Active fermentation after 1 hour!?!?!!?

[clockwise]

I brewed a brown ale last night. Let it sit to cool overnight, siphoned into the fermenter on top of the last batch's yeast cake and shook vigorously to aerate and get it going. It's already got a thick krausen and a ton of activity in the airlock after about an hour!?

Has anyone seen this before?

 

[agrazela]

When going on top of a yeast cake, yes. No surprise to me.

 

[clockwise]

This is my 2nd time doing this, though I halved the volume of the trub and yeastcake the first time. It was vigorous, but not like this. Good since it's virtually the same beer. I'm sure this will be ready to keg/secondary pretty soon then. :rockin:

 

[cannman]

STEP AWAY FROM THE FERMENTER.... and have a beer!

 

[tagz]

Racking on top of a whole yeast cake is a massive over pitch and generally not recommended. Yours may be fine but you could also end up with some off flavors. Next time you can use an online calc to estimate the proper pitch of slurry.

 

[Calder]

You will make beer, maybe pretty good beer, but be aware that you could also have created problems with what you have done.

Normally when you pitch yeast, it goes through a phase of reproduction, creating new yeast cells. If you pitch the 'right' amount, it will grow about 6X in the beer before it starts to create alcohol.

What happened with your beer, is that the yeast in the cake was so large, that very little new yeast was required to get to the right level, so there was virtually no reproduction phase, and very little new yeast cells produced.

You have 'old' and tired yeast fermenting this beer. They will probably get the job done. You may have a higher FG than you would have normally, but you will never notice. You will have less yeast flavors from the reproduction phase. You may also have more fusel alcohols.

Chances are, you will have a good beer and not really see any issues with this practice. Secret is; you would have had a better beer if you had removed some of the yeast and allowed it to go through the reproduction phase creating new yeast to ferment your beer.

 

[ptarmigancraft]

"Over pitching can decrease the lag phase, but each individual cell will not be as healthy at the end of fermentation. Although a brewer may find it reassuring to see fermentation activity within one hour, it is not the optimal condition for the yeast"

- Yeast 'a practical guide to beer fermentation' by Chris White and Jamil Zainasheff

Your beer will be fine I'm sure but that yeast will be pretty stressed for subsequent batches I would imagine.