Author: Marshall Schott
In the last iteration of this xBmt, we found that a beer fermented with relatively old slurry harvested directly from a previous fermentation and propagated in a starter was largely indistinguishable from the same beer fermented with a fresh pack of the same yeast strain. Afterwards, I received a ton of feedback from readers asking if I’d ever considered doing a similar comparison without making a starter, but rather pitching the un-rinsed old yeast slurry directly into a 5 gallon batch of wort. Indeed, it was on the list. I reached out to a few of these folks asking if they’d ever attempted such a practice, a couple reported they had with success, but the large majority said they were hesitant to try out of fear of fucking up an entire batch of beer.
A fear I’ve come to embrace with only scant hesitance.
If you’re wondering why a brewer might be interested in this method, it’s likely because they’re looking to simplify their brewing process– if good beer can be made with un-rinsed yeast slurry without going through the trouble of making a starter, and that yeast was stolen from the bottom of a previous batch, then why not? Plus, reusing yeast is cheaper than purchasing a fresh pitch for every batch. Some of the arguments against this method, which I can’t find any valid practical evidence to substantiate, have to do with carryover of character from the previous fermentation, off-flavors caused by autolyzed cells, over- or under-pitching, and increased potential for contamination. That last one seems obvious, it makes sense to me that risk of contamination is positively correlated with increased handling. Those other arguments I’m not convinced hold much water, if any. At least yet. But I’m certainly open to changing my mind.
| PURPOSE |
To evaluate the differences between a split batch of the same wort where half was fermented with a 3rd generation of old un-rinsed yeast harvested from a prior batch and the other half pitched with fresh yeast.
| METHODS |
I’d recently registered 2 beers for the 2015 BrewUnited Challenge, a Dunkel and a Kölsch, a couple styles I make relatively often and typically do so without much thought. However, given the rather strict guidelines for this particular competition, I was forced to do something I’d never done before– toast my own malt. A couple weeks before brewing, after settling on the recipe, I spread 2.5 lbs of German Pils malt on a cookie sheet while preheating my oven to 350°F. I found an interesting blog article all about home toasting malt that suggested leaving the malt at this temp for 30 minutes, turning it a few times throughout, in order to achieve approximately 250 °L.
I was thrilled with my home toasting job… my wife, not so much. This process created quite the aroma, not necessarily bad if you’re into the scent of burnt popcorn lingering for days. Yeah, this first attempt was also my last, at least using the kitchen oven. I placed the toasted grain in a paper bag, crimped the top, and let it rest until my planned brew day a couple weeks later, at which point the smell in my house had fully dissipated.
If you think the recipe looks weird, it’s the fault of the folks who came up with the competition rules. I was actually pretty stoked to see how this would turn out.
BrewUnited Challenge Dunkles
| Batch Size | Boil Time | IBU | SRM | OG | FG | ABV |
| 11 gal | 60 min | 38 | 4.5 | 1.048 SG | 1.010 SG | 4.9% |
Fermentables
| Name | Amount | % |
| German Pils Malt | 13 lbs | 72 |
| Home Toasted Pils Malt | 2 lbs 6 oz | 13 |
| Gambrinus Munich 10 | 2 lbs | 11 |
| Flaked Wheat Malt | 8 oz | 3 |
| Crystal/Caramel 60 | 4 oz | 1 |
Hops
| Name | Amt/IBU | Time | Use | Form | Alpha % |
| Northern Brewer | ~19 IBU | FWH | Boil | Pellet | 10 |
| Czech Saaz | 40 g/2 IBU | 10 min | Boil | Pellet | 3 |
Yeast
| Name | Lab | Attenuation | Ferm Temp |
| Saflager 34/70 | Fermentis | 85% | 66°F |
The night prior to brewing, I measured out my grains and ran them through my new Monster Mill MM3… holy moley, this thing is a monster! I intend to give it a full review soon, until then, I’m perfectly comfortable recommending it to anyone interested in a high quality mill that provides a consistent crush very quickly (10 lbs in ~1 minute).
With the grain milled, I collected my entire volume of brewing liquor, which I began to heat upon waking early the following morning. I proceeded with my routine single infusion mash process and hit my target saccharification temperature of 150°F on the nose.
I allowed the mash to sit for an hour, briefly stirring every 15-20 minutes, which I’ve found has improved the consistency of my efficiency.
