Does Freezing Miso Kill Probiotics?

img of Does Freezing Miso Kill Probiotics

Quick answer: Freezing miso does not necessarily kill probiotics. The probiotics found in miso, particularly Aspergillus oryzae, can tolerate freezing temperatures. While freezing may affect their activity to some extent, miso typically retains its probiotic benefits even when stored in the freezer. Thawing it properly and avoiding high heat when using it in dishes can help preserve these beneficial microorganisms.

These days, most people are aware that you can use miso for more than just soup!

You can add miso to just about anything, to give it that special kick. I, myself, add a dab to plain rice to dress it up, but some people are more adventurous. My roommate in college would even spread it lightly on toast!

The health benefits of miso are impressive, most notably, the probiotic content. Miso contains a whopping 100 billion CFU (a measurement unit for good microbial bacteria) per gram[i].

How about you? Do you love miso? Do you incorporate miso into your meals regularly?

If you’ve bought miso paste to use in a recipe, you may be wondering how best to store it.

Should you keep miso at room temperature or refrigerate it? Can you freeze miso to extend its shelf life?

The answer is yes! All three are possible, but storing miso paste in your freezer may be the best way to keep its freshness and unique flavor. That said, there are a few things you should know about miso’s probiotics, and how best to preserve them.

How is Miso Made?

Traditional miso uses only three ingredients:

  • soybeans
  • kōji (a type of fungus cultivated on rice or barley)
  • salt

The soybeans are crushed and combined with the kōji and salt and left to ferment. Fermentation can be as short as six days to as long as several years.

During fermentation, probiotics (good bacteria) begin to multiply. The main probiotic strain found in miso is Aspergillus oryzae.[ii]

Fortunately, Aspergillus oryzae tolerates freezing temperatures.

Types of Miso

Several factors change the flavor, texture, and color of misoLength of fermentation

  1. Strain of kōji
  2. Type of grain used to cultivate kōji

These variables determine the flavor and color of miso.

There are four main types of miso:

Table 1: Types of Miso and Their Characteristics

Miso TypeIngredientsFlavorRecommended Use
White or LightSoybeans and riceMildSauces, dressings
YellowSoybeans and barleyComplexDishes, marinades
BarleySimilar to yellow miso, longer fermentationStrong barley tasteHearty dishes
Red or DarkMostly soybeans, up to 6 years of fermentationStrong, saltyRobust dishes, soups
  • White or light miso (Shiro) – made from soybeans and rice, with a mild flavor
  • Yellow miso (Shinshu) – made from soybeans and barley, with a more complex flavor
  • Barley miso (Mugi) – like yellow miso but fermented longer with a stronger barley taste
  • Red or dark miso (Aka) – made mostly from soybeans, fermented for up to six years, with a strong, salty taste.

All varieties of miso contain an impressive level of probiotics. Stronger flavored miso is often used in heartier dishes, while lighter miso is a favorite for making sauces or dressings.

Beware of Pasteurization

As miso has grown in popularity, a trend has begun to emerge – pasteurized miso.

Pasteurized miso may last longer, but it comes at a cost. The pasteurization process involves high heat which kills probiotics.

Check the label. If you’re buying miso for its probiotic properties, skip the pasteurized products.

How to Store Miso

Unopened, you can leave miso at room temperature. Store it away from sunlight and heat sources.

You should refrigerate (or freeze) opened miso. Keep these points in mind when refrigerating:

Table 2: Storage Recommendations

Storage MethodWhen to UseHow to Store It
Room TemperatureUnopened misoAway from sunlight and heat
RefrigerationOpened misoOriginal packaging or resealable
FreezingOpened miso (best)Freezer bag, container, or ice cube trays
  • If you’ve bought miso in a jar or container, leave it in its original packaging
  • If it came in a packet or tube, empty it into a resealable container
  • Always use a clean spoon when scooping out miso. A spoon used for other foods may introduce bacteria and spoil miso

For the best preservation of flavor, you can store miso in your freezer.

Freezing Miso

The great thing about miso is that it doesn’t freeze solid. This is due to the fermentation process. So, no chiseling out frozen miso with a knife. Although it will be firmer when frozen, you should still be able to scoop it with a spoon.

Or, you can freeze miso in ice cube trays. This is an easy way to have a pre-portioned amount ready to add to soups or other dishes.

To freeze miso:

  1. Add it to a freezer bag, freezer-safe container, or an ice cube tray.
  2. Smooth it out to remove any air bubbles.
  3. Seal tightly with minimal air space. (You can wrap ice cube trays in plastic.)

Thawing Out Miso

Depending on what you’ll be using it for, you may not have to do much thawing. As miso never freezes solid, you may be able to just add it to a hot dish and stir.

If you want the miso to be a little softer, a short time left at room temperature should be enough. You can also thaw miso in the refrigerator.  

Avoid High Heat

It’s important to remember that, unlike freezing, heat will kill probiotics. You never want to let the temperature of miso rise above 115 degrees F.

If you’re adding miso to a cooked dish, do so at the end of the cooking process whenever possible.

When reheating miso soup, be sure not to boil it. Heat it gently over low heat and stir to distribute the temperature evenly. This is the best practice for preserving those lovely probiotics!

Other Health Benefits of Miso

Probiotics are not the only thing miso has going for it![iii] A one-ounce serving of miso also contains:

Table 4: Health Benefits of Miso

NutrientAmount per One-Ounce Serving
Manganese12% of the RDI
Vitamin K10% of the RDI
Copper6% of the RDI
Zinc5% of the RDI
Carbohydrates7 grams
Fat2 grams
Sodium (Caution)43% of the RDI

Plus, miso is low in fat and carbs. A one-ounce serving has only 56 calories, 7 grams of carbohydrates, and 2 grams of fat.

Is There Anything Unhealthy About Miso?

Miso does have quite a bit of sodium – one tablespoon contains approximately one-third of the recommended daily value. If you’re watching your sodium, you may want to limit your intake of miso.

Does Freezing Miso Kill Probiotics?

Miso is a great product to keep on hand and freezing it will extend the shelf life.

To recap:

  • Does Freezing Miso Kill Probiotics? Miso retains its probiotics even in freezing temperatures.
  • Miso does not freeze solid, which helps when you just need a spoonful.
  • Use the correct method to thaw miso. Refrigerator or room temperature is best.
  • You should avoid heating miso above 115 degrees F. High heat kills probiotics. Be careful when reheating miso soup and other dishes.

Do you love miso? What’s your favorite dish to add miso to? Have you ever eaten miso in unconventional ways?

We’d also love to hear about your own experiences.

Please feel free to ask any questions or share a story in the comment space below.

Thank you for reading… and stay healthy!

[i] Probiotics: 10 Foods That Promote Digestive Health (

[ii] Why Miso Is Incredibly Healthy (

[iii] Fermentation and the microbial community of Japanese koji and miso: A review – PubMed (

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