Hopsta
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- 29/3/05
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I met up with fellow AHB member Airgead on the weekend, he lives local so we swapped a few yeasts. He told me about using slants to culture and store yeasts, this is new to me so i decided to do a bit of research and post some info on the subject for others that are interested.
I just have one question, one of the instructions is to flame the inoculation loop from the handle to the tip. Stick the tip into the Wyeast packet and swirl it in the liquid and smear the loop over the surface of the growth medium. Now im guessing that i am to flame the inoculation loop very quickly so as not to heat it up, because if it heats up wont it kill any yeast cells that it touches?
If anyone has any simplified methods or shortcuts in doing this let us know.....
Anyway here is the info i found.........
- Hopsta
Culturing Yeast and Using Slants - Part 1
by Bill Bunning
This will be a three-part "Beer Geek Techneeks" on culturing yeast. Part 1 will consist of equipment and supplies needed as well as preparing your blank slants. Part 2 will deal with slanting yeast and preparing starters. Part 3 will deal with obtaining a pure culture from a suspect yeast source.
Why culture yeasts? What you gain is indefinite (practically speaking) storage, assured maintenance of the original generation, and ease of sharing yeast with brewpals. Also, when it comes time to make up a starter to pitch into a batch of beer, you get 500 ml of active starter within 4 days every time. If you are doing slants, 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. Finally, using a new package of yeast every time you brew is expensive. After your initial set-up costs, yeast cost per brew will plummet when you propagate your yeast this way.
Minimum Equipment:
1. A bunch of glass vials or test tubes which have caps that can: (a) withstand pressure cooker temperatures or boiling water temperatures; and ( B ) form a tight seal.
2. An inoculation loop to transfer yeast.
3. Some type of flaming mechanism for sterilization (an alcohol lamp or a butane pencil torch).
4. Something to use for your starter vessel, like an old-style milk bottle, an Erlenmeyer flask (that's what I use), or other glass vessel that has a mouth to which you can affix a rubber-stopper and airlock.
5. The other hardware you will already have if you brew beer: a scale, a big pot to boil in, kitchen stove, refrigerator, and spoons. Additionally, a pressure cooker is ideal for sterilizing solutions (that's what I use).
Minimum Materials:
1. Either agar or gelatin, to use as a growth medium. I use agar and it works great.
2. 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.
3. An additional item which is a terrific time saver is mini-yeast starters. These are 10 ml of sterile wort in 50 ml vials. Brewers Resource sells them, and they're really a must if you culture yeast.
Preparing "Blank" Slants
Bring 1 cup (about 250 ml) water to a boil. Remove from heat, add 2 tablespoons 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. Add 1 1/2 tablespoons agar (or a package of gelatin) into this "wort" and stir till completely dissolved. 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 1/2 full - do not fill them all the way up. Screw the caps on. Now either boil the tubes for 30 minutes or place in a pressure cooker and "cook" for 15 minutes at 15 PSI. The pressure cooker will do a more complete job of sterilization.
Remove from the heat, and have a couple homebrews while it cools off. When the vials have cooled enough to handle (still hot however), loosen the caps a bit and place them at an angle of about 40-45 degrees. When you do this, the surface of the still-liquid-but-cooling agar and malt extract will of course stay horizontal. Let the vials sit like this for 12 hours, after which time the agar and malt will be somewhat solid (still a bit soft and yielding--ideal for this purpose). After cooling, the surface of the medium is at an angle giving a greater surface area, hence the name "slant". These are now ready to be "inoculated" with cells of your favorite yeast. Store these in the refrigerator until you're ready to use them.
Return to the Beer Geek Techneeks index
--------------------------------------------------------------------------------
Culturing Yeast and Using Slants - Part 2
by Bill Bunning
This is part 2 of the three-part "Beer Geek Techneeks" on culturing yeast. We'll learn how to slant yeast and prepare starters. Part 1 dealt with equipment and supplies needed for yeast culturing as well as preparation of blank slants. Part 3 will deal with obtaining a pure culture from a suspect yeast source.
Inoculating Blank Slants With Yeast
So now you have a bunch of slants. At this point, the procedure depends on what the source is for your yeast to be cultured. You may be starting from another slant or a packet of Wyeast or Yeast Lab starter. I'll describe doing it from a packet of Wyeast, and then comment on variations used for other sources.
