1. Snake River Brewers
This presentation has been made for the Snake River Brewers of Idaho and has not been created for profit in any way. The information contained herein is solely for educational purposes.

2. By Matthew Kunzman Snake River Brewers, President
Yeast Culturing
By Matthew Kunzman
Snake River Brewers, President

3. Sections of this Presentation *************************
Repitching from slurry
Harvesting from bottles
Storage and Handling
Culturing
Resources and info about the author

4. Why culture yeast? Cost $$$ Proper pitching Consistency
It may take four to six vials of white labs yeast to properly pitch into a high gravity wort.
Consistency
Geek Factor (knowledge)
Just because you can

5. Repitching from slurry

6. What is repitching from slurry?
Yeast ferment the wort, and after their food supply is depleted, the yeast cells drop out of suspension and form what is known as a yeast cake. Often homebrewers repitch these dormant yeast cells into their next batch of beer. That is what Repitching from Slurry is all about.
It’s basically a full batch of beer as a starter

7. When to repitch from slurry
If your sanitation procedures are already great
Not worth it otherwise
You provided the previous batch proper nutrition. (and oxygen)

8. When not to repitch When yeast is contaminated Dry yeast
By bacteria or too many other particles
Dry yeast
Dry yeast has a lot of contaminants and should not be repitched
After five or six generations
Mutations will start

9. Slurry info
There are about 4.5 billion yeast cells in 1 milliliter of yeast solids (solids with no excess liquid)
With a normal clean ferment still only about 25% of the mass is yeast solids
Viability is around 90% before storage

10. Don’t overpitch IMPORTANT Don’t overpitch!!!
Repitching is usually the only way homebrewers overpitch
Do not pitch onto the entire yeast cake
Yeast need some growth in order for the beer to develop the proper ester tastes for style
IMPORTANT
Don’t overpitch!!!

11. Saving Yeast
When primary fermentation is complete, there will be visible yeast slurry at the bottom of the fermenter. (These are dead and dormant yeast cells.)
When racking beer off of the primary fermenter, leave about 2 inches of beer left above the yeast slurry.
Shake the heck out of the fermenter and mix the beer with the yeast cells.
Cut a small hole in a quart Mason jar lid to snugly fit an airlock. (Make sure you sanitize the jar, lid, airlock)
Pour the mixed solution into the mason jar, filling it about half way
Place the airlock in the hole, filling it with water to the fill line. (Did you remember to sanitize the airlock?)
Place the jar in your fridge. (The yeast will be fine for up to four weeks, but the quicker you brew, the stronger the yeast will be)

12. Washing yeast
Washing yeast cleans a lot of the excess debris from the yeast and leaves a cleaner yeast specimen. It can be done with three quart mason jars. **MAKE SURE TO SANITIZE**
Sanitize the opening of the carboy.
Pour water from a mason quart jar into the carboy. Swirl to agitate the yeast, hop residual, and trub from the bottom.
Pour carboy contents back into the empty jar and replace the cover.
Agitate the jar to allow separation of the components. Continue to agitate periodically until obvious separation is noticeable.
While the viable yeast remains in suspension, pour off this portion, into a second mason quart jar, being careful to leave as much of the hops and trub behind as possible.
Agitate the second container to again get as much separation of yeast from particulate as possible. Allow contents to rest, then pour off any excess water from the surface.
Pour off yeast fraction, which suspends above the particulate into the third container. Store this container up to 1 month refrigerated. Pour off liquid and add wort, 2 days before brewing or repitch into a new brew straight away.

13. Reusing stored yeast
Take the yeast out of the fridge and place in room temperature for about three hours before pitching.
Sanitize the mouth of jar and lid.
Pour off half of the liquid in the jar into the sink.
Shake the jar to mix up yeast, and pitch contents into next batch of wort.

14. Why use an airlock?
Your yeast is not finished fermenting even if there are no visible signs
(Yeast may continue to slowly ferment sugars for up to a year)
Given time, your jar WILL explode
It makes a mess
A rubber grommet can be placed in the hole to make a better seal.
Loosely placed tin foil around the lid will also work (but bacteria could get under it with fridge door opening and closing, moving the airflow.)

15. How much do you pitch?
Pitch about 1 million cells of viable yeast, for every milliliter of wort, for every degree plato.
.75 million per ml of wort per degree plato with ales
1.5 million cells per ml of wort per degree plato with lagers
Formula is: (0.75 million) X (milliliters of wort) X (degrees Plato of the wort)
Check the Mr. Malty Pitching Rate Calculator for more precise numbers.

16. Harvesting from bottles

17. Does your beer contain yeast?
Most commercial beers are filtered, and some are flash pasteurized, before bottling and do not contain yeast.
Only Bottle conditioned beers have yeast.
You can usually see a small layer of yeast gathered at the bottom of the bottle.

