5 generations, why?

[Gab1788]

I've been washing and re-using yeast for a while now. I only go to four generations before I get some new yeast. I know people say that after five generations you can start to get off flavors. But my question is, if we as homebrewers can only go five gens, then where do wyeast and white labs get their yeast? Considering that yeast is 45 million years old, then it must have reproduced a few times over that period. I'm sure someone with more knowledge will chime in. I'm just wondering.

 

[thisone]

Homebrewers typically don't have access to the resources that wyeast and white labs has

For homebrewers, sanitation is an issue for reusing yeast. And there is some stuff that I've heard about yeasts "adapting" to some wort profiles, and possibly not performing so well in others

But if it produces good beer, then go for it

 

[Piratwolf]

I was actually thinking about this yesterday driving home from work. I wonder if "off flavors" means "unpleasant" or just "not true to type". If the latter, I think going beyond 5 generations might be one way to develop a "house strain". Anyone tried this for empirical research? I'm at 4th gen on some rinsed Notty and was going to toss it, but maybe I'll experiment a bit on some small batches.

"All your home brew are belong to us!"

 

[Zamial]

I am NOT a yeast reproduction expert. Admittedly this is my "best guess"...

When growing HEALTHY active yeast they probably use a low OG with the perfect environment for the yeast cells. I am willing to go out on a limb and say that out wort is NOT the preferred environment. This causes stress on the yeast which in turn causes mutations, in a bad way, for our brews.

There are stories here of a older gentleman that only brewed 1 recipe and has been reusing the same yeast on every batch. He also made knives from railroad spikes.

 

[emjay]

They also build up their yeast from *single colonies* which are selected for consistency.

 

[Gab1788]

Wouldn't the mutations ( like darwins evolution ) end up being more suited to the wort it's being pitched in. Like the example of the old man and his yeast.
I understand as homebrewers that our controls are obviously not to lab standards. But where did wyeast and y Labs get their yeast? They must have gotten them from a strain that at some point had been wild. Thus wild yeast must have at some point endured not so optimum conditions. So how do they propergate such pure yeast given that they must have been wild at some point and obviously gone through many (45 million years) generations. And why can't we as brewers keep using the same yeast?

 

[Gab1788]

I guess what I'm asking is, what happens to the generations of yeast in our beer that doesn't happen to yeast that we get from wyeast and white labs. That they must have gotten them from generations old yeast from the wild. What happens to our yeast after a few generations that can be worse than fresh yeast from them that must be millions of generations old.

 

[wailingguitar]

Every brewery I have worked for went past 5 gens, routinely saw 9... I can recall going over 15 gens... there was no "washing" of the yeast going on either. Some places we would xfer yeast tank to tank in a closed system, either directly using hoses or by filling cornies and injecting the yeast into the wort flow... in other cases, the yeast could be harvested into sanitized containers through a bottom port or top cropped from an open fermenter and pitched into the next tank prior to knockout. No issues.

 

[wilserbrewer]

FWIW, I remeber a thread here whereby a homebrewer went upteen baches simply repitching active slurry w/ claimed good results. I save and repitch slurry from the fermenter as SOP without issue. Of course, YMMV

 

[Gab1788]

Oh ok! So it seems that from what you are saying, and have experienced, you can use the yeast over and over. Maybe people say only five generations is max is because as homebrewers we don't have lab conditions so the risk of infection grows after every handling/ washing? Maybe that is what people refer to as off flavours after a few generations? So if you properly handled the yeast (which i know most of us do) then you could go on for many generations.
I guess it's like when you do a starter. You start with 500Ml wait for it to ferment and drop down. Then you ramp it up to 1lt and wait till it ferments again and drops again, then ramp it up again. You get the picture. This means that by the time you pitch it, it's already 3rd or 4th gen (depending on your starter). So after your first batch of beer your yeast is already on it's 4th or 5th gen. Then you wash that yeast once the beer is finished, put in the fridge for a couple of weeks until you brew again. Then you need to re-start the yeast so you make a starter again, another gen. So most of us are probably going beyond 5 gens anyway without really knowing it.

 

[insubordinateK]

They also build up their yeast from *single colonies* which are selected for consistency.

I just assuming, but they probably perform genetic sequencing (this has become very cheap to do) to select these colonies to maintain consistency.

Good question from the OP. I would like to hear more people talk of their experience with maintaining cultures for very long periods.

 

[Airborneguy]

I re-use my yeast, without washing but using starters, around 3-5 times before starting over. If cost was a factor, I would definitely experiment with going further than that, but at $6 and having the LHBS very close to work, I just start over every so often to be safe.

 

[Jester]

I have been wondering the same exact thing lately!!! I have have to do some small samples brews coming up.

