Why don't starters cause massive over-pitching?

[albino314]

I'm planning to start using starters, but one thing still confuses me. If one pack of liquid yeast is ~1/2 as much as a beer needs, and you make a starter, how do you know whether your starter then has the right amount of yeast? If the yeast grows as much as it does in a batch of beer, wouldn't the starter wind up with way more yeast than you need?

Is there something you're supposed to do to make sure the final amount of yeast is correct?

Thanks,
Josh

 

[ong]

People generally use pitch calculators like http://mrmalty.com/calc/calc.html -- or, if you're doing a normal strength ale, somewhere around 1-2 liters is a perfectly good starter size. For a normal strength lager, double that.

 

[flars]

The amount of new yeast cells propagated is determined by how much sugar you feed the yeast. When the food is gone the yeast stop growing new cells. The optimum strength of a starter wort for healthy yeast is 1.037 to 1.040 SG.

A 1 liter starter would then have 100 grams of DME. A 1.5 liter starter would have 150 grams of DME. A 10 to 1 ratio will result in the optimum SG of the starter wort.

A calculator comes in handy for estimating the vitality of the yeast you have according to the age of the yeast and how large of a starter you will need. This is the pitch rate/starter calculator I use.
http://www.brewunited.com/yeast_calculator.php
I use this one for consistency. There are other calculators out here.
http://www.mrmalty.com/yeast-tools.php
http://www.brewersfriend.com/yeast-pitch-rate-and-starter-calculator/

 

[albino314]

Oh, I get it now. The yeast growth is limited to the size of the starter, so if you have the right volume of starter wort you'll get the right amount of yeast. Thanks!

 

[flars]

Oh, I get it now. The yeast growth is limited to the size of the starter, so if you have the right volume of starter wort you'll get the right amount of yeast. Thanks!

Theoretically that is the way it works. Good notes to refer back to on the fermentations also helps.