Sourdough

To bake sourdough is to make real bread truly from scratch.  It’s a near magical process to watch as a simply slurry of water and flour captures wild bacteria and yeast to produce a bubbly, living culture that’s robust enough to leaven bread.  True and authentic sourdough bread is near magical: deeply complex in flavor, fun to make and nutritious.  Even more, it’s an opportunity to connect and embrace the tradition of baking bread through the same process that’s been used since grain was first cultivated tens of thousands of years ago.

What is Sourdough?

Sourdough is any bread or pastry leavened by a mixed culture of wild bacteria and wild yeasts.  This mixture, also called a starter, levain or mother culture, is made by whisking flour and water together to form a slurry.  This slurry, when kept at room temperature and refreshed regularly over about a week, will foster the growth of lactic-acid producing bacteria and wild yeasts.

Working together, these microbiota help to not only flavor traditional bread, but leaven it, too.  Bakers typically use bacteria- and yeast-rich starters to leaven bread, but you can also use a them to leaven any yeasted dough including many pastries like cinnamon rolls, croissants, and some cakes.  It can be made with whole-grain flour, high-extraction flour and white flour.

The naturally occurring wild lactobacillus bacteria cultivated in a sourdough starter give the bread its characteristic sour or tart flavor,

History of Sourdough

Throughout all of human history and up until the late middle ages, bakers produced almost all leavened doughs with sourdough cultures. Those cultures were often carefully tended and then handed down from one generation to the next as an heirloom.

In the late middle ages, bakers began to use barm, or yeast used in the brewing of beer, to leaven bread.  Around 1780, Dutch brewers began selling brewers yeast skimmed from there barrels to local bakers and housekeepers who then used brewers yeast to leaven their breads.  Later, in the middle of the 19th century, fresh brewer’s yeast was refined, compressed and sold as cakes.  Baking bread with refined cakes of yeast quickly replaced baking with mixed cultures of wild yeast and bacteria, both at home and in commercial bakeries. Cakes of yeast eliminated the need to keep, refresh and maintain a starter culture, and also produced a sweeter, instead of sour loaf.

Later, food manufacturers further refined the process of yeast making, and produced dried, isolated varieties of yeast that could be sold in packets.  These packaged yeast varieties are the most common way to leaven wheat bread today, and most bread, both commercially produced and baked at home, is made using this modern method.

Owing to increased interest in fermentation coupled with artisan baking, interest in traditional sourdough baking is rapidly growing and seeing a strong resurgence.

What’s different about sourdough bread?

The biggest difference between traditional and artisan sourdough breads and the modern breads you find in the grocery store or might bake at home centers around its yeast.  Yeast makes bread rise.  And in traditional sourdough baking those yeasts are wild, and they come from the surrounding environment.

In modern bread baking, those yeasts are domesticated and typically come as dried granules in a packet you buy from a commercial yeast maker.  The yeast in sourdough bread often contains more than one variety while the yeast in modern breads only contains one variety – saccharomyces cerevisiae, which is also used in beer brewing.

In addition, sourdoughs have a complex sour flavor that can range from very light to very strong. This sour flavor comes from lactobacillus bacteria in the starter culture. These bacteria metabolize the complex carbohydrates in flour and produce lactic acid, which gives the bread a distinct tartness.

Commercial breads and modern breads risen with packaged yeast lack this characteristic, and have a sweeter and less complex flavor. They also  lack the rich and complex microbial diversity that gives true sourdough its flavor and many of its nutritional benefits as well.

What are the benefits of sourdough bread?

The clear benefit of sourdough bread is that it is delicious, with a richer flavor and more complexity than modern breads. It can be easily and affordably made at home, and it is a fun hobby to undertake: Making bread truly from scratch.

The bigger question you might ask is, “Is sourdough healthy?”

Traditional, slow-rise sourdough bread is generally a more nutrient-rich choice and easier on blood sugar regulation than modern bread.  Its benefits rest in the symbiotic action of the bacteria and yeast that comprise a sourdough starter culture.  The work of these microbes helps to make sourdough bread more nutritious with a lower glycemic load.

The mixed culture of wild bacteria and yeast that leaven sourdough bread make sourdough more nutritious.  During the period in which sourdough rises, the lactobacillus bacteria in the culture metabolize the naturally occurring carbohydrates in the flour and release lactic acid.  This lowers the overall glycemic load of the bread, while also improving its flavor and giving sourdough its characteristic sourness.

