Ah, so that's what diacetyl tastes like... but why?

[PasbitinusBluinusRibbinus]

I just kegged a batch of 1.040 blonde that had been in primary at 63 degrees for day and 50 degrees for a week following. Yeast was Nottingham. Ambient temperature in a vacant house. FG was stable, so I kegged. I couldn't taste any diacetyl in the samples from primary, but now that its cold and carbed there is a strong butter taste in the finish.

Was the low ferm temp and not enough time in primary to compensate the cause?

 

[Cbaddad]

Probably. Need a bit more info though.

 

[dryboroughbrewing]

50 for Notty is pretty low (it's ok in the high 50's low 60's) So I would expect that's your problem, I probably would have raised the temp to at least 65 for a couple of days at the end of such a cold ferment just to make sure to drive off the diacetyl. Also if you're ever concerned you can also do a forced diacetyl test. (search for that phrase and you should get a few hits!)

 

[Doongie]

http://byo.com/stories/item/546-diacetyl-homebrew-science

 

[CRoth36]

Going with the low temp

 

[PasbitinusBluinusRibbinus]

Thanks for the confirmation. I would have done a diacetyl rest, but alas time constraints had me kegging early for a new years party. Maybe the guests will stop noticing it by the time the other three kegs are gone!