18. Is this the yeast you want?
Check to see if the beer uses the same yeast to condition with that it brews with.
Many commercial brewers will filter their beer and repitch with a lager yeast to bottle condition.
The lager yeast will ferment the remaining sugars, will have less added flavor, and will create a fresher, more clean flavor.
Some brewers use multiple strains
There is no guarantee you will get the strain you desire.
Isolating strains is beyond the scope of this presentation

19. What yeast is harder to culture?
Yeast that have been stressed
from heat
Age
high alcohol levels
Yeast that have traveled a long distance
Travel can expose beers to heat
Travel can expose beers to light

20. Sanitation
Sanitation is extremely important when using small amounts of yeast.
Any contamination will be multiplied many times by the time the yeast is pitched.
Bacteria contamination may grow faster than your yeast.
This will render culture useless
Sanitation is more important here than with regular batch of beer.

21. Increasing cell count
Prepare a small amount of wort with DME and water over a stove
Boil for 60 mins
1.030 to gravity
No hops
Pour all but about last 1/16th inch of beer into a glass and drink it. (Be careful to leave yeast in the bottom of the bottle)
Sanitize the mouth of the near empty beer bottle.
Add cooled wort to bottle
Fill about ¾ full
Sanitize mouth of bottle
Place a drilled rubber stopper and airlock in mouth of beer bottle

22. Stepping up your starter
After a few days in the bottle, you can step up the starter. This will basically just increase cell count further.
Just make a to gravity starter with the ml needed for the original gravity of your wort. (This is the wort for the beer you plan on brewing)
This can be calculated to about 1 million cells per ml of wort per degree plato
Calculations more precise can be made at
As always, be sure to aerate both your starter wort and your main batch before adding any yeast.

23. Storage and Handling

24. Importance of storage and handling
Storage and handling is so important I felt it needed it’s own section.
Basic common sense
Be good to the yeast
Don’t stress yeast
Be clean and tidy
Be careful

25. Storage Always refrigerate yeast that is stored for over a few hours
Let yeast warm up for a few hours before pitching.
Keep yeast in the dark
Try not to handle it too much during storage.
Only store for as long as you absolutely need to.
Yeast will be less and less viable over time
Some strains like wheat strains don’t store as well
Lager strains will store a little longer than ale strains

26. Handling Be quick. Time is the enemy
Wipe all the surfaces you work on with disinfectant.
Wash your hands. -- really well
Do as much work in the morning, the air is generally as still as it gets (less air currents)
Hold you breath, and try not to breathe on anything. This is another reason to be quick!
Avoid actually touching anything that could get in touch with the yeast. Only hold tops of lids and sides of Petri-dishes, bottles and mason jars.
Sanitize, sanitize, sanitize --- everything that you can.
Don’t do any work near a vacuum, refrigerator, fan, A/C unit. (Anything that moves air)

27. Culturing

28. Why use Slants? indefinite (practically speaking) storage
assured maintenance of the original generation
ease of sharing yeast with brewpals.
When it comes time to make up a starter to pitch into a batch of beer, you get 500 ml of active starter within hours every time.
Finally, if you are doing slants, then when someone sends you a sample of yeast, or you get one from some other means, you can make yourself a renewable lifetime supply from that sample.

29. Equipment Needed
A bunch of glass vials or test tubes that have caps that can
withstand temps of 100 deg. C
form a tight seal.
30, is plenty, because as you proceed, using the yeast in them, you just reculture into the spent ones as necessary
A dish made of something like pyrex
that can also withstand boiling temperatures without exploding!
Something to use for your starter vessel
an old-style milk bottle
an Erlenmeyer flask
or other glass vessel that has a mouth to which you can affix a rubber-stopper + airlock.
The other hardware you will already have if you brew beer
a scale, big pot to boil in, kitchen stove, refrigerator, spoons, etc

30. Materials you need Either gelatin or agar-agar
Agar-agar is available online, at homebrew shops, or at some Asian food stores. This is the growth medium.
A bag of dried malt extract.
One bag will last you the rest of your life as far as keeping a full supply of yeast slants on hand is concerned.
A bit of ethyl alcohol.
250 ml will last you for years of culturing use.

31. Using Pure Cultures
Now, the assumption here is that you are culturing from a pure source, like a Wyeast pack, one of your bottled beers, or a slant that someone sends you.
If you are culturing, say, from a bottle of commercial bottle-conditioned beer, extra steps are required to isolate pure cultures (bottling strains are rarely pure).