The assumption here is that you are culturing from a pure source, like a Wyeast packet 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). This is much more involved, and will be described in Part 3. A couple days prior to slanting the yeast, smack the Wyeast packet just as if you were going to prepare a starter. You can use the packet for a starter when your finished making your slant. When the packet is swelled, 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. Wash your hands thoroughly and begin. Have your slants, inoculation loop, flaming mechanism, and yeast packet ready to go.
Shake the Wyeast pack well, and then open it using standard procedures. Flame the inoculation loop from the handle to the tip. Stick the tip into the Wyeast packet and swirl it in the liquid. Remove it from the packet and place it near your flame source, but not in it. The air is sterile within several inches of the flame. Open your slant, flame the opening, and smear the loop over the surface of the growth medium. Flame the opening and replace the cap. That's it. Use the remainder of the packet and make up a starter. Make sure you label the slant.
When done, leave the slant out at room temperature 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. You'll need to "burp" the slant every other day due to CO2 evolving from the yeast growing on the slant surface. No big deal - just bleed the gas out by cracking open the cap for a moment. After the week is over, store the slant in the fridge, where it will keep for at least 6 months in a perfectly viable condition. I've used them over 1 year old.
From Slant To Slant
When 6 months is nearly over, I reculture the strain by doing the above to another slant, but using an "old" slant as the source instead of a Wyeast packet. 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. You can also culture yeast from a friend's slant this way.
Making A Starter From A Slant
Before starting, be sure to let your slant sit out for about an hour so it can slowly come up to room temp from fridge. The yeast will be stepped up in three steps: from slant to 10 ml, from 10 ml to 50-75 ml, and from 50 -75 ml to 500 ml. When making a lager I step up to 1000 ml (and it takes an extra day). Here's where the mini-yeast starters come in handy. They're 10 ml of sterile wort in a vial. If you don't have these, you can make mini-starters in test tubes ahead of time. Again, you'll need the inoculation loop, flaming mechanism, yeast slant, and starter. Flame the loop from handle to tip. Open the slant and flame the opening. Scrape some yeast on to the loop (try cooling the loop on some exposed growth medium first). Plunge the loop into your mini-starter and shake off the yeast. Remove the loop and replace the top.
It will take about 2 days for this yeast to propagate. This is stepped up to 50 -75 ml and then to 500 ml. It only takes about 1 day for each of these steps. I use about 1 tbsp malt extract for the smaller volume and 4 tbsp for the larger volume when preparing my starters. After 4 days, you're ready to pitch.
Return to the Beer Geek Techneeks index
--------------------------------------------------------------------------------
Culturing Yeast and Using Slants - Part 3
by Bill Bunning
This is the final part of the three-part "Beer Geek Techneeks" on culturing yeast. We'll deal with obtaining a pure culture from a suspect yeast source. Part 1 dealt with equipment and supplies needed for yeast culturing as well as preparation of blank slants and part 2 dealt with how to slant yeast and prepare starters.
Preparing Plates
The first step is to prepare your petri dishes. You can either purchase plastic plates that you pour yourself or buy pre-poured plates. If you pour your own, prepare them when you make your normal slants; double your medium recipe and place the excess in a mason jar. Boil or pressure cook as described in Part 1. When it's cool enough to handle, pour the liquid into the plates (just a thin layer) quickly a leave to set. Store these wrapped (I use a zip-lock bag) in the fridge until ready to use.
Slanting Suspect Yeast Sources
If culturing from a bottled-beer source, make a small-volume starter and wait until it is fully active. 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.
The steps here are similar to those used in slanting yeast in Part 2. You'll need the prepared plate, the inoculation loop, flaming mechanism, and the small starter you prepared above. Flame the loop from handle to tip. Place in the starter and swirl. Quickly remove the lid from the plate and streak the loop back and forth over one third of the plate. Flame the loop again and streak one third of the plate again overlapping the previous streak. Repeat this procedure one more time streaking the final third of the plate. Replace the lid and store at room temperature. This whole procedure should isolate individual cells of yeast by the third streak. You'll see individual colonies growing in the final area streaked several days later. These colonies are slanted the same as if you were going from slant to slant in Part 2. All the procedures remain the same.
Maintaining Your Yeast Ranch
In no time at all you'll have several different yeasts on slants; I've got over 20! (Editor's note: Bill's refrigerator must not have any beer, or food, in it). Make sure you label each slant with type and date. You'll want to keep track of dates so you'll know when to re-slant a given yeast. Good luck and happy ranching!
edit rogue smiley.
