Introduction: As a brewer without access to advanced scientific equipment, you may find yourself seeking alternative methods to cultivate yeast for your brews. Wild yeast can be found all around us, from the air to the surfaces of fruits and plants. In this guide, we’ll explore the process of collecting and propagating wild yeast for brewing purposes, using simple techniques and materials.
Equipment and Supplies:
- Fresh fruit (e.g., apples, grapes, or berries)
- Glass jars with lids or airlocks
- Cheesecloth or clean cloth
- Wooden or plastic spoon
- Sugar (preferably organic)
- Water (non-chlorinated)
- Malt extract (optional)
- Hydrometer (optional, but helpful)
Collecting Wild Yeast:
- Choose your source: Begin by selecting a source of wild yeast. Fresh fruits, such as apples, grapes, or berries, are ideal for capturing wild yeast strains. Organic fruits with no pesticide residue are preferred, as they tend to harbor more natural yeast.
- Prepare the fruit: Rinse the fruit gently with non-chlorinated water to remove any dirt or debris, but do not scrub or sanitize the fruit, as this could remove the yeast you are trying to capture.
- Prepare the jar: Sterilize a glass jar and its lid by boiling it in water for at least 10 minutes, and then let it air dry. This will ensure that you are starting with a clean environment for your wild yeast to grow.
- Create the yeast starter: In the sterilized jar, add a small amount of sugar (1-2 tablespoons) and fill the jar halfway with non-chlorinated water. Stir the sugar until it dissolves.
- Add the fruit: Place the fruit into the jar, ensuring it is submerged in the sugar water mixture. You may cut larger fruits into smaller pieces to increase the surface area for yeast collection.
- Cover the jar: Cover the jar with a cheesecloth or clean cloth and secure it with a rubber band or string. This will allow air to flow in and out while keeping unwanted contaminants out.
- Fermentation: Allow the jar to sit at room temperature, out of direct sunlight, for 3-7 days. During this time, the wild yeast on the fruit’s surface will begin to ferment the sugar in the water, creating a bubbling and slightly sour aroma.
- Observe the fermentation: Monitor the jar for signs of fermentation, such as bubbles, a fruity or yeasty aroma, and a layer of foam or sediment at the bottom of the jar. Use a hydrometer to measure the specific gravity of the liquid, if available. A drop in specific gravity indicates that fermentation is taking place.
Propagating Wild Yeast:
- Remove the fruit: After fermentation is evident, carefully remove the fruit from the jar, leaving the liquid behind.
- Feed the yeast: Add a small amount of sugar or malt extract (1-2 tablespoons) to the liquid and stir to dissolve. The yeast will consume this new source of sugar and continue to propagate.
- Monitor the growth: Observe the jar for another 3-7 days, looking for signs of continued fermentation and yeast growth. The liquid should become increasingly cloudy, with sediment accumulating at the bottom.
- Separate the yeast: Once the yeast has propagated sufficiently, carefully pour off the liquid, leaving the sediment (the yeast) at the bottom of the jar.
- Store the yeast: The wild yeast can now be stored in a clean jar with a tight-fitting lid or airlock in the refrigerator for future use. Feed the yeast occasionally with sugar or malt extract to keep it healthy and active. Be sure to label the jar with the date and source of the wild yeast.
- Test the yeast: Before using your wild yeast in a full-scale brewing project, it’s a good idea to test its fermentation capabilities in a small batch. This will help you determine if the yeast is suitable for your brewing needs and if any adjustments to your recipe are necessary.
- Use the wild yeast: When you’re ready to brew with your wild yeast, create a starter by combining the yeast with a small amount of wort or sugar water in a sterilized container. Allow this mixture to ferment for 24-48 hours, and then pitch it into your main brewing vessel. Be prepared for a longer fermentation period than with commercial yeast, as wild yeast strains may work at a slower pace.
- Experiment and refine: Working with wild yeast can be unpredictable, but it’s also an opportunity for creativity and experimentation. As you gain experience with your wild yeast strain, you’ll learn its unique characteristics and how to adjust your brewing techniques to achieve the best results.
Conclusion: Collecting and propagating wild yeast for brewing can be a rewarding and fascinating process, allowing you to create unique, locally-inspired beers that showcase the flavors of your region. By following these simple steps, you can become a master brewer with the ability to harness the power of wild yeast, even without access to advanced scientific equipment. Embrace the challenge and enjoy the journey of brewing with wild yeast!