Sourdough refers to the natural leavening process that has been used to bake bread throughout much of history, before the invention of commercial yeast. Instead of adding commercial yeast, sourdough bread is leavened with a natural sourdough “starter.”
A sourdough starter is a mixture of flour and water that is used to leaven bread. The air around us and the flour we use is full of wild yeast and natural bacteria. Left alone, this mixture of flour and water becomes a host for these microorganisms. Soon, a symbiotic relationship develops between the yeast and the bacteria. Yeast can only feed on a single kind of sugar. The bacteria can feed on several different kinds. The bacteria digest these complex starches into the kind of sugar that the yeast can eat. The yeast, in turn, consume this sugar and produce carbon dioxide. It’s this carbon dioxide that is used to leaven bread. That’s why this mixture of flour and water is called a starter. It is where the sourdough bread baking process starts. Like any food supply, the sugars the bacteria in our sourdough starter need to survive is limited. Which is why the starter must be “fed” daily. Feeding is a process where a portion of the old starter is mixed with new flour and water and again left to thrive. This process can continue forever.
Making your own sourdough starter is very simple and requires only flour and water. Here is a great video that shows you how easy it really is.
Regular bread is leavened when yeast consumes the sugar in flour and produces carbon dioxide. Sourdough bread is different from regular bread because of the bacterial fermentation process that happens alongside the normal yeast leavening process. First, the probiotic bacteria feed on the natural starches in wheat that yeast cannot, reducing the number of carbohydrates your body must digest. The probiotic bacteria in the sourdough starter also create an acidic environment which activates enzymes that make the minerals and vitamins naturally available in wheat more accessible to our bodies. The acidic environment also breaks down the gluten in dough.
There are three main benefits to choosing sourdough bread over regular bread.
Sourdough bread has a lower glycemic index than regular bread: Flour contains many kinds of carbohydrates. However, the strand of yeast available in stores can only digest one kind of carbohydrate. Therefore, there are a lot of residual sugars remaining in conventional bread. With sourdough fermentation, the probiotic bacteria are able to feed on the many types of sugars found in flour and convert them into the simple sugars that yeast can digest. As a result, there is a lower proportion of residual carbohydrate in sourdough bread.
Sourdough bread has a lower gluten content than regular bread: Gluten is a protein formed when water is added to flour. The probiotic bacteria in a sourdough culture are more commonly known as lactic acid producing bacteria (LAB). When this acid combines with proteins it is converted into amino acids that your body can easily digest.
- Sourdough bread has a lower concentration of the naturally occurring anti-nutrients found in wheat: An example of an anti-nutrient is phytic acid. Phytic acid is naturally present in nuts, seeds, legumes, and grain. It helps these plants naturally store minerals such as phosphorus, zinc, iron, magnesium, and calcium for when they’re needed. The problem is that humans do not have the enzymes necessary to digest phytic acid and the acid ends up binding with these same minerals, preventing them from being absorbed.