Can you keep sourdough starter forever?

Quick Answer

Yes, you can keep sourdough starter alive indefinitely as long as you continue to feed and care for it properly. With regular feedings, sourdough starter can be maintained for many years or even decades. The key is to keep it refreshed by discarding some of the old starter and adding fresh flour and water. As long as the yeasts and bacteria in the starter are active, it will remain viable.

What is Sourdough Starter?

Sourdough starter, sometimes called a mother starter, is a mixture of flour, water, wild yeasts, and bacteria that is used to make sourdough bread. It serves as a leavening agent that helps bread rise by producing carbon dioxide gas. The starter also gives sourdough bread its characteristic tangy flavor.

Making a starter simply involves combining flour and water and allowing the mixture to ferment. Over a period of several days to a couple weeks, the wild yeasts and bacteria that are present in the flour and the environment will multiply and colonize the starter. Once the starter is mature and stable, it contains a symbiotic community of microorganisms that work together to produce the gases and acids needed for leavening and flavor.

Ingredients in Sourdough Starter

The main ingredients in sourdough starter are:

  • Flour – Usually all-purpose or bread flour provide nutrients for the yeast and bacteria to grow
  • Water – Hydrates the starter and allows fermentation
  • Wild yeasts – Saccharomyces exiguus, Candida milleri, etc. Metabolize sugars into carbon dioxide and alcohol
  • Lactic acid bacteria – Lactobacillus sanfranciscensis, etc. Produce lactic and acetic acids for flavor

These microbes occur naturally in flour and the environment. By combining flour and water and allowing time for fermentation, they are cultured into an active starter. No commercial yeast is added.

What Makes Sourdough Starter Work?

Sourdough starter is able to leaven bread due to the metabolic activities of the yeasts and bacteria it contains:


The wild yeast in sourdough starter consume sugars present in the flour and produce carbon dioxide gas and alcohol as waste products. The carbon dioxide gets trapped in the gluten network of the dough, causing it to rise. The most prominent yeast found in sourdough is Saccharomyces exiguus, which is well-adapted to the acidic environment.

Lactic Acid Bacteria

The lactic acid bacteria metabolize sugars into lactic acid and acetic acid. These acids create the sour flavor in sourdough and also serve as a preservative against spoilage microbes. Common lactic acid bacteria in sourdough include Lactobacillus sanfranciscensis and Lactobacillus pontis.

Acetic Acid Bacteria

Acetic acid bacteria like Lactobacillus acetotolerans can convert alcohol produced by yeasts into acetic acid, contributing to a vinegar-like aroma and taste. The combination of acetic, lactic, and other organic acids help give sourdough its distinctive sour taste.

How to Create and Maintain a Sourdough Starter

Creating and keeping a sourdough starter alive is a simple process, though it does require a little patience and routine care. Here is an overview of starter creation and maintenance:

Creating a Starter

To make a new sourdough starter:

  1. Mix together flour (often rye or whole wheat) and water in a 1:1 ratio by weight in a jar or container.
  2. Cover and let sit at room temperature for 24-48 hours.
  3. Check for bubbles on the surface, which indicate fermentation is underway.
  4. Discard half the starter and add equal weights flour and water to feed it.
  5. Repeat feeding every 24 hours for 5-10 days until starter is bubbly and aromatic.

This process cultures the wild yeasts and bacteria that are present in the flour into an active starter teeming with microbial life.

Maintaining the Starter

Once established, a sourdough starter needs regular feedings to keep it healthy and active. Feed at least once a week, or more often if baking frequently.

  • Discard or use half the starter.
  • Add equal weights flour and water.
  • Stir well until incorporated.

The starter may need a couple feedings to regain activity if it hasn’t been fed for a while. Signs it needs feeding include:

  • Layer of liquid on surface
  • Starter has collapsed
  • Less bubbly or rising
  • Alcohol or acetone smell

Tips for a Healthy Starter

Follow these tips for best results with your sourdough starter:

  • Use filtered or spring water for more consistent results.
  • Keep starter at a moderate room temperature around 70°F.
  • Use only organic, unbleached flours.
  • Choose glass, ceramic, or wood containers to avoid plastics.
  • Mark the feeding date on the jar.
  • If separating, keep a backup starter in case main one fails.

What Happens If You Don’t Feed Sourdough Starter?

If a sourdough starter is neglected and not fed regularly, a few things can happen:

  • It may go dormant. The yeasts and bacteria will go into survival mode but remain viable.
  • Alcohol production increases as it runs out of food, giving off boozy aromas.
  • Acidity decreases allowing undesirable bacteria or mold growth.
  • It can die off completely if not fed for many weeks or months.

A dormant or neglected starter may take a few successive feedings to regain activity. As long as some microbes remain, it can usually be revived and avoid having to start over from scratch. However, severely neglected starters may fail to reactivate and need to be discarded.

Signs Your Starter May Need Discarding

In some cases, a sourdough starter should be discarded and restarted from scratch:

  • Thickness of liquid layer increases dramatically.
  • Pink, orange, blue, or black mold develops.
  • Putrid smell like rotten eggs or garbage.
  • No bubbles or rise after multiple feedings.
  • Presence of black watery layer or dots.

These are signs the starter has become overly acidic, contaminated, or is no longer viable. Starting a new batch avoids spreading potentially harmful microbes.

How to Keep Sourdough Starter Forever

Here are some tips and practices for maintaining a healthy sourdough starter indefinitely:

Regular Feedings

Feed starter once a week minimum, more often if baking frequently. Discard then refresh with flour and water.

Fridge Storage

Store mature starter in the fridge between uses to slow fermentation and minimize feedings. Remove and feed to room temp before baking.

Dry Storage

Dehydrate active starter on parchment until completely dry. Crush into a powder and store airtight in fridge or freezer for up to a year. Rehydrate with water and feed to reactivate when needed.

Give Away Extras

When starter is active and thriving, give some away to baker friends. This ensures backups exist if your main starter fails.

Monitor Appearance and Aroma

Take note of changes in appearance, texture, and smell to catch contamination or inactivity before it’s too late.

Discard Unfed Portions

Always discard excess starter that isn’t being used. Unfed leftovers invited poor flavors and aroma over time.


Can sourdough starter be frozen?

Active starter can be frozen for backup storage, though viability declines over time in the freezer. It’s better to dry for storage. Thaw frozen starter in the fridge before using.

How long can sourdough starter survive without feeding?

In the fridge, starter may go 2-3 weeks without feeding before losing viability. At room temp, just 1-2 weeks max. Feed as soon as possible once inactive.

What temperature is best for storing sourdough starter?

Ideally, room temperature around 70°F to promote fermentation. The fridge at 34-40°F slows starter activity to extend time between feedings.

Can sourdough starter be saved if moldy?

No, discard starter if any mold, even just spots, appear. Mold can release toxins and spoil the entire batch. Start fresh to avoid spreading contamination.

Why does my starter smell like acetone or alcohol?

These aromas indicate overactive yeast producing excess alcohol and other metabolites. Feed more frequently and discard more before it becomes too acidic.


With proper care and routine maintenance, sourdough starter can ferment indefinitely, being passed down for generations. By regularly feeding, monitoring its appearance and aroma, reviving over-neglected batches, and giving away extras, sourdough bakers can keep their starters going forever. The microbial ecosystems in these starters produce the gases, acids, and flavors that make sourdough baked goods so distinctive. With a little diligence, home bakers can cultivate a lifelong sourdough culture.

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