I just have one question, one of the instructions is to flame the inoculation loop from the handle to the tip. Stick the tip into the Wyeast packet and swirl it in the liquid and smear the loop over the surface of the growth medium. Now im guessing that i am to flame the inoculation loop very quickly so as not to heat it up, because if it heats up wont it kill any yeast cells that it touches?
If anyone has any simplified methods or shortcuts in doing this let us know.....
Anyway here is the info i found.........
- Hopsta
Culturing Yeast and Using Slants - Part 1
by Bill Bunning
This will be a three-part "Beer Geek Techneeks" on culturing yeast. Part 1 will consist of equipment and supplies needed as well as preparing your blank slants. Part 2 will deal with slanting yeast and preparing starters. Part 3 will deal with obtaining a pure culture from a suspect yeast source.
Why culture yeasts? What you gain is indefinite (practically speaking) storage, assured maintenance of the original generation, and ease of sharing yeast with brewpals. Also, when it comes time to make up a starter to pitch into a batch of beer, you get 500 ml of active starter within 4 days every time. If you are doing slants, 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. Finally, using a new package of yeast every time you brew is expensive. After your initial set-up costs, yeast cost per brew will plummet when you propagate your yeast this way.
Minimum Equipment:
1. A bunch of glass vials or test tubes which have caps that can: (a) withstand pressure cooker temperatures or boiling water temperatures; and ( B ) form a tight seal.
2. An inoculation loop to transfer yeast.
3. Some type of flaming mechanism for sterilization (an alcohol lamp or a butane pencil torch).
4. Something to use for your starter vessel, like an old-style milk bottle, an Erlenmeyer flask (that's what I use), or other glass vessel that has a mouth to which you can affix a rubber-stopper and airlock.
5. The other hardware you will already have if you brew beer: a scale, a big pot to boil in, kitchen stove, refrigerator, and spoons. Additionally, a pressure cooker is ideal for sterilizing solutions (that's what I use).
Minimum Materials:
1. Either agar or gelatin, to use as a growth medium. I use agar and it works great.
2. 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.
3. An additional item which is a terrific time saver is mini-yeast starters. These are 10 ml of sterile wort in 50 ml vials. Brewers Resource sells them, and they're really a must if you culture yeast.
Preparing "Blank" Slants
Bring 1 cup (about 250 ml) water to a boil. Remove from heat, add 2 tablespoons 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. Add 1 1/2 tablespoons agar (or a package of gelatin) into this "wort" and stir till completely dissolved. 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 1/2 full - do not fill them all the way up. Screw the caps on. Now either boil the tubes for 30 minutes or place in a pressure cooker and "cook" for 15 minutes at 15 PSI. The pressure cooker will do a more complete job of sterilization.
Remove from the heat, and have a couple homebrews while it cools off. When the vials have cooled enough to handle (still hot however), loosen the caps a bit and place them at an angle of about 40-45 degrees. When you do this, the surface of the still-liquid-but-cooling agar and malt extract will of course stay horizontal. Let the vials sit like this for 12 hours, after which time the agar and malt will be somewhat solid (still a bit soft and yielding--ideal for this purpose). After cooling, the surface of the medium is at an angle giving a greater surface area, hence the name "slant". These are now ready to be "inoculated" with cells of your favorite yeast. Store these in the refrigerator until you're ready to use them.
Return to the Beer Geek Techneeks index
--------------------------------------------------------------------------------
Culturing Yeast and Using Slants - Part 2
by Bill Bunning
This is part 2 of the three-part "Beer Geek Techneeks" on culturing yeast. We'll learn how to slant yeast and prepare starters. Part 1 dealt with equipment and supplies needed for yeast culturing as well as preparation of blank slants. Part 3 will deal with obtaining a pure culture from a suspect yeast source.
Inoculating Blank Slants With Yeast
So now you have a bunch of slants. At this point, the procedure depends on what the source is for your yeast to be cultured. You may be starting from another slant or a packet of Wyeast or Yeast Lab starter. I'll describe doing it from a packet of Wyeast, and then comment on variations used for other sources.
