Homebrewers can attempt to cultivate yeast strains using various bottle conditioned beers. By building up the weakened yeast, one can slowly grow the sample into a pitchable amount that can be used for a 5 gallon homebrew batch. This is an advanced technique and should not be attempted unless you are willing to experiment and risk a bad batch of homebrew.
What You Need
- 1lb. Dry malt extract
- 1 Gallon Water
- Set of Erlenmeyer Flask (50ml, 125ml, 250ml, 500ml, and 1000ml–or a set of similar sized ball jars)
- Aluminum foil
- A bottle of your favorite bottle conditioned beer
What to Do
Step 1: Store a bottle aged beer upright for at least two (2) weeks prior to opening.
Step 2: Have your drinking glasses out and be ready to pour the entire beer at once, leaving a few ounces in the bottle.
Step 3: Gently swirl the bottle to loosen the yeast from the bottom.
Step 4: Pour the dregs of the bottle into a sanitized jar or flask where it can be grown.
Step 5: Add the equal volume of 1.040 gravity wort to the vessel and cover with a tight foil cap.
Step 6: On day 2, add another equal volume of 1.040 wort and swirl.
Step 7: On day 3, store in refrigerator for 24-48 hours or until all the yeast has settled to the bottom.
Step 8: Gently pour off, decant the liquid leaving the yeast.
Step 9: Add double the amount of 1.040 wort that was added on day two.
Step 10: Repeat steps 6-9 until you feel you have collected the proper cell count of yeast to pitch in your homebrew beer.
Step 11: Ferment and enjoy, you just pirated another brewer’s yeast. Yarrr!
For a list of various bottles and the yeast they have, check out The Mad Fermentationist’s blog: themadfermentationist.com/2010/06/harvesting-sour-beer-bottle-dregs.html