Yeast Harvesting and reuse

Click on the repitching from slurry tab to determine how much slurry you need

http://www.mrmalty.com/calc/calc.html

 

I'm interested in this as well, because I'm starting to get into yeast washing and storage. How long do people normally store their reused yeast?

 

If you're already making starters, just make them 300ml larger. Once krausen drops, you can swirl, pour off 300ml of slurry into a jar for later, and pitch or cold crash and decant from there. Wort that is 1060 and above will stress out the yeast and can mutate the culture.

 

I harvest the yeast from the latest (non-dry hopped) batch. Fill to the brim in a mason jar, seal and then store it in the fridge. After a week, I then boil water for 20 minutes, pour the settled leftover beer and some yeast off and replace it with the cooled down water I just boiled. I then put back in the fridge until brew day and use the Mr. Malty calculator that @Brew_Betty mentioned above when I pitch the yeast for the next beer. I try to use the yeast within a month of the initial beer being done fermented.

 

Amen to that. I regularly re-use yeast and have found no reliable formula for estimating how much active yeast is in slurry (your basic question), so I developed my criteria through trail and error. My estimate is each ml of healthy slurry (i.e. new yeast that has been started) contains 2 billion cells. This is adjusted to reflect loss due to aging. I use yeastcalculator.com but Brewers Friend or Brewcipher will do the same thing.

Example: If I have 50ml of what was healthy yeast I estimate 100 billion cells and plug this into the calculator. Then reduce the amount by age, then compute the starter size to give me the desired result. Obviously a portion of the slurry will be dead cells, if you're only a month or so old this isn't too bad and can be ignored. I have gone 4+ months (not recommended) and had the yeast re-start. In this case the dead cells will outnumber the living even after re-start. My technique is to "wash" this first start. I.E. make a starter to wake it up, then decant the slurry. On top of this I'll pour a gallon of sterile water and let the "dregs" settle (about 10 minutes) . . . then pour off the liquid. In theory this liquid has the healthiest yeast (slowest to floc). I let this settle (day or two) and apply the 2B/ml rule to the slurry . . this number goes into the calc and it tells me how big a starter for the brew.

Is this accurate? Difficult to know without a hemocytometer, lab grade microscope, and a touch more experience than I have. But the results seem good for me. I'm sure others will say my estimate is off but it's what works for me. Is it cumbersome? Probably . . . but as you mentioned it's cheaper and I have little to no access to commercial yeast during the summer months (it's summer 9 months out of the year where I live). If you search hard you can find estimates anywhere from 1 to 5 billions cells per ml, but the above is my:



A tip: Lots of people post here about making excess yeast before a brew session and storing rather than washing the trub from the primary. Say you need 200B for a brew; make an oversized starter from new yeast and save something like 60 - 100B for the future. Then for your next brew re-start this excess, again making and storing more than you need. This way the yeast never have the stress of a primary fermentation. This should help with your high alcohol/heavy hopped problem.

 

I have kept washed yeast in the fridge for months. Before I use it, I just make a new starter of it, let it ferment out on a stirplate, then leave it in the fridge for a few days until the yeast has settled. Then, on brewing day, in the morning I take the jar from the fridge, pour off the clear wort from above the settled yeast, and let the yeast warm up to fermentation temperature while I brew (doesn't take long since the volume is low once the clear wort has been poured off).

In fact, just 4 days ago, I made a new starter from half of the yeast I had washed on December 20, 2015 (I usually split any washed yeast into two large jars - for lagers, if I brew 5 gallons, I use one of the jars - if I brew 10 gallons, I use both jars). I plan to use this yeast for a brew tomorrow, as the yeast has mostly settled.

If I keep the yeast in the fridge for extended periods of time, I try to make a new yeast starter of it every couple of months, just to keep it healthy (about two months is ideal, but out of laziness, I have left it for up to four months before making another starter as I just did). I then put it back in the fridge, and a couple of months later will make yet another starter. I have done this continually for some yeast for as long as 6-8 months before using it.

 

Thanks for sharing your experience! I've been brewing for a while now, but I'm just starting to get into this yeast washing/reuse thing! Everything I've read warns against storing yeast for anything past 2 weeks. Sounds crazy to me. I'm glad to hear your real life experience with using stored yeast.
I understand why wyeast or white labs warns against this, but as homebrewers we need to be crafty and find ways to save money!

 

I wash and reuse my yeast without making starters prior to reuse. There is usually 6 weeks between uses. I've never had any issues holding the yeast that long.

 

In a perfect world, wyeast and white labs are correct. There's always the chance that some wild yeasts can infect the washed yeast, and some of the yeast mutates. So you never have as pure a culture as what originally came in the package or vial. However, for practical purposes, the good yeast strains still out-number any other yeasts to such a large extent that I usually notice no difference in the final produce, unless I have re-used the same yeast more than perhaps 5 or 6 times. I've been washing and re-using my yeast for more than four years now, and have never yet experienced an off-taste as a result.

