Does Freezing Harm Sourdough Starter?

Your starter will stay strong and usable as long as you keep feeding it. But what if life takes over and you’re no longer getting enough time to bake sourdough bread as much as you used to. Can you freeze it, or will that kill off all the yeast in your starter?

Freezing your sourdough starter will generally not harm the starter if done correctly. Some yeast in your starter may die off, but there will be more than enough that survive to get your starter active again once it has defrosted.

But there is a correct way to do it in order to make sure you protect the delicate balance of friendly bacteria and yeasts that make your bread rise well and taste great. And in this article I’ll walk you through the best methods for freezing sourdough starter depending on your needs…

When Should you NOT Freeze Sourdough Starter?

First things first, let’s talk about when you should NEVER freeze sourdough starter…

If your sourdough starter is less than a few months old, then freezing is not recommended. The yeast and bacteria will not yet have developed enough strength to survive the freezing process.

Although a brand new sourdough starter can take anything from 1 to 3 weeks to become active enough to make bread with, it contains a living community of bacteria and yeast that continue to evolve and grow.

Your fresh new sourdough starter will continue to get stronger over a period of about 3 months, at which time it becomes ‘mature’. This is the time when it has enough strength in terms of the complexity and quantity of yeast and bacteria in it, for it to survive the freezing process.

QUICK TIP: After this 3 month period, your sourdough starter will likely be mature enough to take a little neglect every now and then and still survive. So you can afford to get a little lazy with it after this point! 😉

So if you’ve just made your sourdough starter, it’s not really a good time to freeze it. You’ll need to maintain it and continue to refresh/feed it until a good few months before it’s strong enough to freeze.

TIP: Once your sourdough starter is active (i.e. it rises and you can see bubbles in it), if you don’t want to feed it daily, keep it in your fridge and feed it weekly instead.

And speaking of sourdough starter maturity; if you’re wondering if sourdough starter develops better flavor with age, check out my article here, where I go through what else can affect the flavor of your sourdough starter.

But getting back to how freezing your starter can affect it…

How Does Freezing Affect Sourdough Starter?

We know that you should never freeze a baby sourdough starter, but does freezing sourdough starter have a negative impact on it? Well, yes and no…

Sourdough starter that is mature (i.e. at least a few months old) is actually quite hardy. It can take freezing temperatures quite well and the lactic acid bacteria and yeast can survive even in the coldest of freezers. 

However, some yeasts do die off. The rest of the yeasts remain dormant while they are frozen, and there will still be more than enough to revive your sourdough starter when you defrost it.

So any damage that may have been caused i.e. any yeasts that died off during freezing, will return once the sourdough starter is refreshed and maintained again. So there’s no permanent damage at all.

You can think of freezing your sourdough starter as putting it into hibernation until you want to use it again. And then once it’s revived, it will return to normal within a few days at the most.

Why Freeze Sourdough Starter?

It takes quite a lot of work to get your sourdough starter up and running in it’s early stages. And then it takes months before your sourdough starter reaches maturity.

Note: If you want to know more about the maturity of your sourdough starter, make sure to check out my article “When Does Sourdough Starter Mature?“

Freezing sourdough starter is a great option if you want to take a break from sourdough bread baking, and don’t want to have to make a sourdough starter from scratch again. It means you can simply pick up where you left off as soon as you can begin baking again.

If you want to store your sourdough starter for a longer period of time, such as a few months to a year, then freezing it is a good option.

NOTE: If you want to store it for an even longer period of time, then you can also dry it, which would make it last for years! Check out my article here to have a step by step of how to dry your starter.

How To Freeze Your Sourdough Starter

Freezing your starter will not harm it and is safe to do, but planning your method of freezing properly will mean it will be super easy for you to use and revive later on when you need it, without too much hassle. Let’s take a look at how to to go about it…

How to Freeze Stiffer Sourdough Starters…

If you have a stiffer sourdough starter (i.e. one that contains less water in it and is more solid than liquid), you can:

1. Portion the starter out into the amount you generally use to bake your sourdough loaf.
2. Put these portions into zip-lock bags. 
3. Add an extra 10 grams to each portion (as some of the starter will cling to the bag when you try to use it later).
4. Get a sheet pan and lay the bags full of sourdough starter on it.
5. Place the sheet pan into the freezer.
6. Once the starter is frozen, you can remove the sheet pan and store the frozen starter in your freezer.

How to Freeze Liquid Sourdough Starters…

If your sourdough starter is a liquid starter (i.e. it is quite runny), you can:

1. Put the starter into a piping bag and inject it into an ice-cube tray.
2. Use a spatula to make sure the tops of the cubes are even, (so the starter cubes freeze in the same amount of time).
3. Tap the ice-cube tray on the counter top gently a few times to get rid of any excess air pockets in the cubes.
4. Place the ice-cube tray with the starter into the freezer.
5. Once the starter is frozen, remove the frozen cubes from the ice tray and place them into a zip-lock bag.

