Why do breweries partially bottle condition?

[thefost]

From what I've gathered, a lot of pro breweries use a partial bottle conditioning technique. First, they force carbonate the beer to around 1.5 - 2 vol CO2. At some point in the process the beer is filtered and yeast removed. Then at bottling time yeast and sugar are added back in so that the bottle can condition to get the last little bit of needed CO2. This is why there is so little yeast and dregs in commercial bottles of beer (ex: Sierra Pale Ale).

My question is why not just fully force carbonate? I have a few ideas why but I'm not sure what the real reason is.

 

[FarmerTed]

I don't think they're partially force carbonating; more likely, they cap the fermenter near the end of fermentation, and trap around 2 volumes of CO2. They bottle condition to either meet German standards or just because they think it produces a better packaged beer.

 

[cyanmonkey]

Sometimes they'll use a different yeast for conditioning than during fermentation ie filter, then bottle with say T58 (I think it's what Allagash uses) for a different flavor.

 

[day_trippr]

A thought: "bottling yeast" will consume head space O2.

Considering the rigors that the huge macros go through to purge O2 out of their bottling/canning lines (double or even triple purging) perhaps that cuts the small-scale bottling pita factor...

Cheers!

 

[cyanmonkey]

So will oxygen absorbing bottle caps, I suppose, but then again I suppose it's only absorbing the O2 because it's replaced by CO2.

 

[norcalhomebrewer]

Longer shelf life and less gunk in bottle. Yeast help prevent oxidization in the bottle.