Wild Yeast Isolation
Wild yeast isolation, sometimes known as yeast wrangling, refers to the process of catching wild yeast, and isolating it with agar plates as a pure culture. This article will also contain information for growing up a captured mixed culture in wort rather than isolating pure cultures.
- Special thanks goes out to Bryan Heit from Sui Generis blog and Jeff Mello from Bootleg Biology for providing the information in this article.
Contents
Isolating Pure Cultures
Preparation
- Bryan Heit's video guide to setting up a clean workspace, building and using an alcohol lamp, and aseptic techniques.
- Bootleg Biology's guide on creating agar plates using wort, agar powder, and yeast nutrient.
- Bryan Heit's guide to more types of agar plates, and video tutorial.
Catching
- Bootleg Biology defines three methods of catching a wild yeast.
- Bryan Heit's video tutorial for catching wild yeast from fruit or from the air.
Isolating
- Bootleg Biology's guide to streaking agar plates to isolate the captured yeast cultures.
- Bryan Heit's video guide on how to streak agar plates.
- Bryan Heit's video guide on streaking plates and further isolating yeast.
Identifying
- Bryan Heit's video guide on how to visually identify usable yeasts versus potential pathogens and molds.
Growing Without Isolation
While using agar plates to isolate yeast colonies is the most effective way to culture wild yeast, it is not the only way. Wild yeast should be caught using starter wort as outlined in Bootleg Biology's Method 1 or Method 2. The starter wort's pH should be lowered to below 4.5 to avoid bacteria as much as possible. Molds may still grow in the yeast starter even with the lower pH. Signs of a small krausen within a day or two is a good sign that viable wild yeast has been collected. After another day or two, the yeast will start dropping to the bottom of the vessel [1].
Once the starter has fermented out, decant the beer and pitch the collected yeast into a 500ml of starter wort, again lowering the pH to below 4.5 of the wort. After the starter wort has been fermented, the yeast should have enough of a population to ferment out a 1 gallon batch of wort. Keep the recipe of the wort simple, and in the 1.050 gravity range. The population of the yeast should be high enough to out-compete bacteria that would be harmful, so the pH of the 1 gallon batch does not need to be lowered. After fermenting out the 1 gallon bath of beer, sample the beer to see if the wild yeast is usable or not. Wild yeasts can be highly or moderately estery, or could have undesirable flavors [1].
See Also
External Resources
- Biology provides a full toolkit and materials for yeast isolation.
- Sui Generis blog by Bryan Heit.
- BKYeast, How to Build a Yeast Ranch.