 

[ReverseApacheMaster]

I had a batch of 1338 that definitely went more than five generations from washing. 1338 is very neutral so I never experienced a flavor change but I did notice on the last few batches it had some wild yeast in it and after a few months it would develop a slight off flavor from it. (Wild yeast -- and some saison yeast -- often create small balls of yeast that float towards the top of the beer.)

Five batches isn't absolute but as homebrewers with imperfect sanitation conditions you will eventually get bacteria and wild yeast in your slurry. Although you can acid wash to destroy the bacteria I don't know that it has any effect on wild yeast.

 

[william_shakes_beer]

I have begun saving yeast and doing starters, bit I do it a bit differently. I do not wash from the fermenter. Instead. I harvest from the pre pitch starter, then step up again. Not enough experience to report whether or not this is suprior, but (IMHO) seems likely to reduces the likelyhood of the stored yeast containing wild yeast. Just pitched my first saved yeast last night, I'll see if there's any change in lag time from the original brew.

 

[Piratwolf]

I have begun saving yeast and doing starters, bit I do it a bit differently. I do not wash from the fermenter. Instead. I harvest from the pre pitch starter, then step up again. Not enough experience to report whether or not this is suprior, but (IMHO) seems likely to reduces the likelyhood of the stored yeast containing wild yeast. Just pitched my first saved yeast last night, I'll see if there's any change in lag time from the original brew.

This is an interesting idea. I've read posts about it before, but until now never considered it in light of the "5-gen" rule of thumb.

I'm glad the OP brought this up, and I also hope others will contribute.

FWIW, I think I'm going to combine two experiments. Once is the FWH vs 60-min experiment I've been meaning to do for a while. I'm really enjoying the FWH'd beers I've been making, but want to do a side-by-side on maybe 2-gal batches.

Now I'm going to add to this by taking a Notty 4th-gen slurry from my Imperial Red, splitting it btwn the two for gen-5. Then I'll re-use it on two more small batches after. That'll get me to gen-6 and gen-7 and I'll re-evaluate at each step after for quality control. I'll start another thread on that when the time comes around (probly after New Years). :rockin:

 

[kh54s10]

When thinking of the description of mutations and off flavors I think of what is the deviding line between not to style and bad. Not to style would not really bother me but I do not really want to go long enough to cross over into bad territory.

I have started to amass a frozen yeast bank. From a new vial/smackpack I will make a starter and freeze 4 samples. They are Gen 1. From those I will make 4 more each = 16 at Gen 2. From those 4 more = 64 Gen 3. and 4 more = 256.

Wow! If I do that.. And that is only one yeast strain! I have a lot of brewing to do!!!!

 

[ISUBrew79]

One of the reasons that Wyeast and White Labs are able to produce consistent yeast is that they maintain master cultures of each yeast strain. These cultures are stored at -80 degrees C, if not colder. This cold storage keeps the yeast in a state of dormancy in which little to no metabolic activity or mutation takes place. From these master cultures, working cultures are prepared and then propagated into larger volumes for smack packs, vials, and commercial-sized pitches of yeast.

Periodically, the yeast producers will start new working cultures from the master culture. I believe the yeast producers are now even using molecular biology technology to look for any changes in the genetic makeup of their working yeast cultures. When they start to see even minor changes in the genetic makeup of these cultures, they know it is time to go back to the master culture.

This is not to say that we as homebrewers cannot repitch yeast for multiple generations. As others have stated, many commercial breweries are doing this without ill effects. The very practice of repitching over hundreds of generations or thousands has resulted in the genetic mutations in brewer's yeasts that have given us all of our favorite strains.

 

[broadbill]

I just assuming, but they probably perform genetic sequencing (this has become very cheap to do) to select these colonies to maintain consistency.

I'd be very surprised if they did this. Although this sort of analysis has indeed become much cheaper to perform, its not cheap enough to select clones with the number of strains Wyeast/White Lab works with.

Also, keep in mind that although we know that different strains exist, we don't know what is different about them genetically (other than a couple of genetic locations, perhaps). Even if the analysis was cheap enough, they wouldn't know what makes a Wyest American Ale different from Wyeast Belgian Wit.

 

[broadbill]

Why 5 generations? Most likely because Jamil/Chris White said 5 generations (actually, I think they recommend closer to 3 generations...although I don't know what their book recommends).

Frankly, I think this is it where is came from. I don't know if there is any evidence to suggest that after 3-5 generations yeast are significant different than they are coming out of the smack pack.

 

[kappclark]

I re-use my yeast, without washing but using starters, around 3-5 times before starting over. If cost was a factor, I would definitely experiment with going further than that, but at $6 and having the LHBS very close to work, I just start over every so often to be safe.

I do the same(except I wash) - $6 -$7 for the White labs...after repitching a few times, with starters, it comes to maybe $1 - 1.50/batch before I get a new vial (includes the cost of the DME for the starters)...When I get a canner, I am going to experiment with slants...at that point,if successful, yeast will be on auto-pilot (not like they aren't already!)