I generally pull a small sample of wort from the mash about 5 minutes in to measure the pH. For this batch, I was also super curious how well my home toasted malt would impact the color. It looked pretty spot on to me.
I quickly chilled the sample and took a pH measurement to discover I was just a few points shy of my 5.3 target. Not too shabby for guesstimating the impact of the toasted Pils malt.
My mash timer beeped and I collected the wort, nearly 13 gallons worth in my 14.5 gallon kettle, which was easily managed with the help of FermCap-S.
I added a relatively small amount of hops during the 60 minute boil then chilled the wort in under 12 minutes to 6°F above my groundwater temperature, which during this time of year is an annoyingly warm 76°F.
Separate 6 gallon PET carboys were filled with equal amounts of warm wort, which was gently stirred throughout racking to ensure similar amounts of kettle trub in each. The full fermentors were placed in a cool chamber and left to finish chilling to my target fermentation temperature of 50°F, this took about 6 hours. I then prepared the yeasts to be pitched, rehydrating the fresh sachet for 20 minutes and decanting the jar of sloppy old slurry that’d been warming up in my garage for the last hour or so.
Each yeast was pitched into its respective carboy.
I’ve grown used to the longer lag times that occur when using dry yeast compared to liquid and noticed initial signs of activity an expected 3 days post-pitch. But only in one fermentor.
The sloppy old slurry batch appeared to be doing nothing. At all. I began to wonder if perhaps the harvested yeast had somehow puttered out when I checked the next day.
A full 5 days in and the fresh yeast batch was kicking ass while the beer pitched with sloppy old slurry had absolutely no indications of fermentation activity.
A hydrometer measurement confirmed my concern– the SG of the sloppy old slurry batch hadn’t dropped at all. Would this end up being a failed xBmt?
It was at this point I had to make a decision, as I was heading to Seattle for 11 days to help my father in law recover from a stroke. Usually, this is the point I’d start ramping the temperature up, but the problem was the sloppy old slurry clearly hadn’t progressed into active fermentation. Ultimately, in order to give this xBmt a fighting chance, I chose to disengage the quick lager profile in my Black Box temp controller and allow both beers to remain at 50°F the duration of my trip. Upon returning, I was anxiously optimistic and took hydrometer measurements.
Back in business! Finally, I raised the temp of my chamber to 70°F for a seemingly unnecessary diacetyl rest, crashed to 30°F the following evening, then fined with gelatin a day later. When it came time to package the beers, I removed the carboys from my cold chamber and immediately noticed a difference in trub levels.
The trub cake in the sloppy old slurry batch was obviously thicker and contained much more debris. I was curious how this might impact things later on. I proceeded to rack the beers to kegs.
After 24 hours on 40 psi of CO2, the beers were perfectly carbonated. Data collection occurred the following weekend.
| RESULTS |
The participant pool for this xBmt consisted of 20 people including 7 BJCP judges, a couple professional brewers, experienced homebrewers, and dedicated craft beer junkies, all completely unaware of the variable being tested. Achieving statistical significance with this sample size would require 11 participants (p<0.05) to correctly identify the different beer in the triangle taste. Each blind taster was provided 3 samples of beer, 2 from the sloppy old slurry batch and 1 from the fresh yeast batch, then instructed to select the one that was different. Those who made a correct selection in the triangle test were asked to complete a brief comparative evaluation of the 2 different beers. In the end, only 5 participants (p=0.785) were capable of accurately distinguishing the beer fermented with fresh yeast from the one fermented with sloppy old slurry, a number consistent more with chance than perceptive ability.
A review of the comparative evaluation data from those who were correct in the triangle test yielded little if any meaningful information with no consistency between comments. Some thought the fresh yeast beer was more malty, others swore the sloppy old slurry beer had more malt character. Preferences of the 5 correct participants were also split between the batches.
