Why Not to Pitch On Your Yeast Cake

[cheezydemon3]

I submit that you CAN'T know how many cells are in a starter or even, for certain, a vial or packet.

I guarantee the ancient germans weren't counting cells.

Underpitching is WORSE than OVERPITCHING and is way way way way way more common.

 

[mojotele]

I submit that you CAN'T know how many cells are in a starter or even, for certain, a vial or packet.

You most certainly can. It's just prohibitively expensive for the home brewer.

 

[cheezydemon3]

You most certainly can. It's just prohibitively expensive for the home brewer.

What he said.

 

[masonsjax]

A desire to continue practicing old habits doesn't make the evidence go away, no matter how defensive you get. Some of the posts here make it sound like people are being forced to change. If you're happy with your process, more power to you. RDWHAHB

 

[mojotele]

Another possible explanation for all of this is that Bob didn't address how the effects of over-pitching vary with scale (if indeed they do, I assume they do). For example, I imagine over-pitching by a single yeast cell has absolutely no noticeable effect. However, over-pitching by 100 trillion cells probably has a very noticeable effect. How much more of an effect does it have? It isn't necessarily linear...

Anyway, my point is that if you are over-pitching when you pitch on a yeast cake, how much are you over-pitching?


I suppose the final thing I have to say in regards to this topic is this - it is possible to know how many yeast cells are in a given slurry, and I'm sure the people doing these studies know how much are in theirs within a very small margin of error. It is practically impossible for a home brewer to know, though, as the equipment costs waaaaay too much. The most obvious answer to why your (as in the brewing community's) anecdotal evidence conflicts with the conclusions of these studies is that you're simply doing something different. Perhaps you aren't over-pitching, or perhaps you are but not enough to notice. You can never know. In the end, I think what I learned from this thread is that Bob is advocating a method by which you are least likely to over-pitch or under-pitch. If you find you are not seeing the results of over-pitching with a particular recipe and yeast cake then you should by all means continue to pitch on that yeast cake in that situation.

If you are in doubt, though, you should use Bob's math to estimate the amount you are pitching.

Really, yeast is just another ingredient that a brewer can manipulate. I think people forget that. Just like you may decide to add more hops, you may decide to pitch more yeast. If it doesn't taste as good, though, you'd back it off. Likewise, you may decide to add less yeast. Experiment with your recipes and find what works for you for each particular beer.

 

[SC_Ryan]

I have found this thread really informational. I have pitched on yeast cakes in the past with good results and will continue to do so in the future with some of my beers (albeit with more of a measured approach). I have also found that the longer I have brewed and the more I refine my processes the better my beer has gotten.

I have cooled my wort in an ice bath in the sink over a three hour period with great results, but my hop flavor and aroma are better now with a chiller.

I have brewed with extract with great results but I switched to all grain and now my beer is better.

I have brewed all grain with my plain 'ol tap water with great results but now I adjust my mineral content to match predicted SRM and my beer is better.

I have brewed with an inconsistent and inaccurate thermometer with great results... You'll never guess what happened when I acquired an accurate consistent thermometer! My beers got better and more consistent.

I don't think you can argue the fact that it is "best practice" to pitch a well measured, known quantity (or your best estimation possible) of yeast into your wort and use a freshly cleaned and sanitized vessel for fermentation. That is what I intend to do with all of my "special beers" or competition beers from here on out. That said, I'm going to continue to pitch on cakes for some of my plane 'ol house ales and less important beers and I'm sure those beers will turn out fine.

 

[cheezydemon3]

I will lay all MY cards on the table at risk of ridicule.......

I think that ANY beer, commercial or otherwise could have been at least 2-3% better if some unknown variable had been adjusted....(except stone vertical epic 090909 which is not improvable)

But what is "better"? Any 2 brewers might disagree about whether the tweak was better or worse.



MOST IMPORTANTLY...

JAMIL is great, but I don't believe that brewing has been accurately studied inside and out.

No one can say the EXACT ideal temp to mash a given recipe at. No one can say for sure the absolutely ideal yeast strain and count. No one can say the precise amount of grains that would be ideal.

I take my best shot and say HAIL MARY.

