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Does Miso Go Bad?

Does Miso Go Bad?

Every national cuisine has its own specific flavor worth checking out and some of its staples that make a perfect starting point for this culinary journey. In the case of Japanese cuisine, this go-to dish just has to be the miso soup that has recently earned quite a reputation all over the world.

However, these short ventures into other cultures have one common problem. Namely, most of the dishes you are going to try out don’t become the mainstay on your weekly menu. That leaves us with a lot of great ingredients, some of which don’t have the legs to wait for your next culinary outing.

So the chances out that you have tried the miso soup, you still have a good jug of miso sauce you need to keep safely stored for the next time you want to give a short to this delicious Japanese recipe.

That brings us to one very important question – does miso go bad, and if so, for how long you can keep it on the shelf. Let’s see if we can find the proper answer.

What Exactly Is The Miso Paste?

But, before we proceed to these essential considerations, let us first see what we are dealing with here. In spite of its growing popularity, miso is still considered a bit exotic in most stateside households. Learning more about the recipe will help us to appreciate it and preserve it better.

So, what is miso anyway? The best way to describe this sauce is as the fragmented and salted soybeans mixed with the traditional Japanese ingredient going under the name koji. Essentially, koji is made by boiling rice with Aspergillus oryzae – a filamentous fungus used in Japan for the purposes of fermenting.

This fermented mix provides a very tangy and salty taste that may feel a bit foreign to unaccustomed buds, but it grows on you as time goes by. On the other hand, paste-like texture makes it ideal for making soups, so it shouldn’t be too big of a surprise that one of the most popular recipes where miso is featured is nothing else but miso soup.

And now, let’s see what this bad boy packs when it comes to the nutritional content. We are going to break down one oz (28-gram) serving:

NameAmountDaily value (%)
Calories56 kcal2.8%
Carbohydrates7.19 g2.4%
Fiber1.53 g6.1%
Sugars1.76 g
Fat1.70 g2.6%
Protein3.63 g7.3%
Salt2.68 g

As we can see from the table above, miso represents a well-balanced and caloric blend of virtually all important nutrients the human body needs to get through the day. We are especially pleased with an unusually high level of fiber and protein, which makes it a perfect addition to any kind of healthy diet.

Miso is also rich in healthy elements like vitamin K, riboflavin, vitamin B6, thiamin, niacin, vitamin A and vitamin B12.

Miso Health Benefits

Speaking of health, we have to point out that this unique nutritional content also produces some quite surprising benefits.

Miso Offers Valuable Probiotics

Since miso is fermented, the recipe contains live cultures that, when put through the digestive system, act similar to yogurt. This gives people with lactose sensitivity an ideal replacement to traditional dairy-based probiotics necessary for healthy digestion. Probiotics also have a positive effect on cognitive health, mood, and appetite control.

Miso Prevents High Blood Pressure

As you can see from the breakdown above, miso features a very prominent presence of salt, which is not a good sign for people with cardiac problems. Even so, experimental evidence links miso to the prevention of high blood pressure. These effects are probably the product of the more extended fermentation period of soybeans, which causes the sodium in miso to react differently.

Miso Decrease Cholesterol Levels

If you are unfamiliar with its effects, cholesterol causes plaque to build up in the arteries, prevents blood flow increases the risk of heart disease. Fortunately, a recent study published in Japanese Pharmacology and Therapeutics indicates that regularly consuming miso soup three months in a row result in as much as a 7.6% decrease in total cholesterol levels.

Miso Can Prevent The Growth Of Cancer Cells

As we mentioned above, miso features a high level of beneficial probiotics, vitamins, and minerals. This mix produces excellent effects on the immune system and helps natural cancer prevention. But, going past this common knowledge, the study conducted at Hiroshima University also discovered that miso may have tangible effects in preventing the progression of cancerous tumors and preventing radiation injury.

All the things we talked about above paint a very pleasant picture of the miso sauce. Even if you need some time to get used to the taste, miso is definitely worth including in your diet and preserving for as long as possible. But how long?

How Long Does Miso Last?

Before we start discussing this topic, we have to mention that miso is a fermented product. Since they usually have a pretty strong shelf-life, you can set your expectations too high. Some people claim their jars were able to survive the period of 8  to 9 long years in the fridge before losing any of the quality, but we won’t go that far.

The miso’s life expectancy is usually indicated on the label by the best-by date. Keep note that this bit of info is not obligatory in all countries, so there are chances that your jar may miss one. But what is the best-by date?

To put it simply, this info tells you how long miso can stay stored before losing quality. For instance, if the label tells you that that miso can last a year, the paste will probably be edible even past this point. Still, it will lose quality and, most likely, some of its taste.

And now, let’s take a look at the average shelf times we got by comparing the most popular miso brands.

Unopened1-year best-by (plus 3-6 of additional months of safe usage)
Opened3 months

So let’s break it down. If you store miso in the pantry, you will get a good year before the sauce starts losing its taste. Past that point, the recipe will probably be edible for at least three months. When left in the refrigerator, miso can last way past its best-by date. The time you will get only depends on the way you store it.

The opened jars tell an entirely different story. Even when put into the refrigerator, miso will last only three modest months.

Lpc Does Miso Go Bad

How To Store Miso Properly

In spite of its immense durability, miso, much like all other foods, can be destroyed by the presence of bacteria that cause spoilage. Therefore, your task will be to keep the miso unexposed to external threats and create an environment where the bacteria won’t be allowed to thrive.

So, the first thing you should do to prevent this Japanese powerhouse from going rouge would be to keep the package tightly sealed when not in use. Also, make sure that the utensils you are using to scoop up the cream are as clean as they get. The salty, fermented paste is not precisely the ideal place where bacteria can thrive. Still, you don’t want to leave anything to chance, so keep the foreign food particles out of the jar.

The second thing to do is to keep the package in a dark place away from all sources of heat. Pantry and kitchen cabinets do make a solid pick, but if you want to stay 100% safe, find some room in the fridge. List this as an absolute priority if the jar has already been opened at some point. Microbial organisms don’t need more than a second to compromise the package. Don’t be so polite to give them a warm, cuddly surrounding in which they can multiply.

How To Check If Miso Is Bad

Finally, let us quickly go through some of the easiest ways to check if your miso paste has succumbed to all that nasty bacteria and ended up spoiled.

Like always, your nose will be your biggest ally. So, open the jar, and take a couple of good sniffs. If you notice that the smell is too sour and moldy, you should introduce the package to the nearest garbage bin.

The other way of checking the sauce is by giving it a thorough visual impression. When spoiled, miso will start picking up the mold and lose its natural brownish color. In its natural state, miso’s texture is matte and sharp. As soon as it starts spoiling, the paste will become soft, muddy, and watery.

It’s worth mentioning that in either of these cases, the majority of miso paste can be preserved by removing the spoiled parts. But we wouldn’t gamble with our health. If you notice any of the above-mentioned symptoms, just throw the whole package away.


We hope that you enjoyed this short dissection of miso’s nutritional content and shelf life. When we take a look at all the benefits we have listed above, we can see that including miso soup in your diet is probably one of the best things you can do for your diet. Since it takes only one ingredient in the recipe, miso will, inevitably, be used only sparingly. But now you at least know for how long you will be able to keep it safe and how to stretch that shelf life to the fullest extent.