This article is for those homebrewers who are interested in the wilder side of brewing. Those who like to add a “sense of place” to their beers. “Sense of place” is something I heard in an interview with Jeff Stuffings of Jester King Brewery in Austin, TX. That really stuck out to me when I heard it. Brewing beers to represent where you are located or where you call home. To brew a “local” beer you could use local grown hops, locally kilned malts, or you can do something I’ve recently been very interested in, foraging yeast. Now, I’m not expert by any means. I’ve only recently started brewing with my foraged cultures. What I’d like to do is give some guidelines for those who have thought about trying this out but haven’t due to thinking it was too complicated. In actuality, this process can be very simple. I’ve come up with seven steps to forage wild yeast. All of these have come from talking with brewers who have done it or from reading Bootleg Biology’s website (http://bootlegbiology.com/diy/capturing-yeast/). My process is a little more simplified than what Jeff Mello has on his in that I won’t be using any agar plates and I won’t be isolating any of the different microbes from the culture. There isn’t anything wrong with those at all, but some of us may not have access or the time to use those.

Here are my steps for foraging and culturing wild yeasts:

1. Equipment and Preparation

2. Capture

3. Culture

4. Sensory Test #1

5. Propagate

6. Brew

7. Sensory Test #2

EQUIPMENT AND PREPARATION

Before capturing wild yeast, you need to make sure you have the necessary equipment. Some of the basic equipment needed includes: sanitary vials, sugar and DME (dry malt extract), water (I use distilled), a propagation vessel (something like a mason jar will work), and a hydrometer or refractometer. There are a few other tools that can help make the process easier. I like to use a stir plate and Erlenmeyer flask when propagating the cultures as it feeds it oxygen and keeps the yeast in suspension but you can use whatever you currently use for yeast starters. If you use growlers, that will work too. I advise picking up an alcohol lamp if possible just to make sure you aren’t getting anything from the air when transferring your culture to and from starters or other vessels. I also like to use media bottles to keep my cultures in. If needed, I can feed them in there and just helps keep everything organized. I picked up the media bottles and alcohol lamb tips from Ed Coffey of the Ales of the Riverwards when he posted about re-pitching commercial yeast cultures for different brews (http://www.alesoftheriverwards.com/2016/01/harvesting-and-re-pitching-slurry.html). A pH meter is another tool that would greatly benefit you in testing. It isn’t required as you could check attenuation before sampling but I am more comfortable making sure the pH is safe before sampling for flavor. We are working with wild yeast and bacteria instead of commercial available yeasts and lactic acid bacterias. Much better to be safe than end up with botulism from picking up something nasty. As a general rule, if it smells bad or looks moldy, dump it and start over.

CAPTURE

Now you have your equipment and you are prepared. How do you capture something? Well you need to think about where you would like to attempt to capture your culture. The great thing about yeast and bacteria is that it exists pretty much everywhere. You can attempt to capture yeast from flowers, fruit, pieces of a wood, the air, or even bees! It’s hard to determine what qualities wild yeast and bacteria culture will give a beer. I’m not positive that using flowers will give you a floral character or that collecting from fruit will give you a fruity yeast strain or but that is something I’d like to test.

In my case, I decided to use clover flowers. The morning I went looking for something to use, I noticed bees and other insects flying around the front yard going form clover flower to clover flower. I thought for sure there would be something there. I’ve read and seen where folks have used garden flowers, berries, and a there was a post in the Milk the Funk Facebook group where someone captured yeast from a bee. When you are choosing what you subject for culturing, be sure to do you research. There are plants and fruits all over that are poisonous to humans. From what I’ve read, nothing poisonous should leech out during the process, but I’d remain cautious of using anything like that. This is where your sanitized vials come in. Place whatever material you’ve decided to use in the vials and return home for the next step. Some folks may like carrying around a few of the sanitized vials with them at all times (I do.) This is also useful for when you want to keep dregs form a bottle share or even at a bar/restaurant.

At this point you will prepare a starter with a gravity of somewhere in between 1.010 and 1.020. Pour the starter into the vials and shake vigorously to aerate as well as macerate the material a bit. Leave a little room in the vial for some off gassing. When fermentation starts, there will definitely be CO2 given off. The macerating was a tip I picked up while talking with Gerard Olson of Forest & Main Brewing Co. when I visited them earlier in the year. Another tip he supplied was that while some folks always use DME in the first starter, it may be easier to jump start the culture by using a simple sugar solution. I had run into problems getting no fermentation when attempting this a few other times with a wort from DME so I wanted to try the sugar solution.
After you have the material combined with the starter sugar or wort you will want to give it a few days to show signs of fermentation. These signs can be: bubbling, cloudiness of the wort, or a small krausen forming on top. I placed mine in the warm window sill but others (including the Bootleg Biology website) suggest placing it somewhere dark and at room temperature. When you see signs of fermentation it’s time to move on to the culturing step.

