Sourdough is the oldest form of leavened bread, dating back to Ancient Egypt. Before the use of commercial yeast, all bread was either unleavened or sourdough. It is thought that sourdough bread was first made on accident when unleavened bread dough was left sitting out, and wild yeast began to grow in the dough. In modern times, sourdough is still popular, and many artisan bakeries still make sourdough bread.

Growing up, I used to think sourdough was just tart tasting bread. It wasn't until I started working in a professional kitchen and tasted sourdough next to regular yeasted bread that I realized how much better sourdough bread can be. If you love bread and fermented foods and have already mastered homemade yogurt, kombucha, and kimchi, then the next step you might want to tackle is sourdough.

What Makes Sourdough Special

Sourdough bread is bread that's made with a fermented flour and water mixture, or preferment. A preferment is a mixture where wild yeast and bacteria are able to grow. Bakers use preferments in place of instant yeast to make their bread rise. So, although sourdough does actually have yeast in it, it doesn't necessarily have added yeast, unlike typical white breads or sandwich breads. The type of preferment in sourdough is called a starter.

The Science Behind Sourdough

Natural yeast is everywhere – in the air, on fruit, in flour – but only in very small amounts. When flour and water are mixed and left at room temperature to create a starter, wild yeast and lactobacillus bacteria, naturally present in the flour, grow. Lactobacillus is also found in fermented foods like yogurt, pickles, and wine.

Using a starter in bread dough provides the yeast needed for the bread to rise and the combination of acetic acid and lactic acid produced by the bacteria provides the unique flavor. Once a starter is created, it can be kept alive by feeding it flour and water regularly. Boudin Bakery in San Francisco, which is well known for their sourdough bread, has kept their starter going for over 160 years!

Why Sourdough Is Better

Sourdough breads tend to take longer to rise and maintaining a starter consumes ingredients and time. Considering this, why is sourdough so well-liked?

For starters, they have a better flavor. The acids produced by lactobacilli give sourdough bread a more nuanced flavor that, despite the name, isn't usually sour. While it's possible to make sour sourdough, pretty much all bakeries will take care of their starters to keep the acidity low yet flavorful. The acidity of sourdough also helps to prevent mold and staling, keeping the bread fresher for longer. 

A big reason why sourdough is popular is because it's believed to be healthier than regular store-bought breads. They don't use preservatives because they don't stale as quickly, and studies suggest sourdough causes fewer spikes in blood sugar, improves the absorption of minerals, and is easier for celiac patients to digest. Studies aren't conclusive yet, but there's no doubt that there are benefits of sourdough that you can't get with just instant yeast.

Making Your Own Starter

Phoebe Baker

There are two main ingredients for a starter: flour and water. Different flours can lead to different flavors in the bread due to the bacteria in the flour. A rye flour starter can have a strong fruity, musty smell, whereas a starter made from all purpose flour may smell more like yogurt. This is because whole grain flours and rye tend to carry more natural yeast in them. If you're gluten-free, it's even possible to create a gluten-free starter. As for water, I prefer using filtered water, but as long as your area doesn't heavily treat the water, tap is fine.

Also, it's good to have a kitchen scale when you make a starter. Starters are usually a 1:1 ratio of flour and water by weight (100% hydration), and if your starter isn’t the same ratio as the recipe calls for, then the overall dough might end up too dry or wet. While a cup of flour is roughly the same weight as a half cup of water, there can be inconsistencies. Weighing ingredients is the easiest way to ensure the ratio of flour to water in a starter is correct and keeps every batch consistent.

Maintaining a Starter

A starter needs to be fed regularly to keep it going. Outside of professional bakeries, feeding starters daily is not sustainable. Starters can be refrigerated to slow the fermentation process so you won't have to feed them as much. They won't be as bubbly while they sit in the fridge, and you might find some greenish-yellow liquid seeping out when it hasn't been fed in a while.

Alice Zou

An old, unfed starter doesn't look great, but as long as no mold forms, and it doesn't smell rotten, your starter is still alive and okay to use. Just feed it and let it sit in a warm place, and it'll return to being its bubbly, active self. There’s also a way to dry your starter out if you won’t be able to take care of it for an extended period of time. 

If a starter is continually fed and not all of it is used, eventually you’re going to end up with a lot of starter. In a bakery, starters and preferments are almost entirely used up and the remaining amount is used to feed the starter for the next day. For those who bake bread at home, it's easiest to discard extra starter before feeding it again. Thankfully, there are plenty of ways to use unfed or discarded starter.

Alice Zou

Once you've got a starter going you can experiment with this rye bread recipe or no-knead easy sourdough. Baking with a starter may sound a little intimidating at first, but it's fun to experiment to see what you get. If you're new to bread baking, check out this easy bread baking guide, and if you're too impatient to start your own starter, there are places that sell fresh sourdough starters online. 

Sourdough is a passion for professional and at-home bakers around the world, and it can inspire a lot of emotions. Feeding my starter is a peaceful weekly routine, and I've reached an obsessive point where I'll sit and watch my starter grow. This is a tradition that's been going on for millennia, and it's easy to get started. All you'll need is flour and water.