Campden Tablets - Still fermenting

[skvick]

Hey everybody!

I'm pretty new to the site, it's a pleasure to be here and thanks for having me!

I've just pressed 28L of pear cider and have it sitting in a plastic fermenter barrel.

I pressed it in two lots: one was 18L, then I mixed in 4 campden tablets. The next lot of cider was 10L, which I added to the 18L previously pressed, and added another 4 campden tabs to be sure.

That was about 2 weeks ago, as unfortunately I haven't had the time to pitch yeast etc to get the fermentation going. However, during this time, the airlock is bubbling and a frothy film has developed on the surface. Judging from this and the smell it seems as though it's fermenting despite having added 8 campden tabs for 28L. Bit of a pain!

So here is the question; why is it fermenting, even though I haven't added yeast and the campden tabs should have suppressed any wild yeasts in the cider?
Also, would it be too much to dose the whole lot with more campden tabs to try and stop the wild yeast fermenting before pitching my own yeast? Or would it be fine just to pitch yeast and hope for the best?

Thanks very much!

 

[sboyajian]

I believe to halt fermentation you need both metabisulfate and potassium sorbate.

Looks like you have the metabisulfate covered with the campden tablets, but you are going to need to add the other.

As for why it's fermenting, I'm guessing wild yeast in the fruit?

 

[madscientist451]

If you add sorbate to the juice, you can forget about fermenting it with any other yeast.
Here's a good explanation of how campden tablets work:

http://www.midwestsupplies.com/purpose-of-campden-tablets.html

The campden tablets don't kill the yeast, but make it harder for the yeast to grow. After a while the sulfur compounds dissipate into the air and the yeast can get going again.
If I had the partially fermented pear juice that you have, I'd run an experiment: Split the batch in two, Batch one I'd pitch a cider, wine or beer yeast I wanted to use. Batch two I would heat to 160F, (just briefly at 160) then let cool to room temp and pitch the same yeast as batch #1.
I would then see if there was much of a taste difference between the two methods. Good luck and cheers!

 

[skvick]

Riiight, so the campden tabs only stall the wild yeasts! I hear you. I have about 10L of apple cider which is fresher, so I'm pretty tempted to blend the pear and apple cider then pitch yeast. Any thoughts?

I like the idea of your experiment! Might give that a go too

 

[Yooper]

Riiight, so the campden tabs only stall the wild yeasts! I hear you. I have about 10L of apple cider which is fresher, so I'm pretty tempted to blend the pear and apple cider then pitch yeast. Any thoughts?

I like the idea of your experiment! Might give that a go too

Campden doesn't even stall wild yeast all that well, as far as I know. It is an antimicrobial, but it doesn't kill everything. It does help so that your chosen yeast strain can take hold, and that is why it is used at the beginning.

Since it dissipates, most winemakers will add it at intervals. Generally, the goal is to keep the S02 level at 50 ppm. It is most useful as an antioxidant, though, and not an antimicrobial. It binds to the wine so oxygen can't, and it works as a preservative.

It does not halt or impede fermentation, especially with wine yeast.

 

[skvick]

Oh ok. I guess to kill the wild yeasts you'd need to use heat or UV right? Sounds like doing things in halves has really complicated this process for me, next time I'll press the cider, dose with campden, 24 hours, pitch the yeast and be away laughing! Damn work gets in the way of life sometimes.

In the mean time, I think I'll do some blending and give this brew a crack with apple and pear, hopefully the introduced yeast takes over the wild yeast... or just fingers crossed it tastes alright!

Thanks everyone for your help!