Diacetyl?

I think this is what happens to certain batches of Oskar Blues beer. I've definitely gotten diacetyl in some packs of Dale's Pale Ale, though not enough times to say it's an intended flavor (and it's a much better beer when it's 'clean'). It's usually the older ones, too. I'm guessing it happens at packaging if it's going to happen with them.

 

Diacetyl/buttery flavor is good in some beers. I wouldn't want to taste it in an IPA, however. I also wouldn't want to taste it in pale ales. Perhaps some American blonde style ales are okay with a little buttery flavor, as long as it isn't overpowering. I am not sure exactly...

 

You need to review your Cicerone training materials. If they tell you that diactyl is associated with dirty equipment or packaging you received bad training.

 

I hate it in everything, even when it's "appropriate" like in Czech pils and certain English ales. Blech.

 

It's produced by many microorganisms, and ALWAYS produced by saccharomyces. Are you suggesting that diacetyl is what you pick up when you have a pediococcus infection?

 

correct, diacetyl could be the result of pediococcus. the practical guide to yeast does a good job explaining everything yeast, would recommend.

 

I don't disagree with that fact. Again diacetyl is produced by many organisms and is present in all beer. I disagree with the notion that diacetyl flavor is caused by dirty equipment. In 30 years of brewing I have never heard that suggested that if you have diacetyl flavors, you should suspect infection as the cause. Now if you have inappropriate souring or even phenolics...

Edit: if you have exhausted all other causes like, yeast health and related temperature controls to yeast, well then maybe you might started looking towards weird causes, but if you have a ped infection in a released batch of beer, customers are going to complain of sour flavors not diacetyl.

 

That's true most days.

In practice, we both know the difference between diacetyl and vinegar and will probably assume the usual suspects for each.

 

The only time I've detected diacetyl was in a bottle of the Bruery's White Oak. I remember the mouthfeel being buttery, but personally, I loved it! I can see it definitely not working for other beers, but I guess this off flavor worked with my bottle. I dunno.

 

His traing was fine.

Diacetyl can certainly be the product of an infection. Certain stains of lacto and pedio are major diacetyl producers. In many cases the diacetyl is far more noticable than any lactic acid produced.

I suspect that bacteria is more often the cause than you think.

Oxygen pickup in packaging can also contribute to diacetyl formation.

Improper aging is sometimes the case, but bottle conditioned beer have yeast in them that should reduce a reasonable amout of diacetyl. If the source is bacterial, the yeast cannot reduce the D to acceptiple levels.

How to look for lacto and pedio....

Advanced homebrew or basic lab techiquie: Use HLP media tubes to look for lactro and pedio. Incubate for 2 weeks...some strains are very slow growers, but they can produce diacetyl over time.

Not practical withut a serious lab: The real key to determining the source of diacetyl is to look a the ratio of butandione (diacetyl) to pentandione. Typacly this is a 5:3 ratio. These are generally produced by the takeup of amino acids by yeast. If the ratio is out of wack, a bacterial contamination is likely the source. Using this method with a GC will indicate an infecetion long before it can be detected by plaitng.

Vinegar is a whole differnet bacteria and pathway......

 

This argument is academic. If you get a can of Deviant Dales, and taste diacetyl you shouldn't jump to the conclusion that there's a ped infection. Infection is not the primary cause of diacetyl flavors. When there is a pediococcus infection, the indicator will be sour, acetic acid (vinegar) taste - so much so that it is unlikely that you will even notice any diacetyl produced by pediococcus.

 

Yeah, science!

 

malolactic fermentation in wine produces diacetyl, the amount depending on the strain of bacteria used. There's a tremendous amount of buttery diacetyl flavor in Red Hook ESB. A bit too much.

 

Some produce more diacetyl than others - just like yeast. But Primarily Pediococcus produces acetic acid as yeast produces alcohol. So I don't think there is confusion over what infected beers taste like. I doubt I have ever tasted diacetyl in a beer and missed infection as the cause. However, I could be wrong. The cause is usually the same.

 

Not as much as there used to be -- Red Hook toned it down a while back because of complaints. I was a little disappointed when they did, seemed to lack some of its original character.

 

If you taste diacetyl, the only assuumption you should make is that there is diacetyl in the beer and nothing else.

As the source, you need to look at facts. Anything else is a guess.

Certain lacto and pedio strains are very strong producers of diacetyl.

From a practical (not academic) side, I have seen many commercial examples of beer gone bad that had no noticibe sourness but were loaded with diacetyl from bacteria. I was able to confirm this was from bacteria in the lab by looking at the ratio of butandione to pentandione with a gas crohromatograph and mass spectrometer. These results were later confirmed by a microbilogist who anarobically plated the beers on a media that inhibited yeast growth. Lacto or pedio were present in all samples.

The pH of these beers were not unusaully low, this indicated that a signifigant amout of acid was not produced.

Many lacto and pedio strains produce lactic acid, this is the sourness you are describing, not acetic acid.

If you have acetic acid (vinegar), you may want to look at acetobacter or gluconobacter as possible sources, not pedio or lacto. Acetobacter needs oxygen and alcohol to be active, gluconobactr anc ferment sugar to acetic acid. Acetic acid has a very distinct vinegar aroma.