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Surface molds growing in raw wild cider

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Nursery Log

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We pressed about 20 gallons of cider on Oct 16.

The first thing observable was spots forming on the surface, growing into somewhat of a surface network. The next day, I could tell there were spots of green (probably trichoderma) sporulating, the whole surface looks like a petri dish... with some bubbles. I want to know two things; what to do to save the cider, and how to do it better in the future.
So this is happening in the primary fermentation. I've read that for the primary fermentation stage with cider, it is not necessary to fill the carboy all the way to the top, because excess oxygen would not harm the cider... So my ciders are in 12- and 24-gal fermentation buckets. but I'm thinking that another downside of this surface area is that it creates more space for molds to grow. Should i scrape off the surface contaminants and transfer it to a container with less surface area? If i fill a carboy enough would it be possible to wait for it to ferment enough to blow off the surface bubbles including the surface molds?

How is best to manage a raw un-sulfured batch of cider so this doesn't happen? Does this happen often with wild batches? At what point would you say these molds will ruin the cider (how bad is this)? With sulfites not being an option, and although I don't want a commercial yeast, would now be a good idea to try to pasteurize some/all of it and pitch a domestic yeast? Finally, I'm not familiar with primary fermentation in a mostly full carboy; is there a way to get a small surface area without causing a huge mess and having something to take care of/check on every day?
 

Yooper

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How is best to manage a raw un-sulfured batch of cider so this doesn't happen? Does this happen often with wild batches? At what point would you say these molds will ruin the cider (how bad is this)? With sulfites not being an option, and although I don't want a commercial yeast, would now be a good idea to try to pasteurize some/all of it and pitch a domestic yeast? Finally, I'm not familiar with primary fermentation in a mostly full carboy; is there a way to get a small surface area without causing a huge mess and having something to take care of/check on every day?
If you're not going to pasteurize or use sulfites, you could try adding more yeast at the very beginning, right after pressing, to see if the cultured yeast could outcompete the other microbes. Risky, but possible. If you don't want to use sulfites or a cultured yeast, then yes it will often fail.
 

Miraculix

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Mold means two things, first, that you need to dump it and second that there was oxygen present.

You can prevent mold with an air tight fermentor.
 

doublejef

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Air should not be an issue during first stage of fermentation, when active.
At the opposive, O2 is needed by the yeast to grow so it is recommended to aerate the juice to help this.
And also, when fermenting in a close vessel, fermentation will produce CO2 that will stay on the top of the fermented cider, protecting it from O2.
After fermentation, if you move the cider from the vessel and, doing so, if you put it into a full of air new vessel, then you can get oxydation problem.
Here I suspect something else was into the juice (bad bactery or something like that) but removing air would'nt help to keep it away in my opinon.
 

Miraculix

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The co2 blanket is a myth. If the fermenter is not air tight, oxygen will slowly get in once fermentation slowed down.
 

jseyfert3

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And also, when fermenting in a close vessel, fermentation will produce CO2 that will stay on the top of the fermented cider, protecting it from O2.
The co2 blanket is a myth. If the fermenter is not air tight, oxygen will slowly get in once fermentation slowed down.
A better way of saying that is that fermenting in a closed vessel will produce enough CO2 to flush (almost) all O2 from the headspace, and an airlock will keep O2 from coming back in.
 

Albionwood

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You are replicating my early experience in attempting to get a spontaneously fermented wild cider.

First: That batch cannot be saved, dump it immediately. Even if the mold has not already produced toxins, it has irreversibly tainted the flavor.

Second: Your problem is fermentation never got started. This used to happen to me a lot when I tried fermenting without adding any yeast. There wasn't enough wild yeast present on/in the apples to get enough fermentation going fast enough to use up the oxygen before the mold got going; and once mold gets going, it poisons the must so yeast is inhibited.

Why is sulfite "not an option?" In my experience it is extremely difficult to reliably ferment cider without using any sulfite. I make cider from apples I grow, in a cool moist climate where mold is omnipresent, and the mold invariably grows faster than the yeast. Even if I pitch a cultured yeast, without sulfiting the must first it will get slightly sour and develop unpleasant flavors and odors.

I solved the dilemma by learning to use sulfite judiciously. The amount needed varies depending on the pH of your juice AND on what you are trying to accomplish with it. First, mix up a 5% or 10% stock solution, it's the easiest way to dose the juice. If I want some wild character, I will calculate the amount of sulfite needed for 25 to 50 ppm, and add that directly to the top of the juice in the carboy, without stirring it in. This creates a surface layer of high sulfite concentration so mold is inhibited, but the juice beneath is relatively unaffected. Bacteria and wild yeast will grow, eventually; whether that will give you a good result or not is anyone's guess.
 

doublejef

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The co2 blanket is a myth. If the fermenter is not air tight, oxygen will slowly get in once fermentation slowed down.
Co2 is heavier than O2. O2 won't come into the vessel if there is no lack somewhere. But all those consideration are mostly theorical.
 

Albionwood

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Co2 is heavier than O2. O2 won't come into the vessel if there is no lack somewhere. But all those consideration are mostly theorical.
This is the myth. Oxygen will indeed diffuse into a vessel filled with CO2, unless it is physically excluded. An airlock will mostly do that job, unless the temperature drops and air gets sucked back in. When that happens the oxygen will diffuse through the CO2 and reach the cider. If the airlock dries out, or if the fermenter is not completely sealed, oxygen will continue to enter until an equilibrium concentration is reached.

