Category Archives: Yeast Propagation
Here’s a final follow up for my yeast slant experiment – the WLP001 yeast slant that I stepped up and pitched into my batch of Jade IPA worked great. The OG of the beer was 1.068 and it fermented down to 1.012 in about 5 days, which equals ~ 81% attenuation and matched my target FG for the beer. The IPA was mashed at 148 making it very fermentable which is why I had 81% attenuation. It was fermented at 64 degrees, and brought up to 70 at the end of fermentation.
The taste of the IPA is fantastic, and has the clean taste I’d expect from WLP001 Cali Ale yeast. I washed the yeast from this batch and plan to use it 1 more time in a Imperial IPA I’m brewing on Labor Day. My next slant step up test will be with WLP002, English Ale yeast. This will be used in an English ESB for a batch of beer that I am donating to the Carolina Brewmasters and will be served at the Charlotte Oktoberfest to the people enjoying all the great beers at the festival.
So I’m planning to brew a batch of Jade IPA this afternoon, and I’ve documented the process I used to step up a slant of California Ale yeast (WLP001) to make the colony large enough to pitch into a 5 gal batch of wort. I started the step up 4 days earlier, on a Monday night, and here’s what I did:
Monday night – I removed a slant of yeast from the refrigerator and allowed it to warm up to room temperature for an hour or so. I prepared a clean area by wiping down our flat top stove with some Starsan/water mix and set up my alcohol burner and sanitized my pipette. The purpose of the alcohol burner in this process is to create an updraft to help keep dust particles (contaminates) from falling down into the sterile wort. Before opening either the slant or wort jar, I dipped them both in a Starsan/water mix to sanitize the outside of the containers.
In the picture above I used the sanitized pipette to take out enough sterile wort from the mason jelly jar to fill the slant
vial with the yeast culture in it to about 1/2 full (next time I think I’ll fill it 2/3 from the top). After the wort is added to the vial I resealed the mason jar, since I’ll need the remaining wort for the next step. The yeast slant vial with the fresh wort is closed tightly and shaken for 30 seconds or so to mix the yeast culture into the fresh wort, and to oxygenate the wort a bit too. Then I loosened the lid of the vial just enough so that any pressure created by fermentation could escape and left it on the counter overnight. Slightly loosening the cap is important, since you do not want pressure building up in the vial or the yeast will not grow properly.
Tuesday Morning – when I got up on Tuesday morning the yeast were already active and starting to ferment the small amount of wort in the slant vial.
Since the yeast were actively fermenting, I cleaned and sanitized the top of my freezer to prepare for step 2 in building up the yeast. I added the fermenting wort in the vial to the rest of the sterile wort in the mason jelly jar along with a sanitized stir bar, tightened the lid on the jar and shook it for a minute to aerate the wort. I then loosened the lid just enough to allow any pressure created during fermentation to escape.
Finally, I put the jar on my stir plate in my fermentation fridge where I held the temp at 68. It would be OK to leave at room temp (mid 70’s), but since I plan to pitch the whole starter into my beer without cold crashing and decanting off the fermented wort, I am keeping it cooler to prevent off flavors. Here’s how it looks after I added the yeast to the jar:
Thursday Morning – It took a bit longer for the yeast in the jelly jar to show any signs of fermenting, but after 48 hours I had definite signs that the yeast colony had multiplied and that fermentation had begun. I think the next time I try this I may reduce the amount of wort in the 8 oz jelly jar so it’s only 1/2 full instead of 2/3 full. The jump up in size from the vial to the jelly jar may have been too big of a jump, and may cause unnecessary stress on the yeast (I’m just speculating here, but 48 hours seems a bit too long to see activity). The yeast starter is now milky in color due to the large population of yeast that has grown in the wort:
Thursday night – Ideally at this point I would have liked to let the yeast fully ferment out the wort for a day or so, and then crash cool it in the refrigerator; then I could decant off the beer and add only yeast to step 3 of the starter (EDIT – DECANTING IS NOT NECESSARY). But since I am planning to brew on Friday afternoon I need to make the final step of the starter now.
Step 3 is no different from a normal yeast starter that you would do if you bought a vial of yeast from the home brew store. I’ve decided to do a 1000 ml starter, so I added 100 grams of dry malt extract and a pinch of yeast nutrient to 1000 ml of filtered water and poured it into my 2000 ml Erlenmeyer flask. I also add a couple drops of Fermcap S to keep it from foaming all over the stove when it starts to boil, and covered the top of the flask with a piece of foil. After boiling the wort for 10 minutes I cooled it in an ice water bath to room temp. The final step is to pour the yeast and stir bar from the jelly jar into the cooled wort in the flask, shake it for a minute to oxygenate it, and put it on the stir plate in the fermentation fridge and keep the temp set at 68.
Friday morning – I’ve already got activity in the flask – the yeast are happily eating all the sugars in the final yeast starter.
I’ll be brewing this afternoon, and the final test will be to see how well the yeast perform in the 5 gal batch of beer, and how the final beer tastes. I’ll update this post in about 2 weeks with results!
