Does Freezing Sourdough Kill Probiotics? (Simple Answer)

Quick answer: Freezing sourdough does not kill probiotics; they go into dormancy and become active again when the starter thaws. Probiotics, like lactobacillus acidophilus, found in sourdough, can survive freezing and thawing.

Sourdough bread is a personal favorite of mine! It’s a great way to be able to bake fresh bread at the drop of a hat, and the tangy taste can’t be beat.

But if you’ve ever maintained a sourdough starter you probably know it’s a lot of work. If kept at room temperature, it’s like a pet, needing “food” every day.

I recently was looking for a way to take a little break.

I started wondering: what happens if you freeze sourdough? Does it kill the probiotics? (Probiotics are “good bacteria” found in fermented foods. They aid in digestion and contribute to gut health.)

After some thorough research, I can share this good news!

You can indeed freeze sourdough starter without killing the probiotics. But you do have to take steps to freeze it properly.

First, the truth about sourdough bread

A lot of people think sourdough bread has active probiotics in it. It may surprise you to find out that the baked loaf actually does not! But it did, back when it was just a batter – a.k.a., a starter.

The sourdough starter changed the biochemistry of the wheat. It cultured good bacteria, making the finished, baked loaf healthier [i]. This is why sourdough is a healthy bread to eat.

The truth is this: Probiotics die when exposed to temperatures over 115 degrees F.

As your loaf of sourdough bread is baking, the probiotics are dying off. It’s the starter that’s healthy, being full of probiotics such as lactobacillus acidophilus.

But how did the probiotics get in there, you may ask?

It’s because of the process of fermentation.

Table 1: Probiotic Content in Sourdough

Sourdough TypeProbiotic Strains PresentProbiotic Activity (Survival)
TraditionalLactobacillus, BifidobacteriumSurvives freezing and thawing
Whole WheatLactobacillus, StreptococcusRemains viable in the freezer
Rye SourdoughLactobacillus, LeuconostocProbiotics go dormant but revive

How do you make sourdough starter ?

Sourdough starter only needs two ingredients: flour and water.

No yeast? Nope.

Many people don’t realize that there is wild yeast present in any type of flour.

When you combine equal parts of flour and water and leave them to sit at room temperature, the process of fermentation begins.

The active bacteria in the flour break down the starch molecules, converting the starch into lactic acid and acetic acid.

This is what gives sourdough bread its tangy flavor.

Here’s an excellent, simple recipe for sourdough starter.

What’s so healthy about sourdough bread?

Sourdough is the only bread that’s undergone the process of fermentation. Fermented products contain probiotics.

The probiotics in sourdough starter change the composition of the flour in these ways:

  • Converting sugar and starch into lactic acid, which:

1.      Improves gut health

2.      Boosts nutrient absorption

3.      Acts as an antioxidant

  • Decreasing phytic acid in wheat (called the “anti-nutrient” because it blocks vitamin absorption)
  • Lowering the glycemic index of the bread

Can you refrigerate sourdough starter?

Many people choose to keep their starter in the refrigerator, including me! This will lessen the amount of feeding needed to once per week. You’ll still need to bake regularly, though, as your starter grows in volume.

If you’re looking for less of a commitment, or you’re going on vacation, consider freezing your starter, instead.

Does freezing sourdough starter kill the probiotics?

Fortunately, when you freeze sourdough starter, the probiotics don’t die. They go into dormancy and will become active again when the starter thaws.

There are many strains of probiotics out there. Some of them tolerate freezing temperatures better than others. Sourdough contains lactobacillus acidophilus, the same probiotic found in yogurt. It survives freezing and thawing.

How to freeze sourdough starter

Take into consideration how soon you’ll be wanting to bake bread again. Two weeks? A month? Not till Thanksgiving?

It won’t be an instant process between thawing your starter and baking a loaf. After thawing, you’ll need to get your starter back on a regular feeding schedule. This will take a few days, or maybe even a week.

If you think you’ll be itching to bake again soon:

  • Divide your starter into smaller amounts. A smaller amount of starter will thaw more quickly. (You can skip this step if you don’t care how long thawing will take)
  • Place the starter in freezer bags or freezer-proof sealed containers, and label them with the date.

How long will sourdough starter last in the freezer?

To be safe, we recommend you discard frozen sourdough starter after 1 year. But, some people report having success with starters frozen up to 5 years.

How do you thaw frozen sourdough starter?

To thaw a frozen sourdough starter:

  • Remove it from the freezer and set it out at room temperature.
  • As soon as it softens, chop it in two and discard half of it. (I know it seems wasteful, but don’t skip this step. Doing this will ensure the ratio of fresh probiotics to new probiotics will be in balance.)
  • Resume the feedings as soon as the rest thaws enough to stir. Follow the same method you used before freezing, but initially, let it rest longer. A cold starter will need more time between feedings.
  • Watch for signs of fermentation before feeding again. The starter should bubble and smell tangy when it’s ready for more flour and water.

Once the starter is back on its regular feeding schedule, you can use it to bake again.

Can you use sourdough starter for more than bread?

Absolutely! You can use your sourdough starter to make pancakes, waffles, donuts, cake, and even pie crust! And by using sourdough in these items, you’ll bump up their nutritional value. It’s a win-win!

Check out these recipes for a few ideas.

Does Freezing Sourdough Kill Probiotics

You can freeze and thaw sourdough starter without killing the probiotics. The probiotics merely go into dormancy during freezing.

If you’ve ever felt daunted by the commitment a starter demands, rest easy. You can always take a break by storing your starter in the freezer. Then, when your schedule eases up, you can jump right back into having fresh bread weekly!

Are you a fan of sourdough, too?

We love to hear from our readers!

Have you made any sourdough items besides bread? What’s your favorite way to use sourdough starter? How long have you kept a sourdough starter going?

Please feel free to share your experiences, or ask any questions, in the comment section below.

Thank you for reading, and happy baking!

[i] Does Baking Sourdough Kill Probiotics? – The Dough Academy

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