Understanding the Shelf Life of Sourdough Starters

Can sourdough starter go bad?

Sourdough starters are an intriguing component of bread making, and understanding how to properly care for them is crucial. A sourdough starter is a mixture of flour and water that uses yeast to create a fermented mixture. While sourdough starters are generally hardy, they can go bad if not properly cared for. In this article, we will explore the signs of a sourdough starter going bad, how to prevent it from happening, and how to store it properly.

Understanding Sourdough Starters

A sourdough starter, also known as a leaven, is a type of pre-ferment used in bread making. It is made by combining water and flour and allowing the naturally occurring wild yeast in the flour to ferment the mixture. Sourdough starters serve three main purposes in bread making.
First, they act as the primary leavening agent in many types of bread, including sourdough loaves. Second, they contribute to the texture of the bread by softening it through the production of ethanol as the yeast grows. Finally, sourdough starter cultures impart a distinct yeasty and nutty flavor to the bread that improves with age.

The inner workings of a sourdough starter

To understand how to care for a sourdough starter, it is important to understand its inner workings. A sourdough starter consists of flour and water, sometimes with the addition of instant yeast to aid the process. Once the ingredients are combined, the mixture is allowed to rest in a warm environment to encourage the multiplication and growth of naturally occurring yeast.
Because a sourdough starter is a living organism, it requires regular feeding and favorable conditions to thrive. Failure to provide proper care can result in unfavorable characteristics or even death of the starter.

Signs of a Bad Sourdough Starter

While sourdough starters are generally hardy, there are two ways they can go bad: become inactive or die completely. Recognizing the signs of a bad sourdough starter is critical to maintaining its health.
When a starter becomes inactive, it will no longer have the spongy texture and significant rise that it had before. A healthy starter should increase in volume 3-4 times each time it is fed. However, if the starter dies completely, it will lose its bubbly and airy characteristics and will not resemble a sourdough starter at all.

Factors that lead to a bad sourdough starter

Maintaining a healthy sourdough starter requires careful consideration of several factors. Failure to properly address these factors can result in a sourdough starter going bad. Some common reasons for sourdough starter spoilage include

  1. Insufficient or irregular feeding: A healthy starter stored at room temperature should be fed at least once a day.
  2. High temperatures: Yeast typically dies at about 138°F (59°C), and excessively high temperatures can render the starter inactive or even kill it.
  3. Introduction of undesirable ingredients: A sourdough starter should be fed only flour and water. Ingredients such as sugar or salt can dehydrate the yeast and possibly kill it.
  4. Contamination from “bad” bacteria: Improper storage can allow harmful bacteria to contaminate the sourdough starter, causing it to spoil.

Identifying a bad sourdough starter

Recognizing a bad sourdough starter is relatively easy due to its distinctive odor, texture, and appearance. Here are some indicators that a sourdough starter has gone bad:

  1. Odor: A bad starter emits a strong and foul odor, similar to pungent cheese, sweaty armpits, or vomit. This smell comes from an imbalance of bad bacteria, while a healthy starter has a pleasant yeasty aroma.
  2. Texture changes: A bad starter will have a noticeable change in texture. It will become less airy and spongy, and its growth will slow down significantly.
  3. Discoloration: A deteriorating sourdough starter may develop a pinkish or yellowish hue instead of its usual beige color. It may also have spots of discoloration, including shades of blue, green, or orange. Mold growth on the surface is also a clear indicator of a bad starter.

Longevity of a sourdough starter

The longevity of a sourdough starter depends on how it is stored and fed. A well cared for and thriving starter can last indefinitely. In fact, there are sourdough starters that have been kept alive for over 4500 years.
If a sourdough starter is kept at room temperature and fed daily, it can last indefinitely. However, if the starter is stored in the refrigerator to reduce maintenance, it can survive for 4-6 weeks without feeding. To maintain optimal health, it is recommended to refresh the starter by discarding a portion and feeding it regularly.

Preventing a sourdough starter from going bad

To ensure the longevity and health of a sourdough starter, it is important to follow proper care and storage practices. Here are some tips on how to prevent a sourdough starter from going bad:

  1. Feed regularly: Feed the sourdough starter at least once a day when stored at room temperature. If stored in the refrigerator, feed it once a week.
  2. Consistent maintenance: Discard some of the starter before each feeding to remove any potential buildup of harmful byproducts. This process, known as “refreshing,” helps maintain a healthy balance of yeast and bacteria.
  3. Proper storage: If the sourdough starter is not going to be used frequently, store it in the refrigerator. Be sure to keep it in a tightly sealed container to prevent contamination from other foods.
  4. Avoid dehydration: Do not add dehydrating ingredients such as sugar or salt to the sourdough starter. These ingredients can inhibit yeast activity and potentially kill the starter.
  5. Hygienic practices: Use clean utensils and containers when working with the sourdough starter. Avoid cross-contamination with other ingredients or surfaces.

Reviving a Dying Sourdough Starter

If a sourdough starter is showing signs of inactivity or dying, there are steps that can be taken to revive it. Here is a simple process to revive a dying sourdough starter:

  1. Remove any discolored or moldy parts of the starter.
  2. Discard a significant portion of the starter, leaving only a small amount.
  3. Add equal parts flour and water to the remaining starter, mixing until well incorporated.
  4. Allow the starter to rest for several hours in a warm place, ideally around 75°F (24°C).
  5. Repeat the feeding process every 12 hours for a few days until the starter shows signs of activity and growth.
  6. Once the starter is active again, continue to feed and care for it regularly to prevent it from going bad in the future.


A sourdough starter can go bad if not cared for properly. Regular feeding, proper storage, and avoiding unfavorable ingredients are key to maintaining a healthy and thriving sourdough starter. By recognizing the signs of a bad starter, taking preventative measures, and knowing how to revive a dying starter, bread enthusiasts can enjoy the benefits of a flavorful and active sourdough culture. With proper care and attention, a sourdough starter can be a reliable companion in the art of bread making for years to come.


How long can a sourdough starter be stored without feeding?

A sourdough starter can be stored in the fridge for 4-6 weeks without feeding. However, it is recommended to refresh the starter by discarding a portion and feeding it regularly to maintain optimal health.

Can I use a sourdough starter that has gone bad?

It is not advisable to use a sourdough starter that has gone bad. A bad starter can have an unpleasant smell, unusual texture, discolouration or mould growth, which means it is no longer healthy or suitable for baking.

How often should I feed my sourdough starter?

If the sourdough starter is stored at room temperature, it should be fed at least once a day to maintain its activity and vitality. If stored in the fridge, feeding once a week is sufficient.

Can I revive a sourdough starter that has become inactive?

Yes, a sourdough starter that has become inactive can often be revived. By discarding some of the starter, feeding it with flour and water, and providing it with a warm environment, the starter can regain its activity and vitality.

How should a healthy sourdough starter smell?

A healthy sourdough starter should have a pleasant, slightly tangy, yeasty aroma. It should not give off a strong or foul odour, which could indicate the presence of harmful bacteria or that the starter has gone off.

Can I use dehydrating ingredients such as sugar or salt in my sourdough starter?

It is best to avoid adding dehydrating ingredients such as sugar or salt to the sourdough starter. These ingredients can inhibit yeast activity, upset the balance of the starter and possibly cause it to deteriorate. For best results, stick to feeding the starter with flour and water.