In the early days of sourdough baking, it was common practice to save a piece of fermented dough from the baking day to add to the next batch of dough. This would allow bakers to prepare their recipes right away, without waiting for a new mixture to ferment each day. Building on this idea, the practice eventually evolved into what we call a sourdough starter.
This starter is often called the mother starter, and is a simple mixture of flour and water that perpetually hosts the yeast and lactobacilli culture. When the yeasts and lactobacilli have consumed all the available sugars in the mixture, which happens in a matter of hours at room-temperature, the sourdough culture is kept alive by constantly feeding it fresh water and flour.
Lifecycle of a sourdough starter
After being fed, a starter will go through several different phases – freshly fed, rising, peaking, and falling. Immediately after being fed, it appears as if nothing is happening. On a microscopic level, however, the yeasts and lactobacilli are seeking out the fresh sugars (in the flour) and getting excited.
Soon they will start digesting and breaking down the sugars, and secreting carbon dioxide and lactic acid. The carbon dioxide creates air pockets in the starter (or dough), causing it to rise. If you tasted the starter at this point, it would be only mildly sour.
After a number of hours, the starter will have risen to its peak. It often stays at this peak for some time, until all the sugars have been digested.
When all the sugars have been digested and the structure of the flour has weakened due to lactic acid degradation, it will fall back to its original level. The starter is now fully mature, and would taste quite strongly sour. Time to feed again!
If not fed soon (at room temperature), it would develop a layer of dark liquid called hootch, and begin degrading in quality. Eventually, the culture would die of starvation. Sourdough starters are very resilient, however, and they can almost always be brought back from the brink of death with a few good feedings. Left in the refrigerator, hootch-covered starters can be revived months later.
With proper feeding and care, a sourdough starter can live on indefinitely. Tales abound of 100-year-old starters, passed down through the generations, only getting better with time. Traditionally, only a small amount of starter (1/2 cup to several cups worth) is kept on-hand. Today, sourdough bread is usually made by adding some amount of sourdough starter to the dough as it is being prepared.
Baking with a sourdough starter
There are many ways to bake with a sourdough starter, and each variation can create a vastly different and uniquely flavored loaf. Some recipes call for adding a large amount of starter to the dough, 30-50% of the total loaf weight, while some call for a very small amount, 1%-5%, which requires the dough rise over a longer period of time. As a rule of thumb, the longer the fermentation (rising) time, the more the lactobacilli will develop and more sour the bread will taste.
Grow your own
Making your own sourdough starter can be as simple or complex as you’d like it to be.
At its most simple, you can mix flour and water in a glass jar (with a loose lid), and put it in a warm place for a few hours. Then, take away half of the mixture, add more flour and water, and repeat. Depending on the ambient temperature, fermentation will begin in a matter of hours or days.
The wild yeasts and lactobacilli bacteria that make up a sourdough culture are already present on the grains, your hands and in the local kitchen environment – all you are doing is creating the optimal environment for them to wake up and thrive.
While this is the most basic way to begin a starter, we recommend taking a little more control over the process. Being somewhat consistent with your starter will yield much better results – your starter will be happier, and your bread will be better all around.
The next section will guide you through the process, step-by-step, beginning with some helpful information to get you started.