Yeast Fermenting in Secondary

So here's the setup:

started this batch 3/17/13, pitched yeast, sweetened up with brown sugar, fermented fine in primary. Then I came to a crossroad when moving to secondary, do I leave the yeast alive and add sugar so it can carb in bottle then stove top pasteurize? or do I kill yeast, sweeten with apple concentrate and use a friends keg to force carb.

After thinking on it I decided to use the force carbonation, 1. because I was curious and 2. because I figured it would give me a chance to fill in the headroom in the secondary with apple concentrate to help sweeten it back up / remove headroom while aging/clarifying.
So I pitched in potassium sorbate (this is 3 gal of cider) and let it sit. Then after a few days moved to secondary, added the apple concentrate and was going to leave it to age/clarify for a while. Days later saw it was bubbling, figured it wasn't enough potassium sorbate so added more to stop ferment of the apple concentrate.

Well..checked last night and it was bubbling again. Rage ensued. refridge is too small to get carboy in. So i'm thinking my option now is to let it ferment out again, before bottling mix in open container with the cider and some more concentrate and perhaps priming sugar, bottle, then pasteurize. Is this sound? Why would it be fermenting again? Did I introduce something else via the apple concentrate that may have started it back up (not my original yeast fermenting now?!)

Unless your fermentation was pretty much done after primary, sorbate isn't going to completely stop the yeast that are still in there. It will keep them from reproducing and multiplying, but not kill them. Do you recall your gravity when you added the sorbate? It sounds like it might not have been done.

I'd still go with the Keg Method, to me thats a great option. Since it's only 3 gallons, I'd back sweeten on a Friday...and then drink it over the weekend with a buddy and knock it out. Then on your next batch...wait till she's gone bone dry...cool/cold crash to clear...then sorbate.

Gravity before adding sorbate was 1.002, so I guess I had figured it was all done since there was no activity on surface nor bubbles running up the sides.

Is it possible to use what yeast is left to carb within the bottles? just move to a bucket, add concentrate + primer, bottle then pasteurize? Or should I just let it ferment out again, back sweeten with unfermentable stuff, keg for carbonation.

I'm a big fan of force carbonation because I really hate bottling...so my suggestion would still be the keg. I've never stove top pasteurized so I can't say how that goes. In theory it sounds easy, but I've never wanted to "take a chance" with glass shards flying through my kitchen.

1.002...should have been done, but I bet they were still chomping away in there and not enough had dropped out. So when you added additional fermentables...they just picked up where they left off.

I'd still say just throw a party and knock it out in a weekend...then start fresh with a new batch. That one has sorbate in it, so there's no telling how it will react from here on out. Could be just fine...could make for a sluggish bottle carb.

You could throw some campden tablets in there to stop the fermentation. They are Metabysulphite, and should stop it from continuing.

The other thought is that you might not have given the sorbate enough time to do it's job. I've successfully used sorbate in the way you're doing it, but gave it at least at least 48 hours and stirred after 24 to make sure...do you have sediment at the bottom of your carboy? you could rack it one more time and add the neccessary campden tablets to the tertiarry, give it a few days, and taste to see if it's sweet enough for you.

you could buy one of those UV water purifier units and drop that down in the carboy for a few hours...that would kill em off...

Ya I think what i'm going to try and do is let it settle back out (give it ALOT of time to chill out fermenting wise), attempt to cold crash and rack, and then from there re-add concentrate and keg to carbonate.

God willing, the yeast won't start back up again haha
Thanks Pickled Pepper and Sewer Urchen!

Sewer_Urchen said:

You could throw some campden tablets in there to stop the fermentation. They are Metabysulphite, and should stop it from continuing.

The other thought is that you might not have given the sorbate enough time to do it's job. I've successfully used sorbate in the way you're doing it, but gave it at least at least 48 hours and stirred after 24 to make sure...do you have sediment at the bottom of your carboy? you could rack it one more time and add the neccessary campden tablets to the tertiarry, give it a few days, and taste to see if it's sweet enough for you.

you could buy one of those UV water purifier units and drop that down in the carboy for a few hours...that would kill em off...

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Sulfites do NOT kill yeast- winemakers use them all the time as an antioxidant and preservative. I use 50 ppm in my wines, and that isn't enough to even make the yeast pause. That's why winemakers use sulfites- because brewers yeast and wine yeast is very tolerant of sulfites.

In order to use enough sulfite to kill yeast (or even stun then), you'd have to use so much as to render any beverage undrinkable.

Sorbate doesn't kill yeast, either, but it does inhibit yeast reproduction. In a finished wine or cider, it can be used once the wine is totally clear with no lees on the bottom, to keep any yeast still in suspension from reproducing. If the wine or cider isn't finished, or there is still a ton of yeast in suspension, the sorbate will do nothing.