32. Preparing blank slants
Bring 1 cup of water to a boil. Remove from heat, add half an ounce (15g) of dried malt extract, and stir till dissolved. Put back on the heat and boil for 5-10 minutes to ensure sterility. Remove from heat.
Pour a packet of gelatin into this "wort" and stir till COMPLETELY dissolved. Now pour this mixture into as many of your vials/test-tubes as you can; a small funnel is useful for this step. Fill the vials about 1/4 full-- do NOT fill them all the way up. Keep at least one vial empty for use in the next stage--see below. I typically fill about vials with these amounts.
Now place the pyrex dish mentioned above inside a large pot that has a lid (like your brewkettle). Place your partially-filled slant vials in the dish. Here is one place where having the flat-bottomed vials makes life easy--just stand them up in the dish. (If you have test-tubes, you will need a rack to stand them in, and the rack must sit in the pyrex dish. If your rack is the right shape and size, you may be able to omit the pyrex dish.) Put a couple cm of water in there--be sure it doesn't come up over the lip of the pyrex dish. Crank up the heat so that this water boils (full power will probably not be required), and keep it boiling for minutes. If you wish, you can put the vial-caps in there too, or just sterilize them with your favorite chemical agent--doesn't matter. You can just toss the vial caps into the water that is boiling. What is happening at this stage is that the steam from the boiling water is sterilizing the vials, the growth medium, and the caps (if they are in there too).
Now turn off the heat, and have a couple homebrews while it cools off. What you have at this point is sterilized vials + liquid growth medium. You need to wait for things to cool to at least 104F (40C) before attaching the sterile caps, otherwise the cooling growth-medium will cause the vials to either suck the caps into the vials, or actually implode. Once cool enough, put the caps on the vials firmly. You are now out of the woods as far as sanitation is concerned.
Now you must cool the vials while placing them at an angle of about degrees. You can do this by standing the vials in a box-lid (one with a good tall lip around it, like the box-top to a box of xerox paper), and stacking a bunch of oddments under one end, holding that end up, at the appropriate angle. When you do this, the surface of the still-liquid-but-cooling gelatin + malt extract will of course stay horizontal. Let the vials sit like this for 24 hours, after which time the gelatin + malt will be as solid as it gets (which is still a bit soft and yielding--ideal for this purpose). After cooling, the surface of the medium is at the angle you propped the box-top up to--that is, it's "slanted", hence the name. These are now ready to be "inoculated" with cells of your favorite yeast.

33. Prepare for inoculating
Before you start, you should lay out your working area in an organized way to minimize having to get up and down, reach long distances for things, etc.
Sort out your worldly affairs before beginning--i.e., take a leak, feed the dog, take out the trash.
Then wash your hands thoroughly, and begin. Have your Wyeast pack, slant vials, an unwrapped paper clip or long needle, a cotton ball or folded up paper-towel, your vial of ethyl alcohol, and your starter vessel laid out on clean paper toweling, along with an empty, unused slant vial that has been sterilized, along with its cap.

34. Inoculating the blank slants
As per usual procedure, get your Wyeast ready to make a starter, i.e. by breaking the inner packet and waiting a day or two for it to swell up. Make up a to wort, cool it, and add it to the starter vessel, being sure to aerate it well, as usual. Loosely sit its airlock in place--you want it to be easy to remove with one hand in the Step 2.
Stop breathing. Shake the Wyeast pack well, and then open it using standard procedures. Pour a tiny bit of the Wyeast solution into your empty and waiting vial, and pour the rest into your starter. Cap your vial, and attach your airlock to your starter. Resume breathing. Your starter will be ready to use the in the batch of beer you will brew tomorrow; the small quantity of solution will be used to inoculate slants.
Now repeat the following sequence of actions for each slant vial you wish to inoculate. First, take a deep breath and hold it. Wipe your needle/paperclip with alcohol-moistened cotton/paper towel to sterilize it. Open the slant vial to be inoculated. Then open the vial with the bit of Wyeast solution in it. Dip your needle into the Wyeast, and then lightly poke it into the surface of the gelatin + malt growth medium in the slant vial. Poke it in a bunch of places. Smear it around. Just try hard not to touch the walls of the vial. When done, withdraw the needle, cap the slant vial, and cap the Wyeast vial. Exhale. You now have a fully inoculated slant vial. Keep doing this for as many vials as you wish to inoculate
The total amount of time to do these 3 steps is about 20 minutes for 10 slants, maybe a little more the first time you do it, till you develop the knack.
When done, leave the vials out at room temperature 68F (20C) for a week. Within a couple of days you will see a cloudy film on the slant surface, and a few days later it will develop into a milky white layer about a mm thick. Sometimes, depending on the strain of yeast involved, the ambient temperature, and the richness of your growth medium, the CO2 evolved from the yeast growing on the slant surface may begin to push the cap up off the vial. No big deal-- just bleed the gas out by cracking open the cap for a moment, and press the cap back down firmly. After the week is over, wrap the tops of the vials (where the caps meet the vial walls) with electrician's tape, and put the vials into a ziplock bag and pop them in the fridge, where they will keep for at least 3 months in a perfectly viable condition.
Obviously, if you are keeping more than one yeast type around, you will want to label the vials somehow--masking tape works perfectly for this.

