You can freeze sourdough bread starter and keep it for up to 12 months in the freezer. Once defrosted, carry on feeding and discarding the sourdough starter until it’s active again and then use it in any sourdough bread recipe.
Sourdough starter can be normally stored in a room temperature or in the fridge, but sometimes you might end up with too much sourdough starter, that you just dont’ need. This is one of the reasons, why freezing sourdough starter is a good idea even if it takes a little longer to revive it afterwards, when it’s defrosted.
Let me take you through freezing sourdough starter step by step and explain how to freeze it and defrost it safely. And most importantly how to start feeding and looking after your frozen sourdough starter, so that you can continue using it for baking your sourdough bread.
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Can you freeze sourdough starter? The quick answer
Yes, you can freeze sourdough starter and keep it for up 12 months in the freezer.
However the active natural yeast that’s in your sourdough starter becomes innactive and you need to make sure that you re-vive your sourdough starter before you start using it for baking bread again.
This can add extra 3-5 days to your baking schedule, so it’s worth bearing that in mind when you want to bake your sourdough bread at home.
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Why freeze sourdough starter?
Freezing sourdough starter is a great way to preserve your homemade starter for later, if you for example have too much of sourdough starter, going away or know you are not going to bake as much sourdough bread as you used to.
You can also freeze sourdough starter discard (the bit of your soudough starter that you ment to ‘discard’ or ‘throw away’) in this way and use it for baking or adding to other recipes for flavouring and texture.
I often dry my sourdough starter, but freezing is much quicker and possibly more convenient, if you have the freezer space.
How to safely freeze sourdough starter
If you do decide to freeze sourdough starter, make sure that you follow the safe way of freezing and defrosting your sourdough starter to make sure that the stater carries on living, growing and active.
- Feed the sourdough starter just before you freeze it, so that’s very active
- Use clean and washed containers suitable for freezer
- Defrost in the fridge or room temperature
- Feed 2-3 times before first use
What to expect when you freeze & defrost sourdough starter
The slight problem with freezing and defrosting sourdough starter is that the natural yeast contained in the sourdough starter will become completely dormant.
The wild yeast will then need to be brought back to life by allowing to defrost in a room temperature (or fridge) and then fed 2-3 times until it becomes active again.
How long does sourdough starter last in the freezer
Providing that you’ve carefully frozen your sourdough starter in a freezer suitable container (and your freezer is in a good condition and the temperature doesn’t fluctuate), your sourdough starter should be fine in the freezer for a minimum of 12 months.
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How to freeze sourdough starter
You have quite a lot of options here, depending on what you want to use your sourdough starter for when it’s defrosted.
You can freeze:
- active sourdough starter – separated into smaller containers (such as plastic soup or beakers cups with lids) to be revived as an active sourdough starter after it’s been defrosted
- sourdough starter (discard) frozen in ice cube trays – great for adding to pancake batter, cup in a mug cakes, making bread sauces or other smaller portion recipes.
Freezing medium to large sourdough starter amount
Make sure that the container is plastic or paper and not glass. Glass expands as it freezers, which could shatter the glass bottle and create a mess in your freezer.
I usually fill larger beaker, small soup container with sourdough starter and write a today’s date on a sticker label (so that I know when I put it into the freezer) and place the freezer.
Freezing sourdough starter in large ice cubes trays
If you don’t have a lot of sourdough starter to freeze, you can pour it to ice cube trays. This is also great for a smaller portions of innactive sourdough starter discards, because you can add them straight to pancake batter, sauces or other recipes.
Freezing sourdough starter in a sturdy plastic bags
Another option is to use a sturdy plastic bag, that will allow you to portion your sourdough starter in. Place the bags on a tray, next to each other (not covered) and blast freeze them first for few hours. When they can hold their shape, stack them up in your freezer or add them to a larger container that you can keep them in.
Flat bags also defrost a lot quicker, because you can place them on a baking cooling rack and let the warm air circulate around and defrost the sourdough starter.
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What containers are best for freezing sourdough starter?