I believe that my haphazard approach is more likely to hit on a "perfect" recipe, than someone who is anal about hitting a precise temp, or a precise yeast count.

They are likely laboring towards a point that is, in fact, not ideal.

I take notes, and haphazard is not the word I would use, but it is the word that anyone who owns a refractometer would use about my process.

 

[remilard]

You most certainly can. It's just prohibitively expensive for the home brewer.

Really? What about a homebrewer who already has a microscope?

Personally when I think of the cost of a used microscope and hemocytometer, the word "prohibitive" doesn't come to mind. I understand that some people may have less walking around money than me.

It's more prohibitively time consuming (to do it for each pitch) from my perspective.

 

[SC_Ryan]

I think that ANY beer, commercial or otherwise could have been at least 2-3% better if some unknown variable had been adjusted....(except stone vertical epic 090909 which is not improvable)

But what is "better"? Any 2 brewers might disagree about whether the tweak was better or worse.



MOST IMPORTANTLY...

JAMIL is great, but I don't believe that brewing has been accurately studied inside and out.

No one can say the EXACT ideal temp to mash a given recipe at. No one can say for sure the absolutely ideal yeast strain and count. No one can say the precise amount of grains that would be ideal.

I take my best shot and say HAIL MARY.

I agree with you 100% on this point. There's more than one right way to do things and there is always room for improvement. This is where science ends and the art of brewing comes in and it's one of my favorite aspects of brewing. That said, I still prefer to control what I can (within reason) in my brewing process so that I feel my art is presented in it's best light. But that's just my way of doing things.

 

[mojotele]

Really? What about a homebrewer who already has a microscope?

Personally when I think of the cost of a used microscope and hemocytometer, the word "prohibitive" doesn't come to mind. I understand that some people may have less walking around money than me.

It's more prohibitively time consuming (to do it for each pitch) from my perspective.

You're right, that was a pretty dumb comment.

I agree with your last statement.

 

[cheezydemon3]

I agree with you 100% on this point. There's more than one right way to do things and there is always room for improvement. This is where science ends and the art of brewing comes in and it's one of my favorite aspects of brewing. That said, I still prefer to control what I can (within reason) in my brewing process so that I feel my art is presented in it's best light. But that's just my way of doing things.

Cheers brother.

lol, like your sig. Bitter beer face? Wish I could get that!

Stone ruination barely makes me twitch, much less a full face scrunch.

 

[onemanlan]

I do want to argue with you. If you know anything about microbiology it IS possible to calculate viable cell count of a yeast slurry in final solution. Maybe not to the average home-brewer, but you can achieve relative number to work with. You can also use growth rate constants (for the strains of yeast) along with the understanding what phase of growth the yeasts is in to determine how much yeast will be present in your final solution. You can just use your pitch for inoculation at after a timed period of growth leading to a determined # of cells/unit volume.

Besides your merely going from late log phase or stationary phase to log phase again. There maybe a small lag phase, but the lag phase length of time will be much quicker than pitching the cells because you're not changing the environment up that much. Taking out of the wort and giving them new/different metabolites to grow on, causing the cells a primary lag phase, then introducing them to a wort environment will cause a secondary lag phase. There are such things as catabolite repression and change in log, stationary, and death phases of the cell growth cycles.

Yes, as you said over-pitching is bad, but that doesn't mean you can't restart and regrow your cells if you need to. What if I just wanted to re-use my strain of yeast later and just want to culture the strain for use later on?

Please don't take 'no-argument' approach to your opinions on science. Yes there maybe strong supporting evidence that something could be treated as a fact, but nothing is proven to be 100%. This is coming from some one in science and that kind of mentality leads to bad science and stubborn people.

Good post though. I see your point and why brewers do it. They definitely have their art down for a good reason.

 

[cheezydemon3]

,,,Good post I think....

It is unclear if you are addressing the OP or not.

 

[Palefire]

Ok, bump here, since there was a question earlier in the thread that I've been wondering about too ... thought I'd just post here instead of PM'ing Bob. It's this:

I have a question about the viability of the yeast in the primary. So we know that the viability of a portion of harvested yeast cake drops at a rate of 25% per seven days while in cold storage. We also know that washed yeast stored the same way keeps better but to an unknown degree.