The only time when CO2 really "protects" the must/cider is during active fermentation when the evolving gas creates positive pressure and pushes oxygen out faster than it can get in. Before and after that, the cider is vulnerable regardless of the CO2 concentration in the vessel. This isn't theoretical, I can assure you I have had plenty of batches of cider get oxidized when I left them in the carboy too long, even with airlocks in place.
 

wasully

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A better way of saying that is that fermenting in a closed vessel will produce enough CO2 to flush (almost) all O2 from the headspace, and an airlock will keep O2 from coming back in.
Unless the container is oxygen permeable.
 
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there are a few batches.

One of them was combining two containers of cider with surface mold starting, put into a 3-gal carboy. it fermented enough to blow off the top layer and i removed it, it's looked healthy ever since.

The others tasted like mold right out of the press.


In the future would it be best to fill carboys to limit O2 exposure and surface area, then seal them completely with plastic wrap or with an airlock?

Sulfites are not an option because I want to learn to not need them. I told myself long ago I would not consume 'preservatives' that harm gut microbiota. I want my cider to be probiotic.
 

jseyfert3

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Unless the container is oxygen permeable.
Okay, well if you want to be pedantic then that means literally everything. Oxygen can even permiate through metal, through the rate is so slow as to be negligible over even a lifetime for any appreciable thickness.

PET has a much lower permiation than HDPE, glass is lower then PET (almost nothing), but at that point the permiation through the airlock stopper and through the airlock itself would be the primary means of permeation.
 

jseyfert3

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Sulfites are not an option because I want to learn to not need them. I told myself long ago I would not consume 'preservatives' that harm gut microbiota. I want my cider to be probiotic.
I mean, whatever floats your boat, but I don't think anything with ethanol can be considered to be probiotic. I'm not a doctor but I suspect that the negative effects of ethanol far and beyond outweigh any minor effects of small sulfite additions. Also don't the majority of sulfites leave during fermentation anyway?

One possible idea I have for not using sulfates AND doing wild fermentation is related to a section from How to Brew relating to wild fermentation of beer. Since not all wild fermentation are good (though I suspect apples are different since they already have yeast), the author suggested using a starter wort that was left out for 24 hrs to collect wild yeast, then covered and allowed to, well, start fermenting. He then suggested tasting this wild starter after a couple days, and if it tasted good use it as a starter for a big batch of beer. That way the entire batch of beer didn't have to get thrown out if the wild fermentation didn't taste as expected.

Cider is obviously different, but but applying the idea there's two possible options that come to mind. The first is pasteurizing the majority of the juice, and saving a small portion as a starter. Let that starter do wild fermentation, and if it's good and doesn't get mold then pour it into your previously pasteurized juice. You still get the wild yeast. And if the starter got mold you toss it and pitch commercial yeast into your pasteurized juice. That way you have a chance at doing wild fermentation but don't have to chuck all your juice if the wild fermentation fails.

The second and very related idea would be refrigerating the remainder of the juice while you let the starter do it's thing and see if it succeeds, but is otherwise the same as the first idea, though it gives more time for any possible mold to grow as the juice cools and heats back up.
 

Albionwood

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Sulfites are not an option because I want to learn to not need them. I told myself long ago I would not consume 'preservatives' that harm gut microbiota. I want my cider to be probiotic.
It's possible, but far from easy, depending on where you are and how you get your juice. It's an ideological commitment that puts you at a disadvantage, because sulfite is extremely useful in cider making and its use is well established. If it is used only to suppress mold pre-fermentation, there will be no free sulfite remaining in the finished cider, so it will have no effect on your gut biome.

I see this sentiment expressed often, and I myself made this attempt for several years. Eventually I learned how to use sulfite in a limited way to suppress mold, and my cidermaking improved dramatically. The finished product is still very much alive. (If oxygen gets in it will quickly spoil from film yeast and bacteria.)
 

Ronnb

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Air should not be an issue during first stage of fermentation, when active.
At the opposive, O2 is needed by the yeast to grow so it is recommended to aerate the juice to help this.
And also, when fermenting in a close vessel, fermentation will produce CO2 that will stay on the top of the fermented cider, protecting it from O2.
After fermentation, if you move the cider from the vessel and, doing so, if you put it into a full of air new vessel, then you can get oxydation problem.
Here I suspect something else was into the juice (bad bactery or something like that) but removing air would'nt help to keep it away in my opinon.
I agree. open fermentation is not uncommon. The batch just seems to be infected. I would try to start by cleaning my containers better with star san to avoid contamination with mold and whatnot and making sure my fermentation area was free of mold issues.
Spontaneous fermentation with apples should be fairly easy to start without pitching some other yeast.
 

Albionwood

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I would try to start by cleaning my containers better with star san to avoid contamination with mold and whatnot and making sure my fermentation area was free of mold issues.
Spontaneous fermentation with apples should be fairly easy to start without pitching some other yeast.
Mold spores are invariably present on the apples. It will do little good to carefully sanitize your containers and then fill them with unpasteurized juice. Just clean them well, and learn how to inhibit mold while encouraging yeast.

As for spontaneous fermentation being "easy to start," that's not been my experience. YMMV. It all depends on where and how you get juice.
 
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