How To HARVEST and REPITCH Yeast

rather than pitch a fresh pouch of yeast into every batch of beer most professional breweries reuse yeast harvested from previous batches and that practice is commonly replicated at The Homebrew level but how best to do it and what are the limitations well brosy contributor Jordan folks has harvested yeast for reuse over 100 times and he's going to show us exactly how he does it plus we're going to take a look at the results of an experiment to see if blind tasters could tell the difference between a beer brewed with harvested yeast versus one brewed with a packet of fresh yeast let the yeast harvesting begin this episode is sponsored by great fermentations more on them in a bit hey I'm Jordan folks and I'm one of the contributors to philosophy Jordan I've reused yeast from other batches in a number of different ways I have overbuilt starters and just kept those in my fridge I've frozen yeast and then brought it back to life and I've even just taken a a keg where I fermented in the keg and when it got done I just kind of poured more beer on top of the keg but we want to talk about a process that you're doing with yeast harvesting right so uh I brew a lot of beer and it's really economical and really easy to reuse yeast you know it's a lot easier to just grab it from the refrigerator instead of going to The Homebrew store and uh I'm making great beer with it and you know the pros even say that the best beer is a few Generations down the line so maybe there's some sort of you know organc advantage to it as well the first question I always have is like how many times can I get away with any of this kind of thing if I go more than one or two generations I'm probably going to end up with like some kind of Franken yeast that I don't I don't know what to do with uh but I believe that in commercial Brewing they will actually go through quite a few different generations of yeast yeah you know I'm friends with a lot of local Brewers here in Portland and going up to 10 Generations is not uncom and then those breweries will then pawn it off to their friends at other breweries will go another 10 Generations beyond that at the home brew level uh I think that I tend to stop around five I've had a couple times when the yeast generation went bad and uh you don't know until a few weeks later until the beers you know keg and ready to drink so as long as you're mining your sanitization Ps and q's you're really probably going to be okay for a few Generations so tell me how do you do it so first off I F in kegs but that is not NE necessarily relevant really any fermentation vessel is fine so once you get your beer out of your fermentation vessel there's a big yeast cake left at the bottom and so you got to get it out of your fermentation vessel for me in a keg I swirl it around and I pour it out uh you know a fancy conle you could probably blast it out with some CO2 pressure out of the bottom dump Port but you just got to get it out of there so you get your yeast out of your fermentation vessel into a clean and sanitized jar how much of what you've taken now is just the yeast cake at the bottom I mean do you have little bits of the beer left over from whatever was in there beforehand that's a good point you're going to have to have a leave a little bit of the beer behind in order to actually get it out of there now you could use some pre-boiled water or something like that uh but I just use beer I figured that's the most santiz sanitized you know medium I could possibly use the beer just fermented with the very yeast I'm hoping to collect right and so I would think that the beer on top of it is good enough to be the the medium to actually get it out so you need to leave a little bit behind just so you have some viscosity to actually get it out of the vessel Okay so we've got the yeast slurry out of the vessel what on Earth do we do with it now you want to probably label it because if you're like me you got a lot of cultures in your little refrigerator there and so uh I like to put the generation the you know yeast brand and variety and name and stuff like that and the date in which I Jarred it and then you just seal the lid and you put it in there now you could use uh a flask or some other sort of vessel um but you know just some sort of small thing that holds it um I wouldn't put it in a measuring cup that you just leave out to the open air um and they say that there are some concerns around uh pressure I haven't found that to be the case so I'm comfortable just using a standard kind of mason jar and sealing it tight and then putting in the fridge until I'm ready to use it uh later when I use a packet of commercial yeast it says on the packet how many billion cells approximately I'm going to have in that packet so so Imperial yeast is going to say there's 200 billion cells in that packet if I'm picking up one of these yeast slurries how do I even approximate how many cells are in there right so there in lies the rub but it's actually really easy so I got this method from an old yed article which probably still exists in the depths of the internet and they provided some simple rules of thumb for estimating the cell count based on the slurry uh concentration and so what I did is I just kind of took the fundamentals of that math and rounded it um to even numbers to make it super easy so what you're going to do is uh you're going to put that your yeast in the refrigerator and let it settle because when you collect it it's going to all be homogenized and just be an entire you know yeasty mess after a day or two the yeast is going to fall out of suspension and collect at the bottom of your jar or your settling vessel and above it will be your beer or your water or whatever you use to uh mix the yeast into your collection vessel and so what's really helpful is a lot of mason jars actually have milliliter marks on the sides of them those are the ones I use if you don't have that you could measure it uh and then like use a marker or something to mark it but you