The assumption here is that you are culturing from a pure source, like a Wyeast packet 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). This is much more involved, and will be described in Part 3. A couple days prior to slanting the yeast, smack the Wyeast packet just as if you were going to prepare a starter. You can use the packet for a starter when your finished making your slant. When the packet is swelled, 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. Wash your hands thoroughly and begin. Have your slants, inoculation loop, flaming mechanism, and yeast packet ready to go.
Shake the Wyeast pack well, and then open it using standard procedures. Flame the inoculation loop from the handle to the tip. Stick the tip into the Wyeast packet and swirl it in the liquid. Remove it from the packet and place it near your flame source, but not in it. The air is sterile within several inches of the flame. Open your slant, flame the opening, and smear the loop over the surface of the growth medium. Flame the opening and replace the cap. That's it. Use the remainder of the packet and make up a starter. Make sure you label the slant.
When done, leave the slant out at room temperature 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. You'll need to "burp" the slant every other day due to CO2 evolving from the yeast growing on the slant surface. No big deal - just bleed the gas out by cracking open the cap for a moment. After the week is over, store the slant in the fridge, where it will keep for at least 6 months in a perfectly viable condition. I've used them over 1 year old.
From Slant To Slant
When 6 months is nearly over, I reculture the strain by doing the above to another slant, but using an "old" slant as the source instead of a Wyeast packet. 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. You can also culture yeast from a friend's slant this way.
Making A Starter From A Slant
Before starting, be sure to let your slant sit out for about an hour so it can slowly come up to room temp from fridge. The yeast will be stepped up in three steps: from slant to 10 ml, from 10 ml to 50-75 ml, and from 50 -75 ml to 500 ml. When making a lager I step up to 1000 ml (and it takes an extra day). Here's where the mini-yeast starters come in handy. They're 10 ml of sterile wort in a vial. If you don't have these, you can make mini-starters in test tubes ahead of time. Again, you'll need the inoculation loop, flaming mechanism, yeast slant, and starter. Flame the loop from handle to tip. Open the slant and flame the opening. Scrape some yeast on to the loop (try cooling the loop on some exposed growth medium first). Plunge the loop into your mini-starter and shake off the yeast. Remove the loop and replace the top.
It will take about 2 days for this yeast to propagate. This is stepped up to 50 -75 ml and then to 500 ml. It only takes about 1 day for each of these steps. I use about 1 tbsp malt extract for the smaller volume and 4 tbsp for the larger volume when preparing my starters. After 4 days, you're ready to pitch.
Return to the Beer Geek Techneeks index
--------------------------------------------------------------------------------
Culturing Yeast and Using Slants - Part 3
by Bill Bunning
This is the final part of the three-part "Beer Geek Techneeks" on culturing yeast. We'll deal with obtaining a pure culture from a suspect yeast source. Part 1 dealt with equipment and supplies needed for yeast culturing as well as preparation of blank slants and part 2 dealt with how to slant yeast and prepare starters.
Preparing Plates
The first step is to prepare your petri dishes. You can either purchase plastic plates that you pour yourself or buy pre-poured plates. If you pour your own, prepare them when you make your normal slants; double your medium recipe and place the excess in a mason jar. Boil or pressure cook as described in Part 1. When it's cool enough to handle, pour the liquid into the plates (just a thin layer) quickly a leave to set. Store these wrapped (I use a zip-lock bag) in the fridge until ready to use.
Slanting Suspect Yeast Sources
If culturing from a bottled-beer source, make a small-volume starter and wait until it is fully active. 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.
The steps here are similar to those used in slanting yeast in Part 2. You'll need the prepared plate, the inoculation loop, flaming mechanism, and the small starter you prepared above. Flame the loop from handle to tip. Place in the starter and swirl. Quickly remove the lid from the plate and streak the loop back and forth over one third of the plate. Flame the loop again and streak one third of the plate again overlapping the previous streak. Repeat this procedure one more time streaking the final third of the plate. Replace the lid and store at room temperature. This whole procedure should isolate individual cells of yeast by the third streak. You'll see individual colonies growing in the final area streaked several days later. These colonies are slanted the same as if you were going from slant to slant in Part 2. All the procedures remain the same.
Maintaining Your Yeast Ranch
In no time at all you'll have several different yeasts on slants; I've got over 20! (Editor's note: Bill's refrigerator must not have any beer, or food, in it). Make sure you label each slant with type and date. You'll want to keep track of dates so you'll know when to re-slant a given yeast. Good luck and happy ranching!
edit rogue smiley.