The only issue I've had is sometimes a type of mold might grow on top of the wort in one of the jars kept in the fridge, but I found that the problem was that I had not topped up the jars completely enough with boiled and cooled water. You definitely want to minimize any air space above the stored yeast in the Mason jars. Once I started doing that, the problem disappeared. I don't think that too many of the on-line discussions about re-using yeast discusses or emphasizes that enough.

Another key thing to keep in mind is to make sure that you add yeast nutrient every time you make a new starter. Even though the yeast is dormant, it still needs nutrients while it is stored in the fridge for lengthy periods of time.

When they mention not storing yeast for more than two weeks, I think they mean not to use it to brew more than two weeks after making the starter. If you leave it in the fridge for more than two weeks, even 2 or 3 months, always make another starter from it within a week or so before using it for your brew.

I have to emphasize that most of my brews are lagers (pilsners). Thus I need a significantly larger number of yeast cells than an ale (perhaps 3 or 4 times as much). As kellyst mentions above, you could keep the yeast in the fridge for longer periods of time if you are making ales. I wouldn't rely on that approach for making lagers/pilsners though.

 

I just read an article on Brulosophy saying the same thing. Make a starter then split the starter into multiple mason jars for future starters. Sounds so much easier than washing post primary fermentation. I will be doing this moving forward.



I've never really understood the Mr. Malty calculator though. For example if I plug in 5.5 gallon ale with a 1.040 OG, it says I would need over 10 liters of shaken starter using the default growth rate?! I think I am using it wrong, but making a 1.040 starter using a single smack pack has been working for me so haven't really looked deeper.

 

That might work for ales, but not for lagers. A 2 liter starter from fresh liquid yeast is barely large enough for a five gallon batch of lager. There would be nothing left over to split. Unfortunately they don't make 3 liter Erlenmeyer flasks, as far as I know, which would make splitting a viable option for lagers. For lagers, a 3-liter flask would be much more practical than a 2-liter flask. As it is, I often have to make a double starter, for a 10-gallon batch. I take half of the first starter after made, and make a new starter of that half. Then I combine the two. I suppose in that case, I could also make another starter of the other half, and save half of that for a starter for the next time I brew.

 

Yeah I was more saying get a single vial and make a starter, then split it 3 ways. Giving you essentially 2-3 vials worth for the price of one. Then using one of those jars to really make your real starter. I haven't done a lager yet, but I am sure one could work out building up yeast to enough volume ahead of time to be left with a vials worth for next time.

BTW I did a quick search and saw 3 and 5L Erlenmeyer flasks on amazon.

 

Mr. Malty is a little clunky, odd considering the creators wrote the book on Yeast. Recommend yeastcalculator.com or Vikeman's Brewcipher. They allow you to enter any starting quantity (OP's problem) and are tailored made for multiple steps. What is of value are the two articles at their site regarding pitch rates and starter techniques:
http://www.mrmalty.com/pitching.php
http://www.mrmalty.com/starter_faq.php

As related to the OP's question, if you're re-using slurry you really want to be able to input the amount and of course adjust it for time. It's not uncommon to have to use two steps . . . no biggee, just start a couple of days earlier. It sounds complicated but the calculator does all the heavy lifting.

Here's my 3L flask (Amazon):

But you can accomplish the same thing with multiple steps in a 2 liter flask. Remember, the amount you pour off doesn't have to be enough for a second brew . . . just enough to re-start the process. Sometimes I put away as little as 30ml of excess (estimated 60B) and it may be a month+ before using it again. Just build it up with multiple steps.

 

I usually pour off a pint of my starter and place in the fridge for a week. Then decant all but 1oz, swirl around to agitate all the yeast, and pour back into a White Labs vial. Slap some maskin tape on there with the date and ready to go next time.

 

Thanks, I just ordered it through Amazon.ca. The brew supply stores here don't carry the 3 liter size, although they carry the one liter and two and five liter sizes.

 

Just get the five liter flask, totally worth it.

 

It's a little awkward size for the stirplate. Actually I did purchase a five liter flask a year or two ago, but it was covered with numerous fine cracks - some fairly lengthy! Most were just surface cracks, it doesn't leak, but it just has a lot of potential locations for serious cracking. I got my money back, and they didn't want me to return it, but I never used it, not wanting to risk a losing a starter to the flask breaking.

I was wondering though, if there are any safe epoxies that I could put on the cracks to prevent them from going further? If I could do that, I might still be able to use it, as long as I don't heat it on a stove or accidentally bump it too hard.

 

This is going to sound hokey, but clear packing tape works well.