Fuzzybear wrote:I will probably cop a lot of crap for this but here goes
I thought yeast kept on growing till it used up all the sugar.
So if you did not use the correct amount of yeast, wouldn't it just take a bit longer?
Also what would happen if you were to take the live and thriving yeast culture from a wash in progress and put it in a ready to go wash (sugar and water).
I would of thought the yeast would just take off and multiply until it had used all the sugar.
I would rather stand corrected than ignorant of the truth!
You are correct. Yeast will consume all the sugar if it is not killed off by the alcohol first. You can build up a large culture by feeding up the yeast. I have a 200L fermenter where I continuously culture yeast as I brew. I start with a 48L batch of wort and pitch the correct rate of yeast for it. Once it is at high krauzen I dump on another 50 to 60L batch. A day or two later I dump on more wort, etc until I fill the fermenter.
Many large breweries take a live yeast culture form a fermenting wort and pitch it into another batch. Generally it is done by the krauzen layer, or by the yeast cake. The krauzen cells are ready for direct use. Most breweries would wash the yeast cake to separate the yeast out from the other debris.
You can even pitch your next batch directly onto a yeast cake. A rough rule of thumb is approx half the yeast cake is a great start.