My Impressions: I was able to distinguish these beers the very first time I poured them, didn’t even have to taste or smell them. Because they looked different. I was actually rather surprised how much clearer the sloppy old slurry beer was than the fresh yeast beer the first couple days after kegging, something I hypothesize may be a function of the small amount of gelatin carried over from the slurry’s prior fermentation. After about 4 days in the keg, the beers shared similar levels of clarity and when served quasi-blind in opaque cups, my prowess evaporated, I was wholly unable to reliably distinguish the different beer in multiple trials. If I had to choose a favorite, I’d go with whichever one was in the glass in front of me.
| DISCUSSION |
This xBmt left me sort of puzzled, maybe amused is the more appropriate adjective, not necessarily because slurry produced a beer that wasn’t much different than the same beer fermented with fresh yeast, I actually sort of expected this result. Rather, the fact the lag observed in the sloppy slurry starter beer didn’t seem to have any noticeable impact on the flavor is, well, amusing. I’m only slightly ashamed to admit that the time between pitching and first signs of a krausen is sort of anxiety provoking for me, I’m always concerned some other organism is going to infiltrate and ruin my beer or that the yeast is going to produce off-flavors from being over-stressed. But this didn’t happen, which suggests my sanitation practices are at least decent enough… and I’m likely the one who is over-stressed.
Despite the fact these results corroborate the experiences of some highly trusted homebrewers I’ve talked with, I’m not quite ready to start ditching the practice of preparing sloppy old yeast in a starter prior to pitching, if only because it added 3 days to my turnaround time and I’m impatient. What these results have done is bolstered my confidence that reusing un-rinsed slurry doesn’t guarantee bad beer. I absolutely plan to utilize the vitality starter method when pitching slurry in the future, it seems to be an ideal application for this. Either way, I won’t be advocating for this method, though for those who pride themselves on keeping their gear optimally clean and sanitized, it’s fully possible pitching slurry direct without the aid of a starter, even after being stored for a few months, will produce a fine batch of beer.
Are you a proponent of pitching sloppy old slurry directly? If so, or if you’ve other thoughts/experiences regarding this method, please feel free to share in the comments section below.
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65 thoughts on “exBEERiment | Impact Using Old Yeast Slurry Has On A Munich Dunkel”
Sorry if it’s in there and I just missed it, but how old was the unrinsed yeast slurry?
Whenever I use a portion of the yeast cake, I always make sure to use it within 2 weeks of harvesting. Ideally I try to time it so I transfer the beer off the yeast cake the day of brewing a new batch then then pitch some of the fresh yeast cake in a new batch that day. Obviously that takes a level of planning, but in general the lag times have been 12-24 hours when I do this.
The slurry was harvested in early March and pitched in early August, so about 5 months old.
So just fill a ( sterilized ) mason jar with yeast cake and liquid from the bottom of the nearly empty fermenter and put it in a fridge for weeks or 5 months – until you are ready to ferment again? Wow. So my next packet of S-04 could be my last I ever purchase? Neat.
On brew days I’ve been collecting a couple extra gallons off the grain for a second small batch to screw around with – the perfect use for the prior batch’s jar of slurry. All have started fermentation within a few days with nothing glaringly wrong. The old slurry jar sits in my fridge door (so it gets shaken up a bit) – sometimes for months, I haven’t found a dead one yet but the occasional weirdly long lag time is too emotionally taxing to do in a full 5 gallon carboy.
> but the occasional weirdly long lag time is too emotionally taxing to do in a full 5 gallon carboy.
Oh my goodness, yes it is.
Awesome experiment!
You guys are so funny. Relax and embrace the results of your experiment. You made an excellent beer using a very old slurry, without a starter. Yay! You save a significant amount of time doing it this way. You make it sound like waiting 3 extra days for your beer to start fermenting is like a crap shoot, like the chances are 70% of infection. What logical, practical, or evidence-based reason are your fears based on? Have you had bad experiences in the past with this method? I’m selfishly curious and biased because this is the only way I do it and I haven’t had any infections.
I’m only slightly jabbing you. I know you have independent reasons for making starters the way you do. Also, a quicker turnaround time for your beer is very important, I agree. I just think it’s amusing when an experiment goes against a practice you like (making starters), you tend to downplay the results a little bit. In general you are extremely modest about all your experiments.
Cheers!
Well (not Author on the is one), a few things stick out. #1 – Overall longer process. Just adds time to the Grain-to-glass pipeline with no benefit. #2 – Yeasts action of lowering pH and producing alcohol are evolutionary tools yeasts use to keep food to themselves: They prevent many competitive organisms from gaining a foothold through their fermentation. The longer it takes for that to happen, the more risk there is. Putting a % on it isn’t really possible, since that will vary in each brewery. We’re not doing perfectly sterile closed transfers: There ARE opportunities for other bugs to get in almost all homebrew. Whether they happen to be able to live in beer is an entirely different question. #3 – there’s also the question of “Will it ever ferment”. Seeing quick fermentation says “Yeast isn’t dead”. That’s reassuring.
