The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

yeast rising to the top?

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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.


Thanks.

Dwu3193's picture
Dwu3193

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

Davo's picture
Davo

Sounds baseless to me, otherwise I'd expect my loaves to rise in one part but not the others... Unless there's some other logic that applies.

rockfish42's picture
rockfish42

Generally yeasts used in bread making are top fermenting, that is in a very liquid culture they will be sitting on top until they run out of sugars and then they will flocculate and fall to the bottom of the vessel. Unless your starter is at a ridiculous hyrdation level, you're probably just fine taking a sample from anywhere.

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."