I like sourdough. I make it often and I am generally content with my results. This time, I wanted to go for something a little more... assertive. I wanted my sourdough to be SOUR.

The amazing thing about sourdough is that its flavor profile is so deep and it has the fewest ingredients of any bread: flour, water, salt. The yeast is wild and, with the exception of a little pineapple juice that I needed to start the culture, the yeast is comprised entirely of flour and water (and the microorganisms living in the culture). Even more interesting are the many variables that come into play when determining the sourness of a loaf: the incorporation of whole wheat or rye flour in both the starter and the final dough; the ratio of starter or barm to dough; the hydration of the starter; the temperature of fermentation for the starter and the dough; whether the loaves are retarded while proofing; the length of the bulk fermentation...

Here is the problem in a nutshell: I need yeast to leaven the bread. Yeast like warm environments and, I believe, prefer wet environments (equal parts flour and water). I also need acetic bacteria. Acetic bacteria make the loaf sour. Acetic bacteria like cool, dense environments (think 2 parts flour to 1 part water). Many sourdough recipes call for the creation of a barm. The barm takes a 100% hydration starter (equal parts flour and water) and decreases its hydration. The barm then ferments in a cool environment overnight and, presumably, adds some acetic bacteria to the recipe. The yeast go dormant in cold environments, so presumably the barm allows a baker to keep a good amount of active yeast on hand while also helping the baker add some flavor depth.

My latest approach produced a complex flavor profile, but lacked the sourness I was after. I modeled my recipe on Norwich Sourdough from Susan's Wild Yeast Blog.

The recipe broke down as follows:

120g Rye
600g Bread
200g All Purpose
300g 100% hydration sourdough starter, ripe
200g 50% hydration sourdough starter, following an unfed, 24 hour cool ferment (my stiff starter had 10% rye as well)
560g Water, 76 degrees
23g Salt

Mix everything but salt, 30 minute autolyse
Machine mix for 3-4 minutes
Cool bulk ferment for 4-4.5 hours, with dough's internal temperature at 65, stretch and fold after the first and second hour
Shape into 5 400g batards, proof for 2.5 hours at room temperature
Score loaves (a battle unto itself)
Steam at 475 for 5 minutes, drop heat to 450. Total steam baking time=12 minutes.
Rotate loaves, continue baking for 20 minutes.
Cool for at least an hour, preferably several hours.

What I would do differently next time: retard the loaves. There is no way around this step. Also, I would proof at a lower temperature. I had to proof at room temperature because it was getting late. A really sour sourdough is clearly an all day process, and you don't even get the loaves the same day! Oh well. Next weekend I will give it another go.