Hi Ray: “Just adds time to the Grain-to-glass pipeline with no benefit.”
Making starters takes time and planning, yes? No doing it, therefore, saves time and planning. That’s the benefit. Other than that I agree…lag time is an opportunity for infection.
I’m a fan of pitching slurry, but I’ve never let it sit that long AND not made a starter with it. I brew every two weeks, so on my brew week, I’m typically kegging a beer on Wednesday night and brewing another a couple days later on Friday night. After kegging, I fill a couple of pint mason jars with the old cake and stash them in the fridge, and if I plan to use the same yeast on Friday, I will fill a glass growler about a third of the way with some slurry. I keep that growler in the fridge until Friday morning, then pull it out and let it warm up before pitching on Friday night.
I find that the beers I pitch that two day old slurry in take off as quick or quicker than when I’ve made a starter. If I use slurry that is any older than that two days, I make a starter.
Interesting experiment for sure. I will probably still continue to make starters for my stored slurry, as I too am concerned with lag times. I start to get a little anxious if I don’t see active fermentation within 6-10 hours.
Why do you get anxious? That is the question. Based on what? This experiment suggests the opposite – you don’t have to get anxious (I know, this is just one experiment). Cheers!
I think, for me, it is lack of patience. To keep my pipeline going with my every 2 weeks brew schedule, I want to be going grain to glass in 12-13 days. If I have a 2 or 3 day lag before ferm starts, I will be pushing that schedule out farther than I want. I typically use a big starter of 001 or more recently 090 to make sure I can hit FG in about 3 days, then ramp for 4-5 days, then crash.
In short, I want to drink my beer faster, dammit.
I have found these same results. Most raw slurries have taken off like gangbusters by the next morning. But I have not tried one that old. I pretend it had a best if used by date like all liquid yeasts do. Even if I had a White labs bottle that was past it’s prime I would make a starter. This was good info as usual though!
If I’m going to use a slurry I use it within a month of harvesting it. Any longer than that and you need to make a starter. Especially 5 months after harvesting your viability has dropped too much to pitch as is.
I assumed the same but wanted to test it out. Despite this presumed drop in viability, the beer ended up being largely indistinguishable from the fresh yeast batch. Surprised me, for sure.
How much slurry did you pitch? The whole pint? Was it homogenous?
It was about
2 pints1 pint of dense slurry I previously collected in a 1 quart jar.So, you swirled up the dregs in a carboy and poured off a quart. Then, you put that quart into the fridge until brew day. On brew day, you swirled up a pint and dumped it in? I’ve heard for lagers over-pitching is really not as much of an issue, as you want a boatload of yeast for clean flavors in a lager. Ales *may* benefit from more growth. Who knows.
Do you just sanitize your quart jars with star san or sterilize them by pressure cooking them? Do you just rely on the seal that the metal jar lid makes on top of the mason jar to keep out infection when it’s in the fridge?
Well, the 1 quart of harvested loose slurry compacted to about a pint. I decanted that jar, swirled the remaining contents, and pitched.
Sanitize with StarSan and rely on seals.
I rarely worry about over pitching, even with ales.
have you ever tasted an “over-pitched” ale? i wonder what it would taste like to do a commercial or under-commercial pitch vs a super huge pitch in an ale.
I’ve had beers that were theoretically overpitched, but I couldn’t tell a difference. We absolutely have more pitch rate xBmts planned!
I’ll often reuse slurry with a quick (vitality) starter. Ground water where I live runs about 80-85°F this time of year so I’m lucky to get below 90°F out of my counterflow. I run off ~2L of wort into a flask with the slurry and set it on a stir plate. 6-12 hours later the wort is at pitching temp and the yeast is climbing out of the flask at which point I’ll pitch the entire active starter.
In fact, I just did a lager like this yesterday and the beer was fermenting within 6 hours post pitch.
Nice!
That’s a great idea!
That’s near exactly the procedure I used Saturday.
I have pitched old slurry without a starter a few times with success every time. I generally try to use the slurry within a week or two. For the hefeweizen I have on tap right now, I pitched a one pint mason jar of more than a month old slurry (Wyeast 3068) into the fresh wort. Since it’s a hefeweizen, I wanted to stress the yeast so I wasn’t worried that the yeast was more than a month old. Also, I pitched the yeast while it was cold (straight from the refrigerator) into ±64°F wort. This batch came out better than the last batch I did with the fresh pack of 3068. The beer started fermenting within four hours and has a nice balance of banana and clove.
