While cleaning out your fermenter have you ever wondered if you could reuse the yeast that has collected on the bottom? The answer is yes, you certainly can! You can actually often reuses your yeast 4 or 5 times with out the likelihood of having any ill effects from mutations or high quantities of alternate yeast strains impacting the flavor of your beer. Yeast isn’t cheap at around $7-$10 for a vial of the good stuff, so you might as well get your moneys worth!
Here are some basic things to consider when reusing your home brewing yeast.
It is best to reuse the yeast as soon as possible. You will probably want to consider discarding it after approximately 6 months. If you are pitching the yeast more than 30 days after harvesting it from your fermenter, I would recommend creating a starter with it to help insure viability.
Only reuse your yeast 4-5 times. Each time you reuse the yeast, mutations will occur and the probability of alternate yeast strains impacting the flavor of your beer will increase.
Do not reuse the yeast if the ABV of the beer that you harvested it from exceeds 6.5%. High alcohol levels weaken and destroy your yeast.
Do not reuse yeast from a heavily hopped beer. Like with alcohol, an over abundance of hops (from a dry hopped IPA for instance) will diminish the longevity and potency of your yeast.
Do your best to avoid harvesting the trub along with your yeast. This is most easy accomplished via a conical fermenter. It is also possible transfer the yeast slurry and then rinse and decant your yeast with sanitized water to separate it from the trub.
Yeast should be stored at approximately 36 F in a sanitized vessel. Keep in mind that even at that temperature the yeast may still be active and can create CO2. So beware as your container may explode if too much fermentable sugar remained behind in your harvested yeast solution and the vessel is unable to vent the pressure.
If you are interested in purchasing a conical fermenter or yeast harvesting cylinder; many options can be found here: