What Is Sourdough Starter?

Composed of fermented flour and water, a sourdough starter is a leavening agent that uses naturally occurring yeasts and bacteria to make baked goods rise.

Whether you’re starting a bakery or operating a restaurant, learning how to make a sourdough starter will draw customers to you. Incorporate your fresh bread into innovative new recipes such as a Panzanella salad, or serve it to guests warm. After all, many patrons will frequent a restaurant based on their breadbasket!

What Is Mother Dough?

Sourdough starters are lovingly referred to as mother dough. Unlike other leavening agents, a sourdough starter isn't found on a baking aisle. A sourdough starter is a living organism that requires cultivation and maintenance. When properly fed, sourdough starters live for years and give life to endless loaves of bread.

What Does Sourdough Bread Taste Like?

Sourdough bread has a characteristically "sour" taste because sourdough starters are acidic. Bread leavened with a sourdough starter will have a complex flavor and porous texture that is simultaneously airy and chewy. Much like a fine wine, a sourdough starter only improves with age and will deliver more flavorfully robust and texturally light loaves over time.

While all sourdough leavened loaves of bread have similar textures and carry an acidic flavor, there isn't one kind of sourdough leavened bread. Sourdough is famously associated with San Francisco's unbleached flour sourdough loaves, but you can use your sourdough starter to make a wide variety of bread such as pumpernickel, wholewheat, or barely.

Click Here to Learn How to Make a Sourdough Starter

Sourdough Starter Guide

Sourdough Leavening

Developing your own sourdough starter is a great way to set your restaurant or bakery apart. Because sourdough starters depend on local strains of yeast and bacteria, no two sourdough starters are exactly alike. Your sourdough starter will carry the unique flavor of both your region's flora and fauna, and your restaurant’s specific microculture, resulting in bread that is truly your own. We've created a guide explaining the terms used in sourdough baking, how sourdough starters work, and how to make a sourdough starter.

Sourdough Starter Terms

Niche baking terms can intimidate newcomers. We’ve broken down common sourdough starter terms, so you can easily follow recipes.

Preferment Definition

Preferment is a generic term used to describe the process of individually fermenting a portion of a bread loaf’s ingredients before adding them to the rest of the ingredients. Some varieties of preferments, such as pâte fermentée, biga, and poolish, still use a commercial yeast strand to help leaven bread.

Sourdough and levain are preferments which use an entirely natural leavening process. While each type of preferment has a slightly different cultural origin and unique process, they all fall under the general preferment category.

What Is Leaven?

Commonly referred to as a leavening agent, leaven is the ingredient that makes baked goods rise. Leavening agents exist in both chemical and natural forms.

Baking soda and baking powder are examples of chemical leavening agents. They are best suited to bakers’ confectionery such as cakes, doughnuts, and cookies. Yeast and sourdough starters are natural leavening agents used in loaves of bread, dinner rolls, and bagels.

Sourdough Starter vs Yeast

When you compare a sourdough starter vs yeast, a sourdough starter is the superior natural leavening agent for flavor quality and nutritional value. We broke down the differences between these natural leavening agents:

What Is Yeast?

Yeast is a term used to categorizes over 1,500 single-celled microorganisms. The yeast used in baking is called saccharomyces cerevisiae, a Latinized Greek word meaning "sugar-fungus." Sugar-fungus eats sugar and converts it into carbon dioxide. The carbon dioxide they release gives baked goods light and doughy textures.

Types of Yeast

While naturally derived, the yeast you purchase in the store is engineered in a factory for immediate leavening use. There are three types of yeast:

  1. Instant Yeast has the consistency of fine powder and requires no activation before it is added to dry ingredients
  2. Active Dry Yeast has a granular consistency. It must be activated before it is added to dry ingredients by dissolving it in a liquid.
  3. Fresh Yeast is sold in small, moist blocks that resemble a brick of cheese. Fresh yeast has a limited shelf life and is rarely found in grocery stores.

How Does Sourdough Starter Work?

Sourdough starters begin working when you mix liquid and flour together. Mixing liquid into flour activates the friendly bacteria and wild yeast living in both your flour and your surrounding environment. Once activated, these microorganisms produce carbon dioxide bubbles, which make your bread rise. Additionally, they generate flavor-rich lactic and acetic acids in your bread.

Because it is an entirely natural process, sourdough starters take longer to leaven bread than store-bought yeasts. The extended fermentation time improves the flavor and texture of the bread. Additionally, bread leavened by a sourdough starter contains high volumes of folate, antioxidants, and comparatively lower phytate levels, which help the body absorb nutrients.

How to Make Sourdough Starter

Bread leavened with a sourdough starter offers the greatest flavor complexity and nutritional benefits. Read on to learn how to make a sourdough starter.

Sourdough Starter Video

Use the following video to learn how to create your own sourdough starter:

Sourdough Starter Ingredients and Supplies

Sourdough Starter Ingredients
  • Whole grain flour contains wild yeast, which is vital for giving your sourdough starter life. There are many types of flours to choose from, so select the whole grain flour that meets your flavor preference. Stay simple with traditional whole wheat, or go for unique rye or hearty barley, the choice is yours!
  • Water in the temperature range of 68 to 70 degrees Fahrenheit creates a welcoming environment for friendly bacteria and wild yeast to live and grow. While some baking aficionados swear by distilled water, tap water will normally suffice. If your tap water has a chemical odor indicating heavy treatment, opt for distilled water.
  • A non-reactive container is essential for storing your sourdough starter. We recommend using a non-reactive container made of see-through material so you can observe your sourdough starter’s progress. Select a minimum 1-quart capacity container to provide space for your sourdough starter to expand.
  • A baker’s portion scale will ensure accurate ratios. Measuring cups leave too great a margin of error.

Sourdough Starter Recipe Instructions

Sourdough starter rising over time

Following a sourdough starter recipe is a lengthy, rather than complex, process. Since it is a living organism, cultivating a sourdough starter is much like growing a plant or caring for a pet; you have to feed and water it. Follow our step by step sourdough starter recipe instructions and cultivate a healthy and effective sourdough leavening agent.

Day 1

Sourdough Starter Appearance: Your sourdough starter will look like a wet dough with thoroughly incorporated flour.

Sourdough Starter Aroma: The new sourdough starter will have a minimal aroma that smells like fresh, wholesome grains.


  • Weigh 113 g of the whole grain flour of your choice and 113 g of room temperature water.
  • Combine your flour and water in a minimum 1 qt. capacity, see-through, non-reactive container.
  • Stir until no dry flour remains.
  • Loosely cover the container.
  • Leave your mixture to rest for 24 hours. The room it occupies should be in the 70 degrees Fahrenheit range. Cool environments will slow your sourdough starter’s growth.

Day 2

Sourdough Starter Appearance: Your sourdough starter may have slightly expanded or formed small bubbles, but it is perfectly normal for no activity to have occurred at this point.

Sourdough Starter Aroma: There should be no strong smells coming from your sourdough starter within the first few days.


  • Whether you begin to see bubbling or your starter is still dormant, discard 113 g (approximately ½ cup if you aren’t using the recommended portion scale).
  • Add 113 g (just shy of 1 cup) worth of your chosen flour, and 113 g (½ cup) of water.
  • Thoroughly mix your ingredients.
  • Let your sourdough starter rest at room temperature for 24 hours.

Day 3

Sourdough Starter Appearance: Your sourdough starter should start showing visible signs of activation such as bubbling or expansion.

Sourdough Starter Aroma: Your sourdough starter should omit a fresh and fruity aroma.


At this point in the process, you will need to increase your sourdough starter’s feeding schedule to twice daily and optimize your feeding method.

  • Before each feeding, thoroughly stir your starter.
  • Once it is stirred, reserve 113 g of starter and discard the rest.
  • Mix 113 g of flour and 113 g of water into your 113 g of remaining sourdough starter.
  • Cover the mixture and leave it to rest for 12 hours at room temperature before repeating.

Days 4, 5, & 6

Sourdough Starter Appearance: By the end of the fifth day, your sourdough starter should have at least doubled in volume. Look for signs of activation such as multiple bubbles and small pools of surface water containing tiny bubbles.

Sourdough Starter Aroma: Your sourdough starter should release acidic essences that are tangy but not overpowering.


  • Follow the same steps as ‘Day 3’.

Day 7

Evaluate your sourdough starter to determine your next steps. If your sourdough starter contains few bubbles and has barely expanded, repeat the steps from days 3-6 until your starter is bubbly and ready for use.

