Wild Fermented Cider

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How to use the wild yeasts and microbes found on apple skins to ferment cider.

Originally Posted: September 3, 2020

Wild cider, high fermentation — A batch of wild-fermented cider at high fermentation. Later on, the wild yeast will sometimes form a pellicle film on top of the liquid.

Table of Contents

Quick Specs

OG = 1.035 – 1.045, depending on your juice
ABV: 4.6 – 5.9%
Taste Profile: Semi-sweet to dry (it’s up to you)
Time: 2 – 4 weeks
Yield: Depends on your batch size

Pressing apples, 2020 — Fresh-pressed juice is the most direct way to obtain wild yeast for cider. The yeast is naturally present on the skins of apples.

Intro

The original form of alcoholic fermentation (in cider-making or any other type of brewing) was to use wild yeasts present on the skins of fruit, or trapped inside honey, or on the husks of grain. Wild yeast is still used today in many soured beers, such as Belgian lambics. It’s also used in sourdough starters (the best source of wild yeast for sourdough starters is already present in unbleached flour, not in the air like many people think).

During my first Cider Pressing Day with friends in August 2019, I was given a mason jar of the fresh-pressed and unpasteurized juice to take home with me. I decided to test it out and grow it into a one-gallon batch of wild-fermented cider. After a lag period, it fermented vigorously and left me with a completely dry, tart, complex cider.

Because of that successful experiment, I convinced my friends to let one of our 5-gallon buckets to ferment naturally during our next Cider Pressing Day. The results were even better than with the store-bought juice, though I suppose that’s not that surprising.

Ingredients

Fresh-pressed apple juice
- You can simply allow your fresh-pressed juice to ferment on its own.
- You can also use a portion of fresh-pressed juice to inoculate store-bought apple juice with yeast. This still makes a tasty, dry cider, but you lose some of the complexity that you gain from fermenting fresh-pressed juice.
Spices or other flavorings (optional)
Yeast nutrient (optional with these wild yeasts, but I’ll add it to anything)

Equipment

Sanitizer
PBW (for deep-cleaning fermenters)
Fermenter
Airlock and stopper

Wild cider starters — My original test batch of wild-fermented cider (right) next to my first attempt at growing a few drops into another one-gallon starter (left).

Instructions

There are three basic ways to make wild-fermented cider: just allowing fresh-pressed juice to naturally ferment, using a wild yeast starter from fresh-pressed juice, and creating a wild yeast starter using some fresh-picked fruit skins and juice. At this time, I only have experience with the first two, but I’ll attempt to describe the third method based on reading I’ve done.

Fresh-Pressed Juice

If you have access to many, many apples and some crushing and pressing equipment, you can make the freshest and most complexly flavored wild cider. Even though I’ve done several apple pressings now, I never really paid attention to an average juice yield per pound of apples. A quick Google search gave me a preliminary answer: it takes an average of 15 lbs. of apples to get a gallon of fresh juice.

You start by roughly chopping the apples, then throw them into the crusher to shred them to smaller bits. Place these pulped apples in a mesh bag-lined fruit press and press out the juice. Continue these steps until you’ve run out of apples or clean fermenters.

At this stage, you could add Campden and then a cultured yeast strain to ferment your cider. Or you could allow the wild yeast that were living on the apple skins do all the work for you. Yeast from apple skins is well-suited to metabolizing the nutrients found in apples, so you’ll be left with a very dry and complex cider once it’s finished.

Transferring wild starter into fresh juice — A starter at high fermentation being siphoned into store-bought apple juice.

Continuous Wild Yeast Starter

After my first Cider Pressing Day, I was given a mason jar of fresh-pressed juice to use however I wanted (as I mentioned earlier). I decided to do an experiment and add it to a gallon of store-bought apple juice in a one-gallon fermenter. Once it had fermented completely dry, I decided that instead of bottling it, I would grow it into a 5-gallon batch. I ended up proudly placing this batch in my newly purchased kegerator.

Using store-bought juice like this makes for a refreshingly dry cider, but it lacks some of the complexity of making cider directly from fresh-pressed juice. However, the upside to this method is that you can keep it going just like you would a sourdough starter. I’ve found that just a small amount of wild starter from a turkey baster can ferment a one-gallon batch of juice, which can then be grown to a 5-gallon batch at high fermentation. Just expect up to a week of lag time in some cases.

Creating Wild Yeast Starter from Scratch

This is the only method of these three that I have no personal experience with yet, and I believe it falls under the definition of “yeast wrangling“. Since I have no direct experience with it, I’ll paraphrase a process used by some brewers to produce a lambic-style wild-fermented beer (as described in American Sour Beers by Michael Tonsmeire).

Basically, you inoculate a starter of juice or beer wort with yeast from the skin of some fresh-picked fruit or berries. From there, you could grow your starter into a larger batch of wild-fermented cider or wild-fermented faux lambic beer.

Variations

So far, I’ve made two variations of this cider: two plain, dry batches of cider, and one spiced with a cinnamon stick and 5 – 6 cloves. The second one was meant to be a hybrid between wild cider and my basic “apple pie cider”; this was a bit of a compromise for me, because I like the wild cider a lot, but my family likes the spiced cider a lot.

Like other ciders, you can also experiment with letting this one ferment out dry, or arresting the yeast early to leave some residual sweetness, or kill off the yeast at the end and back-sweeten. However, in the last of those options you won’t be able to use any of that batch as a future starter, so maybe keep an extra batch of wild starter in a separate fermenter.

I haven’t tested out the alcohol tolerance of wild yeast yet, but I’m interested in doing a wild-fermented 12 – 14% cyser mead one of these days. Maybe I’ll even add that to my Solera Cyser Blend Project at some point. The pellicle that forms on the surface could potentially emulate the sherry flor they use in Jerez, Spain and keep barrel aged mead from oxidizing too fast.

Tips & Tricks

I haven’t had any problems yet with wild yeast becoming less viable or mutating and throwing off unpalatable flavors. This is even the case with wild starter that I’ve left alone in a fermenter for most of a year. More recently, however, every time I grow a starter into a 5-gallon batch, I also start a new one-gallon starter to give the yeast some fresh juice to eat. I usually do this when I transfer a large batch into a secondary fermenter.

Transferred wild cider next to PBW — Wild-fermented cider in secondary (left) while the primary fermenter is soaked with a solution of PBW and hot water.

If you’re worried about cross-contaminating your “clean” ferments with wild yeast, soak your fermenters in a PBW solution and hot water, and scrub well. Keep your wild ferments in a separate room if you want to be extra careful. I haven’t had any cross-contamination yet from my kegs or kegerator, but I always flush my beer lines with Star-San every time I’m swapping out kegs.