In the last 20 years bakers around the world have revived the art of baking with a sourdough culture. At first this revival was related to flavor, but increasingly bakers are turning to sourdough cultures in the interest of health. It’s possible that the unique qualities of sourdough cultures may offer hope to those who think they are gluten intolerant or have an allergy to wheat.
A very short history of bread yeast
Louis Pasteur figured out that yeast makes bread rise and ever since commercial baking has depended on a powerful strain of yeast, Saccharomyces cerevisiae, to make bread rise quickly. But even before Pasteur, bakers used the yeast remaining from beer making (also a strain of Saccharomyces cerevisiae) to make doughs rise. Sourdough cultures are not as powerful and predictable, so it’s understandable that commercial bakers would want a more dependable alternative.
What is in a sourdough culture?
There are many strains of yeast in sourdough cultures, but the main one is Candida milleri. Candida milleri is tolerant of highly acidic environments which distinguishes it from Saccharomyces cerevisiae. Another unusual characteristic of Candida milleri is that, unlike commercial baker’s yeasts, it doesn’t digest maltose.
These two characteristics allow Candida milleri to team up with Lactobacillus sanfranciscensis (which does like to digest maltose). Lactobacillus sanfranciscensis, a relative of the bacterium that ferments yogurt and sauerkraut, is the bacterium that gives sourdough bread its distinctive tang. In a sourdough culture Lactobacillus sanfranciscensis exists in far greater quantities than Candida milleri–100 to 1.
Is there a health benefit to sourdough?
The high quantity of lactic acids in sourdough breads increase the bioavailability of nutrients as well as digest the phytates that interfere with the absorption of those nutrients. Sourdough breads have a lower glycemic index and the culture may also digest the infamous glutens that people seem to be having trouble with. According to research conducted in Ireland,
Sourdough fermentation can modify healthiness of cereals in a number of ways: it can improve texture and palatability of whole grain, fibre-rich or gluten-free products, stabilise or increase levels of various bioactive compounds, retard starch bioavailability (low glyceamic index products) and improve mineral bioavailability.
It’s not that commercial yeast (Saccharomyces cerevisiae) is bad. Studies have show that Saccharomyces cerevisiae has health benefits. However, bread made with Saccharomyces cerevisiae is not going to have the additional health assets of Lactobacillus sanfranciscensis.
Sourdough is a confusing word. “Wild yeast culture” or the French “levain” are better terms. Sourdough has come to be associated with San Francisco sourdough breads which, if you buy them in the supermarket, are probably made with commercial yeast flavored with acetic acid. In other words the big commercial bakeries cheat and you’re not getting the health benefits of a bread fermented with an authentic culture. You’re just getting quick fermented white bread flavored to simulate a real sourdough culture.
To add to the confusion, it’s a myth that there is something unique about the bakeries of San Francisco. Lactobacillus sanfranciscensis has been isolated in sourdough cultures around the world. It’s simply the handling (long fermentation times or those tricky additives) that give San Francisco sourdough that tangier flavor.
To get breads made with a real fermented culture you’re going to have to seek out a good bakery (rare) or make it yourself. Choosing the DIY option will save you a lot of money and is not that difficult once you get the hang of it.
The new/old horizon of baking with sourdough cultures
There are other factors at work, of course. I had a meeting recently with Glen Roberts who runs Anson Mills. He described what he believes to be the ideal loaf of bread. It’s made with heirloom grain grown by small farmers with healthy soil, freshly milled and placed straight into the fermentation process. Very few bakeries are milling their own flour and baking 100% whole wheat breads. But you can do this at home if you own a small mill (something on my Christmas wish list). None of the breads I make involve any kneading, so the time investment is minimal.
I think fermented breads and home milling offer hope to people who mistakenly believe they are gluten intolerant. And as Anson also pointed out, nobody has studied the effects of the exotic ingredients in gluten-free products.
In the coming year I hope to post recipes for 100% whole wheat fermented breads. Stay tuned . . .