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Sourdough Starter Smells Like Sour Milk – The Reasons

Sourdough Starter Smells Like Sour Milk – The Reasons

Much like beer and wine, you activate a sourdough starter with yeast. When yeast mixes with flour, it begins the fermentation process.

A sourdough starter will produce many different aromas as it grows.

Some odors will be pleasant, while others will run you from the room.

Sour milk is only one of the odors your starter will take on as it ferments.

The different aromas of sourdough starter let you know how it is progressing.

Continue reading to learn why sourdough starter smells like sour milk.

Sourdough starter smells like sour milk

The aroma of sour milk is what a good loaf of sourdough bread smells like. The sourdough starter has different odors, whether adding yeast to flour or allowing flour and water to form yeast. When making a starter at room temperature, it takes about five to seven days for the fermentation process. The odors over that time can range from sour milk to the scent of acetone. These odors are produced as bacteria feed on the flour’s carbohydrates in the sourdough starter.

Making a sourdough starter takes time.

Developing a great sourdough starter takes time and patience.

You can make it with flour and water alone or add bread yeast to speed things along.

Over time, you will learn the aromas of fermenting flour and yeast and will be able to determine what is normal.

You can make a sourdough bread starter at room temperature or under refrigeration. The difference in the two methods is a matter of time.

The starter cultivated at room temperature will grow faster than that produced under refrigeration.

Using either method, the sourdough starter will go through several phases before it becomes a frothy, bubbly bread starter.

The odors produced during the growth process of a sourdough starter indicate whether the mix is hungry or not. Hungry, you say. Let’s eat!

Odors of sourdough starter

Your sourdough starter will take on bad odors if you don’t feed it enough or if you feed it too much. For example, a starter that smells of vinegar is normal.

The aroma comes from the acetic acid produced as the bacteria eats through the carbohydrates you are feeding it.

A sourdough starter that smells like alcohol

If your sourdough starter smells like alcohol, feed it.

When your starter doesn’t have enough food, it will feed on the yeast of the starter and any waste, and the result is an odor of alcohol.

Feeding your starter will bring it back into balance, and keeping it fed will prevent it from smelling alcohol.

Getting into the habit of feeding your starter at the same time every day will help you make a great sourdough starter.

Crusty sourdough starter

A sourdough starter that does not have enough liquid in the mix can develop a crust over the top. If yours does so, remove the crust and feed the starter.

Sluggish sourdough starter

Sourdough starters can get sluggish and lack vigor. This issue with your starter could be due to the temperature you store it.

Your sourdough starter is most active at about 70 degrees Fahrenheit. In addition, at this temperature, it will leaven bread more quickly than a cold product.

Discolored or moldy sourdough starter

A sourdough starter that is discolored or moldy can be caused by a dirty container or from the yeast becoming weak due to improper feeding procedures.

If a batch of yours develops this issue, it is best to discard it and start from scratch.

Tips for success when making a sourdough starter

Making a sourdough starter is not difficult; however, the process is lengthy and requires your attention for a few minutes every day.

The food for your starter is 1 cup of flour mixed with ½ cup of water.

Be sure to use clean containers and utensils when handling and blending the starter. Dirty containers could contaminate your starter and ruin it.

Before adding to your starter, stir it, remove ½ of the starter, place it in a bowl, add the water and flour slurry and mix it well.

You can discard the remainder of the old starter or use it in a recipe.

The sourdough starter kept at room temperature will need to be fed twice a day.

However, if you keep it in the refrigerator, you can get by with feeding it once a week.

How you store your starter will depend on how often you want to make sourdough treats. Keep it refrigerated unless you plan to bake, often.

If you feed it properly, its typical smell will be sour milk. The slightly sour smell is what makes sourdough bread appealing.

Sourdough is the oldest of all leavened bread produced long before modern packaged yeast was available.

So whether you use packaged yeast to make your starter or make it from a slurry of flour and water, you can develop a signature loaf of bread that is all yours.

Frequently Asked Questions About Sourdough Starter Smells Like Sour Milk

What should sourdough starters smell like?

Sourdough starters should have a sweet, tart odor, and the mix will be bubbly with a creamy color.

How do I know if a sourdough starter is bad?

Sourdough doesn’t go bad. But, it gets out of adjustment, and you must feed it to get back into balance to continue to grow.

When sourdough starter smells like sour milk – is it bad?

While making a sourdough bread starter, the mix will go through many phases, and the odors produced range from sweet to very sour. The odors produced by a growing sourdough starter are part of fermentation. If your mix gets too obnoxious, feed it, and it will calm down.


A sourdough starter will grow and expand as long as you feed it.

Sourdough starters exist that are hundreds of years old and are being fed regularly to be around for hundreds more.

You, too, can develop a sourdough starter to use yourself and give to family and friends because everyone loves fresh bread.