Let's say your primary fermentation conditions were optimal and your fermentation completed in 4 days. How much if any viability is lost post fermentation while the cake is sitting at the bottom of the primary? I will primary my beers for 1-3 weeks depending on my schedule.

That's my question too: is there a general rule of thumb for how much viability decreases (if at all) during post-fermentation time in primary? I.e., can we assume that Bob's estimate of there being "~1 billion active cells in a ml of harvested slurry" holds whether the beer's been in the primary for 3 weeks or whether it's been in there for for 5 weeks (say)? If not (i.e. if there are fewer active cells the longer the beer's been sitting in primary), do we know what a good rule of thumb for calculating the difference would be?

I'm assuming that a super-long primary (just guessing, something like 6+ weeks for a standard-sized beer) would leave the less somewhat less viable, though I could be wrong about that too.

I'm really hoping not to revive the other debates here about process vs. product, etc., just to find out if a) post-fermentation time in primary decreases yeast viability, and b) if so, if there is a rough guideline for calculating the rate of decrease.

Thanks!

 

[broadbill]

That's my question too: is there a general rule of thumb for how much viability decreases (if at all) during post-fermentation time in primary?

I would guess that viability certainly decreases over time post-fermentation since yeast viability is known to change in Wyeast smack-packs the older they get. Since

Jamil's Mr. Malty calculator actually takes yeast viability into account when deciding required starter size. I wonder if you can extrapolate from the data set used to make that calculation and use it to roughly determine yeast viability of a yeast cake post-fermentation....

A quick play with Mr. Malty:

Smack pack packaged today: 97% viable
1 month ago: 75% viable 23% decrease
2 month ago: 54% viable 44% decrease
3 month ago: 32% viable 67% decrease
4 month ago: 11% viable 87% decrease
5 month ago: 10% viable n/c from 4 month
6 month ago: 10% viable n/c from 4 month


Pretty much what I would expect in terms of decreases in yeast viability, IF you assume that changes in yeast viability are similar between Wyeast packs and sitting in the bottom of the fermenter.

If anything, I would guess that the decreases in yeast viability may be more pronounced in the fermenter (larger decrease in yeast viability)...the fermenter/ yeast cake would be stored in the 60s (ale fermentation temps) where Wyeast smack packs are stored in the refrigerator.

 

[cheezydemon3]

I had yeast stored warm in a bucket until it was dry and cracked. 5-6 months I believe.

It sprang to life no problem and made great beer.

I think dry stored yeast has longer life.

 

[broadbill]

I had yeast stored warm in a bucket until it was dry and cracked. 5-6 months I believe.

It sprang to life no problem and made great beer.

I think dry stored yeast has longer life.

A couple of points on this:

It probably wasn't completely dry, it might have had enough moisture to keep on kicking...

The data I show above indicates that after 5-6 months there is still 10% viability. So its entirely possible that viable yeast could have come from that cake to ferment the beer. Optimal conditions?...probably not.

The method they use to dry yeast is much different from letting it slow-dry like you did. Its actually freeze-dried I believe. Either way, dry yeast does have a much longer life.

 

[cheezydemon3]

A couple of points on this:

It probably wasn't completely dry, it might have had enough moisture to keep on kicking...

The data I show above indicates that after 5-6 months there is still 10% viability. So its entirely possible that viable yeast could have come from that cake to ferment the beer. Optimal conditions?...probably not.

The method they use to dry yeast is much different from letting it slow-dry like you did. Its actually freeze-dried I believe. Either way, dry yeast does have a much longer life.

Far less than ideal.

That was my point.

I now pour out all but 1/4 of my cake and pitch on that.

That has been successful for 8 consecutive batches now.

*man this thread is a ZOMBIE!!!!lol*

 

[Palefire]

I wonder if you can extrapolate from the data set used to make that calculation and use it to roughly determine yeast viability of a yeast cake post-fermentation....

A quick play with Mr. Malty:

etc.

Damn, that's smart. Or, rather, pretty straightforward, just far too sensible for me to have figured out on my own. :rockin:

Seems like a good variable to add into the equation. Worst case scenario would be a slight overpitch, but since we're playing with estimates anyway, better safe than sorry, I think.

