Troubleshooting a Sourdough Starter with Acetone/Nail Polish Remover Odor

Sourdough starter smells like acetone/nail polish remover – What to do?

Baking with sourdough is a journey that combines art, science and the beauty of natural fermentation. However, sometimes your beloved sourdough starter gives off an unexpected and unpleasant odor reminiscent of acetone or nail polish remover. This is a strong indication that your starter isn’t healthy and has an acid or bacterial imbalance. But don’t worry, this article will walk you through the process of dealing with a sourdough starter that smells less than appetizing, as well as provide tips on how to prevent it from happening again. Let’s dive into the world of troubleshooting and restore the aromatic glory of your sourdough starter!

Understanding what a sourdough starter is

A sourdough starter is a natural leavening agent used in bread baking, created by the fermentation of flour and water. To make a sourdough starter, equal parts of flour (typically whole wheat or rye) and water are combined and allowed to sit at room temperature. This encourages the growth of wild yeast and beneficial bacteria naturally present in the environment and on the flour.

The process

To make a sourdough starter, combine equal parts flour and water in a clean container. Stir well to incorporate air and cover loosely with a muslin cloth. Over the next few days, known as the “fermentation period,” the mixture will undergo transformations. It may show little activity at first, but over time bubbles will form, indicating the growth of yeast and the production of carbon dioxide.

Maintaining the starter

During the fermentation phase, it’s important to periodically “feed” the starter by discarding some of it and adding fresh flour and water. This process, known as “refreshing” or “discard and feed,” helps maintain a healthy balance of microorganisms in the starter. Starters are typically stored at room temperature and require regular feeding, usually once or twice a day.

Aging starters

As the starter matures, it develops a unique flavor profile and becomes more reliable for baking bread. The sourdough starter is used as a leavening agent in bread recipes, replacing commercial yeast. During the bread-making process, a portion of the mature starter is combined with flour, water, and sometimes salt. It is then allowed to ferment for a period of time called “proofing”. This process helps develop the bread’s characteristic flavor, texture, and rise.

Why does your sourdough starter smell like acetone/nail polish remover?

When a sourdough starter develops an acetone or nail polish remover-like odor, it indicates certain imbalances or conditions within the fermentation process.

Cause 1: Insufficient Feeding

If a sourdough starter is not fed regularly, or is not fed for an extended period of time, it can develop a pungent, acetone-like odor. This occurs when the yeast and bacteria in the starter have consumed all available nutrients and begin to break down waste products, resulting in the production of acetone-like compounds.

Cause 2: Temperature Fluctuations

Rapid temperature changes, such as exposing the starter to excessive heat or cold, can affect the balance of microorganisms in the starter. Yeast and bacteria can become stressed and produce acetone-like compounds as a result of metabolic changes within the starter.

Cause 3: Imbalanced microbial activity

The microbial composition of a sourdough starter is delicate and depends on a harmonious balance between yeast and bacteria. Disturbances in this balance can lead to overgrowth of certain bacteria, particularly those that produce acetone-like compounds. Imbalances can occur due to changes in feeding ratios, hygiene practices, or other environmental factors.

Cause 4: High acidity

Sourdough starters naturally produce lactic acid and acetic acid during fermentation. However, if the acidity level becomes too high, it can contribute to the development of an acetone odor. This can happen if the starter is not refreshed often enough or if acidic ingredients are added, such as excessive amounts of whole grains or acidic fruits.

Cause 5: Contamination

Occasionally, a sourdough starter can become contaminated with unwanted bacteria or wild yeast strains that produce off-flavors, including acetone-like odors. This can occur when the starter comes into contact with unclean utensils, water, or ingredients. Following proper hygiene practices when handling the starter can help minimize the risk of contamination.

Preventing a sourdough starter from smelling like acetone

Preventing a sourdough starter from developing an acetone-like odor is always better than trying to fix the problem later. Here are some basic tips:

1. Feed regularly

Keep a consistent feeding schedule for your sourdough starter. Ideally, feed daily or every 12 hours, depending on your specific routine and the activity of your starter. Regular feeding ensures that the microorganisms have an adequate supply of fresh nutrients and prevents the buildup of waste products that can contribute to unpleasant odors.

2. Proper feeding ratios

Maintain a balanced feeding ratio of flour to water. A common ratio is equal parts by weight (e.g., 1:1:1, equal parts flour, water, and starter). However, you can adjust the ratio slightly based on the needs of your starter and the desired consistency. Providing enough food to support microbial activity without overwhelming the starter will help maintain a healthy balance and minimize the production of off-flavors.

3. Optimal temperature control

Keep your sourdough starter in a stable temperature environment. Most starters thrive between 70-85°F (21-29°C). Avoid exposing the starter to rapid temperature changes, as this can stress the microorganisms and lead to the production of acetone-like compounds.

4. Hygiene Practices

Maintain proper hygiene when handling your sourdough starter. Use clean utensils, containers, and water to avoid contamination. Wash your hands thoroughly before working with the starter and ensure that all equipment is properly cleaned and disinfected.


A sourdough starter that smells like acetone or nail polish remover indicates an imbalance or problem in the fermentation process. By understanding the causes of this odor and following preventive measures such as regular feeding, proper feeding ratios, temperature control, and good sanitation practices, you can help maintain a healthy and aromatic sourdough starter. Remember, prevention is the key, and taking care of your starter from the beginning will lead to better results in your sourdough baking endeavors.


Why does my sourdough starter smell like acetone or nail polish remover?

If your sourdough starter smells like acetone or nail polish remover, it indicates an acid or bacterial imbalance in the fermentation process.

Can I still use my sourdough starter if it smells like acetone?

If your sourdough starter smells like acetone, it is best to avoid using it until you have addressed the underlying problem and restored its health. Using a starter with an unpleasant odor can affect the taste and quality of your bread.

How can I prevent my sourdough starter from developing an acetone-like odor?

To prevent your sourdough starter from developing an acetone-like odor, maintain a regular feeding schedule, use proper feeding ratios, control the temperature, and practice good hygiene when handling the starter.

Is it normal for a sourdough starter to have a slight odor?

Yes, it is normal for a sourdough starter to have a slightly tangy or sour odor due to the natural fermentation process. However, an overpowering smell similar to acetone or nail polish remover indicates a problem that needs attention.

How can I restore the health of my sourdough starter if it smells like acetone?

To restore the health of your sourdough starter if it smells like acetone, you can try refreshing it by discarding a portion and feeding it with fresh flour and water. In addition, maintaining a regular feeding schedule, providing optimal temperature conditions, and practicing good hygiene can help restore the balance of microorganisms in your starter.

Can contamination be the cause of the acetone-like odor in my sourdough starter?

Yes, contamination can be one of the causes of an acetone-like smell in a sourdough starter. It is important to ensure that all utensils, water, and ingredients used in the starter are clean and free of unwanted bacteria or wild yeast strains.