I brewed a Blue Moon clone a few weeks ago and have a distinct butter flavor in the beer. I have never had Diacetyl in any beers much less with a fairly cleanl;y fermenting ale yeast like SAF-05. The beer had an OG of 1.051 and finished at 1.011. I used a single sachet of rehydrated SAF-05. The beer had 1 oz of corriander and 1 oz of sweet orange peel, both added with 15 minutes left in the boil. The beer fermented at 64 degrees for 12 days before bottling. Any ideas on what I could have done difererent?

Doesn't look like you did anything wrong. Just let it sit for another few days and let the yeast clean up their junk.

You can raise the fermentation temp towards the end, and also leave it on the yeast a little longer (12 days doesn't seem too rushed to me though, unless you did something silly like use a secondary). But the most important thing you should do is taste your beer before bottling. Assuming this is not caused by an infection in the bottle (in which case clean/sanitize your bottles better), the diacetyl was already there before you bottled, and you should have tasted it. Then you would know to ramp up the temp, give the fermenter a swirl and let it sit a couple days and retaste.

The diacetyl may well not have been there before he bottled. It is quite possible , however, that alpha-acetolactate, the precursor, was. Diacetyl is often formed in the package when acetolactate is non enzymatically oxidized. To prevent this happening you need to either make sure there is absolutely no air in the bottle (impossible) or that there is enough yeast in the bottle to take up the diacetyl that forms.

There is a simple test for acetolactate in beer. Just heat a sample and expose it to air. This accelerates the conversion of acetolactate to diacetyl and, if you have potentially problematical levels of it, you'll smell the diacetyl. You can, in such cases, leave the beer on the yeast longer before bottling or bottle with yeast.

Interesting. Thanks for setting me straight. This point is not mentioned (or maybe my eyes just glazed over when I saw a word with that many syllables) in the common homebrew books. This article seems to imply that given a healthy fermentation, you are unlikely to have significant levels of alpha-acetolactate laying around.

Another variable is are you bottle conditioning and, if so, how are you doing it? If you are adding additional sugars to start secondary fermentation you need to give the yeast additional time to clean up as well.

my 2 cents,
Alan

I got my newest issue of BYO in the mail yesterday and was stunned when the cover read Prevetnting Diacetyl. I read the article and have a pretty good feel now for what happened. The article stated that any time you use a high percentage of non-malt adjuncts the diacetyl production goes up. This recipe had almst 2 lb of rolled oats and 1 lb of flaked wheat. Knowing what I know now I will allow for additional cleanup time with these beers in the future. I normally primary for about three weeks and only secondary if I am dry-hopping. With this beer I rushed a bit b/c I was not concerned about clarity. In the future I will also taste the sample prior to getting set up for bottling/ kegging. I always have tasted during that process but not before. Honestly I had about 10 bottles capped before I figured out what I was tasting and had my "oh shit" moment. Ihad never tasted it before and actually percieved it as a vanilla tone at first.

Haven't seen that yet and will read it with interest unless I've let my subscription expire and don't get the issue.

That aside, I suppose the logic behind the non malt adjunct thing relates to the fact that alpha-acetolactate is a byproduct of valine synthesis by the yeast. The best solution to potential diacetyl problems is, thus, to insure that the wort is rich in valine but as malt analyses don't generally list that you are pretty much stuck with what you get.

Proper management of the fermentation and especially "lagering" based on the general priciples outlined in the earlier post should take care of any diacetyl that is produced by the yeast. As you might expect the yeast strain involved has quite a lot to do with diacetyl levels in beer. Some strains are known to throw lots of it and others less. Diacetyl produced by infection is another matter. When it is really high brewers call it "sarcina sickness" and it is nothing like what yeast produce normally.