want to know approximately how many milliliters of pure slurry is collected at the bottom of your jar the math here is really simple all you're going to do is you're going to take the milliliters of pure slurry at the bottom of the jar and you're going to multiply that by two that's how many billion cells you have a approximately at the starting point of the yeast highest level of viability so if we have 100 milliliters of pure Le yeast slurry at the bottom of the jar that is approximately 200 billion cells of fresh yeast so at that point when it's time to use that slurry in an upcoming beer then I suppose if you already know what the starting point was you can use a typical yeast calculator to figure out what the viability is at the time you're pitching it when you're ready for next Brew exactly because I'm typically not Brewing the same day I'm collecting the yeast and so maybe the next week when I'm ready to brew again uh it's settled out I can just take the the estimated cell count pop that into the calculator and then discount the viability and so if I started with let's say 200 billion cells and then a week later it says it's down to 180 then I can use that uh as a starting point so I'll frequently collect a ton of yeast because these fermentations produce maybe four times the amount that you started with so it might take even a couple jars if you want to collect the entire uh fermentation vessel's amount and so I typically don't have to even use the entire jar do you take this straight out of the fridge and then pitch it directly do you let it warm up to room temperature first do you give it any kind of preparation do a Vitality start or anything like that if the yeast was super old and it was like a gallon of slurry was 100 billion cells maybe I do a star the day before or a Vitality St starter but generally speaking no I'm just pitching straight As long as the numbers out so how many times would you say you've done this and has it always been successful I don't know how many I don't think I could count over a 100 easily and uh I've only been burned twice and it was the same yeast pitch unfortunately maybe fortunately because it's really only happened to me once but out of 100 plus times only had a problem with one of the cultures so that's Jordan's process and to me this sounds both fairly simple to P off and has delivered reliably good results but I have heard of situations where harvesting yeast would be let's say less than ideal let me ask you Jordan a couple of limitations and you tell me if you think this would be a problem or not and let's start with what if I am taking yeast from a dark beer and then using it in a let's say a light logage this is a common concern and in my experience it's not been a problem in fact I currently have a check pay logger on draft right now that was repitched from a check dark logger now the check dark logger yeast or if you did a stout or something like that the yeast slurry at the bottom is noticeably darker my guess is there's a lot of you know dark beer caught up in the the yeast itself um as opposed to a paler beer it tends to be more wider and wider and so the pale check logger that's on draft right now perfectly yellow perfectly clear in no way did it come out Amber because of this little bit of yeast pitch that went into the beer all right what about if I have dry hopped in my original beer right so this is when you might want to consider rinsing or washing your yeast uh as I recall rinsing is simply using like clean boiled water or something like that to separate the pure yeast slurry from any sort of non- yeast particular with that might be in solution uh washing is a more of a chemical process that H don't really do involving acids or something like that I at that point me personally I would just toss it because the whole assumption there is you a pure slurry to begin with now the last limitation I've heard is that you shouldn't use a yeast that was from a high Gravity beer in A Low Gravity beer because it's more likely to be stressed and kind of worn out and won't be able to do an awful lot my guideline as long as I'm you know below 1070 I'm comfortable repitching that but if I was to brew a super high Gra you know Bourbon Barrel AG destined Imperial Stout I think that's one andone the other concern that you've heard that we often hear is Kettle soured beers that the fermentation the acidic fermentation is too rough on the yeast and you wouldn't want to repitch that I actually tested that before I was a member of brulosophy and I made a kulch following a Brin bisa that turned out great so I think that there is some risk involved with any of these methods related to kind of harsher fermentation environments in the um prior generation but you know your mileage may vary you might get away with it now we did perform an experiment on the impact of harvesting yeast but before we get to that a quick word on today's sponsor great fermentations family owned and operated for more than 25 years great fermentations obviously huge range of brewing supplies and equipment great fermentations are well known for their top-notch customer service which I can personally attest to I brought my very first Brewing System from these guys and even though I was a complete novice they're helpful EXP got me up and running in no time great fermentations offer the ability to custom build your mold bills in fractional amounts so you're not forced to order a full pound incent when let's say you only need a half or a quarter pound or something and shipping is free on most orders over $59 check them out at great fermentations decom one of the things you mentioned Jordan was that you were a little bit uncomfortable with high gravity beers and then using those and rep pitching so we found the high gravity experiment I could find on bry.com to see how that worked out this one's from Marshall shot and Marshall brw a bar barley wine it had an OG of $10.99 so well be on your threshold you probably would not be reusing and harvesting this yeast right