Probably not recommended, but I figured I share.
wow, cool. Never thought of doing that.
Another cold-pitcher! Yeah!
I have had great results reusing the yeast slurry with a quicker and much more vigorous fermenation but I usually reuse within the month, more likely within the same weekend.
I believe the extended lag time was caused by the age of your slurry. I have often just drained the BK right onto the cake after kegging a beer, and have sometimes had active krausen over with within 48 hours and needed to use a blow-off tube to contain it. You lost a lot of viability in those five months I think. This would probably be a good experiment to repeat with a fresh slurry. I believe you’ll be impressed with the fermentation the next time around! Cheers!
I fully agree about the lag.
My own experience mirrors this. I frequently (maybe as much as half the time) pitch new wort right onto an old cake, and in fact I’ve done this multiple times in the same carboy. You just have to plan for it (i.e., not pitch a blonde ale onto a stout cake). I usually get fermentation starting within two hours and finished in 48. The main drawback is trub buildup, but since I brew 10L batches, if I know I’m going to do this, I ferment in a 23L carboy. That said, I never do more than three batches on one cake. That’s just asking for trouble. 🙂
As an aside, the guy who initially taught me this technique likes to joke that when he brews a blond ale with fresh yeast, he’s actually making a 5-gallon starter for his IPA. 🙂
I am delighted discover you used precisely the video clip I’d hope you would use for Olan. 🙂
I even time-stopped it (or whatever you call that).
Hey dude. These results are exactly what I have experienced with unwashed “sloppy slurry”. I usually only brew ales though.
I prefer to use your vitality starter method (although I aerate via swirling) and have had great results with it. In fact I have seen a sloppy slurry batch take off in 6 hours using this method (it blew the blowoff right out of the carboy too). My last batch I didn’t bother with the starter and pitched about a cup and a half of 1 month old slurry (2nd gen US-05) and it took at least 2 days to start. I did get off flavours in my non-starter batch, but I do not suspect the yeast in that case. I suspect a bad recipe.
I know other people have said it, but 5 months is a long time… The slurry-carboy was severely under pitched due to low viability – and yet it made no difference. Brilliant. I’ve always felt advice on pitching rates is at best suspect and at worst unscientific nonsense and this supports my suspicions.
I once made a starter by pitching slurry that was 18 months old. Very long lag and it smelt foul when it got going – perhaps infected. I let it ride out to acidify and poison the bugs with alcohol. Then I decanted the liquid, acid-washed the slurry in starsan at standard dilution, and started over. Made a beautiful clean pilsner with no off flavours.
I lost 25 gallons of beer doing this over the summer. Needless to say I’m freaked out and confused where I went wrong. All slurry now freaks me out! I wanna get back on the horse. How many repitches do peeps do of the same slurry from beer to beer? And any tips on the best way to avoid over pitching and under?
It is a risky method, to be sure, not sure I have any tips to offer other than mind your sanitation.
Perhaps the “sloppy old slurry” beer was initially clearer because your process of harvesting has somehow selected more flocculant yeast…or maybe that’s just how 34/70 behaves after several generations. Like you said, gelatin could also have something to do with it.
I usually pitch two sometimes three times on un-rinsed yeast slurry. I will rack the same day that I am pitching on the yeast. I take my finished batch and rack to a keg and add clarifier to keg. I then take my new wort and put into the carboy. This eliminates transferring of the yeast and ensures the yeast is still healthy. If for any reason I believe the first batch is contaminated, I just by new yeast and use a clean carboy. Using this method I don’t have any more lag time that pitching a new batch of yeast from a starter. Thanks for the great experiments.
How do you not overpitch this way?
I have done this way for years. I have never had any issues with over pitching. I usually do put some though in the order I brew. Lowers gravity and preferable light color first moving to higher gravity. I believe the greater benefit is reducing contamination. Cleaning yeast and transferring to me is a bigger risk of off flavor than over pitching yeast. Has there ever been an experiment that over pitching clean yeast causes a detectable off flavor?
In a lot of your experiments the more experimental beer has a longer lag time but turns out finein the end. This could be a case of something that would be a problem IF you weren`t doing everything else right. For example you`re obviously very good with sanitation but being a bit sloppy with sanitation is going to be a bigger problem with a beer with a long lag time than one that explodes out of the gate.
