second half of the first pour (first part normal discarded)
first half of the second pour (part normally kept as clean yeast)
second half of second pour (second part normally discarded)
A couple weeks back I wrote a post about the results of "washing" four difference strains of yeast. None of them washed successfully. For completeness I decided to wash an entire slurry from a beer made with fruit to really allow the yeast washing to work. Although the washing didn't effectively separate live cells from dead cells perhaps it would be suitable for separating fruit partials from yeast cells.
In a nut shell yeast washing, or more accurately referred to as yeast rinsing goes as follows:
1) Add water to the slurry and mix. Wait 20 minutes.
2) Pour off the top part of the slurry that hasn't settled. allow this to settle for 20 minutes.
3) Pour off the top of the slurry into jars to save the "washed" yeast.
The result is much less yeast that you started with. In the picture above all three of the different stages were saved instead of being discarded so that they could be compared. The one in the middle is what would be saved. Notice how there is very little yeast in the jar. This has packed much denser than the one on the left, but the viability is about the same in all three jars.
First discarded yeast (pour 1-2)
Second discarded yeast (pour 2-2)
Retained yeast (pour 2-1)
In summary, yeast washing was successful at separating the fruit from the yeast, but at the cost of loosing an enormous about of good yeast. (95% of the total cells produced) If you just put the yeast into jars from the fermentor you will have 25 times more yeast that is about as viable as the water washed yeast.
Great info who knew washing/rinsing removed 95% of the total yeast cells produced. Curioius now about how you determined your previous washings "None of them washed successfully", so you were unable to save enough yeast from your previous yeast washings? Personally I have successfully revived 2+ year old washed yeast using a starter.ReplyDelete
Thanks! I guess my verbiage wasn't very clear. I have never had washing yeast successfully separate dead cells from live cells. All of the washed yeast has been viable enough to use, but not any more viable than it was before washing.Delete
Thanks, fyi, I store my water washed yeasts in 100% full capped Corona bottles in a very cold beer fridge. An easier storage media since I always wash/sanitize more bottles than needed when bottling. Curious is a 100% full capped Corona bottle better/safer/more airtight or worse than a partially filled canning jar shown in your washing examples for long term storage?ReplyDelete
Will be pouring the yeast directly from the fermentor to save 25 times(=95%) more yeast cells, a bit concerned about keeping 100% of the bottom trub goop for long term storage effectiveness compared to "cleaner" water washed yeast.
Some bacteria and molds need oxygen to survive, so filling the containers to the top may reduce the chance of infection. The way you are doing it sounds like a fine way to store yeast. My concern with filling a storage container to the top is trapping material on the seal of the container which could make the seal ineffective.Delete
I'm fine with keeping the entire cake, I did this for a long time anyway. The only thing I care about is knowing how many viable yest cells are in that cake, being that it has a large percentage of non-yeast. If I'm trying to calculate how many cells I have in the mason jar containing an entire cake, for instance, well, how many do I have? I generally use Mr. Malty and play around with the thickness of slurry and the non-yeast % but I guess I'm asking how to determine the non-yeat %?ReplyDelete
Good Question. The typical cell density that I see for a thick yeast slurry from a fermentation is about 1 billion cells per ml.Delete
Another way to estimate the cells is based on the amount of sugar that was consumed during fermentation. In a few weeks there will be a post on that. But in a nut shell 1/5th of the slurry is the correct pitch for a beer of equal gravity under most circumstances.
These methods will probably get you within a factor of 2. I have found that the Mr. Malty slurry estimator can be way off. (My experience was a factor of 20)
There isn't a good way to know for sure how many cells without a microscope. That would get you to about 10% accuracy.
