Collecting Wild Yeast

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Yeast can be the difference between a good recipe and a great recipe. I have been making cider, wine and mead for over a year now and I am learning quite a bit about the strains out there and what they can bring to the table. While experimenting with the prominent strains found at my local home brew shop is fun and rewarding, I wanted to go one step further.
My supervisor at work (I work at a craft brewery), who happens to be my source for all my information involving fermentation, was telling me about Lambic style beers and how they use wild yeast and spontaneous fermentation to achieve their goals. This got me thinking about how I could try this in my tiny "office" at home.
I researched ways in which people collect wild yeast. Most of what I found was for bread making purposes, but I did find out that raisins are a common source for natural occurring yeast. And that they are very high in natural sugars making them an ideal candidate for this experiment
Looking into raisins and other fruits, I found that often dried fruits are sulphited to eliminate bacteria and of course this would kill off the yeast I am trying to culture. So I had to be sure to get dried fruits that have no sulphites in the ingredients. The bulk food chain I used lists any and all ingredients including sulphites, sulphur dioxide, oils etc...
I decided upon four different fruits, because I happened to have four mid-sized mason jars handy. I decided to go with Jumbo Flame Raisins, Medjool Dates (which I de pitted), Goji Berries, and Bing Cherries. I chose these four because they were of course unsulphited and had no added sugars. I wanted the purest form of the fruit possible.

Once home with my fruit choices I had to make a nice environment for my yeast to grow in. Using a medium sized pot I brought tap water to a simmer and let stand at that temperature for a few minutes before turning off the stove and letting cool to room temperature. I did this to help eliminate any chlorine in the water, as my city's tap water is pretty bad sometimes. Once the water was at a workable temperature I poured one cup into each sanitized Mason jar, added one tablespoon of dextrose and one eighth teaspoon of yeast nutrient. Because this is an experiment, these volumes are strictly a guess, but I figure it is a good starting point.
With my growth environment already rich with sugar and nutrient it was time to add the fruit, one quarter cup of each fruit was put into its own jar. The dates were pitted and chopped roughly, the cherries were also chopped. Once each jar was sealed I gave them all a quick swirl to get things moving. I noted that three out of the four fruits sank immediately, only the goji berries remained floating.

Dried Fruits Used Should Not Have Sulphites

Day two I opened the jars for a moment, long enough to give each one a swirl to introduce a little oxygen into the mix. Leaving them in a nice warm area of my apartment I went to work. After coming home I noticed the dates and the goji berries both had a small amount of bubbles forming on the outside edge of the jar. Looking a little closer it almost looked like krausen had formed on the goji berries, while the raisins and cherries remain unchanged other than the colour of the water. Shining a light into the two that seemed to have some activity, I could see tiny bubbles rising to the surface, so I opened them just slightly. The goji berry jar let out a hiss of CO2. I achieved fermentation in approximately 30 hours.

Fermentation In Approximately 30 Hours

Raisin Fermentation By Day Three
The third day in this mad science experiment, the raisins which had been pretty lifeless thus far have all risen to the top of the water, and there are quite a few bubbles sticking to each one. Yet another jar beginning its fermentation journey.

By Day Four All Fruits Were Fermenting Nicely
Day four the cherries have joined the other three fruits and started to bubble. All four of the jars had to be opened because there was a co2 build up in the jar. All four gave a pleasant hiss when they were loosened.
The raisins seem to be picking up speed, and are doing better than the other three. Although it took 3 days to get started, and only one day for the goji berries and the dates, the amount of fermentation going on in the raisin jar is substantially higher.
On day five the fermentation in the cherries and raisins had seemed to begin to slow. The goji and dates had already slowed their bubbling so I decided to move onto phase two of the experiment.
I separated the fruit from the liquid and drained approximately half of the remaining liquid off. I used what was left to swirl the yeast into suspension and poured them each into their new fermenters. Each one was put into a litre of sugar water with a gravity of 1.045, and tsp. of nutrient was added. The new fermenters were placed back where the original mason jars were kept.

Secondary Fermentation Produced Lots Of Yeast
A couple days into their second ferment, and they all were doing well. The cherries seemed to be doing the best with a nice yeast cake forming on the bottom. Each one is bubbling away at a good pace. Further, they all have some krausen on the top; the Goji has almost 3 inches of it. They remained in these fermenters for 5 days in total.
The last step I took was to rinse and separate the yeast. I first allowed it to settle and form a nice layer on the bottom of the vessel. I racked off the liquid and transferred the remaining yeast back to the mason jars with some distilled water. That sat for about 4 hours, and then I carefully sucked up the water with a turkey baster, leaving as little liquid as I could. Another small splash of distilled water to get the yeast back into a suspension and I transferred one final time into their small containers to be stored in the fridge.

Final Results Lots Of Free Wild Yeast

The final result is a nice little yeast supply cultured in my own make shift lab.


how did the starter wort smell/taste while you were washing/decanting the yeast? What do you plan on brewing with your newly cultured yeast? maybe a 4-way split SMaSH-batch to see how each yeast does?
Since most of what I have made is cider, I am going to be doing 5 single gallon batches of cider. One for each wild yeast and one as a control using the regular strain that I am used to. I will be taking notes on that as well for a future article.
Great article, what was the ratio for your 1 liter of sugar water?
Also, how did you separated the fruit did you sterilize the equipment?
Can you give a brief definition of "Nutrients" fed to the yeast?
I'm anxious to try this at home.
Fantastic article. Thank you for sharing!!
Awesome experiment! Are you planning on plating the cells to separate the yeast from bacteria and other fungi, or just going to ferment with the entire microflora? If you are interested in plating you can find details here:
Great article! I'm interested in hearing what you plan to use the yeast for and how that turns out. Maybe split a 5 gallon batch into five 1 gallon jugs and separately pitch the 4 fruit yeasts and 1 neutral commercial yeast.
Cool article and well done, but I only really care about how the final product ends up tasting! They could all taste like the bottom of my recycling can :p
I've harvested (from juniper berries) based on Colobrewer's experienced doing the same. I did plate mine out, but did nothing with the resulting colonies. Under the scope, I did find some bacteria in the yeast that I grew.
BTW, the resulting beer was mediocre. It had some odd belgian flavors in it. It was a pale ale, so not the best beer for those flavors.
@DICKERBEERthanks for the comment. this is the plan. im proba bly going to do 5 ciders tomorrow. one for each yeast harvested and one using lalvin ec-1118.
@WoodlandBrewluckily for me the brewery at which i work does have its own lab.I will likely be going there soon to see what i can do with what i have
Wouldn't it have been better to use apple juice instead of sugar water in order to train your yeast up right? Or is that not as much of an issue with cider as it is with beer?
Cool experiment & good article! I'm curious to see just where this goes. How these 4 yeasts & the end products compare to commercial yeasts post fermentation.
Regards, GF.
No, I got a bunch of identical colonies. At the time I was just learning how to plate for single-cell colonies, so my technique calls into question my results.
In my best Morpheus voice: "You think that's YEAST, you're growing?"
My question is really the same as Steven (WoodlandBrew) -that you are highly likely growing both yeast and bacteria.
And my follow-on question is the same- plan on putting these guys under a microscope to see what you've got and plate it out to get to pure colonies of just yeast or are you going to go for a wild / sour fermentation going forward?
I've got a batch of spontaneously fermented cider from my yard. The wild microbes had no problem fermenting on their own even after been frozen for a few weeks. It took about 2 months before all the off-flavours disappeared but now it has really come around.
I'm thinking of collecting the trub and maybe doing a beer starter... Is this just a stupid idea or maybe it could be the beginning of something delicious?