How To Freeze Sourdough Starter? 

When it comes to preserving your sourdough starter for future baking adventures, the good news is that freezing can be an excellent solution. Freezing your sourdough starter offers a reliable method for long-term storage, ensuring its freshness and viability whenever you’re ready to dive back into the world of artisanal bread-making. In this article, we will explore the ins and outs of freezing sourdough starter, including the best practices and techniques to maintain its quality throughout the freezing process. So, if you find yourself with an abundance of sourdough starter or need to put it on hold for a while, keep reading to discover the optimal way to freeze your sourdough starter for convenient, long-lasting storage.

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Why Freeze Sourdough Starter? 

Freezing your sourdough starter can be a convenient way to store it for long periods while maintaining its viability. There are various situations where freezing your sourdough starter becomes a practical choice.

If you find yourself with an excess amount of sourdough starter that you cannot use immediately, freezing allows you to preserve it for future baking endeavours.

Additionally, if you need to take a break from your regular feeding schedule or anticipate being unable to tend to your starter for an extended period, freezing can ensure its survival and save you from restarting the entire fermentation process from scratch. It is:

• A convenient way to store excess sourdough starter for future use.
• Ideal for situations where you cannot maintain a regular feeding schedule.
• Ensures long term storage of sourdough starter without the need for frequent refreshments.
• Helpful when taking a break from baking or temporarily suspending sourdough activities.
• Preserves the viability of your sourdough starter for a long time, saving time and effort. 
• And it’s the best way to keep a backup in case something happens to the starter you store in the fridge (I’ve been there, I needed that backup… don’t ask…)

What Container is Best For Freezing Sourdough Starter In?

There are a few options for containers you may consider freezing your sourdough starter in. Experiment to find the best option for yourself. 

1. Freezer bag: you may simply scoop your active sourdough starter into a freezer-safe bag, seal it, and place it in the freezer (double up to protect it from freezer burn). 

2. Portion your starter into some type of silicone mould, like canele mould, silicone ice-cube tray or any other mould. This way, you can freeze your starter in the mould, then remove the shapes from it and place the portioned sourdough starter into sturdy plastic bags for future use. 

3. Freezer-safe plastic containers: Look for airtight plastic containers specifically designed for freezer use. These containers should have a tight-sealing lid to prevent air exposure and freezer burn.

Step-By-Step Guide To Freezing Sourdough Starter

Follow these simple steps in order to store your sourdough starter in the freezer safely:

1. Prepare the sourdough starter: Ensure that your sourdough starter is active and at its peak before freezing. This ensures the best chances of revival after thawing.
2. Portion the starter: Divide the sourdough starter into convenient portions based on your future needs. 
3. Transfer to freezer-safe containers: Place each portion of the sourdough starter into separate freezer-safe containers. Options include airtight plastic containers, heavy-duty freezer bags or icecube trays/ silicone moulds. Leave some headspace (but not much) in the containers to accommodate expansion during freezing.

4. Label and date the containers: Use labels or markers to clearly indicate the contents and date of freezing on each container. This helps with organization and keeps track of storage time.
5. Freeze the sourdough starter: Put the containers with the sourdough starter portions into the deep freeze. If you’re freezing your starter in ice cube trays or silicone moulds (or anything that will allow you to remove them from the moulds easily), freeze the starter in the moulds for 4-6 hours, until frozen solid. Then pop them out and transfer them into ziplock bags. 
6. Maintain a consistent temperature: Ensure that your freezer maintains a consistent temperature, below 0°C (32°F). Fluctuating temperatures can affect the quality of the frozen sourdough starter.

How To Revive Frozen Sourdough Starter?

To successfully bring your frozen sourdough starter back to life and make it ready for baking, proper defrosting and revival techniques are essential. Follow these steps for the best results:

1. Defrosting the frozen starter: Take your frozen sourdough starter out of the freezer and allow it to thaw gradually. Place the container in the refrigerator overnight or until fully thawed. This slow thawing process helps maintain the integrity of the starter.
2. Preparing for revival: Once the sourdough starter has thawed, place it into a clean glass.
3. Creating a warm spot: Find a warm spot in your kitchen where the sourdough starter can rest and develop. Ideally, the temperature should be around room temperature, between 24°C and 28°C (75°F and 82°F). This warmth helps stimulate the fermentation process and encourages the starter to become active again.
4. Feeding the starter: To your starter, add an equal amount of flour (such as bread flour or all-purpose flour) and lukewarm water. Stir the mixture well until thoroughly combined. Leave the mixture for 12 hours before feeding again. 
5. Regular feedings and monitoring: For the first few days, continue with regular feedings every 12 hours. Discard a portion of the starter and feed it with equal amounts of flour and water. Observe the signs of activity, such as bubbles and a slightly tangy aroma, indicating that the starter is coming back to life. We find it typically only takes 2 feeds to revive the starter and see the live yeast in action again. If using a rubber band, secure it around the container to mark the level of the starter before revival. This will help you assess the starter’s growth during the revival process. Your starter should at least double in volume within 4 hours at room temperature if it is ready to be used in baking. 