35. How many vials? How many vials should you inoculate at a time?
3 or 4 vials of a given yeast type in a session becomes more than enough, because most brewers rarely use the same yeast 4 times in 3 months.
When 3 months is nearly over, simply reculture the strain by doing the above to 3 or 4 new slants, but using an "old" slant as the source (instead of a vial with a few ml of Wyeast solution in it.) Otherwise the procedure is identical.
Reculturing in this way does not increment the strain generation-number because the yeast have not made enough copies of themselves for mutation to occur.

36. Bottled beer source
If culturing onto slants from a bottled-beer source, you should make a small-volume starter and wait until it is fully active, then pour off most of the liquid, swirl around what is left, and put several ml of that into the empty vial as the source.
WARNING! Many types of bottle-conditioned beer use either a different kind of yeast in the bottle than they fermented the beer with, or it is the same kind but has mutated, or any of several other possible complications. If you culture from a bottle of commercial beer, taste the small starter you make from it when inoculating your slants. If it tastes good (or at least, not bad) you are probably OK. But you should still test the yeast on a small, pilot batch of beer before committing your entire batch to it. Even when using a bottle of your own homebrew, things can happen, so I would recommend these cautions in that case as well.

37. Making a starter from a slant
Before starting, be sure to let your slant sit out for an hour or two so it can SLOWLY come up to room Temperature from fridge Temperature.
Now make a starter as usual.
After boiling up your starter mini-wort (1.030 to 1.035), cool it
Then pour a bit into your slant vial (a sanitized funnel is useful here too).
Swirl it around to loosen as much yeast as you can. Usually not all the yeast comes off the slant surface by simple swirling, so have your needle and alcohol ready in this case.
You just wipe the needle sterile with the alcohol, and then gently scrape the slant surface until the yeast comes off (don't worry if some of the gelatin tears loose– it doesn't matter).
Then pour that into your starter vessel (along with the rest of the mini-wort of course) and attach the airlock. At deg. C, the amount of yeast on a typical slant will produce a vigorously working starter in hours; a little more time is required at cooler temperatures.
As always, be sure to aerate both your starter wort and your main batch before adding any yeast.

38. Cleaning the slant vials
Hot water will dissolve the gelatin or agar-agar it after you have used the yeast to make a starter.
Just add some, swirl, and dump out over and over until it is dissolved away. Don't worry too much about making them spotless, because they will be sterilized next time you make a batch of blanks.

39. Things that can go wrong
The most common problem in making your own slants is that mold can take hold on the slant surface.
When this happens, it is absolutely unmistakable--a big greenish fuzzy patch just grows like wildfire. Simply ditch that slant--it is hopeless. This is why you should always make at least three new slants when propagating from an "old" one--so that you will be more likely to have one pure one if things go wrong.
It is also possible for bacteria to get a foothold too.
As long as the slant surface looks "good"--i.e., a nice milky layer of yeast, no other colors or shapes--you should be fine.

40. Resources

41. About the Author
Matthew Kunzman is president of the Snake River Brewers of Idaho
Developed the Help files for the Mr. Malty Pitching Rate Calculator
Matthew’s Homepage can be found at:
Matthew’s Myspace page can be found at:
Matthew’s address is:

42. Resources
Leistad, Rog, Yeast culturing for the Homebrewer, GW Kent Inc, Ann Arbor, MI, Dec 1983
Crenshaw, Donald G. "Yeast cycles and Fermentation", Zymurgy, American Homebrewers Assocation, Boulder, CO, Fall 1983
Eckhardt, Fred, The Amateur Brewer, J.I. Takita, Portland, OR, Summer 1979
J. Mellem and M. Raines, Growing Commercial Liquid Yeasts (Brewers Resource, Woodland Hills, California, 1992).
M. Raines, "Methods of Sanitation and Sterilization," BrewingTechniques 1 (2), (1993).
P. Rajotte, Belgian Ale (Brewers Publications, Boulder, Colorado, 1992).
Siebel Pure Yeast Cultures, Instructions for propagating bottom fermenting brewing yeast strains (J.E. Siebel Sons' Co., Chicago, Illinois).
G. Reed and H. Peppler, Yeast Technology (AVI Publishing Company, Westport, Connecticut, 1973), pp
Jamil Z, Mr. Malty Homepage,
Wyeast labs, Yeast Washing for the Home Brewer,
Chris Colby, BYO Magazine, “Yeast Culturing from Bottles: Techniques”, September 1995
Spencer W. Thomas, “Culturing Yeast Using Slants”, (Open Source) January 1995

43. Snake River Brewers
This presentation has been made for the Snake River Brewers of Idaho and has not been created for profit in any way. The information contained herein is solely for educational purposes.