Stepping up yeast starter

I'm confused about the limitations of doing this in a 2L flask.

I started out with 1 smackpack of 1056 into 2 cups of water, 1/2 cup DME, set on a stir plate for 2 days.

Then I chilled for a day, decanted the wort and added 2 more cups of fresh wort and put it back on the stir plate.

But now I am reading that you get less and less new yeast each time you do this but I don't understand why.

What is limiting the yeast? I could add 4 cups of fresh wort instead for my step up.

My goal here is to get a starter that will work for my beer that is going to be around 1.090 OG.

Thanks!!

For a beer that big a 2L flask really is not big enough. You will have to step that thing up 10 times so you can get enough yeast. You really just need to get a larger container. A 5L flask would be best. But you can use almost any large container. Needs to be at least a gallon.

Growth rate is in relation with inoculation rate (millions/ml), so if you pitch too much (or too little) yeast in certain amount of wort you"ll get suboptimal growth rate.
According to C. White"s book "Yeast", largest growth rate (yield factor) is when inoculation rate is between 50-70 M/ml.

That said, if you pitch every step in same wort volume you"ll get smaller and smaller growth rate (because inoculation rate is rising with each next step- more cells per milliliter of wort).

There is nice calculator, so you can play with numbers and see what you"ll get with different approaches:
http://www.yeastcalc.com/

If you take your first 2L starter and figure roughly how many yeast that will produce, you can then divide that starter in 2 or 3 and then step each of those up with a 2L starter and you should be able to grow more yeast that way. It takes more steps and starters but you can get more yeast by doing it that way.

Or just buy multiple smack packs.

BeerSmith says my beer needs 400 billion yeast cells.

If I tell it I have a 2L starter, stir plate and the package date of my yeast it says I will get just under 444 billion cells.

Is BeerSmith wrong or am I doing something wrong.

diS said:

Growth rate is in relation with inoculation rate (millions/ml), so if you pitch too much (or too little) yeast in certain amount of wort you"ll get suboptimal growth rate.
According to C. White"s book "Yeast", largest growth rate (yield factor) is when inoculation rate is between 50-70 M/ml.

That said, if you pitch every step in same wort volume you"ll get smaller and smaller growth rate (because inoculation rate is rising with each next step- more cells per milliliter of wort).

There is nice calculator, so you can play with numbers and see what you"ll get with different approaches:
http://www.yeastcalc.com/

Click to expand...

Thanks! That calculator says if I step up my 2l starter I will get 533 billion cells.

That should be plenty for my beer right?

Just to be safe I decanted a second time, added another 1056 smack pack and then added FOUR cups of fresh wort and put it back on my stir plate.

I think that should give me enough yeast for my big beer.

There are a few different references that I used to educate myself about stepping up yeast when I started slanting yeast. A simple one is billy brew

http://billybrew.com/stepping-up-a-yeast-starter

A scientific one is Maltose falcon website on Propagation and Maintenance

http://www.maltosefalcons.com/tech/yeast-propagation-and-maintenance-principles-and-practices

However to answer your question about why stepping up your starter (or rather not stepping up but just stepping sideways as you are not increasing the the quantity) you have to think about what yeast need to multiple. Yeast will multiply while they are healthy enough to do so, and yeast health require a food source, oxygen (anaerobic fermentation taxes yeast health eventually) and nutrients. So yeast will continue to multiply when you have enough O2 and sugar and nutrients. Now as cell density in a solution increases they consume all available nutrients O2 and sugar before they have increased their health enough to divide.

I have read that stepping side ways (aka small steps) can lead to lazy yeast as significant portions of the cells in the yeast have not had an opportunity to eat the more complex sugars (eg maltotriose) and therefore the yeast you are breading have lost the enzymes and processes needed to ferment these complex sugars. So when they get into your brew they need to adapt to the new requirement and hence your attenuation will suffer. In the references I have read different breweries use different step rates some use x10 other use as low as x5. I would not step smaller than x 2.

Hope this helps, if you enjoy playing with yeast try freezing or slanting to start your own yeast farm, after one or two brews you will gain confidence in your ability to produce good healthy yeast.

Clem

If I don't decant, should I use the added volume or the total volume on each step-up in yeastcalc.com. I made a 0.35 L starter, added 0.85 L for a total of 1.2 L, and plan to add another 1.4 L for a total of 2.6 L. If I use 0.35 L, 0.85 L, and 1.4 L I get 281 billion cells. If I use 0.35 L, 1.2 L, and 2.6 L I get 406 billion cells.