Thanks, I was using 1/4 slurry per batch as my "guesstimate" for repitching into equal gravity, equal volume beer without a starter, within a few months of harvest. I then started trying to figure out how many cells I had and sometimes I'd make a 800ml or 1L starter for 24-48 hours just to get the yeast active. Have you used any nutrient and do you have any thoughts on that with regards to using harvested yeast?ReplyDelete
I haven't done that much work with yeast nutrients. When using malt extract I don't use yeast nutrient. If I'm propagating a wine yeast, such as EC-1118, I'll use table sugar and yeast nutrients. My understanding is that between the malt and the trub in the slurry the yeast have everything they need.Delete
I just racked a wheat beer to keg. I swirled the trub left in the fermentor and poured out 3 pints of the slurry. If I rebrew the exact same beer can I use 2 of those and just pour them back into the new wort? 2 pints would be about 1/4 of the slurry.ReplyDelete
Yes, two pints should be just about right. Depending on the ABV of the beer the slurry was pulled from 1 pint might be enough. See here for details: http://woodlandbrew.blogspot.com/2013/01/abv-effects-on-yeast.htmlDelete
Is there a general process being advocated here? This article says: "If you just put the yeast into jars from the fermentor you will have 25 times more yeast that is about as viable as the water washed yeast."ReplyDelete
The previous article mentions that “the bacteriological content was much higher in the top portion of the yeast containers than in the lower parts.” The conclusion says: “When washing yeast, discard the liquid when washing yeast to remove bacteria. Keep the thick slurry and add clean water on top of it for storage and to wash out additional bacteria.”
So I am wondering what you might see as the best process to retain enough yeast to support 3 or 4 additional batches while minimizing the amount of bacteria contamination.
You've outlined the important parts. The way I do it is as follows:Delete
1. After racking the beer off the cake into kegs or a bottling bucket swirl the fermentor to suspend the yeast.
2. Pour the slurry into sanitized mason jars. Cap loosely to allow CO2 to escape. Place in the refrigerator.
3. After the slurry has settled, pour off the beer and replace with water.
pH is a good indicator of health. Record the pH with the water added. When this rises about 1 pH point the yeast is mostly dead.
Steven - do you also prepare a starter with your stored yeasts or just pitch as-is?ReplyDelete
If I have enough yeast I'll typicaly pitch right from the slurry. 1 billion cells per ml is a resonable estimate most of the time, but I normaly do a cell count first just to make sure.Delete
Steven Im doing this for the first time. I ended up taking the entire cake and have it sitting in 1 qt and 1 cup mason jars. You pitch right from the slurry, and I understand the 1 billion per ml. Would using Mr. Malty's calculation for a repitch in a same sg wort be just 100 ml? To me it seems extremely low and would only be a few ounces of the slurry. One last question if I only use 100ml out of 1000ml could I add sterilized water to replace the lost volume? Sorry got off topic but just thought I would ask.Delete
That sounds fine.Delete
"pH is a good indicator of health. Record the pH with the water added. When this rises about 1 pH point the yeast is mostly dead."ReplyDelete
Your last sentence confuses me. It sounds like your goal is to raise the pH one point and kill most of the yeast. Isn't that exactly what you don't want to do?
That sentence could be worded better. As the yeast ages, and some cells die, the pH will increase. Once it has increase 1 point most of the yeast is dead.Delete
How long can I keep yeast safely in the fridge. That is if I don't want to monitor pH etc...ReplyDelete
A few months is normally safe. Some people have used yeast stored for over a year. Here is some more information: http://www.woodlandbrew.com/2012/12/refrigeration-effects-on-yeast-viability.htmlReplyDelete
Ok this is my first time giving this a go! I brew IPA and IIPA 10 gallon batches..... I have an IIPA that is 1.076 OG.... obviously lots of trub in the yeast cake. I boiled a gallon of water and poured onto the trub after the water cooled. I gave it a big swirl or six and then poured 4 qt of it into a flip top vessel. I put the vessel into the fridge where it has sat for roughly a month. I just transferred yesterday into smaller vessels. I used a turkey baster to suck up the best looking yeast off the top. Just curious how you feel about the viability. I have read a few things about people frowning upon the use of yeast thats been used in such a big hoppy beer. Fyi... it will be pitched back into the same beer. Thanks for your time and sorry if this has been asked before! Cheers!ReplyDelete
Viability doesn't drop much over a few months unless there is a significant amount of alcohol. See here:Delete