- Large ice cube trays
- Medium size containers suitable for the freezer (beakers, soup mugs with lids etc)
- Sturdy thick plastic bags with suitable ties or strong handles that can be tied in
Whilst I often keep my sourdough starter in a glass jar, I would never freeze it in one. This is because glass will contract and move as it freezes and can shatter as a result. And the last thing you want in your frezer is a heap of broken glass!
How to defrost sourdough starter
Medium to large containers of sourdough starter
You will need to take out your frozen sourdough starter from the freezer about 3 days before you want to bake sourdough bread again.
Leave out the sourdough starter container to defrost in a room temperature. The wild yeast should be brought back to the room temperature slowly, althought I’ve once tried to use the defrost setting on my microwave and it worked too. You just need to be careful not to make the sourdough starter too warm (and definitelly not hot), as this would damage the wild yeast.
Once defrosted, you might find that your sourdough starter has separated, but you can bring it back together by whisking it with fork as you feed the sourdough starter.
Sourdough bread starter ice cube trays
If you are freezing sourdough starter in ice cubes trays, you are more likely to use the sourdough starter as a discard and in that case there is no need to defrost the whole trays.
Just take out whatever you need and add the frozen sourdough starter cubes into pancake batter, cake in a mug recipes, sauces or to thicken soups.
You can also use these smaller amounts to make sourdough starter without discarding. You can start with one ice cube of sourdough starter and then add the same amout of fresh flour and water. Keep going for 2-3 feeds (without discarding anything) and you’ll build up slightly bigger amount of sourdough starter to use for your baking.
Can I re-freeze sourdough starter?
Althought sourdough bread starter will not go off as such, I would never re-freeze it immediatelly when it’s defrosted. This is because the natural yeast completely slows down and stops it’s activity when frozen and it’s difficult to revive it again.
What you can do, howerer is that once you start to feed your sourdough starter, the flour (and the natural yeast) will start to get revived with fresh water and flour. This means that after a few week, you can freeze again whatever you don’t need, withouth worrying that you’ve ruined your sourdough starter.
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How to revive sourdough starter (after it’s been frozen)
Transfer the sourdough starter into a suitable container
You will need a suitable container – either plastic or glass with a lid that you can keep your sourdough starter in.
The container should be at least 3-4 times bigger than your sourdough starter (or depending on whether you are used to keeping smaller amount of sourdough starter or larger one.
Weight or measure your sourdough starter
Once your sourdough starter is brought back to a room temperature, weight (or measure out) your sourdough starter. This is important, so that you know how much fresh flour and water you need to add in.
Take out 1/2 of your innactive starter (skip if you are growing your sourdough starter)
You can skip this step, if you are increasing your sourdough starter in size. I do that for example to grow my sourdough starter to share with my bread baking students or you might be just about to bake a lot of sourdough bread.
If you are keeping smaller amount of sourdough starter, then take out about 1/2 of the starter and use it for baking regular bread (with yeast), making pancakes or any other recipes that you like.
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Feed your sourdough starter
Add 50% water and 50% flour of the total amount that you’ve just taken out. For example if you’ve taken out 1/2 of your sourdough starter and the 1/2 weighed 50 grams (or 3 tablespoons), you need to add 25 grams of fresh flour (1 1/2 tablespoons) and 25 grams (millilitres) of water (1 1/2 tablespoons).
This doesn’t have to be absolutely precise, but you should roughtly replace what you take out with the same amount (that’s combined from fresh flour and water).
If you are not discarding your sourdough starter, because you want to build up your soudough starter, then just add the same amount of flour and water to mix in.
Keep in the room temperature (if you want to bake soon)
Close the lid (or loosely close) and keep the sourdough starter in a warmer part of your kitchen. You can even keep it close to a warm cupboard, but don’t let the starter to become to warm (no more than 23-25C).
Keep in the fridge (if you don’t need to bake straightaway)
If you don’t want to bake sourdough straightaway, you can keep your sourdough bread starter in the fridge. The coldness of the fridge slows down the natural yeast activity and means that you don’t have to feed your sourdough starter more than once a week.
Repeat 2-3 times or until active again
Repeat this process of feeding (and discardig) 2-3 times or until the previously frozen sourdough starter becomes bubby and active again.
Use in your sourdough bread baking
Final step is to use your newly revived sourdough starter for baking sourdough bread acording to your favourite sourdough bread recipe.
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