Well, I did a test inoculation of a couple slants and a petri dish with some yeast from the bottom of a bottle of a commercial Rogue beer and realized pretty quickly that my first batch of agar/wort mix was not going to work. I had put way too much agar in the mix and it was so thick that I couldn’t even get my inoculation needle to scrape the surface. So, I cleaned out all the petri dishes and slant vials and remade a new batch of wort/agar following the process in the previous post, and this time I used 7 grams of agar for 500 ml of wort. The results were much better, I ended up with a much more usable substrate to grow some yeasties on. Here’s what the new batch looks like:
Since I recently picked up a new vial of White Labs WLP002 English ale yeast for a special bitter I’m brewing this weekend, I decided to try inoculating a few of the vials with the yeast.
I fired up my home made alcohol lamp to sterilize the inoculation loop, and rested the loop in a jar of Starsan and water. I ran the loop thru the flame a couple times, dipped it in the yeast and then quickly jabbed it into the wort/agar mix in one of the vials a few times and then capped the vial. I repeated this for all 5 vials, the whole process only took a couple minutes. About 3-4 days later this is what the vials look like:
The white stuff growing on the surface is yeast that has colonized the agar. The vial on the far right, however, has been infected by something and is growing mold. The mold is the bluish, fuzzy spot about a 1/3 of the way up from the bottom. Here’s a closer look:
This vial will not be kept since the mold will soon take over the surface of the agar.
After a few more days the non-infected vials should have yeast covering most of the agar surface, and at that point I’ll label the vials and store them in the refrigerator. I wrapped black tape around the cap too, to make the vial air tight. They should be good for 6 – 12 months, and if they start to get old I can always re-slant them in a fresh vial.
On the 16th I brewed a batch of American Wheat beer and before pitching some washed WLP001 California Ale yeast I streaked a petri dish with yeast using the same basic method shown above. After a couple days it had yeast colonizing on the dish, so I scraped some yeast from the dish and inoculated 3 vials with WLP001. My yeast library now has 2 strains!
In the future I’ll document the process of stepping up the yeast colony to a size that can be used in a batch of beer. I plan to use a pipette to add about 10 ml of sterile wort into the vial, letting the yeast multiply for a day, and then shake and add the wort/yeast mix into the 8oz mason jelly jar of sterile wort with a stir bar and let the yeast grow more while it mixes on a stir plate for a day. The final step will be to pitch the yeast mix into a 1000-1500 ml wort mix in a flask on a stir plate overnight before adding to a batch of beer on brew day.
Ain’t science fun?!?!
So, yesterday I decided to put on my mad scientist cap and put together the stuff I need to start culturing yeast slants. What this means is I will be able to store yeast samples in vials in the refrigerator for up to a year, so I won’t need to buy yeast anymore. It may turn out to be more hassle than it’s worth, but never the less I’m going to try anyways. For those of you who want to play along at home, this is the process I’m trying to copy:
To start I mixed about 40 grams of dry malt extract with about 500ml of water and a pinch of hops in a pan and warmed it on the stove. Then I added about 25 grams of agar agar powder (available at many Asian markets) and stirred it in. Turns out 25 grams is too much agar and it came out much thicker than planned, but it should work anyways (EDIT – THIS DID NOT WORK, IT’S WAY TOO MUCH AGAR). Then I added it to the petri dishes and vials and got them ready to sterilize. I also have 1 small mason jar of just plain wort (dry malt extract and water) without the agar that I’ll use later to re-grow the yeast for a batch of beer. Here’s what everything looks like:
Next step is to sterilize everything in the pressure canner, and I’m also throwing in 3 jars of tomatoes that we are canning so I can make full use of the canner. If you try this at home make sure to leave the lids of the vials open just a crack so they don’t explode. I have the vials in a pint mason jar with foil over the top. So in everything goes:
After 20 minutes at 250 degrees and 15 psi (let the pressure cooker cool for an hour before opening) I took everything out and laid out the vials on an angle so the wort/agar mix would thicken up and form a slant.
After everything cooled completely I closed all the lid vials tightly and wrapped them with black electrical tape, and also taped around the edge of the petri dishes to keep them from drying out. It’s important not to open them until you are ready to use them or they may no longer be sterile. I’m going to leave them at room temp for a few days to see if anything undesired starts to grow on them, indicating an infection. Here’s my collection of vials, dishes and sterile wort that is ready to use:
Next time I make beer I’ll take a small amount of yeast from that batch and inoculate several vials with the yeast. It will form colonies on the surface of the wort/agar mix and then I can store it for up to a year in the fridge. When I want to use it I can add the yeast to a small wort starter, and build up the colony until I have enough for a batch of beer. It shouldn’t take more than a couple days to do that (EDIT – takes about 4-6 days). The petri dishes can be used to capture wild yeast, which some people have done successfully and brewed a decent beer from wild yeast. It can also be used to create single cell yeast colonies and to test the viability of yeast from a bottle of commercial beer (like Rogue or Bell’s beer). I could propagate the yeast from a bottle of Bell’s and brew a batch with their specific strain of yeast.