The Fresh Loaf

News & Information for Amateur Bakers and Artisan Bread Enthusiasts

Fermentation. Does it need yeast?

Bread rat.'s picture
Bread rat.

Fermentation. Does it need yeast?

I've learned that the longer a sponge or biga is left to ferment the less yeast is needed. Right now I have both fermenting away to see difference each will make in bread tomorrow. Both using two cups of flour (11 oz ) and 1/4 teaspoon of yeast. They have both been active for over two hours now. Both have gone from that wet dough smell to a wonderful yeasty aroma. Tomorrow is going to be a good day. 

The question. Is yeast really necessary in the fermentation of dough? I know yeast breaks down the starches and consumes the resulting sugars. Is this process of exchange important to the fermentation? Would good fermentation occur without yeast? 

Here's what I'm getting at. Is this possible. 

First to make a batter using equal parts water and flour out of a bread recipe. Let this batter ferment. Then build the bread like you would in a direct method. 

Thought of a mad scientist. If the yeast and natural bacteria are competing for the sugars leaving out the yeast would result in a quicker flavor maturity time. Thus cutting the time ( estimate ) in half. A four hour time to two, eight to four and the like. 

Or if I do this am I on the way to making a fuzzy pet? Does the yeast act as a control for the natural bacteria? Much like salt does for yeast. 

This then opens yet another question. Would salt in this yeastless batter control the bacteria? 

Deeper thoughts on this from the mad scientist. I'm taking on the assumption that starts where originally done to either capture wild or stretch purchased yeast. Then yeast was traditionally added to starters as time passed. We now have yeast that doesn't need proofing. Can be added directly to flour. Making capturing wild or stretching out what little you would have obsolete. Is the idea of adding yeast to a sponge obsolete as well? 

Thanks everyone. 

And as a side note. I've made my first bread recipe calling for eggs. Turned out great! But as far as personal taste goes I like bread better without. Still learning. Still having fun! 

Lechem's picture
Lechem (not verified)

Isn't that sourdough? Isn't yeast + bacteria the cause of that fermentation too? If not done using a starter though then it'll be uncontrolled, take too long and it'll go mouldy or the dough will break down long before you get a bread out of it, fermentation through bad bacteria, the list goes on. 

When you out flour and water together things do happen. Starches get released. It is the beginning and an important part of fermentation but it's the yeast and bacteria feeding on these starches that is the process of fermentation. So yeast and bacteria are most important I would think. 

Colin2's picture
Colin2

Something has to actually do the fermentation i.e.eat sugars and give off CO2 to raise the dough.  (https://en.wikipedia.org/wiki/Fermentation)

Maybe there exist bacteria that can do that alone, but every bread recipe I know of uses yeast (a eukaryote) to handle that reaction, whether the yeast comes from a jar or you've captured and cultivated it yourself. 

Sourdoughs use an interacting combination of yeast and bacteria, but its still the yeast that puts out the CO2. In commercial-yeast doughs bacteria do not play, or at least are not supposed to play, a role.  

So with a commercially-yeasted dough, you are right that you can typically cut the initial yeast to a very tiny amount, like 1/8 of a teaspoon.  But what happens when you do that is that it takes longer for that tiny initial amount of yeast to reproduce until there is enough of it to raise the dough.  In other words you will still end up with the same amount of yeast in the dough when it's finally risen.  

If you start with just flour and water your'e basically trying to start a sourdough culture.  You can look up the directions for how to do that, but they all involve a lot more steps.

 

 

 

 

 

Bread rat.'s picture
Bread rat.

This isn't about the CO2 levels or the yeast's job of making the final dough rise. Nor is this about a sourdough starter. This is just the fermentation of the flour itself. What is, in the end, the flavor that is achieved by starting a dough with either a biga or sponge. The yeast would be added when the dough is built up according to the recipe. 

