carbing and attentuation question

proton · 05-04-2007, 03:21 PM

Here's something I've been wondering about. Should you take into account the attentuation potential of your yeast when deciding how much priming sugar to use when bottling? It seems like if you use a yeast with high attenuation, and you have a complete ferment, you'd need more sugar to achieve the same level of carbonation that you would with a less attenuative yeast. Or is the difference between yeasts too small to matter? Or am I totally misunderstanding the whole concept?
For example, I brewed a saison with Wyeast 3522 (attentuation 76 percent), used about 3/4 cup of corn sugar to prime, and it's definitely under-carbed (though still mighty fine). On the other hand a I brewed a bitter with Wyeast 1099 and 3/4 cup of corn sugar resulted in like 6 inches of foam from each bottle. I would guess that incomplete fermentation is the most likely culprit, but I'm curious if it could be a yeast issue.
I guess kegging would solve all my problems, but I'm just not there yet.

zoebisch01 · 05-04-2007, 03:54 PM

Quote:

Originally Posted by proton

Here's something I've been wondering about. Should you take into account the attentuation potential of your yeast when deciding how much priming sugar to use when bottling? It seems like if you use a yeast with high attenuation, and you have a complete ferment, you'd need more sugar to achieve the same level of carbonation that you would with a less attenuative yeast. Or is the difference between yeasts too small to matter?

I think you mean the other way around in that a higher attenuating yeast should theoretically yield a higer amount of carbonation. This is a good question though, and I would imagine it has an impact, but if it is measurable or not is really the question. Since most folks don't concern themselves with this I am guessing that it doesn't matter.

I think in general, the concern should lie in making sure you have enough healthy yeast left over to do the job, sufficient priming potential, proper priming temps and also adjust for residual C02.

Evan! · 05-04-2007, 03:54 PM

It's probably not an issue. The difference in carbonation between bottles has more to do with temperature during initial conditioning, as well as how long it's been aging in secondary. How long did your saison age? If it sits for a long time, enough yeast can drop out and shut down that you may need to repitch with some dry yeast at bottling time. My rule of thumb is if it sits in secondary for more than a month, I repitch with a few pinches of rehydrated dry yeast at bottling.

Overcarbing is typically either caused by a bacterial/yeast infection (the unwanted nasties eat the sugar that beer yeast can't, thus producing excess co2 and drying the beer out), or by an incomplete primary fermentation (resulting in leftover fermentable sugars that get fermented in the bottle alongside the priming sugar).

The difference in attenuation between yeast strains is rarely enough to make a big difference in carb level.

**BierMuncher** · 05-04-2007, 04:02 PM

My carbing levels were consistent when I bottled, regardless of the yeast strain.

Only two exceptions:

One batch was not fermented enough and I ended up with mild gushers...barely drinkable.

One batch I added some beano to unstick a fermentation and while the hydrometer said that fermentation hade finished (after what seemed like forever), apparently, beano has a low-slow effect on starches and those bottles continuned to ferment. Undrinkable gushers, they were.

**the_bird** · 05-04-2007, 04:12 PM

Assuming that the bottles are primed after fermentation is complete...

The difference in attenuation between yeast strains refers to how completely that yeast can ferment out maltose. If you're using corn sugar, it's going to be essentially 100% fermented regardless of the particular yeast strain you use.

Now, if you are priming with DME, your question does seem to be valid - but given the small quantities of sugar we are dealing with, a 5% or 10% difference in attenuation would seem to be so minor as to be irrelevant. Consider - do you measure out EXACTLY five gallons that you are bottling, or is it closer to 4.8 gallons, or 5.2? Do you factor that into your measurement of how much priming sugar to add? Do you even know that before you rack into your bottling bucket (and you've already measured and sanitized your priming sugar)? That would have just as much of an effect, if not more, on how much sugar is added (and ultimately fermented) per bottle.

I'm guessing "no." There's always an element of variability at work, and the difference in yeast attenuation when priming with DME seems to be so minute as to get lost in all of the other variables.

So, RDWHAHB!

homebrewer_99 · 05-04-2007, 04:24 PM

Quote:

Originally Posted by the_bird

...Consider - do you measure out EXACTLY five gallons that you are bottling, or is it closer to 4.8 gallons, or 5.2? Do you factor that into your measurement of how much priming sugar to add? Do you even know that before you rack into your bottling bucket (and you've already measured and sanitized your priming sugar)?......get lost in all of the other variables.

Exactly why I rack to the bottling bucket prior to preparing my priming sugar...then there's the addition of more water with the DME/CS...1 cup or 2?

proton · 05-04-2007, 09:29 PM

Thanks for the knowledge, folks. I'm guessing that most of my over-carbing issues have been due to unfinished fermentation, and under-carbing probably due to long aging in the secondary. My undercarbed saison sat for at least a month before I bottled it.

Guess it's time to get an aeration system!