Thanks.

 

[cheezydemon3]

Damn, that's smart. Or, rather, pretty straightforward, just far too sensible for me to have figured out on my own. :rockin:

Seems like a good variable to add into the equation. Worst case scenario would be a slight overpitch, but since we're playing with estimates anyway, better safe than sorry, I think.

Thanks.

And far more chanc of under than over in my estimations.

 

[crlova2]

Alright Bob I have read through about half of this thread and my head hurts now because it is so long. Thus, I don't want to go back through and find the answer to the question I know have. Sounds like you know a lot about this stuff so I wanted to clarify that if I make a starter from a fresh vial of whitelabs or wyeast that 238ml of slurry would be an estimate for an appropriate amount for a 1.048 OG beer? Or is the 238ml number for unwashed yeast that is only 25% viable yeast which would mean you only would need a fourth of the 238ml from a fresh vial?

 

[broadbill]

Alright Bob I have read through about half of this thread and my head hurts now because it is so long. Thus, I don't want to go back through and find the answer to the question I know have. Sounds like you know a lot about this stuff so I wanted to clarify that if I make a starter from a fresh vial of whitelabs or wyeast that 238ml of slurry would be an estimate for an appropriate amount for a 1.048 OG beer? Or is the 238ml number for unwashed yeast that is only 25% viable yeast which would mean you only would need a fourth of the 238ml from a fresh vial?

I'll take a stab at this:

I don't think I would worry about slurry amounts if I were starting from a fresh vial/smack pack. Use Mr. Malty to make the appropriate sized starter and pitch that (or crash cool and pitch whatever is left after pouring off the liquid).

Slurry amounts is for figuring out how much of a yeast cake to pitch (i.e. what is left over at the bottom of a fermenter after removing beer).

Hope this helps...

 

[Bob]

Close. When the starter is finished and crashed, the slurry at the bottom is still slurry; it's just more pure than what's in the bottom of the fermenter -there's infinitely less trub.

If you use the math to calculate your slurry amount with the slurry from a fresh starter, you'll possibly be overpitching, but not so much as I'd let it disturb my slumber. I don't have fresh-starer-slurry cell count numbers to back up an adjustment to the calculation, anyway. Anybody with a haemocytometer want to take that on?

Bob

 

[cheezydemon3]

I think rather than an ideal pitching rate, a range would, in fact, be more accurate.

I am sure that different strains perform differently and have different ideal numbers.

If I ever get so worried about it that I start counting yeast, remind me that all the fun has gone out of brewing and to hang myself.

i am pretty sure that 1 cup of yeast is within 1 or 2 yeast cells of absolutely ideal.

 

[1971hemicuda]

Ok...here's a wrench in this discussion...

So, I have a yeast cake...I'm not brewing that day, but I would like to save it again. I wash the cake, remove some of the trub and store it. So my question

Should I...

A) Create another starter, pitch the WASHED yeast and build another starter
B) Just pitch what was in the wash and let them go to work...

I would GUESS it would be to create another starter...the little yeasties have gone to sleep, been put in the cold for storage, etc, and need to be woken up....am i right? What size starter?

Jason

 

[masonsjax]

Yes, make a starter. How large depends on the beer style, the batch size, how much slurry you collected, how long it was stored, etc..

 

[cheezydemon3]

If you save roughly a cup of yeast, a starter would be overpitching.

 

[SpanishCastleAle]

But that depends on how long (and how well) the yeast was stored. If it's a week or less I just pitch the slurry but if it's been more than a week I make a starter (but from a smaller amount of slurry than I would have pitched in a full batch). The yeast health is paramount.

 

[cheezydemon3]

Good response Spanish, but since Whitelabs liquid yeast is viable for 6 months, and dried yeast, several years, why is our yeast so feeble?

Sorry! I don't buy it.

 

[NewBrewB]

How does one "wash" yeast?"

(I'm picturing standing awkwardly at the kitchen sink with a soapy sponge in one hand, trying to scrub a handful of slurry in the other.... haha I'm sure it is much more scientific & sanitary than that)