl as buttery/butterscotch. My preference is for diacetyl to be so low that I can’t perceive it. Something like 20% of the population is ‘blind’ to diacetyl so the presence of diacetyl in beer should not be an issue to those folks.

As has been mentioned, diacetyl can also be a result of a pediococcus infection. This will take some time to occur and could be a potential reason for why aged beers have perceptible diacetyl.

Below is a link to a discussion of diacetyl formed during fermentation.

Cheers!

http://www.whitelabs.com/files/Diacetyl_Time_Line.pdf

 

"Taste of diacetyl - Some characterize diacetyl as butterscotch, while others describe it as "movie theater popcorn." But these are not same flavors to me. Are differences in taste simply attributable to the amount of diacetyl present in a beer? Or are there different "types" of diacetyl?"

During the recent National Homebrewers Conference I attended a presentation on off-flavors and beers which were doctored with off-flavors were provided. One of the beers had diacetyl added and it clearly tasted like butter/butterscoth to me. The person giving the presentation made mention that he could perceive diacetyl in beer but to his palate it was not butter/butterscotch; I can't specifically recall what flavor descriptor he stated. So, diacetyl can indeed have differing flavors for different individuals.

Cheers!

 

"It tastes like i should be dipping crab meat in it" great tasting note from my friend

 

The average tasting threshold for perceiving diacetyl in a light lager is around 30 ppb, which is insanely sensitive. Acetaldehyde is in the 10 ppm range for comparison.

Obviously, if you have more flavorful stouts or IPAs, the diacetyl detection threshold increases.

 

Some diacytyl is fine for Czech pils

 

When I was in school in Germany, I stopped drinking a lot of German Pilseners because of diacetyl. It seemed like about half of them had diacetyl. This was true even or German brewers that mocked other breweries for having beers wth diacetyl in them. It really irked me how they would perpetuate the myth that German beers are the best in the world, yet so many of them had flaws.

 

http://www.bjcp.org/docs/OffFlavorFlash.pdf