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Can Sourdough Starter Go Bad?

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Sourdough starters are fascinating! Especially when you are just getting into the science of making and maintaining your own. However, one thing we struggled with a lot is understanding the workings behind a starter.

Yes, there is more to it than just regular feeding. A sourdough starter is a mixture of flour and water that uses yeast to produce a fermented mixture. This mixture is very fragile, yet so many people seem to get it right.

So, can a sourdough starter go bad? Yes, you can even kill your starter if you don’t take good care of it. When making and maintaining a healthy starter, you should feed it regularly, store it at favorable temperatures, keep it away from foreign objects, and prevent it from coming into contact with dehydrating ingredients.

Sound overwhelming? Well, luckily for you, we’ve made it easy! This guide will explain exactly how sourdough starters work. This will enable you to easily recognize how to keep it healthy and when it is going bad.

Our guide today includes a list of signs that your starter is becoming inactive, how to revive it, and how to correctly store the starter from the get-go.

What Is A Sourdough Starter?

A sourdough starter, also commonly referred to as a levain, is a type of pre-ferment. They are made from a combination of water and flour that is allowed to ferment using the naturally occurring wild yeast in the flour itself.

Pre-ferments have three main functions when it comes to bread-baking.

The first, and arguably most important, is that it acts as the main leavening agent in many types of bread. Sourdough starters are specifically produced to make sourdough loaves.

Secondly, they have a tenderizing effect on the texture of the bread. This is thanks to the ethanol that the yeast produces as it grows. 

And finally, pre-ferments add a delicious yeasty and nutty flavor to the bread that makes it unique. The older your sourdough starter is, the better flavor and texture it will give your sourdough loaf.

How It works

It is important to understand the inner workings of a sourdough starter, including the ingredients used to make it. This will help you understand how it works, what will affect the culture, and how to prevent certain things from happening to it.

So, first things first, a sourdough starter is made from flour and water as we have mentioned. Sometimes, additional instant yeast is used to help make the starter. 

Once the ingredients are initially combined, the mixture is allowed to rest in a warm area so that the naturally occurring yeast in the flour can multiply and grow. 

Now, because we are working with essentially a living organism, it needs to be constantly fed and kept under favorable conditions. If not, it has a high probability of developing unfavorable characteristics or even dying.

Can A Sourdough Starter Go Bad?

While these starters are pretty tough, they still have a high possibility of going bad if they aren’t taken care of.

There are a ton of factors to consider when maintaining a healthy sourdough starter, so naturally, there are a ton of areas where things can go wrong.

There are two ways in which a sourdough starter can go bad. It can either become inactive or die completely. It is easy to recognize when the starter is becoming inactive. This is usually the first stage before it begins completely dying.

The starter won’t be as spongy and won’t rise as much as it used to. A healthy starter should multiply between 3-4 times in volume every time you feed it.

But, if it completely dies, it won’t be fizzy, bubbly, or airy. Basically, it won’t have any characteristics of a sourdough starter.

Most common reasons sourdough starters go bad:

  • You didn’t feed the starter enough or regularly enough. A healthy starter that is kept at room temperature should be fed at least once a day.
  • Your starter was kept at too high temperatures. Yeast typically dies at about 138°F (59°C). While it may seem impossible to heat the starter to that extent at room temperature, remember, the higher the temperature goes, the more inactive the starter becomes. Eventually, it will be so unhealthy that it will be extremely difficult to save and it will die.
  • Unfavorable ingredients were introduced. This is an extremely common mistake people make. Your starter should only have flour and water – that’s it! Never feed it with any other ingredients like sugar or salt. Sugar and salt actually can completely kill yeast through dehydration! Salt especially, which is why it should never come into direct contact with your sourdough starter.
  • “Bad” bacteria made their way into the mixture. If you didn’t properly store your sourdough starter, other bacteria will also want to get to where the good stuff is (the food, the moisture, and the heat).

How To Tell If Sourdough Starter Is Bad

Trust us, you will know! Because you are working with a ferment, it will have a naturally yeasty and acidic odor. However, when this goes bad you will immediately notice it in the starters’ color, texture, and odor.

1. Off Smell

It’s hard to describe the exact smell of a bad starter. This is mainly because each starter will react in its own unique way. But, what we can say is that it has a very recognizably strong and foul smell.

Think about a very pungent cheese, sweaty armpits, and, sorry for the next one, vomit. Yes, it gets that bad!

These smells develop when the starter has too much bad bacteria. The normal yeasty smell that starters have is due to the good bacteria. It is essential that you take proper care of your sourdough starter to ensure it has a good balance.

2. Texture Changes

This is probably the first thing you will notice, even if the sourdough starter is only becoming inactive.

The starter, which is usually very airy and spongy, will stop moving entirely when the yeast has died. When activity slows, the growth will just become slower as well.

To test whether or not your starter is still active or alive, you should feed it twice a day for three days. If healthy, the starter should quickly double in size. If it isn’t very healthy, it will only start doubling after a couple of days. But, if it’s completely dead, it won’t react.

And, before you ask, even if you do keep your starter in a fridge to slow its activity, it should still be active. It will simply take longer to double in size. But, when it doesn’t move at all, it should be taken care of.

3. Discoloration

As with any fresh ingredient, there will be visible signs that it is going bad. For sourdough starters specifically, the beige color turns into a pinkish or yellowish hue.

It also sometimes develops spots of discoloration, in which case it still isn’t healthy. Other common colors you will see include shades of blue, green, and orange.

And, of course, when bad mold gets out of control, you will quickly see moldy spots on the surface of the starter.

But, before you throw the entire starter away, check first if it is possible to remove the mold from the surface (and maybe an inch or two of the top starter).

How Long Does A Sourdough Starter Last?

This depends entirely on where you store the starter and how often you feed it. If you have a completely happy starter that is healthy and thriving, it will last forever.

Believe it or not, but there is actually a starter out there that is over 4500 years old!

If you keep your starter at room temperature (under the correct temperatures), you should feed it at least once a day. It should last forever if taken care of properly.

And, if you keep the starter in the fridge to cut back on the maintenance, it will be fine for about 4-6 weeks without being fed.

However, we would still recommend feeding it at least once a week to ensure it stays as healthy as it can be.

How To Correctly Store A Sourdough Starter

First, it is important to store your sourdough starter in a completely clean (stain and odor-free) container. This will help prevent it from developing strange colors, coming into contact with unfavorable objects and bacteria, and developing bad odors.

Then, you want to keep it inside of a container that is at least 4 times bigger than the just-fed starter. This will give it enough room to expand without bubbling over.

You also want to cover the open top of your container or jar with a porous cloth. We prefer using cheesecloth or muslin cloth and securing it with an elastic band.

This allows oxygen to still enter the container (so the yeast can breathe) but prevents other elements from entering.

And finally, actually storing your starter. If you store it at room temperature, keep it away from direct light and extreme heat. Ideally, it should be between 80-90°F (27-32°C). This is when fermentation does best.

But, if you cannot consistently keep your starter at optimal temperatures, you should keep it inside of the fridge. The activity will slow, but the starter won’t become damaged.

Up Next: 61 Easy Sourdough Discard Recipes

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