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Does a More Mature Levain Increase Sourness?

May 23, 2020

In my first attempt at a sourdough loaf, I made the levain from the starter the night before any of the other steps. I left it, covered with a cotton cloth, by a window and a fan--measured at around 65F--overnight. It didn't work out well: the levain was terribly bitter by the time I went to use it the next day. Maybe it would have been fine, but I was worried about wasting additional flour if I put it in a dough, so I ended up making a new one.

My second levain was a success: after a two-hour rise at room temperature, I mixed the levain into a freshly-made dough, and let it autolyse (or "fermentolyse", since the levain is included) for one hour, which wasn't enough of an autolyse for a 70% whole wheat/30% AP sourdough. I added salt and began the bulk fermentation from there. The final loaf had a nice sour note to it.

For the 50/50 Sourdough, I autolysed the dough alone overnight in the refrigerator, made a levain that rose over three hours, and then incorporated it into the dough, allowing a 1hr fermentolyse from there. I remember the levain tasting faintly sour, but less so than before.

On May 23rd, I followed the same procedure for another 50/50 sourdough, but let the levain rise over about five hours before incorporation into the dough. The levain had a noticeably stronger sourness, though the baked loaf had just a touch more sourness than before. One complicating factor is that I don't think I properly mixed the salt in this loaf, so it may be that more sourness would have come through with a more even salt distribution.

My guess is that the main venue for building sourness has to be either the bulk fermentation or the final rise, or both. In Tartine, Chad Robertson says that the bulk fermentation is an important part of building flavor and strength and, later, that a longer final rise will build more sourness. Sourdough already takes a whole day, so maybe I'll keep the time the same and wait for summer to turn up the heat ¯\_(ツ)_/¯