Yeast is tougher than I realized...

[Grape Expectations]

I made a kit. It came to the end of fermenting after 14 days (at 0.992 SG) and so I added the kit supplied stabilizer sachet (two "E" numbers I can't remember, E202 and E224?) along with Finings A (Kieselsol) and Finings B (Chitosan) and the included "add back" flavour.

After a few days, I syphoned off only what I intended to drink, into a 5L spring water bottle.

I drank that over about 5 days and syphoned another 5L off again, into a 5L spring water bottle.

At no point did I do any degassing or any syphoning, thus the main container with the wine remained as it was, with about 12L left.

After about 12 days this main container started gassing off again, I mean its last measured SG level was 0.992 SG 12 days prior, and yet here it is gassing off again and surprisingly frequently, considering.

So why does this happen? I assumed it was impossible in fact - it's been stabilized. It seems the yeast is as tough as nails/old boots and even though it's has the kit stabilizer added... because that original sediment is there, it's starting up again?

Like I care!

This is only a good thing to me, it means the wine will be even drier with a slightly higher ABV... but how come supposedly stabilized wine can start up again?

The bottles I did syphon off, with no sediment, never started gassing off, or rather, I never unscrewed the cap off those and has a "tssss". Of course if there's no sediment then there's little to no yeast to maintain a colony and although the main bottle with the half amount from the kit was left with all the yeast, stabilized 12 days back, it's started gassing off again. Very surprising to me.

 

[Rice_Guy]

If you had a microscope you would see suspended yeast. This is enough to generate some gas. Clarifiers aren’t 100% effective, just good enough to make the wine look good.
It is possible that the potassium sorbate had absorbed some humidity and list some effectiveness. The other E number is potassium metabisulphite, it is possible it absorbed some humidity and isn’t 100% effective.

 

[Grape Expectations]

It's not the microscopic suspended yeast... all the original yeast remains in the "stabilized" and "clarified" wine. It's a 1 inch layer at the bottom, flatter than a pancake after 12 days... but it seems to be coming back to life again like a zombified version!

After reaching 0.992 SG that yeast sediment was maybe 1 inch thick at the bottom, after 2 days clearing and the rest of the wine looking clear.

Now 10 days or so after that, the yeast sediment is maybe half that thickness, like it's compressed down or something, but I guess it's the effect of the clearing agents, that it makes any solid matter denser and compact together more? It's weird to observe but that's what seems to have happened. Despite that, the wine sort of began fermenting again, despite being at 0.992 SG and having stabilizer added.

 

[sour_grapes]

I suspect you are just seeing offgassing from any CO2 that was already in the fermented wine. With the SG at 0.992, there really wasn't food (sugar) left for the yeast to eat! I don't know why it started outgassing 12 days later: Did the temperature change recently?

 

[VinesnBines]

and the included "add back" flavour.

What was the package of “add back flavor”? It may have contained some form of sugar - juice concentrate or other sweetener.

 

[Grape Expectations]

What was the package of “add back flavor”? It may have contained some form of sugar - juice concentrate or other sweetener.

It does have a slight sweetness to it, even though the kit says it's a dry wine. Now you mention it I think it must be that. I always assumed if it had stabilizer added it can't start up again.

 

[VinesnBines]

Never say can’t! Now if you wanted it to restart. No chance.

 

[winemaker81]

I always assumed if it had stabilizer added it can't start up again.

How old was the kit? Note that it could have sat on the vendor's shelf a while.

Sorbate has a limited shelf life. In the typical packets in kits, it's protected from air and light, so it should be good for 2+ years from date of manufacture. However, the older it gets, the more it degrades.