Does Miso Paste Go Bad? How To Tell For Sure

Quick summary: Miso paste will hardly spoil, but some flavor loss can happen over time. Still, you’ll have plenty of time to use up the whole amount.

Miso is a paste made by fermenting soybeans with salt and kōji. These are the main ingredients, and depending on the recipe, it may also contain other additives. It is thick and actually very resistant to spoilage precisely because of the high presence of salt. 

Although this spice is very popular in Asian countries, it is not bad to include it in the diet because it is full of positive qualities for health. You will hardly encounter deterioration in the classical sense of the word, but quality decay is possible over time. Here’s how to best store miso and how to recognize when it’s time for a new package.

How Long Does Miso Last?

We have already said that miso is not prone to spoilage. A simple abundance of salt and a fermented environment is not a friendly environment for bacteria to live in. However, this does not mean that the package of miso paste you have will last forever. It won’t necessarily spoil, but the quality will decrease over time. Here is the approximate period you can count on.

Unopened miso

Miso has a very stable quality before opening. Depending on the laws in your country, you will generally come across a best-by date and sometimes just a date of manufacture. But you can be sure that miso paste is good for about a year from production. In fact, if you have a best-by date on the package, you can extend it by three to four months without fear. These are pretty safe limits. As miso does not spoil very often, your product will probably be good for a long time. However, check if the quality is up to par.

Opened miso

After opening, the situation changes somewhat, but this does not mean you need to use up the leftovers in a hurry. It is a fairly safe estimate that it will be good for at least the next three months and probably longer.

Can Miso Go Bad?

This is always a tricky question when it comes to food. No, under normal conditions, miso will not spoil in the classic way. However, the quality of the taste will deteriorate over time because the product does not stop fermenting, so this will be a sign that you should throw away the leftovers. However, the devil is in the details when it comes to food. There are always a few cases that defy the rules, so spoilage can also occur due to improper storage conditions.

Sign 1: Smell is off

The rule of thumb is if your nose tells you something is wrong, listen to it. A suspicious foul smell usually means that some negative changes have occurred.

Sign 2: Mold appeared

Since miso is not an attractive habitat for bacteria, neither is it for mold. But if you accidentally use an unclean spoon to introduce dirt into the jar of miso paste, mold can appear, and you must throw such food away.

Sign 3: Taste is dull 

This will be more of a sign of quality deterioration than spoilage, but it is still vital. Faded miso will not magically make a delicious miso soup, so you can immediately throw such a product in the trash.

Which is the Best Way to Store Miso?

Miso paste belongs to the ranks of super easy foods to keep. Here are the basic guidelines for having long-lasting and high-quality miso paste.

Tip 1: Keep at a suitable temperature

You can keep the miso paste at room temperature before opening it. Pantry or kitchen cabinet, it doesn’t matter. It is essential, however, that it is a bit far from the stove where you are cooking, as heating and changes in temperature could affect spoilage.

Tip 2: Keep in the refrigerator after opening

Many manufacturers will not provide instructions for mandatory storage in the refrigerator after opening. However, we recommend that the leftovers be kept at a stable cold temperature in order to maximize the shelf life and preserve the quality.

Tip 3: Maintain hygiene and seal well

These are perhaps the most critical steps to prevent that rare spoilage we mentioned. Always close the package well before putting it away, and also, always use a clean spoon.


How can you tell if miso is bad?

A foul smell or the visible appearance of mold are clear signs of spoilage. Also, changes in color or texture are possible indications.

How long can you keep miso paste after opening?

Three months is a safe period in which miso leftovers should be good. However, this period will likely be extended for a few months longer with proper storage.

Can miso give you food poisoning?

Even after the expiration date, miso should not cause any ill health effects, only if there is severe deterioration, which is a really rare case.

Asian cuisine is usually associated with healthier foods, which is also the case with miso paste. Although it contains a significant amount of salt, many nutritionists will recommend this spice as beneficial for health. 

Miso is a very durable condiment, and you can keep it at room temperature before opening it and count on it for at least three and possibly six months after the expiration date. After opening, store the leftovers in the refrigerator and use them within three to four months.

Miso paste is sometimes recommended as a replacement for tamari sauce. Find other dish ideas in our list of tamari substitutes

*image by brebca/depositphotos

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