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frostyp 01-10-2013 10:01 AM

Yeast starter
 
When making a yeast starter utilising a stir plate.
If doing a stepped starter lets say 250ml, 500ml and 1 litre, do you need to chill and decant wort between each step or can you just add the next size of wort to the original and at the end of the desired volume chill and decant thanks.

Pie_Man 01-10-2013 11:55 AM

No, you don't need to decant in between the starter steps. I only do so if I need to make a little room in the starter vessel.

Odin_Brews 01-10-2013 12:55 PM

While Im sure you can skip decanting I think optimal for yeast production would be to decant between steps.

I was just reading something about how optimal yeast reproduction occurs at 1.036, post 16 on this thread http://www.homebrewtalk.com/f163/worth-harvest-371948/index2.html.

So if you don't decant let's say your starter ferments each step to 1.010, then you mix that 250 with 500 ml at 1.040 and you get about 1.030 for your second step. That again ferments out to 750 ml @ 1.010 which you mix with 1 liter getting an SG on your third step of around 1.025.

See what I mean? So you would definetly reproduce cells but not likely in the same way that you would or as optimally as you would by decanting each time.

grem135 01-10-2013 12:55 PM

Why do you step your starter if you have the room to do 1 large starter?

Odin_Brews 01-10-2013 01:03 PM

Good question! Your first step gets the highest growth rate so it would seem if you can 1 step is optimal. But to be honest I have no good answer for you, Im hoping someone else will chime in so I can see what they have to say.

frostyp 01-10-2013 02:20 PM

Thought by doing smaller step ups would not stress the yeast and get a more consistent rate of growth, hopefully doubling up each time

Pie_Man 01-10-2013 03:16 PM

I'd recommend playing around with the numbers on yeastcalc.com. That site will allow you to see if a single step, or multiple steps, will get you to your target cell count. Your cell count doesn't always double with each step.

Pie_Man 01-10-2013 03:28 PM

Quote:

Originally Posted by Odin_Brews (Post 4769233)
While Im sure you can skip decanting I think optimal for yeast production would be to decant between steps.

I was just reading something about how optimal yeast reproduction occurs at 1.036, post 16 on this thread http://www.homebrewtalk.com/f163/worth-harvest-371948/index2.html.

So if you don't decant let's say your starter ferments each step to 1.010, then you mix that 250 with 500 ml at 1.040 and you get about 1.030 for your second step. That again ferments out to 750 ml @ 1.010 which you mix with 1 liter getting an SG on your third step of around 1.025.

See what I mean? So you would definetly reproduce cells but not likely in the same way that you would or as optimally as you would by decanting each time.

Good point. This approach does seem optimal. The only downside I see is the level of planning this would take. If you're going to cool/get the yeast out of suspension, decant, then add fresh starter wort at every step, you'll need to start your starter earlier than usual. Probably about a week, or more, before your brew day. I don't usually need a multi-step starter, but I'm going to try this approach the next time I do.


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