Is This Diacetyl?

[MattC]

Hi brewers, I have just recently brewed my 3rd AG lager. My first (Bohemian Pils) and My second (Euro lager) both develpoed this flavour. Im not sure that it is a buttery flavour but more of a light honey/ sweet flavour and aroma. The flavour appeared after about a week in the keg. My last effort was a vienna. Pitched at 10 deg and brought it up to 12 deg over 2 days and left it for 2 weeks. I then upped the temp to 18 deg for 2 days, then filtered, kegged and carbed. One day after kegging I was so proud to smell the clean crisp aroma and taste the awesome flvour of my best lager ever. 4 days later GONE, the wonderful malt aromas and clean lager taste was replaced with the same flavour and aroma as the last 2 lagers.

I know 2,3 pentanedione has a honey like aroma and flavour but the taste threshhold is 10 times higher than diacetyl, so it couldn't be could it? And as I mentioned I dont really think it has a buttery flavour or aroma. I have perfomed a diacetyl rest, then chilled for 2 days, filtered and kegged.

What could this possibly be? Does diacetyl or 2,3 pentanedione take a few days to develop or is there from the start if its there at all?

 

[shonky]

My guess is diacetyl. I have had it appear after filtering and kegging even after extended (2 months) cold conditioning. Diacetyl can appear if it hasn't been completely cleaned up during primary fermentation if you beer has any contact with oxygen.

That is my guess, diacetyl is difficult to decribe but once you know it it is unmistakeable - it can be more of a fullness of body than an actual buttery taste. Your description of honey though sounds right to me.

What yeast are you using? Is it dried?

Here's a quote from Fix from an article in Brewing techniques, I got this from my notes and don't have the link to hand.

"Indeed, a widely observed but little discussed phenomenon occurs when diacetyl appears spontaneously in a beer that seemed to have normal flavors. Strong evidence indicates that this can occur when marginally dysfunctional yeast have been used in the main fermentation -- they tend not to metabolize all the acetolactic acid in the wort. The acetolactic acid spills over into the finished beer and later is oxidized to diacetyl. Mechanical abuse of packaged beer can promote this; headspace air is the oxidizing agent. Elevated temperatures augment the effect"

Unless you have an enormous starter my advice would be to pitch warmer, say 16-18 and slowly bring down to ferm temp over a day or two.

Hope this helps

Cheers

 

[Adamt]

Diacetyl (and I would assume other diketones) tend to pop up early in fermentation and your 18C rest would've cleaned them up. If it was diacetyl you would know, it's buttery and unmistakably so, that is if you are able to taste it (some people can not).

Sounds like it could be an infection of sorts, and considering they've all popped up after being packaged, maybe there's an issue with the filter and/or the kegs?

 

[acoulson]

Diacetyl (and I would assume other diketones) tend to pop up early in fermentation and your 18C rest would've cleaned them up. If it was diacetyl you would know, it's buttery and unmistakably so, that is if you are able to taste it (some people can not).

Sounds like it could be an infection of sorts, and considering they've all popped up after being packaged, maybe there's an issue with the filter and/or the kegs?

Agreed -if it's diacetyl you can't miss it- butterscotch candy. Also agreed- probably a really low level lactic infection. I've not experienced a bright beer or storage beer that has gone from clean to diacetyl without an infection.

 

[MattC]

Shonky - the description of fullness of body sounds spot on!! I would say fullness of body with a slight honeyish flvour aroma!

Im using dry yeast at present W34/70.

Adamt -Was the first time I used the filter and ran through the sanitary regime to a T, so shouldnt be that. As far as the kegs go, Im not sure either, as all ales I have brewed have turned out fine!

Could it be that I should leave it on the yeast longer ( say another week ) at lower temps after the diacetyl rest??

 

[shonky]

Hi Matt,

Same yeast that I used and had the same experience, I am pretty sure it is diacetyl (it definitely was in my case).

Was it Fermentis yeast or repackaged?

 

[MattC]

Hi Matt,

Same yeast that I used and had the same experience, I am pretty sure it is diacetyl (it definitely was in my case).

Was it Fermentis yeast or repackaged?

yeah Re-packaged yeast.

How did you overcome this?

 

[shonky]

yeah Re-packaged yeast.

How did you overcome this?

I fermented the same beer in two batches one with repackaged 34-70 and another with Danish lager yeast, both cold conditioned and filtered at the same time. I only experienced this with the 34/70 batch, I didn't throw the batch it wasn't even bad - just not right and the lovely crisp and hoppy character was overpowered by this full/slickness. It didn't degrade further but I have experienced this to a much greater extent before with this yeast (supposedly a low diacetyl producer).

I refer back to the Fix quote, perhaps stick with yeast packaged under laboratory conditions?

 

[katzke]

We did a tasting class and I did not get the taste of Diacetyl but I could smell it and it did have a slick feel to the pallet. It can also be described as creaminess in the mouth.

The way to detest it is do like the wine testers do and swirl the glass, stick your nose in and then take several short sniffs. It was like buttered popcorn to me. Like the microwave or theater popcorn.

One thing I did find out at the class is that this is all a developed skill. We did 4 samples and most of them were just different and not at all like they were supposed to be. You would think that at 3 times the threshold buttery beer would well be buttery, veggie beer would be veggie, and stinky cheese beer would be stinky. The only one that was easy was Acetic. I do not recall anyone having trouble with that one.

 

[Wasabi]

Diacetyl (and I would assume other diketones) tend to pop up early in fermentation and your 18C rest would've cleaned them up. If it was diacetyl you would know, it's buttery and unmistakably so, that is if you are able to taste it (some people can not).

Sounds like it could be an infection of sorts, and considering they've all popped up after being packaged, maybe there's an issue with the filter and/or the kegs?

Pediococcus infections also produce diacetyl, and it can take awhile to produce enough to reach threshold......

 

[Adamt]

Pediococcus infections also produce diacetyl, and it can take awhile to produce enough to reach threshold......

For a Pediococcus infection, wouldn't the lactic acid be more noticeable? Is the diacetyl synthesised in the same way as for Saccharomyces? If so, could a further diacetyl rest remedy it?


Something I just thought of... what kind of filter are you using? I would think if it was a pretty low pore size, you could have stripped out a lot of flavour compounds leaving you with a bland beer...

 

[Brewman_]

Reading with interest.

I have at times experienced something similar and have also use pre-packed 34/70? I must say it does not always happen, but comes on after kegging and does not go away at all.

What I found intersting is that some of the same batch that I bottled and left for much longer on a shelf did not exhibit the same character a the keg. Also the bottled beer was way over corbonated - not a gusher but very fizzy. The bottled beer had no sign of infection.

I was thinking that beer is under attenuated and so the keg cointains un fermented sugars that give that fullness and a sweet / fruitiness. Reason being is that in the bottle after the yeast cleaned up all residual sugars the flaw was not eveident but is was obviously over carb'd - so there must have been some extra sugars there.

Just a theory.

Fear_n_Loath