The reason you portion out your starter is so when you want to bake sourdough bread, you can just thaw out enough starter for the amount of bread you want to make without reviving the whole starter.

QUICK TIP: Make sure you seal the zip-lock bags properly. You may want to use two or three bags to protect your sourdough starter from freezer burn, as this can change the taste of your sourdough.

How Long Can I Freeze Sourdough Starter For?

You can store your starter in the freezer for up to one year. After that it will slowly start to degrade, and will become more difficult to revive as time goes by.

However, if you need to store it for longer than a year, the best way is to dry it. Check out my article here on step by step illustrated instructions on how to dry your starter. I’ve also got instructions on which storage method is best depending on how long you want it stored for in this article.

Can you Re-Freeze Sourdough Starter?

Once sourdough starter has been frozen and revived once, it is NOT recommended to freeze it a second time. The delicate balance of bacteria and yeast will be degraded beyond repair if a sourdough starter is frozen a second time. Having said that, this is only in the case where you are going to defrost it, revive it, and then freeze it again. That won’t work.

HOWEVER, if you have a ‘once upon a time’ frozen sourdough starter, that you have been regularly refreshing/feeding and using up in bread, then the original defrosted part of the sourdough starter will be so minimal that refreezing at this point will be fine.

So in conclusion, it’s not recommended to re-freeze a sourdough starter that has recently come out of the freezer (e.g. only a couple of weeks ago). But if your sourdough starter has been used and refreshed many times over since it was last frozen, then re-freezing after this point is fine.

How To Revive A Frozen Sourdough Starter

Now that your sourdough starter has been frozen, here is a method you can use to revive the starter when you want to bake again so you get the best sourdough bread you can.

Decide how many sourdough starter portions you will need; this will be based on how many sourdough breads you want to make.

Once you have decided, take the right portion size out of the freezer and place it in the fridge. Leave the starter to thaw in the refrigerator for the day. 

Once the sourdough starter is thawed completely, take it out of the fridge. Now you need to feed your sourdough starter. You need to resume regular feedings for your starter to get it up and producing again. 

Depending on your kitchen’s temperature, you will need to feed your starter one or two times a day to keep it happy. After one day of regular feeding, you should start seeing signs of activity in your starter, such as bubbles forming and your starter growing.

If you don’t see these signs after a day, don’t worry; every sourdough starter is different. Just keep feeding your sourdough starter regularly as per your usual schedule, and you should start seeing signs of life in your starter soon.

Once your sourdough starter has started showing signs of life, it is ready to be used for baking your sourdough bread. 

(Check out my sourdough starter troubleshooting guide here for any issues you might come across).

Other Storage Methods For Sourdough Starters

If you are concerned about freezing your sourdough starter, there are other ways to store it if you won’t be using your sourdough starter for a while. The following are two alternatives to freezing.

1. Storing sourdough starter in the refrigerator.
2. Drying your sourdough starter and storing it in your cabinet.

Storing Sourdough Starter in the Refrigerator

Storing sourdough starter in the refrigerator is an easy, quick and common way to store it if you find you’re getting too busy with other things. Here are the steps:

1. Feed your starter to make sure it has plenty of nutrition to last in the fridge.
2. Place your starter into a clean and airtight glass container. Make sure there’s enough empty space in the jar so as to leave room for your starter to breathe and grow.
3. Tightly close the jar’s lid and then put the jar on the top shelf of your fridge, (as this is the coldest part of your fridge).

If your starter is three months old, then it should be able to last in your fridge for about two months. Once the two months are up, and if you’re still not going to use your starter, then you can feed your starter again to keep it alive and then put it back in the fridge. Easy peasy!

Drying Sourdough Starter for Longer Term Storage

Another alternative way to store your starter is to dry your starter and store it in a cabinet. This is an excellent long-term storage solution for your starter, as it can last years like this! In fact, a starter that has been dried can be stored like this indefinitely. Here’s how it’s done:

1. Feed your starter.
2. Leave at room temperature until it is active and bubbling.
3. When the starter is active, get some parchment paper and spread a thin layer of your starter onto the parchment paper. (The thinner the starter is spread, the faster it will dry out).
4. Let the sourdough starter air dry for at least twenty-four hours. 
5. Once the starter is dried completely, you can break it off the parchment paper and crumble it into smaller pieces.
6. Put the dried starter pieces in an airtight container and place it in a cool dark place, like a cabinet.

Both these alternative methods of storing your sourdough starter are easy to do and will keep your starter viable. (If you’d like illustrated instructions on these methods, check out my article here).

The method you choose to use needs to be determined by how long you will not be using your starter for, as some ways are only suitable for a small period of time. But it’s definitely worth storing rather than not, as making a sourdough starter from scratch can take weeks, but reviving one, even from long term storage takes a couple of days!

For step by step guidance on which storage method is best for you, including how-to guides for each method, check out my article here.