The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

yeast rising to the top?

cake diva's picture
cake diva

yeast rising to the top?

I read not too long ago in one of the threads somewhere here that when feeding starter, one must take the sample from the top as that is where the yeast cells are.  Is this true?  I'm no biologist; I just want to understand why there would be more population on top.  I can't recall reading anything before about this.


Dwu3193's picture

The strain of yeast in sourdough is probably a top-fermenting yeast. But you can just stir the starter to redistribute the yeast cels.

Debra Wink's picture
Debra Wink

Yeast cells will be present throughout the starter, but they multiply fastest at the surface exposed to air. Oxygen is absorbed slowly into your starter from the atmosphere. It doesn't penetrate to any degree, because it gets scarfed up so quickly by the cells at the surface. Yeast can make up to 38 ATP of energy through respiration for each molecule of glucose consumed vs. only 2 through fermentation. So they can put a whole lot more energy into reproducing themselves. I would follow the adivce of the first poster and "just stir the starter to redistribute the yeast cels."