Sorry germophobes, but naturally occurring yeast and bacteria are all around you all the time. Just try not to think about it. Thousands of years ago, in the ages way before what I refer to as “industrialized yeast” this was all there was for making bread. Sourdough starter has yeast and other things living in it just waiting to make delicious bread. That means sourdough is effectively just the stuff that makes bread rise.
Today, going to the grocery store is all it takes to get a packet or jar of single strain instant yeast. This yeast works amazingly well and is very consistent. It also adds nearly no flavor to the bread. That does not make it bad, and in fact for some things that’s probably better, but in the case of sourdough, we have ulterior motives. We want our bread to rise and we want it to have that delightful tanginess that sourdough has.
At it’s most fundamental, sourdough is just flour and water with some yeast and bacteria living in it. There is a bit of an equilibrium at work here.
- Water is a nice place to live for little creatures.
- Flour gives the bacteria something to eat.
- Bacteria produces sugars that yeast likes to eat.
- Bacteria also produces lactic acid that makes it sour.
- Yeast farts make bread rise.
As this cycle continues, flour is consumed for food. That means you need to keep feeding it to keep it happy. After each time you feed it, you have to give it time for the bacteria and yeast to spread out through the new food. Without new flour from time to time the whole ecosystem would fall apart by simply starving to death or it could die in an acid bath thanks to lactic acid or of alcohol poisoning from the yeast. Fear not though, while it may sound like your starter is just constantly trying to come up with creative ways to fail, it’s really not. A bit of fresh food and water every now and then and it’ll be happy.
It’s also important to point out that adding sourdough starter to a recipe doesn’t automatically make it sourdough flavored. Just like in your starter jar, you have to give the sourdough creatures time to do their thing. When you make something with your starter you have to let the colony of sourdough bits expand through all the new food you just gave them in the form of the flour and water in the dough. It’s pretty normal for sourdough to be delicious but not especially sour and that doesn’t mean you’ve done anything wrong.
A cool side effect of having all of this stuff living in your sourdough starter is that the little creatures you actually want there build up a sort of army. When other things arrive that can ruin your sourdough starter, the army mobilizes and takes out the invaders. That tends to make your starter pretty stable and also pretty safe from scary things, but it is not a guarantee. If your starter starts to grow mold or have scary sorts of smells then it may be beyond saving and should be thrown away. Note, that sourdough itself has a fairly wide variety of possible smells that are all more or less totally normal, so you should mostly be on the lookout for things that your built in instinctual response says is bad.
Finally, I would like to state that I always maintain my starter as 100% hydrated. This makes it a consistent amount of moisture for recipes and also makes it very easy to do the math on everything. For example, if you feed it 50g of flour, give it 50g of water too.
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