Resurrecting sourdough

I have kept a sourdough starter in my fridge for at least five years or so. I knew very little when I started, but followed a range of web-based instructions for how to get started. I quickly tired of the twice-daily “feedings” of flour and water (not to mention the perceived wastefulness of discarding half of it each time). When I discovered the starter could be maintained in the refrigerator, with feedings spaced to as much as once a week, this seemed like a natural choice.

The feedings ended up coinciding with various bread-baking ventures, so I’d just add the half of the starter to my bread recipe whenever needed, and replenish the used flour and water. Since I used a 100% hydration starter (equal amounts of flour and water), the math was easy. As the refrigerated starter wasn’t particularly active (“unfed”, in sourdough terms), I used instant yeast in whatever amount was called for in the recipe, assuming the starter wouldn’t add much leavening power.From time to time, I’d try various experiments with using the starter as the main source of leavening, but it was so much weaker than the commercial yeast, it didn’t seem worth the effort.

With home sourdough mania spreading almost as fast as COVID-19, it seemed like the right time to give it another shot. After some re-reading, I realized that I had probably never been letting my starter become active enough to serve as the main sole source of yeast. I brought it back to room temperature and started the twice-daily feeding regimen again. Since we have started composting, the “discard” didn’t seem so offensive, and I’m spending a lot more time at home regardless. I had converted the starter to whole wheat (which I’m told favors rapid resurrection of the yeast), but started converting it back to white since I now have plenty of white flour and it’s reportedly more predictable once the yeast starts reactivating. Indeed, within a few days, the starter was visibly active, full of a bubbly texture that rose and collapsed between feedings. I tried the “float test” (adding a small amount of starter to a glass of water to see if it floats) and, whlie the results were mixed, I decided to charge ahead.

I added 100 g of starter to 350 g of bread flour, 8 g of salt, and about 2 g of diastatic malt powder (for some extra insurance), along with 230 g of water (for a 70% hydration dough). After some vigorous stirring and stretch-and-fold kneeding, I let it rest. It took about 2-3 hours to double (a bit longer than commercial yeast, but nothing egregious ). I shaped a batard and put it in a proofing basket. About an hour later, it was ready to go into my preheated covered baker. I baked covered at 500 ºF for 12 and a half minutes, 450 ºF for the same amount of time, then left it uncovered for the last 10 minutes to allow the crust to crisp a bit. The internal temperature was nearing 210 ºF at this point (a bit hotter than ideal), so I may cut it to 20 minutes of covered baking next time, but the results were much better than I had anticipated. The flavor was not particularly sour, but it had a depth and complexity that was just not possible with the instant-yeast equivalent.

I’m sold, at least for now. While commercial yeast can be more forgiving and predictable, I’m eager to try new experiments with this beast. In fact, my bagel recipe is currently, I hope, slowly leavening a batch of bagels in my refrigerator right now. The residual fear of a failed-rise led me to proof for 15 minutes prior to refrigerating and to extend the refrigeration time from 24 to 36 hours, but tomorrow will be the real test.

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