Also, how much should gravity drop before I step up or pitch. Wyeast says gravity should drop 50-75% before increasing volume - http://www.wyeastlab.com/com-propagation.cfm - that would have a 1.040 starter dropping to 1.010-1.020. Any thoughts on this?

BUMP!!

So a question to follow up on this. I'm doing a brew this weekend....haven't input the recipe into BeerSmith yet, but it's gonna be a simple 5%ish one. I'm picking up my yeast today for the starter and wanted to ask a question to that effect.

I usually do just a 1 step starter because all I have is a 1L flask. I don't know the production date as I haven't picked it up yet, but I'd like to get clarification on my method I'm planning to use if I need to do a 2x step. I'm going to do a 1L step to start. Cold crash and decant and pour off the liquid and save the cake. I then plan on splitting that in 2 and doing another 1L step with that.

I'm expecting that the starter wort will not be over populated with yeast to avoid lazy reproduction because it is split in half. Is my thinking in line here? I can do this to both halves of the 1st step and continue on as to save one for later use maybe.

All help and thoughts are appreciated. Cheers!

This is a good calculator (http://www.brewersfriend.com/yeast-pitch-rate-and-starter-calculator/) as it gives you the inoculation rate. I've heard that 50M-70M cells/ml is ideal. Example: 50 billion cells in 1L without shaking would be 50M cells/ml and increase to 104 billion. Splitting in half would give you 52 billion and another 1L starter would take that to 106 billion without shaking. Higher cell counts and aeration methods would obviously give you more cells, for instance 100 billion cells with shaking would go to 201 billion, and thus the second starter would go from 100.5 billion to 202 billion.

So what your saying is that when I do my 2nd starter, I should take a smaller portion of the 1st starter (approx 50 - 70 billion cells which I'd have to measure by weight) and do another starter with it to make sure I'm getting equaly as healthy yeast for pitching. I'm assuming I'd do a similar starter as the first in terms of volumes and DME.

Am I thinking about this correctly?

You're not going to get down to dry yeast when you make a starter. Even after cold crashing and decanting, you'll still have some liquid on top. Since you would still have to cold crash before decanting anyway, once your 1st 1L starter is finished, just shake it up to make sure the 100-140 billion cells are evenly distributed, then split it into two 500 ml portions with 50-70 billion cells each. After cold crashing and decanting, add enough wort to get back to 1L. If you are able to decant enough of the liquid off the other 500ml portion, you might even be able to fit it back in the container the yeast came in, and at that point it will be just as good as the yeast you originally bought and you can use it over and over again.

Ahhh that's a great idea! I'm glad at least my thinking was correct, just a change in the method will be needed. Now I need to get my hands on some cleaned/used yeast viles.

Thanks again!

So I did the first step to this....broke it into two equal portions and cold crashed. Once everything was settled, I decanted and put away one of the portions and then began and a new started with the other half.

Now....after running it on the stir plate for the night, I came downstairs to find an over flowed flask with yeast/foam that poured out. I split it up into 2 equal portions again and am cold crashing, but I'm hoping it didn't loose too much yeast.

I had no over foam issue with the first run, but this 2nd run is what had the issue. I'm thinking that because I had approx 120B cells compared to the initial approx 80B cells that might have caused the increased activity and caused the over flow.

Any thoughts on this?

Starters can have a violent fermentation sometimes. If a stopper and an air lock won't cut it, I'd suggest a blow-off tube.

Thread revival!!! Here’s the math I use to determine starter size and/or step-up starter size …

White and Zainasheff have data in their yeast book for total number of cells that come out of a starter with a fixed number of starting cells for varying starter volumes. You can normalize this data to get yeast growth factor as a function of inoculation rate and get a really good curve fit which is:


Where “GF” is growth factor (i.e. 1x, 2x, etc.) and “IR” is inoculation rate in billions of cells per liter of starter.

Here’s an example. If you pitch 100 billion cells into a 2 liter starter, your IR (inoculation rate) is 50 billion cells per liter. Your GF (growth factor) will be 2.09 which means your ending cell count will be 2.09 * 100 billion cells = 209 billion cells.

To demonstrate the sensitivity to starter size, if you than repitched the 209 billion cells into another 2 liter starter, the ending cell count would only be 311 billion which is only a GF (growth factor) of 1.49.

This data was based upon a starter which didn't have any supplemental oxygen, stirring, shaking, or aeration. This can boost the growth by 1.5x to 3.0x. However, that would only work for a low inoculation rate.