Amount of yeast to use

[thechemister]

I'm new to brewing and I notice some recipes call for oddly specific amounts of yeast. Does it really matter? Because yeast is a living organism that multiplies extremely fast (it can double its population in 20 minutes). So if the yeast reproduces, theoretically can't you put in a very small amount of yeast, and within a certain amount of time your fermentation will be going full throttle?

 

[eastoak]

in theory you could do that but it would not make for a very good beer. yeast that are stressed from a severe under pitching may not be able to finish fermenting the beer and develop various unpleasant flavors. there is much more to it than that but that's a start.

 

[FuzzBeckersHB]

http://www.mrmalty.com/pitching.php. Here is a good explanation. Hope this helps..

 

[CA_Mouse]

Yeast can be propagated this way, yes. I would not suggest doing in a full batch of wort though. As previously stated you will get stressed out yeast that may not finish fermenting properly and give off flavors. This is why most of us are making appropriate sized starters for our yeast. It makes sure that we have healthy and happy yeast and ensures that we won't get off flavors because we've stressed them out. I would much rather pitch the correct amount or slightly more than needed, instead of under pitching and potentially ruin a good batch of beer.