how to stop fermentation

I put my porter in the primary on Friday (1.060) and today I've hit my gravity (1.016). My problem is I mashed at 148-150 instead of my target 154, and as a result fermentation is still going. bubbling evert couple of seconds and still about an inch - 2 of kraussen. I've made about a dozen or more brews in the past two years and haven't had problems with fermentation going too far.

What are your preferred methods for stopping fermentation?

I transferred to a secondary and things seem to have slowed a bit. I have a thin layer of new kraussen and the blowoff doesn't seem to be releasing any gas.

I've heard of people throwing the carboy into the fridge to help the yeast fall out, I'm just not sure how to deal with a beer once it's been chilled. I usually condition at 68 for a few weeks before I chill it down.

It will stop on it's own. If you get the same gravity reading two or three days in a row it's done. Bubbles don't necessarily mean much. There is a lot of CO2 in there that will come out over time.

It's done. Bottle or keg. Be sanitary.

Conroe said:

It will stop on it's own.

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I don't want it to stop on its own. I don't want it to get much past 1.015. I want to ruin the party before it runs its course.

Not to be contrary: But with the low mash temp, it could keep going for a couple more points.

Since you already have it in a secondary, you can keep it there for another week or so to make sure it's actually done. If you want to cool it off to cold-crash the yeast, you can do so... to "deal with the cold beer", you can just pull it back out of the fridge and warm it for 1 day before bottling or kegging as normal.

Chriso said:

Not to be contrary: But with the low mash temp, it could keep going for a couple more points.

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That's exactly why I want to stop the fermentation. I don't want it to go a few more points.

My understanding was that if you cool it down, that'll slow fermentation dramatically.

I don't think there's a real good way. I would let it run it's course and let it ferment out. If you think it's a little light on the body, you can add a little maltodextrin.

You could get creative.

Bottle it. Sample until you hit the carbonation level you want (it's still fermenting, you don't need to add priming sugar). Obviously you don't want to forget about it while this is going on.

At that point, pasteurize it. Load the bottles into a cooler or pot (or dishwasher?) and make with the hot water bath. Other than they force-carbonate, it's what the factory beers do, as I understand it. Fill, wash with hot water to both wash the outside and pasteurize the beer, then label.

The only thing that will truly "kill" yeast is Campden tablets (used as sterilisant in wine) but that will make bottle-carbing impossible. I don't suspect it will drop more than 1 or 2 additional points. I would let it ride out. I just wanted to mention the *possibility* just in case it were to result in bottle bombs. I don't think it *WILL* happen. I'm just putting it out there as a slight factual possibility.

Chriso said:

The only thing that will truly "kill" yeast is Campden tablets (used as sterilisant in wine) but that will make bottle-carbing impossible. I don't suspect it will drop more than 1 or 2 additional points. I would let it ride out. I just wanted to mention the *possibility* just in case it were to result in bottle bombs. I don't think it *WILL* happen. I'm just putting it out there as a slight factual possibility.

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Agreed, but I've read that Campden tablets won't necessarily stop yeast when fermentation really gets going.

Professor Frink said:

Agreed, but I've read that Campden tablets won't necessarily stop yeast when fermentation really gets going.

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Very possible. I don't know the answer to that. The only time I've tried to use C-den to stop ferment was with Brettanomyces. And it didn't work.

Now that I have a bottle, I pretty much just use C-den to bust the chloramines out of my water before I mash in.

Chriso said:

Now that I have a bottle, I pretty much just use C-den to bust the chloramines out of my water before I mash in.

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It took me a while to learn this, but a very good idea.

A few Campden tablets plus 1/2tsp per gallon of potassium sorbate will stop fermentation. Search for "stabilizing wine".

If you do this you will want to degas the beer before kegging to remove the excess SO2 from the Campden tabs (it does not taste good). A sanitized mash paddle in the carboy agitating for 2-3 minutes will do the job.

If you do this the yeast will be dead and you will have to force carbonate. If you want to bottle you are out of luck and will have to let the fermentation run its course...