I Have a Question

[hansolo]

How would the cooling wort affect it? I've always read diacetyl was a product of yeast respiration, and that the yeast would clean this out during fermentation if left in suspension long enough. How long did you ferment for?

Oops my mistake I was thinking of something else. I did find this though on John Palmer's site.

Diacetyl
Diacetyl is most often described as a butter or butterscotch flavor. Smell an unpopped bag of butter flavor microwave popcorn for a good example. It is desired to a degree in many ales, but in some styles (mainly lagers) and circumstances it is unwanted and may even take on rancid overtones. Diacetyl can be the result of the normal fermentation process or the result of a bacterial infection. Diacetyl is produced early in the fermentation cycle by the yeast and is gradually reassimilated towards the end of the fermentation. A brew that experiences a long lag time due to weak yeast or insufficient aeration will produce a lot of diacetyl before the main fermentation begins. In this case there is often more diacetyl than the yeast can consume at the end of fermentation and it can dominate the flavor of the beer.

[Mylo]

It sounds like it may be due to a lower pitch rate and under-aeration. Couple that with your 66 degree fermentation temp and you probably have your culprit. Get yourself a little, glass "theif". Next time, give it a taste at the end of your fermentation. If it tastes buttery, then raise it up to 75. Either way, you might want to consider a bigger starter next time. What kind of lag times are you getting?


Mylo

[Dirk McLargeHuge]

Usually 24 hours.

[siwelwerd]

It sounds like it may be due to a lower pitch rate and under-aeration.

That seems a little counter-intuitive to me. If there's less yeast and less 02, then there will be less diacetyl produced. Unless there just aren't enough yeast to scrub it out during fermentation?

[Dirk McLargeHuge]

How would the cooling wort affect it? I've always read diacetyl was a product of yeast respiration, and that the yeast would clean this out during fermentation if left in suspension long enough. How long did you ferment for?

Oops my mistake I was thinking of something else. I did find this though on John Palmer's site.

Diacetyl
Diacetyl is most often described as a butter or butterscotch flavor. Smell an unpopped bag of butter flavor microwave popcorn for a good example. It is desired to a degree in many ales, but in some styles (mainly lagers) and circumstances it is unwanted and may even take on rancid overtones. Diacetyl can be the result of the normal fermentation process or the result of a bacterial infection. Diacetyl is produced early in the fermentation cycle by the yeast and is gradually reassimilated towards the end of the fermentation. A brew that experiences a long lag time due to weak yeast or insufficient aeration will produce a lot of diacetyl before the main fermentation begins. In this case there is often more diacetyl than the yeast can consume at the end of fermentation and it can dominate the flavor of the beer.

That answers a lot of questions. But I have a couple more then. The first time this happened, I had a nice, malty Marzen. Tasted fine in the keg. Bottled it. Gave a few away, drank some. Tasted great. About a month later I entered a contest, and after shipping I sampled a bottle, and it was all butterscotch. So, can the diacetyl develop over time? Or was I tasting what I wanted to taste and not noticing the diacetyl?

[bub]

If you don't taste it at the beginning and you taste it later it is most likely an infection. Change out all your hoses and plastic.
BUB

[Dirk McLargeHuge]

That sounds a like a logical step one. Thanks, Bub.

But shouldn't I be getting diacetyl in everything, not just the maltier beers? I have brewed three wheat beers--nothing. A wheat porter has no off flavors. Just the Maibock and the Marzan.

[polski]

forget it. go the liquor store route. OR it might be the fact that you are tasting the caramelization that you are getting on maltier beer due to the condensed boil and you have misread/tasted it as butterscotch. If you are putting more malt extract in for your maltier beers, then boiling for 60 min in 3 gallons that might be why you only taste it in those beers.