Sourdough Starter Smells Like Acetone/Nail Polish Remover – What to Do

Baking with sourdough is a delightful journey that combines art, science, and the beauty of natural fermentation.

However, what happens when your beloved sourdough starter emits an unexpected and unpleasant scent reminiscent of acetone or nail polish remover? This is a strong indication that your starter isn’t healthy and has an imbalance of acid or bacteria.

But don’t fret, as this article is here to guide you through the process of dealing with a sourdough starter that smells less than appetizing.

We’ll explore the potential causes of this issue, the steps you can take to address it, and provide tips for preventing its recurrence. So, let’s delve into the world of troubleshooting and revive your sourdough starter’s aromatic glory!

Understanding What a Sourdough Starter Is

A sourdough starter is a natural leavening agent used in bread baking, created through the fermentation of flour and water.

In summary, making a sourdough starter involves combining equal parts of flour and water and allowing it to sit at room temperature, encouraging the growth of wild yeast and beneficial bacteria naturally present in the environment and on the flour.

The Process

To make a sourdough starter, begin by mixing equal parts of flour (typically whole wheat or rye) and water in a clean container. Stir well to incorporate air and cover loosely with a muslin cloth. The oxygen aids in the fermentation process.

Over the next several days, known as the “fermentation phase,” the mixture will undergo a series of transformations.

Initially, it may exhibit little activity, but as time passes, bubbles will form, indicating that the yeast is growing and producing carbon dioxide.

Maintaining the Starter

During the fermentation phase, it’s essential to “feed” the starter regularly by discarding a portion of it and adding fresh flour and water.

This process, known as “refreshing” or “discarding and feeding,” helps maintain a healthy balance of microorganisms in the starter.

Maintaining a sourdough starter requires consistent attention. Typically, starters are kept at room temperature and require regular feeding, usually once or twice a day, depending on the activity and vigor of the starter.

Maturing Starters

As the starter matures, it develops a unique flavor profile and becomes more reliable for bread baking. 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, then allowed to undergo a fermentation period called “proofing.” This fermentation process, which can take several hours or even overnight, 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 smell, it indicates certain imbalances or conditions within the fermentation process.

While there could be hundreds of reasons for this happening, here are five main reasons that will most likely be your culprit.

Cause 1: Insufficient Feeding

If a sourdough starter is not regularly fed or is left without feeding for an extended period, it can produce a sharp, acetone-like smell.

This occurs when the yeast and bacteria in the starter have consumed all available nutrients and begin to break down waste products of their own, leading to the production of acetone-like compounds.

Cause 2: Temperature Fluctuations

Rapid temperature changes, such as exposing the starter to excessive heat or cold, can impact the balance of microorganisms in the starter.

Yeast and bacteria can become stressed, causing them to produce acetone-like compounds as a result of the metabolic changes occurring within the starter.

Cause 3: Imbalanced Microbial Activity

The microbial composition of a sourdough starter is delicate and relies on a harmonious balance between yeast and bacteria.

If this balance is disrupted, it can lead to an overgrowth of certain bacteria, particularly the strain-producing acetone-like compounds. This imbalance can occur due to changes in feeding ratios, hygiene practices, or other environmental factors.

Cause 4: High Acid Content

Sourdough starters naturally produce lactic acid and acetic acid during fermentation. However, if the acidity levels become too high, it can contribute to the development of an acetone smell.

This can happen when the starter is not refreshed frequently enough or when acidic ingredients are added to the starter, such as excessive amounts of whole grains or acidic fruits.

Cause 5: Contamination

Occasionally, a sourdough starter can become contaminated with undesirable bacteria or wild yeast strains that produce off-flavors, including acetone-like odors.

This can occur if the starter comes into contact with unclean utensils, water, or ingredients. Maintaining proper hygiene practices when handling the starter can help minimize the risk of contamination.

How to Prevent a Sourdough Starter From Smelling Like Acetone?

Preventing a sourdough starter from developing an acetone-like smell is ALWAYS better than trying to fix the problem later.

Below are some basic, yet extremely helpful tips for doing so.

Regular Feeding

Maintain a consistent feeding schedule for your sourdough starter. Ideally, feed it every day 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, preventing the buildup of waste products that can contribute to off-putting odors.

Proper Feeding Ratios

Maintain a balanced feeding ratio of flour and 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 your starter’s needs and the desired consistency.

Providing enough food to support the microbial activity without overwhelming the starter helps maintain a healthy balance and minimize the production of off-flavors.

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 extreme temperature fluctuations, as it can stress the microorganisms and lead to off-flavors. If necessary, find a warm spot in your kitchen or use temperature-controlling techniques like using a proofing box or adjusting ambient room temperature.

Maintaining Proper Hygiene

Practice good hygiene when working with your sourdough starter. Wash your hands thoroughly before handling the starter, and use clean utensils and containers.

Avoid cross-contamination by keeping the starter away from other fermenting foods or ingredients. A clean environment helps prevent unwanted bacteria or yeast strains from affecting the starter’s balance.

Monitoring Acidity Levels

Keep an eye on the acidity levels of your starter. While a mildly acidic environment is essential for the sourdough fermentation process, extremely high acidity can contribute to off-flavors.

If your starter consistently produces strong acetone-like odors, you can try reducing the acidity by adjusting the feeding routine, refreshing with fresh flour and water, or incorporating a small amount of baking soda to neutralize excessive acidity.

How to Fix a Sourdough Starter That Smells Like Acetone?

Using a sourdough starter that smells like acetone is generally not recommended. The presence of an acetone-like smell suggests that the starter may be in an imbalanced state or undergoing stress.

Here are some steps you can take to help fix your starter. This process may take a while and may not even be successful. But it’s the best option you have.

Step 1: Assess the Overall Condition

Evaluate the intensity of the acetone smell and check for any other signs of spoilage, such as unusual colors, mold, or sliminess. If the starter appears unhealthy or exhibits severe signs of spoilage, it’s best to discard it and start fresh.

Step 2: Refresh the Starter

Begin by discarding a portion of the existing starter, leaving only a small amount in the container. Add fresh flour and water to the remaining starter, maintaining a balanced feeding ratio.

For example, a 1:1:1 ratio of starter, flour, and water (by weight) is commonly used. Mix well to incorporate the fresh ingredients.

Step 3: Adjust the Feeding Frequency

Increase the frequency of feedings to help restore balance and provide the microorganisms with fresh nutrients. Feed the starter at least once or twice a day, depending on its activity and response.

Consistent feeding helps dilute any accumulated waste products and promotes the growth of healthier microorganisms.

Step 4: Temperature Control

Maintain a stable and moderate temperature for the starter. Aim for a range of 70-85°F (21-29°C), as extreme temperature fluctuations can stress the microorganisms and contribute to off-flavors.

Step 5: Observe and Repeat

Monitor the starter closely after each feeding. Look for signs of improvement, such as increased bubbling, a more pleasant aroma, and a reduction in the acetone smell. If the smell persists or worsens after a few days of consistent feeding, it may be necessary to consider starting a new sourdough starter.