One week diacetyl rest, still have some off flavors

A while back I brewed a an all-grain light doppelbock, OG 1.074, but rather than using lager yeast, because I don't have the capability of reliably maintaining lager temperatures, I went for White Labs German Ale/Kölsch yeast which ferments at temperatures as low as 55F. I'm still learning a lot about the finer points of brewing. I was not aware that for a high gravity beer such as this one I should have made a yeast starter, so I just pitched the yeast directly from the vial at 70F and gave it a good sloshing (I need to improve my aeration techniques as well). Now, all these poor yeast practices aside, the gravity dropped to 1.020 within a week. At this point I brought the primary up to around 65F for a week-long diacetyl rest, after which I transfered to conditioning for a week, and then bottled. I know carbonation on high-alcohol beers is supposed to take a little bit longer, but about a week and a half after bottling and sitting at about 65F for a week and a half, I opened one up to see what was going on, and it had really strong honey taste. Diacetyl gives the beer the butterscotch taste, but 2,3-pentanedione gives the honey taste. Does the diacetyl rest take care of diacetyl and not pentanedione. How could the beer be heavy in one and not the other? If I let these sit in bottles for a few more weeks, could that possibly take care of the pentanedione?

Time heals all beer.

COLObrewer said:

Time heals all beer.

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'cept when it doesn't!

I've never heard of a diacetyl rest cleaning up pentanedione. I am no scientist, but I think the stressed yeast (from underpitching and such a cool temperature, which greater stresses the yeast) is the cause. Aging might help, but usually aging doesn't fix things like diacetyl, pentanedione, esters, fusels, etc.

Yooper said:

'cept when it doesn't! . . . . . .

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Well, there is that

I'm not giving up however.

Thanks guys. I really need to improve my yeast wrangling. I recently finished making a stir plate so that ought to help me avoid this in the future. The worst part is I can tell that it would have a great malty taste if not for the crazy honey flavor.

Ah, I just checked out White Labs stats for this yeast strain and it looks like fermenting on the lower end of the temperature range for this yeast almost triples the amount of diacetyl and 2,3-pentanedione. Cold ales are not for the unskilled brewer I suppose.

http://www.whitelabs.com/beer/strains_wlp029.html