How do you isolate wild yeast?

Answered by Jesse Garza

Isolating wild can be an exciting and rewarding process, as it allows you to capture unique and diverse strains that can add complexity and character to your homebrewed . While using agar plates is the most effective method for yeast isolation, there are alternative approaches you can take.

One popular method for capturing wild yeast is through the use of DME (Dry Extract) wort. This involves creating a simple wort solution using DME and , which serves as a nutrient-rich medium for yeast to thrive. The DME wort is prepared by dissolving a specific amount of DME in water and then boiling it to sterilize the solution. Once the wort has cooled down, it is exposed to the environment to allow wild yeast to be captured.

To capture wild yeast using the DME wort method, you can simply leave the prepared wort uncovered in a shallow container, such as a petri dish or a sanitized mason jar with a breathable cover. Place the container in a location where it can be exposed to the air, such as an open window or near a fruit tree. The yeast present in the air will eventually find their way into the wort and begin to ferment it.

It is important to note that capturing wild yeast using DME wort can be a hit-or-miss process. The success of isolating desirable yeast strains depends on various factors, such as the location, time of year, and the presence of other microorganisms. Patience is key, as it may take several days or even weeks for visible signs of fermentation to occur. Once fermentation is evident, you can transfer a small sample of the actively fermenting wort to a separate vessel or bottle and allow it to continue fermenting.

Another approach to yeast isolation, known as the Yeast Bootcamp method developed by David Thornton, involves creating a starter culture using a mixture of fruits, such as grapes, berries, or apples, along with a non-hopped malt extract. This method aims to capture wild yeast that naturally reside on the surface of fruits. By macerating the fruits and mixing them with the malt extract, you create a fermentation environment where the wild yeast can thrive.

The fruit and malt extract mixture is allowed to ferment for a period of time, typically a few days, while being closely monitored for signs of active fermentation. Once fermentation is observed, a small sample of the actively fermenting mixture can be transferred to a separate vessel or bottle for further cultivation.

While the DME wort and Yeast Bootcamp methods are effective ways to capture wild yeast, it's important to note that not all captured yeast strains will be suitable for . Some strains may produce undesirable flavors or have poor fermentation characteristics. It is essential to conduct rigorous testing and evaluation of the captured strains before using them in a brewing recipe.

Isolating wild yeast can be done through various methods, including agar plate isolation, DME wort capture, or the Yeast Bootcamp method. Each approach has its advantages and limitations, and experimentation is often required to find the most suitable method for capturing desirable yeast strains. Remember, capturing and cultivating wild yeast can be a fascinating journey, filled with surprises and discoveries along the way.