yeah I wouldn't feel comfortable with that you know it's just too much of a risk indeed but old the name of science so Marshall was brewing a blond ale so he collected for 400 m of the yeast sry I'm curious in the article does he mention the viability loss or the jarring date and when he's brewing so yes he did he does and it was the next day right and so at that point you pretty much have no viability loss so uh as long as the OG of the subsequent beer that was a good pitch rate it sounds like at least you have enough cells and Marshall also notes that he did allow time for compacting as well so as you mentioned before you start off with actually a high volume and then it compacts down and in this case it did compact down to what he was looking for which is 400 milliliters right so I mean at the very least as far as we can tell it sounds like he's pitching the right amount but I think the real question is are there any sort of off flavors or fermentation flaws that might occur indeed okay so Marshall goes through his brew a so he's brewing a big batch of blonde ale then creates basically two Vitality starters into a couple of one liter Growlers so in one he pitches the W and the slurry and in the other he pitches the W and a fresh packet of Flagship yeast so he was going through the Vitality process which you said you don't typically bother with if you are pitching the right amount of yeast in this case yeah and you know I used to do it as a rule of thumb if it was too old but I just started trying it without that step and it I was still making great beers with no fermentation problems that I could notice uh but you know given how High an OG this was I think this is a reasonable piece of insurance 4 hours later those Vitality starters were pitched into two separate fermenters 8 hours post pitch he took a peak into the fermenters and there's clearly more activity going on with the yeast slurry than there was with the fresh yeast yeah and this doesn't really surprise me that much even though I guess it could have gone either way I would think that either that would be the case because uh the fresh yeast might have some sort of lag phase associated with being stored in package meanwhile the repitch had just been fermenting a beer you know a couple days prior uh or maybe I would expect nothing would happen because the yeast would just be dead from such a high OG fermentation so uh at the very least it seems like the yeast is alive it does and that is borne out in the final gravity readings which is to say that they both had the same final gravity of 1.0 07 right and so clearly at the very least it successfully fermented the beer but what I want to know does it actually taste the same for better or worse so a total of 21 people took this experiment each participant was served one sample of the beer fermented with fresh yeast and two samples of the beer fermented with the slurry then asked to identify the unique sample at this sample size 12 tasers would have to identify the unique sample in order to reach statistical significance which is exactly how many were able ble to do so indicating participants could reliably distinguish a blond ale fermented with a fresh pitch versus one made with a slurry from Bary y does Heiss anything about Tas or preference was it split was one better than the other the 12 participants who made the accurate selection were then asked to specify her preference a total of seven tasers reported preferring the beer fermented with the fresh yeast four said they like the beer fermented with the high OG slurry and one tast of reported perceiving no difference right so almost a 2:1 ratio what did Marshall say what was his perspective of the eight semiblind triangle tests that Marshall took he accurately identify the unique sample six times and he was able to detect it primarily by aroma so he says where is the beer fermented with a fresh yeast smelled like a pretty standard Pub style blonde ale the one pitched with the slurry had a sort of rubbery thing going on it wasn't overwhelming but it was something that was very noticeable so I think at this point we have a piece of evidence that suest that there could be some concerns with fermenting a new beer that previously that used yeast that previously fermented a high OG one we're getting an off Aroma and this really doesn't surprise me this is consistent with what we hear in the literature or at least with the old wibes tales that you know this stuff it it's just had such a long and arduous Journey it's maybe time to you know hang up and give that one you know a rest Vindicated Jordan you're absolutely Vindicated with your uh your cut off period there for the high gravity beard is but even then I'm going up to 1065 or so and repitching and uh you'll hear people say don't repitch about 1050 so uh I think there's some wiggle room there but at a certain point there might be a point of no return now just last question for you Jordan if I was to to take a peek in your fridge how many jars of slurry would I find in there well I also have a lot of sour cultures in there as well so I probably got 10 or so at any given time but uh these days have kind of just been really enjoying fermenting everything with ler yeast so I'll ferment my ALS and my loggers with clean strain like Global or pilgrimage and uh it's really reduced the number of jars I have in any given time in my fridge well thank you Jordan outside of those High OG beers I do think this is something I'd like to try a bit more often now is yeast harvesting part of your own Brewing process and do you do anything different to Jordan's process if so please let me know in the comments I'd love to hear about it now and I'll alternative to storing harvested yeast in the fridge is to freeze it and there it can remain viable for years so to learn how to do that watch this video here

Channel: The Brülosophy Show

Views: 19,010

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Id: dz9fd-p6ntM

Length: 17min 41sec (1061 seconds)

Published: Thu May 23 2024