So I'm questioning the purpose of the yeast when used in a biga, poolish, sponge and the like. A process who's only purpose is to add flavor by fermentation. Modern yeast is dependable. It doesn't need to be proofed. So my question is, If the yeast is left out of the poolish or biga would this speed up or harm the end product. What actions does yeast do in a starter that effect it's overall flavor. Is there a symbiosis between the yeast and common bacteria? Or do they compete against each other. One keeping the other in check. 

I'll try to explain the process better. Have a standard bread recipe you want to start with a poolish. Take a portion of the flour and water and make a paste. Let this paste ferment like you would a poolish. Once matured add the remaining liquids, and the yeast to this paste. Then your enhancers , fat, sugar, eggs, whatever the recipe calls for. Then your salt. Finally the rest of the flour to make the dough. Kneed and rise as what's called for in the recipe. 

The yeast would be added when the dough is put together. There should be plenty of starches in the remaining flour to keep the yeast fed. You could even use less yeast to insure a slow rise. Possibly giving more flavor to the bread. 

Thanks for the responses! Sorry I was a bit confusing in my opening post. 

Colin2's picture
Colin2

As noted below you can do an autolyse of just flour and water.  You can find discussions of long autolyses on this forum.

Sorry for the pedantry, but by "fermentation" chemists generally means a process of turning a carbohydrate into alcohol plus CO2.


{\displaystyle {\ce {C6H12O6->{2}C2H5OH{+}{2}CO2}}}

And this is how the word is generally used in bread-making.  I think you are using "fermentation" to mean something different.

In any case, if you are not doing sourdough, you normally don't want bacteria playing any role at all (you will get cheesy, funky, off-flavors).  Autolyse is not a bacterial process, but an enzymatic one.  (I think this applies to soakers as well, but I don't know for sure.)

The basic reason for using yeast in pre-ferments is that the yeast does useful work.  It's also common to add some more yeast when you make the final dough out or the pre-ferment.  

There'd be no harm trying out prolonged autolyse versus pre-ferment!  Take a recipe with a pre-ferment plus extra yeast when the full dough is made up, and try just autolysing instead of prefermenting.

 

 

tgrayson's picture
tgrayson

Yes, you can create what's essentially a soaker without yeast and it will develop flavor. Reinhart calls for this in his whole wheat book. But he also calls for a biga, so I presume that the flavor profiles are different.

Lechem's picture
Lechem (not verified)

Where the flour has a chance to soak up the water and release the starches ready for the yeast to feed off it? 

The reason why dropping the amount of yeast and increasing the fermentation time is better than putting in a lot of yeast to quicken the fermentation time is because there is more going on inside the dough than just yeast multiplying. It's been asked on this forum before as to why it will taste better and have a better crumb if in the end both doughs have been saturated with yeast fermenting the flour. 

The problem with doing a poolish with no yeast is that you might get unwanted fermentation from bugs you don't wish in the bread. Doing a poolish stretches out the fermentation time but is still controlled and not spontaneous.

Long autolyses are done at low temperatures as to slow down "fermentation" until the yeast is added and if too long the flour begins to degrade. But it is the yeast (and bacteria) which ferments the dough be them wild or bakers yeast. 

tgrayson's picture
tgrayson

No, it's not an autolyse. An autolyse is short--20 minutes or so. This--soaker--does its work overnight or over the course of a few days and only contains a portion of the flour.

 

 

Bread rat.'s picture
Bread rat.

This is what I wanted to know! Yes I guess I was using the term fermentation wrong. Letting it rot on your counter would have been closer to what I was getting at. Complete newbe here and it shows. 

Because it's impossible to keep natural occurring bacteria out I thought this played a roll in the flavor of a poolish. Thank you. Now I know yeast both plays a part in keeping bacteria in check and is the main provider of the overall flavor and effect of the poolish. 

I've read something about a soaker. Using moisture and time to soften grains to be used in bread. Please correct me if I'm wrong. 

Thank you everyone for taking the time to help me. I'm not trying to reinvent the wheel. Just trying to learn how it all works. 

Now I have something new to discover. Autolysis. That should take place in a different thread. You can bet I'll come up with something off the wall. Always do. Always thinking.