Further, the acidic nature of the dough helps to deactivate food phytate, a naturally-occurring substance in whole grains, pulses, nuts and seeds, that makes the minerals they contain difficult to absorb.  When food phytate is deactivated or mitigated through sourdough leavening, the minerals in the flour become more readily absorbed by your body.  So while sourdough baking doesn’t increase the minerals in bread, it certainly increases your bodies ability to take advantage of them.

• It is a better source of minerals than modern bread.  Sourdough sees an increase in the availability of magnesium, phosphorus (source), iron and zinc (source). As a result your body gets more absorbable minerals with every bite.
• It is lower on the glycemic index than modern bread. Because the carbohydrates in these traditional breads are pre-digested by the lactobacillus bacteria in the starter, who produce acid as a byproduct of fermentation, the glycemic load of these breads is typically lower than modern breads.
• It is rich in beta-glucan.  Beta-glucan is a complex carbohydrate and prebiotic that helps support optimal cholesterol levels (source), blood sugar regulation and cardiovascular health (source), and sourdough breads are richer in this nutrient than modern breads.

Is sourdough bread gluten-free?

Sourdough bread is not traditionally gluten-free because it is typically made with wheat or rye flour; however, it can be made gluten-free.  If a baker uses a gluten-free starter culture and exclusively gluten-free flours, any bread he or she bakes will be gluten-free.

Celiac disease is an autoimmune condition in which the consumption of gluten triggers inflammatory reactions in the small intestine.  Gluten is a protein that you find in many grains as well as foods made from them like bread and pasta.  Preliminary research suggests that the lengthy fermentation time required in making true, slow-rise sourdough bread may degrade the gluten in sourdough to the extent that it becomes safe and nontoxic for adults and children with celiac disease (source, source). While such research is promising, neither the researchers themselves nor celiac disease watchdog groups recommend sourdough bread for celiacs.  Further research and trials are necessary to determine if sourdoughs are truly safe for those with celiac disease.

Some people who may not have celiac disease still report being gluten-intolerant. For many of these people, the issue is not strictly the protein gluten, as it is with true celiacs; rather, they are sensitive to the complex carbohydrates found in grains such as fructans.

Fructans is a FODMAP, or one of many complex carbohydrates that can cause gastric distress among people with compromised gut microbiomes. The fermentable complex carbohydrates in grains are degraded during the long and slow leavening process of making sourdough bread.  As a result, people who are sensitive to FODMAPS or may consider themselves gluten-intolerant, but who do not have celiac disease, can often tolerate true sourdough bread, particularly when made from ancient grains like spelt or einkorn (source).

How do you make sourdough bread?

To make sourdough bread, you must first make a starter by whisking flour and water together until it become bubbly with the activity of wild yeast and bacteria. Once the starter doubles with each feeding, it is ready to bake bread.

After mixing a small portion of starter with flour, water and salt to form dough, you’ll need to allow that bread to rise and then you bake it on a baking stone, loaf pan, Dutch oven or in a cast-iron insert.

Wild yeast cultivated in starter cultures can be unpredictable, and so these traditional breads leavened often benefit from a longer rising period than do breads made with commercial yeast.

How do you know if sourdough is authentic?

Many commercially manufactured breads are sold as sourdough; however, they may not be authentic.  True, authentic sourdough bread should contain only flour, water, salt and levain or starter.

Commercial breads often achieve a sour flavor in their breads by adding vinegar or lactic acid to the dough, rather than through the use of a starter culture.  As these commercially manufactured breads lack a starter culture, they are leavened with commercial baking yeast.  While they may be sour in flavor, since that sourness is not achieved through the microbial action of a starter, these breads would lack any of the potential benefits found in true and authentic sourdough breads.

How long does sourdough last?

Sourdough bread lasts longer and is more resistant to mold than bread made with commercial yeast. The acids that make this bread sour act as a natural preservative, and help it to last longer and stay fresher for a longer period of time.  Homemade loaves will last about 1 week, properly stored.

The best way to store bread is in a bread box, a cotton bread bag or a paper bag.  This allows the bread to breathe, and it keeps it away from moisture that can make it taste stale. To refresh bread, place it under running water up to one minute, and then set it in an oven heated to about 300F.  Allow it to warm in the oven up to 10 minutes, and then serve.

You can also store it in the freezer up to six months.