In the simplest of terms, beer fermentation consists of yeast converting simple sugars into alcohol. There are versions of this process happening all over the world, to all sorts of sugars, by innumerable strains of yeast. What this means for you, is that your local homebrew shop isn't the only place you can get yeast for making your beer.
In this article, I'm going to go through some simple steps that with a bit of luck will get you a local yeast strain of your own to brew with. This topic can and does fill stacks and stacks of books, but we're going to stick with just the basics today.
The equipment you'll need for this project can range from stuff you can find in your kitchen up to a lab that would make the CDC jealous. Just like the rest of the homebrewing hobby, yeast ranching can be a real gear treadmill, but it doesn't have to be.
Things you'll need...
To start with, make a small batch of starter wort. If you've not done that before, there are examples and videos galore already out there to explain, but the underlying goal is to boil some 1.040 OG wort made from your malt extract. Add the raw lemon juice to the starter wort to lower the ph balance of your wort. The amount that you should add should be 10% of your original volume.
We're lowering the ph because while the yeast that we're after prefers a slightly acidic environment, mold, and other things we don't want, do poorly in acidic environments. Some of the cool kid brewers might add hops to this starter boil for the same reason, but it's not strictly necessary.
If you have petri dishes or shallow containers for this project, I recommend adding the appropriate amount of gelatin to the solution to make it a semi-solid after cooling in your sanitized containers. In a pinch, this isn't necessary, but it helps.
Cover tightly with sanitized foil and let cool until you're ready for the next step.
Inoculating your medium...
When looking for a location to capture your yeast, it's best to aim for a cool location that is undisturbed by passing animals, ill behaved children, and belligerent drunks.
I've lost several yeast collecting mediums to this guy...
The best place to find wild yeast is in the area of naturally occurring sugars. Knowing this, it's preferable to place your open container nearby trees or plants with fruit. Trees leaking sap are a particularly attractive spot.
In addition to the ph considerations, yeast prefers cool temperatures more than competing mold and other undesirables. This makes fall an ideal time for capturing yeast. Ideally, you should place the container in the late afternoon or evening after the heat of the day is gone.
Leave your container open for several hours or overnight, but not much longer. Recover with sanitized foil and leave undisturbed for at least 48 hours.
Another method is drop wild fruit directly into the starter wort or onto the surface of the dish, as yeast lives on skin of fruit. Juniper berries have worked for a few people I know, and of course grapes are another good source.
Selecting your yeast culture...
If your dish was indeed inoculated, you stand a good chance of seeing a change in the surface of your medium by 48 hours. If you don't see something growing on the surface, or in the case of the non-gelatin route, if you don't notice any change in color, then re-cover your dish and give it another 48 hours.
If after four days, you still have no show, make another attempt at collecting. It's not unusal to see a few swings and a miss.
When you see something growing on the surface of your dish, it's time to make your best effort at selecting the yeast and growing it in another batch of starter wort. The chances are high that you caught not only multiple strains of yeast, but also some mold and bacteria as well.
Mold cultures tend to have a furry or spiky shape to their colonies, while yeast will be whitish in color and have a more slimy appearance. You can see in the picture below an example of multiple organisms growing all on this dish.
This is an example of both yeast and mold growing on a plate. Notice that the off-white yeast is has a shiny slimy look to it, while the mold looks like hairy or spiky puffs.
If you've opted to not use gelatin, and you ignore this step while hoping for the best.
After sanitizing a straightened paper clip or other metal prong, scrape off some of the yeast being careful to avoid anything else on the surface of the dish.
Scrape this new yeast into a fresh container of acidified starter wort and wait for it to grow. If you have a stirplate, this is a great time to use it.
Growing the starter culture...
There is good information out there that suggests it is preferably to step up yeast cultures in small increments rather than putting a very little yeast in a comparatively large amount of starter. For me, this is an unnecessary complication for the first effort. We're trying to keep this simple for now.
Within a day or two, your starter should become cloudy and have a small krausen or foam on the top of the container. Within a day or two more, your yeast will have fermented the starter and have been dropping out of suspension leaving a small yeast cake on the bottom of the starter.
Bonus growth phase with 2nd starter...
Considering that we've been doing our amateurish best to create an environment that favors beer fermenting yeast more than anything else, our yeast at this three to four day mark should have far outstripped the other organisms that take longer to grow.
I like to take a small portion of the flocculated yeast cake and pitch it into one last batch of acidified starter wort that I will grow to pitchable size. I do this because the proportion of yeast cells to those of other organisms is likely to be much more in our favor after the first starter, then at the time of the initial scraping.
This is an example of a yeast cake settling out of suspension. A yeast starter after a few days won't have nearly so large or a cake and the separation won't be as clear, but you get the idea.
You should step up the starter to 1 liter for a five gallon test batch or if you're the sensible type, you can stick to just a pint and do a one gallon test batch.
Testing and Final Thoughts...
It's best to use a simple and fairly neutral for your test recipe. You want the flavor of the yeast to come through without being obscured by the over hopping or an overly complicated grain bill. Stick to something that starts near 1.050 OG and has moderate hop addition.
Over the next few weeks, watch your gravities and see what happens. The results range from complex estery strains, efficient but bland strains, and of course stuff that might taste simply awful.
As you've noticed, this isn't an overly scientific or precise method. Rather than a single yeast strain, you've probably collected a blend of yeasts, but it's a great way to have fun getting a "house strain" of your own.
There is a nearly infinite amount of further information to consider when it comes to this topic. If you'd like to know all there is to know about it, I've heard that a master's degree in microbiology from Johns Hopkins is a great place to start. This little article is just to get you started.
Whether the results are great, good, or bad it's a fun project at any rate. Roll the dice and see what kind of beer your backyard wants to brew.