Don’t be discouraged if it takes several weeks for your starter to activate completely. Remember, sourdough starters are dependent on the natural bacteria in your environment. Subsequently, certain regions will take longer to develop active sourdough starters than others. If you live in an arid climate, expect your starter to take longer to activate than if you live in a humid or foggy location.

How Do I Know When My Sourdough Starter Is Ready to Use?

sourdough starter overflowing in jar

In baker's terms, a sourdough starter that is ready for use is considered “ripe”. How can you tell when your sourdough starter is ripe and ready to use? Your sourdough starter is ripe when it doubles in size 6 to 8 hours after being fed.

Tip for tracking your sourdough starter’s expansion:

  • Before feeding your sourdough starter, place a rubber band around its container at the fill line.
  • 6 hours after feeding your sourdough starter, check to see if the rubber band is now marking your sourdough starter’s midpoint.

Final Step in Your Sourdough Starter Recipe

Here are the steps you need to take before you bake with your ripe sourdough starter:

  • Feed your starter its normal diet of 113 g flour and 113 g of water.
  • Allow your sourdough starter to come to an active, bubbling state by leaving it to rest at room temperature for 6 to 8 hours after you feed it.
  • Bubbles should still be breaking the surface when you incorporate your sourdough starter into your recipe. The bubbles allow your sourdough starter to act as the flavorful natural leavening agent you’ve worked so hard to create.

How to Make a Sourdough Starter Last

Sourdough starter in jar

With a little maintenance, your sourdough starter will live for years, serving as a leavening agent for countless loaves of unique varieties of bread. You can store your ripe sourdough starter at room temperature or in your fridge. Regardless of where you store your sourdough starter, you’ll need to continue to feed it.

Remember, your sourdough starter works as a natural leavening agent because of the good microorganisms living inside it. The less you feed them, the weaker they become. Discover the feeding schedule for each storage method below:

Maintaining Refrigerated Sourdough Starters

  • Feed your refrigerated sourdough starter at least once a week in the same way you grew accustomed to while following our sourdough starter recipe.
  • The sourdough starter should rest on the counter for 1 to 2 hours after being fed so it can begin to bubble before it is returned to the fridge.

Maintaining Room Temperature Sourdough Starters

  • Sourdough starters stored at room temperature remain highly active and require feeding every 12 hours.
  • Since it is harder to keep unrefrigerated sourdough starters active, we recommend refrigerating your sourdough starter unless you are using it too frequently to maintain refrigeration.
  • Feed your sourdough starter in the same way you grew accustomed to while following our sourdough starter recipe.

While your sourdough starter will usually revive even if it is left unfed in the back of your refrigerator for months, it will take time and care to bring it back to a ripe state. If you want to keep your sourdough starter in a ready-to-use state, follow the appropriate feeding schedule for your storage method.

Need a Refresher on How to Feed a Sourdough Starter?

  1. First, measure 113 g of the starter and separate it from the rest.
  2. Discard or bake with the remaining sourdough starter.
  3. Feed the 113 g of sourdough starter by thoroughly mixing in 113 g of water and 113 g of flour.

How Do I Know If My Sourdough Starter Is Bad?

Expired sourdough starter in jar

Similar to the kombucha fermentation process, cultivating healthy bacteria can sometimes give rise to bad ones. Here is how you can know if your sourdough starter is bad:

  1. It smells like acetone. While your sourdough should smell, well, sour, it should be a clean sour smell that is strong but not unpleasant.
  2. It is visibly moldy or tinted with orange and/or pink.

Note: If your sourdough starter is left unfed, the liquid layer on top of your starter will turn from clear to dark. This doesn’t mean your starter is bad, it’s just hungry! Give your sourdough starter a meal, and the liquid will return to a clear state.

While the steps may seem lengthy, cultivating a sourdough starter is a long-term investment that will pay off for years if properly maintained. Whether you’re a novice baker still learning the difference between bread flour vs all-purpose flour or an experienced artisan baker elevating your methods with homemade starters and dough proofing strategies, developing your own sourdough starter will set your restaurant or bakery apart.

Posted in: Recipes | Menu Tips | Bakeries | By Corrinn McCauley
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