Yeast Reuse and Storage - Creation of your own yeast library!
Yeast Reuse and Storage - Creation of your own yeast library!
Saving Yeast: To save and reuse a batch of yeast simply rack off the fermented beer from the primary fermenter into the secondary taking care to keep the primary from becoming contaminated (leave the lid mostly on and your fingers mostly out). This will leave a residual volume of wort plus the thick yeast cake in the bottom. Swirl carefully to suspend the yeast in the liquid and then pour carefully into a 1 pint jar and cap. Refrigerate until cool to refrigerator temperature.
Washing Yeast: To prepare yeast for storage, you must wash out the residual wort with water to remove growth media and force the yeast to become quiescent (resting) and metabolically inactive. Wash the yeast by first pouring off the residual liquid leaving behind the settled yeast cake in the bottom of the jar. Fill to top with cold sterile water, cap tightly and mix thoroughly. Unscrew cap a little to relieve pressure and put back in refrigerator and allow the yeast to settle again. Repeat this washing step 3 more times or until the wort/color is diluted out of the wash water. Pour off most of the liquid and store in the refrigerator. You can mix again and aliquot into smaller pitchable tubes or small jars. I have re-used yeast up to at least 5-6 times without problems. This assumes you are using good sterile technique.
Yeast Starter: In a small pot on the stove top combine ½ cup DME (dry malt extract), 1/8 teaspoon yeast nutrient (sodium phosphate and urea – both food grade) and about 3 cups water (aged overnight on the counter at room temperature is best). Heat to boil stirring frequently until all is dissolved. Turn down to gentle boil and let simmer for 15 min (watch for boil-over at the beginning). Cool in a sink of cold water (about 2 inches deep) until 37oC or less – 99oF with a sterile thermometer.
At the same time sanitize a bucket containing the starter vessel (I use a 2 liter flask), a piece of aluminum foil for the top, a large funnel to fit the flask and a thermometer (I have a glass one for this purpose). Let soak in a bucket of bleach (1 cup per 5 gal) for 30 min. Rinse well with hot tap water and assemble the funnel onto the flask. Pour in the stored yeast followed by the boiled and cooled wort. Cap with rinsed foil, mix well making as much foam as you can without spilling any and incubate on the counter until it foams. This can take several days if it is an old culture or a few hours if fresh. Given it a shake periodically during the day. Pitch directly into your new wort on brew day. It is ok if the starter reaches high kreutzen (foamy growth) or beyond prior to brew day as the yeast will still be quite fresh.
I have also taken a bottle of commercial beer and made a starter from the residual yeast in the bottom. You must be patient and culture for longer and may even have to take this through a second starter to make enough yeast.
Washing Water & Containers: I clean and sterilize 3 pint mason jars with bleach and extensive washing in hot tap water (10+ rinses). Cap and place on counter. Fill 2 jars with boiled water (at least a 5 min boil) cap and cool to refrigerator temperature.
Storage Containers: Use old hop bottles, small jars or old White Labs vials, that have been cleaned and sterilized, and fill them with the yeast from the washed batch to about 2/3 full. You can pitch the entire vial into the starter wort. Such containers can be stored like this in the fridge for months ready for pitching into the starter. Be sure to label them well and keep track of the generations by marking 1st, 2nd, 3rd etc. on the vial with a Sharpie. You can build up a library of yeast this way.
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