Sourdough Starter Smells like Vinegar

When your sourdough starter smells strongly like vinegar you likely have an unbalanced starter but luckily this can be easily remedied. During fermentation, the bacteria and natural, wild yeast in your starter break down the sugars (carbohydrates) in the flour into ethanol and carbon dioxide. The carbon dioxide gas is what produces the air bubbles that cause the starter to expand and rise during the feeding process.

The ethanol is one of the components that produce the sour smell of sourdough, and in some cases, the starter smells strongly of vinegar. The sourdough starter can also sometimes smell like acetone, nail polish remover, alcohol (beer or wine), or even fruit. All of this is perfectly normal and no reason to toss out your sourdough starter. Your starter has not died, it is just out of balance, but the microbial environment creating these smells will eventually be adding delicious flavor to your bread!

How do you fix a sourdough starter that smells like vinegar?

It’s easy to fix your sourdough starter when it smells like vinegar, however, you need to diagnose the exact problem first. (And if your starter smells like something else be sure to check out our guide.) Sourdough culture produces two main acids: lactic acid and acetic acid. Acetic acid (ethanol) is essentially a precursor to vinegar and gives the sourdough bread its sour and tangy flavor. However, when the vinegar smell is too strong you need to adjust your starter.

1. Feed your sourdough starter more often

In most cases, you need to feed your sourdough starter more often to fix the vinegar smell. What’s happening is that your sourdough culture, a mix of bacteria and yeast, is eating the carbohydrates in the flour quickly and leaving a vinegar smell through the production of acetic acid. If you’re feeding your starter once a day try increasing that to twice a day. After a few days, in most cases, the vinegar smell of your starter will be gone.

If you don’t feed your sourdough starter at all then the microculture of yeasts, bacteria, fungi, and enzymes begins to break the structure of the food (flour) into its component parts, liquid, solid, and waste. You want to avoid this as it won’t be a useful starter for creating sourdough bread, and will often create a pungent or vinegary smell. However, even a starter in this state can be saved by putting it back on a regular feeding schedule. Simply pour off any liquid and stir the rest of your starter until you have achieved an even consistency. Then commence your normal sourdough starter feedings and it should bounce back and be ready to bake within a week or two.

2. Adjust the temperature of your sourdough starter

A warmer sourdough starter is a more active starter and will eat through the nutrients of the flour feedings more quickly than a cooler starter. If you can adjust the temperature of the environment of your sourdough starter, try bringing it down a couple of degrees. If you aren’t able to do this, you may need to increase your feeding schedule to adjust.

You should avoid storing your sourdough starter at temperatures above 90°F or 32°C as this will encourage too much microbial growth and may be the cause of the vinegar smell. A sourdough starter that is too hot will eat the flour quickly and produce a vinegar smell at times.

Ideally, you can find a controlled environment in your home where you can keep your sourdough starter at or below 77°F or 25°C.

3. Change the flour you feed your sourdough starter

Different types of flour can speed up or slow down how quickly your starter consumes the nutrients.

Whole grain flour is more nutritious for people, but also the microbial environment of your sourdough. This increased nutrition causes the bacteria and yeast to become more active (similar to the effect of a warmer temperature), which in turn makes the culture eat more quickly and produce a stronger vinegar smell sooner. Changing to all-purpose flour will slow down the rate of consumption of your sourdough starter and can fix the vinegar smell.

4. Make sure your sourdough starter has enough air in its container

A sourdough starter is an aerobic fermentation so you need to make sure it has enough oxygen present to be healthy. To do this, simply make sure there is at least the same amount of air as there is starter in your jar. A sourdough starter jar that is filled to the top will not have room to expand and double in size, but more importantly, won’t even be able to do so because it will be starved for oxygen. Instead, an anaerobic fermentation will take place (with no oxygen) which can cause bad smells like a strong vinegar scent, and not produce a healthy starter required to bake sourdough bread. Patience here is key. If you have to transfer the starter to a new jar make sure it is clean and has plenty of room for air, and then give yourself 1-2 weeks to get the starter back into baking shape.

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