The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Fermentation ??

AZ Chuck's picture
AZ Chuck

Fermentation ??

What is the bad thing about over fermentation? I  know it will fall but as soon as I move it , it is going to fall anyway. Then it comes back to life when I proof it.

That bring up another question. If I stir down the starter before it falls, will it rise up again? Can I keep it active this way with out feeding it?

I have a lot to learn, but that is the fun of it all.  



golgi70's picture

Bad thing.  To the max degree your dough will run out of food become exhausted and all the life created will start to die ending in a bad loaf of bread.  To more moderate degree it can bring off flavors, damage the structure of the bread making a very even crumb, and decrease the overall volume of the loaf.  

As for stirring your starter.  If it hasn't peaked there will still be food left and it will rise again.  But if you just kept doing this and didn't feed your starter it will eventually run out of food and not rise again.  The word feed is used because the culture needs "food/flour" to survive.  It needs to liquid to facilitate its feeding.   With a complete lack of water it would become dormant just needing some water to wake it back up.  Without food it will certainly die.  


dmsnyder's picture

It sounds like you are asking specifically about fermentation of your starter, not about your final dough.

Fermentation is the chemical reaction that occurs when yeast consumes sugar (coming from the breakdown of starch by amylase enzymes). Think of sugar as "food for yeast." This energy goes into the yeast's basal metabolism and its reproduction - making more yeast. The byproducts of fermentation are primarily alcohol (which evaporates) and carbon dioxide (which accounts for the bubbles in your starter and it's expansion).

Fermentation of sugar by yeast is just one of the chemical reactions going on in your starter after it is fed. Others include gluten formation and, over time, breakdown, and the production of other chemicals by yeast and bacterial metabolism that impact flavor, gluten strength and other physical properties. 

Keeping it simple, over-fermentation means that the sugars available for the yeast and bacteria to maintain vigor and reproduce are exhausted. In addition, the acidity has increased to the point it interferes with metabolism and the gluten has broken down due to protease activity.

Over-fermented starter has decreased ability to get right to work raising your dough once it is added to additional flour, water, etc. In addition, the chemicals present in exhausted sourdough starter may introduce undesirable flavors.

In fact, as you gain experience, you can use the "age" of your fed starter as well as it's hydration and fermentation temperature to control the flavor profile of your bread.

Hope this helps.


lepainSamidien's picture

One cannot take as granted that the bread will always rise again after the bulk fermentation; in fact, over-fermentation for a dough means that the dough will not rise again (no Easter for that dough), because all of the food on which the yeasties and bacteria were snacking has been used up, so they just kinda "pass out" until you feed them again (which you probably won't do during a final proof). It's like college kids at a party: they consume and consume and consume, burping out CO2 and booze, and the party will go on . . . so long as there is still booze for them to consume. When the keg is tapped, the kids are all overfermented and end up passing out. Shake them or stir them as you will, they ain't gonna party like before until you feed them some more !

AZ Chuck's picture
AZ Chuck

Thanks guys

It all makes good sense but dough seems to have a mind of its own.

I just made a batch of dough for a sandwich bread in a bread pan. I forgot to feed my starter and it has been siting out for 3 days. It looked all dead and lifeless. What the heck, I through a ¼ cup in my 6 oz of water with 1/8 tsp salt. Added maybe 2 1/2 cup flour until I could handle the dough. Put it is a greased bowl 2 hours later not much happened. 4 hour, raised 1/3, 5 ½ hours and it tried to get out of the bowl. It must have raised 300%. I put it in the bread pan and ½ hour it doubled and it is still going. I going to bake it before it get mean. It is 100 deg in my house. Good old AZ.

David, I was talking about the dough.