Amount of Yeast vs Fermentation Time

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Brutus Brewer

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I brewed a wheat beer 4 days ago and used 2 smack packs of yeast, one containing 100 billion cells and one with 25 billion cells. Since there are essentially 25% more yeast cells than the standard 100 billion cell smack pack would fermentation time decrease?
 
Brutus Brewer said:
I brewed a wheat beer 4 days ago and used 2 smack packs of yeast, one containing 100 billion cells and one with 25 billion cells. Since there are essentially 25% more yeast cells than the standard 100 billion cell smack pack would fermentation time decrease?

No, but you may have gotten a little quicker start, so I guess technically that means it will finish a little sooner, even though the actual fermentation time is the same.

Actually, increasing the cell count by 25% is not *all* that significant. With a big starter, you increase the cell count by a lot more than 25%.
 
The difference would be minor. Probably less than an hour. The first stage of fermentation is the yeast growth stage. Yeast cell count doubles every two hours until the oxygen is gone, so going from 100B to 125B at the start wouldn't even knock off one doubling time. Going from 25B to 125B would cut the growth period by about four hours.

If you let a starter cook for 24 hours you get 2^12 or 4000 times as many cells.

For a set amount of oxygen in the wort, the final yeast cell count will be approximately constant. More O2, more cells, faster ferment.

Once the growth phase is done, sugar -> CO2 & alcohol starts.
 
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