In this article, I'm going to go through some simple steps that with a bit of luck will get you a local yeast strain of your own to brew with. This topic can and does fill stacks and stacks of books, but we're going to stick with just the basics today.
The equipment you'll need for this project can range from stuff you can find in your kitchen up to a lab that would make the CDC jealous. Just like the rest of the homebrewing hobby, yeast ranching can be a real gear treadmill, but it doesn't have to be.
Things you'll need...
- A handful of small containers (mason jars work fine)
- Malt extract for making starter wort
- Raw lemon juice or acid blend powder
- Plenty of sanitizer
- Access to a park or a back yard with plenty of vegetation in a cool time of year
- Gelatin
- Stir plate
- Petri dishes
To start with, make a small batch of starter wort. If you've not done that before, there are examples and videos galore already out there to explain, but the underlying goal is to boil some 1.040 OG wort made from your malt extract. Add the raw lemon juice to the starter wort to lower the ph balance of your wort. The amount that you should add should be 10% of your original volume.
We're lowering the ph because while the yeast that we're after prefers a slightly acidic environment, mold, and other things we don't want, do poorly in acidic environments. Some of the cool kid brewers might add hops to this starter boil for the same reason, but it's not strictly necessary.
If you have petri dishes or shallow containers for this project, I recommend adding the appropriate amount of gelatin to the solution to make it a semi-solid after cooling in your sanitized containers. In a pinch, this isn't necessary, but it helps.
Cover tightly with sanitized foil and let cool until you're ready for the next step.
Inoculating your medium...
When looking for a location to capture your yeast, it's best to aim for a cool location that is undisturbed by passing animals, ill behaved children, and belligerent drunks.
I've lost several yeast collecting mediums to this guy...
The best place to find wild yeast is in the area of naturally occurring sugars. Knowing this, it's preferable to place your open container nearby trees or plants with fruit. Trees leaking sap are a particularly attractive spot.
In addition to the ph considerations, yeast prefers cool temperatures more than competing mold and other undesirables. This makes fall an ideal time for capturing yeast. Ideally, you should place the container in the late afternoon or evening after the heat of the day is gone.
Leave your container open for several hours or overnight, but not much longer. Recover with sanitized foil and leave undisturbed for at least 48 hours.
Another method is drop wild fruit directly into the starter wort or onto the surface of the dish, as yeast lives on skin of fruit. Juniper berries have worked for a few people I know, and of course grapes are another good source.
Selecting your yeast culture...
If your dish was indeed inoculated, you stand a good chance of seeing a change in the surface of your medium by 48 hours. If you don't see something growing on the surface, or in the case of the non-gelatin route, if you don't notice any change in color, then re-cover your dish and give it another 48 hours.
If after four days, you still have no show, make another attempt at collecting. It's not unusal to see a few swings and a miss.
When you see something growing on the surface of your dish, it's time to make your best effort at selecting the yeast and growing it in another batch of starter wort. The chances are high that you caught not only multiple strains of yeast, but also some mold and bacteria as well.
Mold cultures tend to have a furry or spiky shape to their colonies, while yeast will be whitish in color and have a more slimy appearance. You can see in the picture below an example of multiple organisms growing all on this dish.
This is an example of both yeast and mold growing on a plate. Notice that the off-white yeast is has a shiny slimy look to it, while the mold looks like hairy or spiky puffs.
If you've opted to not use gelatin, and you ignore this step while hoping for the best.
After sanitizing a straightened paper clip or other metal prong, scrape off some of the yeast being careful to avoid anything else on the surface of the dish.
Scrape this new yeast into a fresh container of acidified starter wort and wait for it to grow. If you have a stirplate, this is a great time to use it.
Growing the starter culture...
There is good information out there that suggests it is preferably to step up yeast cultures in small increments rather than putting a very little yeast in a comparatively large amount of starter. For me, this is an unnecessary complication for the first effort. We're trying to keep this simple for now.
Within a day or two, your starter should become cloudy and have a small krausen or foam on the top of the container. Within a day or two more, your yeast will have fermented the starter and have been dropping out of suspension leaving a small yeast cake on the bottom of the starter.
Bonus growth phase with 2nd starter...
Considering that we've been doing our amateurish best to create an environment that favors beer fermenting yeast more than anything else, our yeast at this three to four day mark should have far outstripped the other organisms that take longer to grow.
I like to take a small portion of the flocculated yeast cake and pitch it into one last batch of acidified starter wort that I will grow to pitchable size. I do this because the proportion of yeast cells to those of other organisms is likely to be much more in our favor after the first starter, then at the time of the initial scraping.
This is an example of a yeast cake settling out of suspension. A yeast starter after a few days won't have nearly so large or a cake and the separation won't be as clear, but you get the idea.
You should step up the starter to 1 liter for a five gallon test batch or if you're the sensible type, you can stick to just a pint and do a one gallon test batch.
Testing and Final Thoughts...
It's best to use a simple and fairly neutral for your test recipe. You want the flavor of the yeast to come through without being obscured by the over hopping or an overly complicated grain bill. Stick to something that starts near 1.050 OG and has moderate hop addition.
Over the next few weeks, watch your gravities and see what happens. The results range from complex estery strains, efficient but bland strains, and of course stuff that might taste simply awful.
As you've noticed, this isn't an overly scientific or precise method. Rather than a single yeast strain, you've probably collected a blend of yeasts, but it's a great way to have fun getting a "house strain" of your own.
There is a nearly infinite amount of further information to consider when it comes to this topic. If you'd like to know all there is to know about it, I've heard that a master's degree in microbiology from Johns Hopkins is a great place to start. This little article is just to get you started.
Whether the results are great, good, or bad it's a fun project at any rate. Roll the dice and see what kind of beer your backyard wants to brew.
