Can You Use a Sourdough Starter That Smells Like Acetone?

Sourdough bread not only has a distinctive, tangy flavor but it’s also believed to be healthier and easier to digest. However, there are many factors that can affect the quality of the sourdough bread.

One common issue that sourdough bakers encounter is a starter that smells like acetone. In this article, we’ll explore what causes this smell and whether or not it’s safe to use a sourdough starter that smells like acetone in your bread-making.

A faint smell of acetone is considered normal and harmless, and you can use it safely. On the other hand, if the sourdough smells strongly of acetone, you should discard a portion of the starter and feed it more frequently until it becomes balanced.

Acetone is a compound that is produced during the fermentation process of sourdough, and it is usually an indicator that the starter is not being fed frequently enough. To avoid these issues, bakers should regularly feed their sourdough starter to ensure that it remains healthy and active.

Causes of Acetone Smell in Sourdough Starters

A sourdough starter is made by combining flour and water and allowing it to sit at room temperature for several days to develop a culture of wild yeast and lactobacilli bacteria. As the starter ferments, it becomes more acidic and develops a sour flavor, hence the name “sourdough.”

The acetone or nail-polish-remover-like smell in sourdough starters is caused by the presence of the species of bacteria known as Acetobacter. These bacteria are responsible for producing acetic acid, which is one of the primary acids produced during the fermentation process in sourdough starters. As the bacteria produce acetic acid, they also produce small amounts of acetone as a byproduct.

Acetone is a volatile organic compound that has a distinct, somewhat sweet, and fruity odor, and can give sourdough starters a slightly sweet and tangy smell. The presence of acetone in sourdough starters is generally considered normal and is not necessarily an indication of spoilage or contamination.


However, if the sourdough starter has a strong, unpleasant odor, it may be a sign of an overgrowth of certain bacteria or yeast strains, and the starter may need to be discarded and restarted.

Feeding the Sourdough Starter

A sourdough starter needs to be fed regularly to keep the yeast and bacteria healthy and active. If the starter is not fed often enough, it can become too acidic and produce an acetone smell. Aim to feed your starter once or twice a day, depending on the temperature in your kitchen.

In a warmer environment, sourdough ferments more quickly and needs to be fed more frequently. Conversely, it requires less frequent feeding when stored in the refrigerator.

When feeding sourdough, equal amounts of flour and water are typically added. For example, 50 g of flour and 50 g of water are added to 50 g of sourdough. Adding slightly more flour will result in a thicker sourdough, which requires less frequent feeding.

Easy Sourdough Starter Guide

The Importance of Smell in Sourdough Starters

Smell is a crucial factor in determining the quality of a sourdough starter that contains a community of wild yeast and lactic acid bacteria. The smell of a sourdough starter is an indicator of the activity and health of these microorganisms.

A healthy sourdough starter should have a pleasant, slightly sour aroma. The aroma may vary depending on the type of flour used, but it should not have any unpleasant or off-putting odors, such as a strong alcohol smell or a putrid smell. These types of odors may indicate that the starter is not healthy and that harmful bacteria have taken over.


The aroma of a sourdough starter is an essential indicator of the fermentation process. When flour and water are mixed, wild yeast and bacteria start to consume the sugars in the flour, producing carbon dioxide and lactic acid. The by-products of fermentation contribute to the aroma of the sourdough starter. A strong, pleasant aroma indicates that the yeast and bacteria are active and producing the right by-products.

Moreover, the smell can help to distinguish between different stages of sourdough starter development. For example, a newly mixed sourdough starter may have a slightly sweet or yeasty aroma, while a mature sourdough starter may have a more complex aroma with notes of acidity, fruitiness, or nuttiness.

sourdough bread ball in a proofing bowl lined with a tea towel sprinkled with flour

In general, a sourdough starter should have a pleasant, sour aroma that is slightly tangy or vinegary. Other smells that may indicate a problem with the starter include:

  • Rotten, musty, or putrid smells, indicate the presence of harmful bacteria or mold.
  • A strong alcohol smell, which may signal that the yeast is producing too much ethanol and not enough acid.

If you notice any of these smells in your sourdough starter, it’s a good idea to discard it and start over with a new batch. Additionally, it’s important to keep your sourdough starter in a clean and hygienic environment and to feed it regularly with fresh flour and water to keep the yeast and bacteria in balance.

Final Thoughts

In conclusion, a sourdough starter with a weak acetone smell will not adversely affect the quality of the bread. On the other hand, a strong acetone smell indicates that it is time to feed the sourdough starter.

The smell of a sourdough starter is an essential factor in determining its quality. A pleasant, slightly sour aroma indicates that the starter is healthy and active, while unpleasant odors may indicate a problem with the fermentation process.



My name is Debora, the founder of My Delicious Sweets, and a qualified confectioner with broad experience in the confectionery industry. On my blog, I will share important, interesting, and fun facts about food, along with some of my favorite recipes.

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