Carbonation in cider after adding potassium sorbate and back sweetening.

[Gunshowgreg]

I made a cider about a month ago. Added some potassium sorbate to the batch as the instructions called for. Waited about a day and a half. Back sweetened bottled and several weeks later started drinking them. All of them have been flat but the one I had 2 days ago. It was slightly carbonated and I was wondering what may have caused this. I'm not complaining though. It was very nice.

It was a 2 gallon batch of just apple cider and a mix of brown sugar and stuff. Finished at a 7%ABV

Thanks hopefully I gave enough information

 

[Miraculix]

You've been either visited by the carbonation fairy, or some yeast is still healthy enough to do the fairy's job!

 

[JimRausch]

Sorbate prevents yeast from reproducing, but won't kill the ones present. So apparently you had some viable yeast in there and they slowly have munched on your backsweetening sugar.

 

[Maylar]

Else the sorbate wasn't mixed well enough and some yeasties escaped its effects.

 

[Gunshowgreg]

Thank you for the replies. It was a pleasant surprise regardless. Has anyone else encountered this before?

 

[ebbelwoi]

Recently, I opened the last 1.5L bottle of a batch that had been stabilized with sorbate, then force carbonated. I had finished the rest of the batch a month or two earlier. When I opened this one, it was a gusher. I figured I hadn't stabilized it properly (adding 1/4 teaspoon of potassium sorbate per bottle). It had also been stored at room temperature.

It was also bone dry, so the yeast had indeed consumed the backsweetening juice.

I've since changed my method to adding 1/2 tablet of potassium metabisulfite (Campden) and 1/2 teaspoon potassium sorbate per 4L batch, then bottling. We'll see how that goes.

 

[dmtaylor]

Like @JimRausch mentioned, sorbate doesn't kill yeast. If your yeast are lively, they'll continue to eat sugar until they grow old and tired. If the yeast are old and tired, sorbate can end fermentation more quickly. It's a spectrum, and might take a little experience to learn when the right time to add is and what effect it will have.

 

[RPh_Guy]

I'll deliver the bad news.
You have yeast fermenting the sugar in the bottle. If the yeast consume too much sugar, there is risk of gushing and ultimately bottle bombs.

Be wary. Safety first.

Missing details:
What kind of bottles and closures?
What were the specific gravities before and after backsweetening?
Was the cider fully clear and removed from the yeast sediment when you added the sorbate?
How much sorbate was added? Do you know the weight/mass? A "teaspoonful of this and a pinch of that" isn't really the best approach in my opinion.
What was the temperature of the cider when adding the sorbate?
Did you also add sulfite? How much?
Did you dissolve the stabilizers before adding?

There's definitely a learning curve with stabilization. It doesn't help that there's also a lot of misinformation floating around online.

 

[Gunshowgreg]

I'll deliver the bad news.
You have yeast fermenting the sugar in the bottle. If the yeast consume too much sugar, there is risk of gushing and ultimately bottle bombs.

Be wary. Safety first.

Missing details:
What kind of bottles and closures?
What were the specific gravities before and after backsweetening?
Was the cider fully clear and removed from the yeast sediment when you added the sorbate?
How much sorbate was added? Do you know the weight/mass? A "teaspoonful of this and a pinch of that" isn't really the best approach in my opinion.
What was the temperature of the cider when adding the sorbate?
Did you also add sulfite? How much?
Did you dissolve the stabilizers before adding?

There's definitely a learning curve with stabilization. It doesn't help that there's also a lot of misinformation floating around online.

Bottles were some regular pry off cap bottles and some swing top bottles. The carbonated one was from a pry off.

SG: 1.060
FG: 1.000 or about 1.001 before back sweetening. I didn't not take another measurement after back sweetening. (Is this common practice)

I raked to secondary a d cider appeared to be clear IMO. I will post some pics

I did not weigh the sorbate. I added 1 tsp per gallon based on instructions on bottle.

Temperatures were around 65-68 degrees

Did not add sulfite.

I added the potassium sorbate directly to the fermenter (1 gallon each) and let sit for about 24-48 hrs before bottling.

I think i got them all [emoji2]

 

[Gunshowgreg]

SG and FG

 

[RPh_Guy]

Might want to check the other bottles to make sure they're not fermenting. Glass bottle bombs really aren't something you want.
Each gravity point fermented generates about 0.5 vol CO2 and it becomes dangerous above 4 volumes.

The amount of potassium sorbate you added was quite a lot, well above legal limits for commercial products. Odd that a kit suggests that much.
If the cider was clear and racked off yeast before the sorbate was added, I'm not sure why it's still fermenting... Perhaps it just wasn't mixed properly or MLF is generating CO2.

It's recommended to always use sulfite along with sorbate, otherwise a "geranium" off flavor may develop.

 

[ebbelwoi]

I started off using sorbate only, but have since changed to a combination of k-meta and sorbate, to be on the safe side. I've read (somewhere? a few places?) that sulfite makes sorbate more effective.

 

[RPh_Guy]

I've read (somewhere? a few places?) that sulfite makes sorbate more effective.

Sorbic acid inhibits Sacc growth but doesn't stop bacteria.
Molecular SO2 inhibits bacterial and wild yeast growth. At concentrations used in bottling it won't inhibit Saccharomyces.

Without sulfite, Lacto can produce "geranium" off-flavors in the presence of sorbic acid.

To my knowledge, it's not a matter of effectiveness... but either way it's recommended.

Cheers