A Symbiotic Culture: Sourdough 101

“All things are difficult before they are easy.” -Saadi Shirazi

Sourdough. What is it? It’s a bread that has recently become a buzzword, a search term on Google. Over 47 million web results pop up with just the simple word sourdough. It is a very simple bread loaf to make. All it needs to start is flour and water. Yup, go back and read it if you like, but you are not mistaken. Just two ingredients are needed to start a sourdough. All the rest of the ingredients are found in the air we breathe. Yeast and bacteria, specifically lactic acid bacteria feed off of each other creating a carbon and flavor-filled sourdough starter. Once you have a starter then you can make a loaf with some more flour, water, salt, a little bit of sugar, and a little bit of that starter and you’ve got a loaf of bread.


The list of ingredients may be short, but the culture of microbes that live inside the sourdough is quite complex. Knowing and understanding how sourdough works can lead to a greater understanding of all kinds of bread, digestive health, and culture.

Sourdough Starter- white flour


Let’s start at the beginning. Sourdough is a process of fermenting yeast and bacteria naturally. This process has been occurring for thousands of years and is one of the oldest leavening bread in human history. Ancient Egyptians were recorded using sourdough to create a leavened bread. The word sourdough is a verb and a noun, being used to describe the process of fermenting, and when talking about the bread itself. The fermenting process is interesting because it means that we are creating and sustaining a culture of microbes that are alive.





That’s right, look at any sourdough starter and know that there are living, breathing, hungry and feeding organisms in that thing. It is truly beautiful and can be as cute as a pet. Many people name their starters and have more than one, and will document when they started their sourdough. A starter can be kept alive with diligent feeding every week for years and years to be passed down to generations. But of course like it is in life, some microbe cultures can’t sustain themselves, with either not the right water or the wheat from the flour is no good and it will die. Also not having a starter at the right temperature, too much water, or too much flour could ultimately be a sourdoughs doom.


This makes the fermenting process a bit tricky but, as I’ve mentioned, it is relatively simple for us. Just mix water and flour in a jar, and let it set in the fridge. There is a two-week process of feeding the starter with more flour and water every day. But once the microbe culture has settled in, built homes and started their families, then it only needs to be fed once a week if kept in the fridge. The health of a sourdough starter depends on the type of flour and water used. Distilled water is the best because it has been rid of any impurities that water from a tap will have. The type of flour depends on what kind of sourdough you are looking for but in general wheat flour is the most popular.


But here is where we can start singing the “Circle of Life” because wherever in the world your wheat is milled into flour will determine the health, flavor, structure, and really everything of your sourdough. This is because the microbes that are found in the soil that the wheat is grown in, are found in the flour that is feeding and creating microbes in a starter. Boom! Full cycle, from earth to grain, to flour, to dough, to bread. And, get this, we humans have microbes in our gut, that will feed off of the other microbes that we put into our bodies. Basically, life is a never-ending cycle of microbes going from one place to another, they are everywhere.


Microbes may be everywhere but they are not all created equal, which is one of the reasons why sourdoughs differ so much in look and taste around the world. In the U.K. flour grains carry more natural microbes than in the U.S. making a sourdough more active in England vs Oklahoma. The other contributor to differences in taste is the type of yeast and bacteria that live in an environment. If you live in Wichita, Texas, and are trying to make a San Francisco sourdough loaf, then you are just going to be disappointed. For whatever reason San Francisco has an abundance of yeast floating around, making it a great place to get down and make some sourdough.



I keep floating around the words yeast and bacteria, but what actually are these microbes that get together, get freaky, and make a starter that will leaven any bread, all nat-ur-al. First, there is yeast, which is a type of bacteria that you’ve properly seen before because scientists found a way to get this previously invisible bacteria into a substance that is now sold in brown glass jars, thanks science! But yeast has been floating around in the air forever, and there is, in fact, many types of yeats. Yeast and enzymes feed on sugar and work together with lactic acid bacterias or LABs. And to see these bacterias and yeast working together in fermentation is a beautiful sight.


The LAB will produce different types of acid that break down starches in the flour into simple sugars. This process creates CO2, which raises the dough, and creates ethanol which gives the dough flavor. All of this breaking down is good for digestive health. Because phytase enzymes break down phytic acid this helps unlock nutrients that are good for digestion. Basically a microbe culture in sourdough is the breakdown and feeding of other microbes, over and over again.


First the LAB’s break down the flour from polysaccharides into simple sugars such as glucose. Then microbes such as yeast and other bacterias will eat the glucose, creating more LAB and acetic acids like phytic acid which then go on their way to continue to break down more flour. It is a perfect symbiotic relationship that is shared between the yeast and bacterias.


In this basic chart is the cycle of a sourdough starter culture:



Typically in every sourdough, there is a dominant yeast, and hundreds of bacteria circle it, call the yeast the supreme ruler, and dance around it singing kumbaya. But all the microbes must work together to create the fermentation process that gives us leavened bread. It is amazing to watch a starter grow and experiment with taste. The older a starter is the more of a tang that it will have. Soon taking care and nurturing a sourdough is just like any other pet. It becomes easy to feed them on a routine and they start to sustain themselves. I mean a dog likes to be talked to and pet, which you can do with a starter, but, yeah that’s really not necessary… But it is alive! All those microscopic microbes are working really hard to bring us the joy of bread. And it should be celebrated.




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