CULTURING

Culturing is basically putting the yeast and bacteria into an environment that encourages growth. You’ve got some active fermentation going on in the vials. There has to be something good in there right? Well, while it is likely wild yeast and bacteria growing in there you still need to build it up to something viable that you can do some sensory tests on. After the initial fermentation in the vials, I like to move the entire contents of the vial (or vials) into a sanitized mason jar. I leave everything in the jar including whatever material you’ve chosen to collect your culture from. I do this for the first culture step as there may be some slower acting yeasts and bacteria that haven’t had a chance to start working. Create another starter either with the sugar solution or this time you may go ahead and use a DME starter of the same gravity 1.020. You are feeding the culture another step to cultivate anything you have captured.

After you see signs of fermentation again, it’s time to separate the matter from the solution. I used a sanitize strainer covered with a hop bag (cheese cloth will work as well) to keep out as much of the vegetal matter as I could. That way what makes it through is the yeast and bacteria and no bits of material you captured your yeast from. This will help the culture be clean and prevent any mold from forming on floating bits and pieces. You are now culturing your wild yeast and bacteria.

SENSORY TEST #1

It may take a few days to see signs of activity but if you have captured something aggressive, it will show signs of fermentation quickly. Remember the signs of fermentation are: bubbles, cloudiness, or a krausen on top of the wort. After the signs of fermentation have stopped or slowed (could be 2 days, could be a week or longer) you will be able to do your first sensory test.
With the first test, I usually just stick to aroma. What does it smell like? Are there pleasant aromas or things you enjoy in your beers? Or does it smell like a diaper or something terrible? If it’s the latter, dump it and start over. Nothing lost but some sugar, DME, water and time. If it does smell nice (mine was tart with some earthiness and notes of honey sweetness) then you can probably proceed to the next step. If you are able to take a pH of the starter, you could taste it at this point as well. But I would make sure there was nothing spiking the pH with the possibility of bad bacteria growing in there.

PROPAGATE

Propagation is the key to building up enough yeast to do a test batch of beer. You need to make sure there are enough cells to ferment the beer. At this point, my process is far from scientific. I am using past experiences with commercial yeast starters instead of lab equipment. It may takea few steps to get the yeast cake where you need it to be. I like to start with a 1.030 600mL starter and work my way up from there. If you are getting good reproduction and building a larger yeast cake, you may be able to do fewer steps.

This is also a time that you can check the gravity of the starter to see if you are getting good attenuation. With a 600mL starter, you should have enough to check the final gravity with a hydrometer or refractometer. My initial starter I saw attenuation of the 1.030 gravity wort down to 1.008FG. There is definitely some yeast at work. The step after that was 1.006 down from 1.040. My clover flower culture seems to have some pretty attenuative yeast strains in there.
The alcohol lamp tip is used here. Light it when you are transferring your culture from starter to starter. This will keep out anything that may be in the air when you move from vessel to vessel. Some may not care but I really wanted to keep what I had been growing free from any saccromyces or brettanomyces that may be floating around in the air of my kitchen. I work with a ton of yeasts making lots of starters. It’s highly possible there are things in the air. Now you are ready to use your foraged culture!

BREW

We’ve made it to the fun part, brewing beer. Now you can decided what type of beer you want to brew. You could also keep it simple and brew a simple pale wort with minimal hopping to see what type of beer you will produce. If you use little or no hops, the bacteria in your culture could be the dominant player. If you are looking to see what the yeast itself will do, you may want to hop your beer to 10 IBUs or higher. With my test batch, I’m going for 20 IBUs and hoping and can get something like a Saison or farmhouse beer out of it. With the honey aroma an flavors I had in my starters, it may be something that will work nicely with a Bière de Meil or even a blond Bière de Garde.

SENSORY TEST #2

After you have brewed your beer using your techniques and equipment you normally use, you can do the final sensory test. Do you lie the beer that came from the culture? Maybe you can change the malts or hops to suit the yeast a little better if that’s what it needs. Either way, you can repeat these steps with other plants, fruits or anything really. The world is your oyster, as they say, at this point.

I will have all of my foraging experiences up on my website for anyone to reference. If you click the foraging tab, it will list all the posts about using my foraged culture. I plan to use this technique regularly and maybe even do some different vintage and seasonal beers with it. Either way, I’m going to have fun while doing it!

Good things!

Andrew “Gus” Addkison
The Farmhouse Obsession
www.thefarmhouseobsession.com