Time For A Little Culture!

If there was any doubt at all that what I showed in my last post was a "culture" as opposed to a "starter", any and all doubt was removed the moment that I took the lid off the jar.  A sourdough starter has a slightly sweet and very pleasant smell that resembles beer.

What I encountered when I removed the lid of my jar was...  unpleasant.  We've all returned from a long trip, only to discover that we left some vegetables in the crisper drawer of the fridge, and in our absence they have turned into a foul smelling puddle of slime.  Ok, maybe you haven't.  But I certainly have.  The odor being emitted by my jar of flour and water most closely resembled the odor of rotting vegetables.  This is perhaps not a real surprise.  After all, I took mixed plant-based food with water, set it on my counter, and essentially allowed it to start rotting.  Now there is a battle being waged for the heart and soul of my future sourdough starter.

The evolution of a starter is complex, and proceeds through a number of stages.  From an observational perspective it goes something like this:

1. Flour and water get mixed
2. Eventually bubbles form, and the mixture starts to rise.  It smells foul.
3. You take a small amount of the noxious mixture (discarding the rest), and add it to yet more flour and water.
4. The whole thing appears to die.  A few small bubbles may form, but the mixture does not rise substantially.
5. You continue to dispose of most of the mixture each day, and add the remaining mixture to a 50/50 mix of flour and water (by weight only, please!)
6. Eventually the smell of the mixture changes to something resembling vinegar.
7. You continue to dispose of most of the mixture each day, and add the remaining mixture to a 50/50 mix of flour and water
8. Suddenly the odor changes from vinegar to beer, and the mixture begins to rise again.  This is the point at which your "culture" has turned into a "starter".

Underneath the observational perspective, there is a lot going on.  From the very beginning, a war is being fought between various bacteria, and yeast.  The early rising of the mixture (Stage 2 above) is primarily driven by bacteria.  In these early stages the bacterial activity is largely driven by lactobacillus, which is the same bacterium responsible for the fermentation and souring of yogurt. At the same time there is some yeast activity as well.

As the culture continues to mature, the digestion of the flour by the lactobaccilus decreases the pH of the mixture.  Lower pH means more acid content.  At some point the mix is acidic enough to be a hostile environment for most bacteria, and many strains of yeast.  At this point the acetobacteria (the bacteria responsible for vinegar) take hold, further reducing the pH of the culture.  This is Stage 6, above.  

Now we're getting close.  Our culture is now acidic enough that the range of bacteria and yeast that can thrive in it is very limited.  The battle is now down to lactobaccilus, acetobacter, and yeast.  Stage 8 is reached when a stable balance, between the 3, is reached.  When Stage 8 is reached, you are ready to make bread!

So, what does this process look like?  Let's go to the game film!  My last post took us through Stage 2, so we'll pick up our coverage at #3 above, in which we feed a fresh mix of flour and water to a sample of the noxious compound produced earlier.

We start by putting a small amount of "noxious mixture" into a mixing bowl.

Now we add some water.  As we're working toward a "starter", we need to start establishing a proper hydration level.  In my case I work with starter that is at 100% hydration, meaning that it is a mix of 50% water and 50% flour by weight.  So, with that in mind, we weight the water.  Here, 100 grams of water has been added.

 

Yeast, bacterial, and other living things love oxygen, so we give them a good head start in life by whisking the mixture to dissolve the paste into the flour.

Now comes the food.  We add the same amount of flour, by weight, as the water.  So, in this case, we add 100 grams of flour.

Now we mix it up, and dump it into the jar to grow!

Fast forward to the next day, and here's what we have.  The mixture is no longer noxious smelling, but it is not rising much anymore.  And it has taken on a vinegar odor.  We're well on the way to a starter!

Now the trick is to not get impatient.  This takes time!  Each day a small amount of the fermented culture must be added to a 50/50 mix of flour and water.  I'll be back in a few days when the whole thing reaches equilibrium and starts to rise!