 

[MrManifesto]

what i wonder is, how are we counting "generations". how many times does each cell replicate to go from a white labs vial to my starter? each cell must go through a ton of replications to get to the cell count you get from just a starter, not counting after fermentation. but we only count that as "one generation".

 

[maxpower76]

what i wonder is, how are we counting "generations". how many times does each cell replicate to go from a white labs vial to my starter? each cell must go through a ton of replications to get to the cell count you get from just a starter, not counting after fermentation. but we only count that as "one generation".

Cool Thread, thanks OP! In the lab, we count generations as cell doublings. Under optimum conditions (medium/temperature/agitation) and depending on the yeast you could expect 1-2hr doubling times.

As you continually use your yeast, you're selecting for yeast cells that can outgrow the rest of the population, which alters the culture dynamic. I would imagine that this could alter the character you're going for by using that particular yeast strain.

 

[MrManifesto]

Cool Thread, thanks OP! In the lab, we count generations as cell doublings. Under optimum conditions (medium/temperature/agitation) and depending on the yeast you could expect 1-2hr doubling times.

As you continually use your yeast, you're selecting for yeast cells that can outgrow the rest of the population, which alters the culture dynamic. I would imagine that this could alter the character you're going for by using that particular yeast strain.

hehe isn't my thread, just a question that popped in my mind.

this backs up my thinking. if doubling takes place in 1-2 hours, then there must be like five generations in just a starter. once you pitch, active fermentation can take at least 3/4 days so that's, what, 36-48 generations at the least?

i'm starting to think the use of the word "generation" is grossly inaccurate. we're talking more about "uses" or "sessions" (session yeast!).

 

[insubordinateK]

Here is a nice study which suggests some strains resist genetic variation for hundreds of generations when there is little selective pressure. It also suggests the number of times that a commercial brewery will re-pitch the same yeast before re-propagation will depend on the susceptibility to genetic drift.

http://www.scientificsocieties.org/jib/papers/2007/G-2007-0420-478.pdf

 

[kwikcutz]

I know of two local craft breweries that go 12 and 15 generations. One told me industry standard was 30 generations and one brewery on west coast had used same yeast over 200 times.

 

[phattysbox]

Really what your after is less bud scars...

One yeast cell will bud a finite time before bud scars prevent cell membrane fluidity and permeability. With more scars, the yeast is less able to actively transport secondary sugars such as maltose and maltotriose. The ability to bud is less as well.

The reason brewers yeast has been selected for thousands of years is the ability to bud a new daughter cell (asexually) without any bud scars. This new yeast cell would be generation zero so to speak. In the lab, commericial or academic, yeast cells are grown from single colonies that have relatively few bud scars so what you're getting in a Wyeast pack is first generation.

 

[Calix_Meus_Inebrians]

In terms of who has the right practice, Macros are probably the best example to follow. This isn't to say that most craft breweries are doing it wrong. Also what you can get away with and what is best usually don't go hand in hand.

I agree that home brewers biggest issue is most likely sanitation.

Lots of people don't bother to look into "whys" or just don't ask them, so the 5 generation suggested limit helps to give the largest number of people the best consistent result. If you are looking to start your own house yeast, mutations can be a good thing but when you buy a vial of yeast expecting a specific flavor profile for that yeast then mutations should be limited along with potential contamination.

 

[ChillWill]

We do 10 at work by direct transfer conical to conical. Another brewery I've been to used the same yeast indefinitely; acid washing after 10 generations. You can only do this by top cropping I believe. Also have to be more liberal with nutrients (zinc!). They had some stashed in a bank if anything went wrong like wild yeast infection.

 

[Piratwolf]

Lots of people don't bother to look into "whys" or just don't ask them, so the 5 generation suggested limit helps to give the largest number of people the best consistent result. If you are looking to start your own house yeast, mutations can be a good thing but when you buy a vial of yeast expecting a specific flavor profile for that yeast then mutations should be limited along with potential contamination.

that makes a lot of sense to me, Calix

"All your home brew are belong to us!"

 

[Wilden]

From my experience in working in a craft brewery I can tell you this. We use our yeast for 35 to 40 generations. We measured a generation as starting with the first brew G1 then when using that yeast for the next brew as G2 and so on. Note that if we pitched from the same conical twice say from G2 to G3 then the yeast in both of the new conicals was G3. We average about 2 brews a week and use the yeast for about a year and a half or about 170 brews. In commercial brewing there are three rules sanitation,sanitation, sanitation. We cleaned, sanitized, and pasteurized our conicals and then cooled them under pressure before then venting via a sanitary blow off bucket before yeast or wort ever saw the inside. There is a small amount of drift in the yeast as the generations go by and the yeast adapts to the wort profile and the brewery itself. In my experience after about the 15th to 20th generation the yeast settles down a bit being much more vigorish in fermentation before this point.