Thanks for doing this one. Very interesting.
My 2c:::
I think its important to control the pitch rate in this experimental design. Otherwise we may be testing the pitch rate over the yeast type (dry vs 3rd gen) and vitality.
Maybe a calculation based on average cell density , volume and cell viability to match maybe two packets of dry yeast.
Possibly (just by eye balling), The sloppy slurry might have been a four fold overpitch, even after the 5 month viability drop.
If we are to make any conclusions from this. I think we have to control the experimental variable.
I suspect , without a better idea of a comparable pitch rate here.
We may have just tested two samples of very dissimilar viable cell counts. Which may have contributed to the results.
Yea, but that would basically only be true, ie. a problem, should someone decide to use a very small portion of sloppy slurry. If a standard sized slurry is used, the result indicates that it works just as well as alternative methods – albeit the lag time.
True. Although maybe the 3rd gen yeast would have had a more favourable outcome at the correct pitch rate, Over the rehydrated yeast. Or maybe not. I don’t think we can conclude from this experiment. Due to the pitch rate inconsistency.
Personally. I estimate my unrinsed slurries cell counts and revitalise for four hours before repitch. Works wonderfully, as others have commented. Although I have no real empirical comparison. But what brulosophy is trying doing here attempts a real experimental comparison. Great stuff! Keep it up!
I am curious if the date on the slurry was the harvest date or when the yeast was pitched to the donor beer? I assume harvest date. I just made a starter from some WLP550. My traditional method is to make an over sized starter and harvest. Typically I have roughly the same volume of settled yeast in my repackaged vials as came in them to begin with. Well, I brewed a Belgian single back in mid March and made the starter last week. Brewed a Tripel and pitched the starter in. That starter was CRANKING within 3 hours of pitching. I mean absolutely destroyed it. I had it filled to 1600ml in a 2l flask and I below Krausen all over my stir plate. First time that has happened (I made the same sized starter for the Single back in mid March, though my basement was 67F then and not the 74F it is now).
48hrs, then cold crash for 18 and pitched the next day in my Tripel (a little batch, only 3 gallons, but in a 5 gallon carboy to be safe). What a friggen monster! I have about 4 inches of Krausen. More than any other yeast or beer I’ve ever fermented. It is 1.090 and fermenting at 74F ambient (thermometer says it is cranking at 74F, mind you it is on the concrete slab which keeps things about 2F below ambient once fermentation has subsided, and that is 3 days post pitching. I’ve been on a business trip the last 2 days before there was more than a finger or so of krausen). It is settling down with only an inch or so of krausen now after 3 days, but fermentation activity was noticeable within 2hrs and airlock bubbling after 3. Also the fastest activity of any starter I have used.
One very positive change between my March Belgian Single and this Belgian Tripel, is that the Single fermenting at 67F, with the slab at 65F produced a staggering amount of HS2 from WLP550. Like the devils pisspot. Took about a month for it to settle down enough for me to be confident in bottling. This time I notice no hydrogen sulfide being produced. The yeast sure seems to like it on the warm side of things. My experiment for this fall is going to be brewing a Dubble using the White Lab WLP550 Belgian yeast compared with White Lab Abbey yeast (I forget the number), Just to see how both do with my favorite Belgian beer. I’ll do the same things spring with a Belgian Wit, just to see.
Awesome test BTW. Keep up the experiments!
The date on the slurry jar is the date I collected it from the “donor beer” (great term!).
What I’m getting as the message across all of the yeast prepping and pitching exBeeriments I’ve read is that if you do enough things right, you can get away with one or two “wrong” practices and get good beer, and often get the same beer.
This makes sense to me. Yeast will do what they want to, and as long as they have enough nutrients and oxygen, the temperature is close enough, and there’s just about enough of them to start with to overcome competition from other bugs, then they will make beer in the way you want them to. It’s only when they are too stressed in one direction or another, or several at once, that bad beer happens.
Here I assume that there wasn’t much yeast in the slurry, but the sanitation was good, there were plenty of nutrients and O2 to allow for a long growth phase at the right temperature without off-flavor development, and the yeast variety is stable enough to tolerate a long growth phase without mutating to something that gave a different yeast character to the beer.
It may well be that a different, less stable yeast, or one with a much stronger yeast character, would give noticeable differences. Trying the same experiment with one of the more fussy saison yeasts, or even something like 3711 which will reliably attenuate, could be interesting.
