Those of you who have embarked on the strange quest to cultivate your own sourdough can empathize. You mix your first starter with freshly milled whole grain flour and uncholorinated water, leave the container swaddled in a warm place, and are rewarded mere hours later with a vigorously bubbling boi. Huzzah! The fermentation gods, pleased with your tribute, smile. You offer up more flour and water. But the gods are fickle, (even to our friends at phickle) and activity stalls. You wait, but nothing-- until slowly but surely, spores of red white and blue mold make a fuzzy patriotic stand. What the hell happened, and why do you suck at this?
You’re not alone; even the professionals suck at it. A little back story: right after our lovely panettone-filled 2017 holiday season, we began maintaining our starters with whole grain flour milled fresh on our brand new stone mill. Activity soared, and in order to keep our mothers from maturing too fast, we reduced the proportion of old starter (seed amount) used in every sourdough feeding. After consulting with a venerable baker friend, we dropped our seed down to less than 1% (e.g. 1 gram old starter for every 100 grams fresh flour). To our utter surprise, fermentation activity never really slowed. Our bread kept rising, though not exactly as expected. Now, a year and many failed panettone later, we think we know why, and it is the same reason your first starter faked you out: Leuconostoc bacteria.
Our freshly milled flour teems with life, so we were now delivering a broad-spectrum dose of microbes with every starter refreshment. The typical first phase when beginning a new starter involves vigorous growth of Leuconostoc mesenteroides, which generate acid and gas. These are the guys that get your hopes up before your new starter goes dormant. As they grow, the build-up of acid actually renders the environment inhospitable to Leuconostoc themselves, and eventually primes it for a mix of acid-loving bacteria (ex. L. sanfranciscensis) and yeasts (ex. C. humilis & S. cerevisiae) that are important members of a healthy sourdough culture. By dropping our seed % so low, we were reducing the amount of acid transferred into the new starter with every feeding, creating a pH neutral environment without enough acid to hinder leuconostoc and encourage our other microbial friends. We were essentially replicating that first phase of creating a new starter with every feeding, rather than propagating a mature and healthy sourdough starter.
If we were culturing the wrong microbes, why did our panettone fail but the rest of our bread rise just fine? Well, it turns out that members of the Leuconostoc genus are happy cohabitants on flora the world over. L. mesenteroides, a particularly robust species, is an early fermenter in a diverse set of traditional foods, including sauerkraut, sourdough, idli, and dosa. In the latter two, which are delicious Indian treats somewhat related to bread, L. mesenteroides is actually the primary leavener. Not only can it produce carbon dioxide gas needed for leavening in baked goods, it can also secrete exopolysaccharides, sticky substances that, when present in doughs or betters, add desirable structure, and can even stand in for gluten. It’s no surprise, then, that we were able to continue creating delicious bread with our new starter. Panettone, however, is a different story. Saturated with sugar, fat, salt, and acid, it is not a hospitable environment for microbes in general. You need a particularly vigorous culture to make panettone, hence the over-the-top arcane starter maintenance, and our Leuconostoc-rich but yeast-poor culture simply could not rise to the challenge.
How did we figure this out? Well, the launch of our grain share program means we have grain on the brain 24/7, rather than just most of the time. We are deep into the ethnographic, agricultural, and scientific research available on a broad spectrum of grains and grain-based products, and the findings are mind-boggling. In this case, our love of idli and dosa set us on a path to recreate them with local grains, which led to interesting findings about l. mesenteroides. Coupled with a review of the serious inquiries into sourdough cultures by microbiologist and home baker Debra Wink, we were able to corroborate our theories about our starters immediately when we switched to using primarily salt and temperature to modulate fermentation activity rather than primarily seed %.
Some interesting tidbits to chew on:
Bulletin 824: The Sauerkraut Fermentation, a rigorous review of the microbiological studies available at the time of publication (1969) on sauerkraut and other vegetable ferments.
Much of what we have read seems to suggest that l. mesenteroides could play a part in producing excellent gluten-free sourdough breads, between its vigorous gas production and its secretion of exopolysaccharides, structural components often added to gluten-free products in the form of xanthan gum. See this study on corn-based breads, for example.
This page is not a primary resource we consulted for information about dosa and idli fermentation. However, the crazies on that website are behind an origami, paper-based microscrope project. What the heck?? AMAZING!!!
There’s a lot more, but all this writing has us tired and grumpy. Ask Alex about this microbiological odyssey if you see him in person; he is always happy to find a victim for his pseudosciency ravings.