Sourdough 101: How To Make (And Maintain) the Perfect Sourdough Starter

While sourdough bread may have exploded in popularity during the early days of the pandemic (IYKYK), it’s actually one of the oldest breads in the world, dating back some 5,000 years. In fact, before commercial yeast became widely available in the 19^th century, sourdough was one of the *only* types of leavened bread.   

While creating a loaf of sourdough from start to finish can seem intimidating at first, the process is very similar to baking a regular loaf of bread, but with one key difference: The starter. Rather than using a packet of instant yeast from the grocery store, sourdough relies on the power of wild yeast (which is yeast that’s literally in the air), in the form of a sourdough starter, in order to rise. 

So, what *is* a sourdough starter?

In short, a sourdough starter is a living colony of bacteria and wild yeast. It’s made from just two ingredients—flour and water—that are mixed together to form a loose, gloopy paste. (Delicious.) With the proper care, the mixture goes through a process of fermentation that results in both gas (which helps bread to rise) and acids (which lend flavor).

A sourdough starter needs regular “feedings” of fresh flour and water in order to encourage the right kind of bacteria to grow and keep out any dangerous pathogens that can cause spoilage or foodborne illness. If cared for correctly, a sourdough starter can last indefinitely—an Italian baker has even claimed to use one that was created in 1848.

How does sourdough starter actually work?

When a starter is fed, the yeast and bacteria eat the sugars present in the flour. As the yeasts eat, they produce carbon dioxide gas, which helps the bread to rise.

The bacteria in a sourdough starter can mostly be categorized as acid producing bacteria. When these bacteria are fed, they produce lactic and acetic acids, which prevent spoilage and contribute to the hallmark sour flavor that sourdough is known for.

Getting started with your starter

The fastest way to begin baking sourdough bread is to get some starter from a friend or your local bakery (just ask—a bakery is often happy to sell, or even give you, a bit of their sourdough starter). You can even buy sourdough starter online! But if you love the idea of creating your own life (okay fine, living culture), making your own starter is easy. Just know it takes about a week of regular care before it’s ready to use.  

1. 1.
   To begin, you’ll stir together flour and water in a clean jar until it forms a loose paste. Cover the jar, place it somewhere warm and toasty, and leave it to sit for 24 hours.
2. 2.
   The next day, you’ll add a small portion of this paste to a new, clean jar and throw the rest away. To the clean jar, you’ll also add fresh flour and water, then mix it all together and leave it to sit for another 24 hours. This is called a feeding and the portion of the starter that you threw away is called discard.
3. 3.
   You’ll repeat this process for up to seven days, eventually switching to two feedings per day. Over the course of the week, you’ll begin to notice gas bubbles forming in the starter, and soon, these gas bubbles will cause the starter to grow and expand. You’ll know your starter is ready to use when it is consistently doubling in size between feedings.

Most recipes for creating your own sourdough starter are very similar but may vary in the exact amounts and ratios that they use. Find a good recipe (like this one from King Arthur Baking Company) and follow it closely for the best results.

Feeding your starter

“Feeding the starter introduces a fresh influx of nutrients to the microbial community, promoting growth and preventing any invasive microbes from establishing—like the microbes that turn your starter pink or black if you leave it unfed for too long,” says Erin McKenney, assistant professor of Applied Ecology at North Carolina State University. In other words, feeding your starter is crucial to maintaining an environment that yeast and good bacteria are able to thrive in.

Every time you feed your starter, it will bubble and grow as the yeast eats the nutrients in the new flour and then produces gas. At this point, your starter is considered “ripe” and ready to bake with.  

A sourdough starter can be stored on the counter or in the refrigerator. The warmer the environment, the more frequently you’ll need to feed it. A starter stored at room temperature should be fed twice a day, whereas one stored in the fridge can be fed just once a week. 

Martin Philip, Baking Ambassador for the King Arthur Baking Company and a co-author of their new book, The Big Book of Bread, stresses that a starter will perform best when stored at room temperature. He recommends taking your starter out of the refrigerator a day or so before you plan to bake bread to make sure it’s fully active. “As long as cold periods are followed by a “wake-up” period,” he says, “you can still make great bread.”

I hate waste! Do I have to throw my discard away?

If you were to feed your starter every day and never throw any of it out, it would become truly gigantic—quickly outgrowing your jars, and even your biggest mixing bowls.

Now you don’t have to actually throw your discard away—there are tons of ways to use it. A quick Google search for “sourdough discard recipes” will yield hundreds of results including recipes for pancakes, scones, cookies, and more. Sourdough discard won’t necessarily contribute any rising power to these recipes, but it will add a tangy, complex, fermented flavor.  

Oops! I forgot to feed my starter. Now what?

“Missing a feed or two will not be a problem,” says Philip, but notes that “more prolonged neglect can lead to unhealthy conditions and bread which doesn’t rise as well.”

A healthy starter should smell yeasty, perhaps with a hint of sourness or fruitiness. A starter that misses a few feeds may begin to smell strongly of vinegar, acetone, or alcohol. You might also notice a grey or black liquid pooling on the surface—this is called hooch, and is a mixture of water, alcohol, and other volatile compounds. These are indicators that your starter is underfed, but not necessarily beyond saving. A few days of regular feedings should soon have your starter back in business.

How will I know my starter has gone bad?

Sourdough starters are resilient, but not indestructible. If you fail to feed your starter for a longer period of time, it may develop mold or an unpleasant smell.

“Turning pink, black, grey, and/or fuzzy indicates that an "undesirable" (potentially harmful) microbe has invaded and proliferated,” says McKenney.

If you notice any signs of mold or pungent, unpleasant smells (fishy, garbage-like, or any other nasty aromas that cause you to recoil), it’s time to throw your starter out and begin again. Don’t be tempted to bake one last loaf—McKenney notes that toxins produced by food spoilage may be able to survive the baking process and potentially make you sick—so when in doubt, throw it out.

Baking bread with your starter

Okay, now that you’ve nailed the care and keeping of your starter, you’re ready to bake some bread (here’s a great recipe to start with). You’ll begin by mixing a dough and then leaving it to rise (this first rise is called “the bulk fermentation”). As the dough rises you’ll perform a series of folds on the dough (this helps activate gluten in the same way as kneading). Next, you’ll shape the dough into a loaf and after a final rise (also known as the “final proof,” your bread will be ready to bake.

All in all, the process is very similar to making bread with commercial yeast—though, depending on your recipe, you may encounter some additional or unfamiliar steps such as building a levain (an optional step that comes before the final dough is mixed). But really, the major difference is that sourdough takes a lot longer—and it all comes down to the time it takes for the dough to rise. While bread made with commercial yeast rises for a total of about two hours. With sourdough, that time is at least doubled.

“Functionally, commercial yeast has been bred (pun intended!) to produce lots of carbon dioxide (and not much else) in a relatively short amount of time,” says McKenney, “Compared to commercial yeast, ‘wild yeasts’ produce a LOT of different products in addition to carbon dioxide—some of which also contribute to rise, while others build complex aromatic profiles.” In other words, commercial yeast is developed with speed in mind and while sourdough is a slower process, it delivers far more in terms of flavor.

A final word of advice for beginners

It can take a few tries to get the hang of making sourdough bread, but Philip says that shouldn’t stop you from getting started. “The best thing you can do in the beginning of your sourdough journey is to make hybrid loaves,” he explains, “What I mean is, make some recipes that combine sourdough with a little bit of commercial yeast (it’s a trick we call “spiking”).” 

Philip says this technique allows the bread to still get a good rise, while the baby starter provides that sourdough flavor. “It will help your loaves while you figure everything out,” he says.