Butter In My Bottles But Not In Keg

[OneEye]

Hey Guys!

I brew full sized batches that are eventually split in half, after fermentation has finished. I have a small place and half of my batches go into my 2x9L kegs, for two different brews, in my bar fridge and the other half of my batches get bottled. I've been noticing that my bottles are noticeably buttery (diacetyl i'm guessing) whereas my kegs are fine (fantastic if I don't say so myself )
The bottles are bulk primed for ~2.5vol usually and kept in my ferm chamber at a cozy 20C. I like to think my sanitation habits are fairly thorough but can diacetyl come about from poor sanitisation??

 

[Nick JD]

...can diacetyl come about from poor sanitisation??

Yes. From a type of pediococcus (that's pretty much lacto's cousin). Though it being in ALL the bottles is weird. It's the kind of thing you'd get in one, or two - not all.

 

[Bizier]

It could be pedio, but it could also be alpha acetolactate, the diacetyl precursor.

It is easy to work out which by using a forced diacetyl test on your kegged beer.

 

[Thirsty Boy]

I suspect just oxidation in the bottles - you probably are quite careful to purge oxygen from your keg, and you probably believe that "the yeast takes care of any oxygen in a bottle" - it doesn't.

Try reducing your headspace and filling the bottles more carefully.

If its not that - then you have some yeast pitching/wort aeration/yeast health issues that (as bizier says) could mean that you have excess aal in the beer. Its not converting to diacetyl in your kegs because there is less oxygen and they have been kept cold - it is converting to diacetyl in your bottles because they have more oxygen and they have naturally been warmed up in order to condition.