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Old 05-03-2012, 11:01 PM   #1
banderberg
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Default 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!!

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Old 05-04-2012, 05:35 AM   #2
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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.

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Old 05-04-2012, 05:43 AM   #3
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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/

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Old 05-04-2012, 06:01 AM   #4
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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.

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Old 05-04-2012, 03:07 PM   #5
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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.

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Old 05-04-2012, 03:18 PM   #6
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Quote:
Originally Posted by diS View Post
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/
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?
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Old 05-05-2012, 05:49 AM   #7
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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.

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Old 05-05-2012, 01:49 PM   #8
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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

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Old 11-16-2012, 06:29 AM   #9
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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?

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Old 04-15-2013, 05:03 PM   #10
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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!

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