Throughout the revival process, it is important to use fresh water and high-quality flour for feeding. This helps provide the necessary nutrients for the starter to thrive. As your sourdough starter thaws and revives, it will gradually regain its full strength and be ready to use for baking delicious bread.

Will Freezing Affect The Starter?

Sourdough starter is highly resilient and can withstand freezing temperatures. Even in the coldest freezers, the lactic acid bacteria and yeast present in the sourdough culture can survive. While some yeast may die off during freezing, the remaining dormant yeast in the culture is sufficient for revival upon defrosting.

There is no permanent damage caused by freezing a sourdough culture, as the yeast colony will quickly reestablish itself once the starter is refreshed. Although sourdough starters thrive in warm temperatures, freezing is a safe option. For less chance of freezer burn, consider double bagging or using aluminum foil for added protection.

How Long Can You Freeze Sourdough Starter?

If you have properly frozen your sourdough starter in a suitable freezer container, and your freezer is well-maintained with stable temperatures, your sourdough starter should remain in good condition for at least 12 months. 

Why You Should Never Freeze A New Starter?

Freezing a new and fresh sourdough starter isn’t a good idea because it takes time for it to develop into a robust and mature state.

While a brand-new sourdough starter can take anywhere from 1 to 3 weeks to become active enough for bread-making, it contains a living community of evolving bacteria and wild yeast. Over a period of approximately 3 months, the fresh starter gradually strengthens and reaches a mature stage.

During this time, it acquires the necessary complexity and quantity of natural yeast colonies and lactic acid bacteria to withstand the freezing process. Therefore, if you’ve recently created your sourdough starter, it’s important to maintain and regularly feed it for several months before considering freezing it.

Essential Dos and Don’ts

1. Do use active sourdough starter: Before freezing, ensure that your sourdough starter is healthy, active, and at its peak. Freezing active starter will increase the chances of successful revival after freezing.
2. Only freeze mature sourdough starter: a good sourdough starter suitable for freezing is one that has been kept and maintained for at least 4 months. The natural yeast colonies need to be strong enough to withstand the freezing process. 
3. Do remove excess air: When transferring your sourdough starter to a freezer-safe container, make sure to remove as much air as possible from the container. Excess air can lead to the formation of ice crystals and affect the quality of your starter. 
4. Don’t freeze an unfed starter: It is not recommended to freeze a recently fed starter. Feed and refresh your starter to its active state before freezing to enhance its chances of revival.
5. Do label and date your containers: To keep track of the freshness and freezing time of your sourdough starter, label each container with the date of freezing. This helps you prioritize and use the oldest starters first.

Frequently Asked Questions

Alternatives To Freezing Sourdough Starter

There are a few different ways to store your sourdough starter. If freezing your starter isn’t the right method for you, consider the following: 

Store Sourdough Starter In The Fridge: If you feed your starter regularly, and bake with it often, there is no need to freeze it. For short periods of time, simply feed your starter and store it in the fridge for a couple of days (but no longer than 5-6 days). Whilst the starter can be stored in the fridge for as long as a couple of weeks, you will need to feed it for many consecutive days to revive it creating lots and lots of sourdough discard! 

Here’s what you need to do to fridge it safely:

• Make sure your starter is freshly fed and placed in a clean glass container (we store our starter in mason jars or reused glass jars). 
• Ensure enough empty space for the starter to rise and breathe, as it may rise a little even at cold temperatures. 
• Screw the lid on tightly and place it in the fridge. 
• To revive your starter, feed it for a few consecutive days until it passes the fit-for-purpose tests described in our sourdough starter guide. 

Dehydrate Your Sourdough Starter: A great way to store a backup sourdough starter long-term (indefinitely) is to dehydrate it. 

• Feed your starter one last time and leave it to become bubbly and active. 
• Spread a very thin layer of active wet starter on a large sheet of parchment paper (you may place it on a baking sheet for easier mobility) and leave to air dry until completely dry and crispy (usually 24-36 hours, but it depends on the humidity and temperature of the environment). 
• Crumble up your dry starter into small pieces or crush it into a powder.
• Store it in an airtight container in a dark and dry place.
• To rehydrate, add equal parts of dried starter and water and cover the bowl partially. It should rehydrate within a couple of hours. Then revive it as usual with regular feeding. 

Don’t Yet Have Your Own Sourdough Starter?