Now does the old adage “pitch with slurry from a low abv / lightly hopped” have any effect on this method? Or can that be tossed out the window too?
It’s on the list 🙂
Jamil Z. always used to talk about repitching from low alcohol, low hop beers when he was “just” a homebrewer. Now that he is professional, I heard him say he has kind of thrown that out the window. It’s just not practical or cost effective to strictly follow that rule on a professional level. I’m sure if he is doing it, then there is no or little negative effect as long as the yeast is healthy. maybe part of the key is how good your fermentation was. if you have a great fermentation (good attenuation and flavors) then try a repitch. it should be fine. i’d like to see the exBeeriment on that too! repitching barleywine vs mild yeast into the same beer and see which is better!
Hi Marshall,
Like so many others here, I too have enjoyed all your work and love the dispelling of our brewing “facts”! Keep ‘me coming!???? I just came across this one, so hope you see this response as I have a bit of a different experience.
I use slurry most of the time, past 6mos almost exclusively, unless I need a strain I don’t have. I ferment in a conical and have been straining the wort into my fermenter, and now with the Grainfather I have even cleaner slurry. I capture about 300ml of slurry (moving to metric!), and is quite clean/white- not as white as new or an overbuild but can be close, except when from a dark beer!
I have used ones two months old, no starter (I only make a starter if I feel I need more yeast than I captured, never to proof it) and find they take off quicker! I was quite surprised to read your experience. I have no idea why, maybe a new exbeeriment- conical slurry v yeast cake slurry, clean slurry v dirty slurry or so.
I do think the clean slurry has quite a bit more yeast per ml than dirty and maybe that’s why our different experience. I just wanted to add that slurry doesn’t, in my experience, make for a longer ferment.
“Like so many others here, I too have enjoyed all your work and love the dispelling of our brewing “facts”! Keep ‘me coming!????”
I’m not sure the rest of us are enjoying Brulosophy that much…
Haha! I couldn’t find an edit button after I posted that! ????
Had to rib you on that one…
For the slurry, did you do a diacetyl rest prior to re-using the slurry? I ask because I have a pilsner fermenting on WLP830 and I’d like to put an Oktoberfest on the cake. Do I do the diacetyl rest on the Pilsner and then put the O’fest on the cake? Or rack the Pilsner to secondary for the rest and put the O’fest on the primary slurry?
Yeah, d-rest first.
I saved three quart jars of Conan from a NE IPA brew from about 2 weeks ago. I brewed up a batch of NE IPA this weekend and pitched in the entire quart that I had saved. There was probably 450mL of thick sludge in and 350mL of beer on top. I had a rocking fermentation 24 hours later. I’ll see how it tastes!
Hey Marshall – Was the slurry from a batch that you’d used Fermcap with? Curious as to if you know if Fermcap would have any impact on the ability to reuse yeast, as I typically use slurry, but want to try Fermcap out. Thanks!
Of course! I use FermCap as a matter of course.
I do this all the time i pour directly from the old carboy into the new one and fermentation always starts within 6 hours . I am confused at how long this expmt took .
On bottling day, I usually brew a second, smaller batch of more experimental and cheap beer that I pitch directly into the old fermenter. Typically I will scoop out around a quart of old trub and leave the rest. Been doing it for a couple years and so far no problems.
I use 05, straight pitch,- no lag time.
totally, bro. i pitch a pack in and it starts fermenting in like 10 seconds, no lag time. rock on!
I’ve been re-using a lot of sloppy slurry lately, with good results. The door of my fridge is full of mason jars with yeast I harvested from prior batches. Viability definitely goes down with storage time, and lag time increases. I’m not sure that is a problem – after all, what is “yeast nutrient” but dead yeast cells and an old slurry has plenty of them! Sometimes I will build a 1-L viability starter to get the old slurry active before repitching.
I’m skeptical of the validity of online yeast pitch calculators. The equations are correct, but the uncertainty around input variables makes the results questionable. The homebrewer simply has no confidence in the % of viable yeast, either in a smack pack or a saved slurry.
The other thing I’ve been thinking about, is that the conditions for optimal yeast growth rate are not necessarily the same as those for optimal beer flavor. The research out of White Labs etc. is focused on counting yeast cells and growth rate, etc. But homebrewers are not running a fermentation bioreactor – so what if the number of cell divisions is not perfect? The end results for beer flavor can be excellent across a wide range of yeast performance conditions.