How Long Can Miso Last (And Why)?

How Long Can Miso Last (And Why)?

Exact Answer: More than 20 years

Miso is a popular ingredient used in several notable Japanese delicacies. The miso paste is made by fermenting soybeans with salt and a microbial culture called ‘Koji’. The Koji mold may also be cultivated by fermenting rice, barley, or other cereal grains. This chemical composition of the miso paste accords it the coveted shelf life.

The miso paste is part of the culinary heritage of the Japanese culture. It is commonly used to add flavor to various dishes like miso soups, salads, grilled fish, etc. The versatility of the paste makes it a great ingredient for preparing marinades and rubs. The taste of the miso paste will vary according to the proportion of soybeans to Koji, the fermentation process, and the conditions of its storage.

How Long Can Miso Last

How Long Can Miso Last

The popularity of the miso paste is based on its flavoring abilities as well as its durability. The miso paste has the distinction of procuring a formidably long shelf life as compared to the other pastes and packaged flavoring agents.

An unopened jar of miso can last for up to 20 years. This is one of the longest shelf life time frames for any edible item ever recorded. Authentic Japanese restaurants use miso pastes that are up to 20 years old. However, one must be cautioned that the sealed miso jar must be properly stored to retain its usability. The catch is to store it in the freezer. Leaving a sealed miso jar out in the open will considerably reduce its shelf life. People have also used miso paste aged over two decades. The taste of the miso has remained fresh due to the astute conditions of storing the jar.

Alternatively, an opened jar of miso can last for almost 9 to 14 years. Again, the longevity of the miso paste will be determined by the conditions in which it is stored. If it is kept out in the open, especially in the presence of sunlight, the quality of the paste will rapidly deteriorate. In such cases, miso will not last for 14 years. The key element in prolonging its usability is to immediately refrigerate the jar after using the paste. This helps slow the process of decay and keeps the paste fresh and safe for consumption. Consuming contaminated miso can be extremely harmful to the health of the individual.

In Summary:

Condition of the JarShelf Life  
Unopened Jar of MisoMore than 20 years
Opened Jar of MisoUp to 14 years

Why Does Miso Last this Long?

The secret to the lasting shelf life of a jar of miso paste is owed to its ingenious chemical composition. The process of manufacturing miso helps augment its longevity and keeps it safe for a considerable amount of time.

The fermentation of soybeans with Koji culture induces a certain endurance in the miso paste. This fermentation process aids in extending the shelf life of the paste. The addition of salt to the concoction also contributes towards increasing the durability of the product.

The seal helps prevent the entry of any dangerous microbes inside the miso jar. Keeping this jar away from direct sunlight and high temperatures helps slow down the fermentation process. This increases the durability of the paste to more than 20 years. However, if the paste is not stored in a cool, dry place or in a freezer, it will be decay over time.

When an opened jar of the miso paste is refrigerated, the cold of the freezer prevents the acceleration of the fermentation process, thereby halting any possible degeneration. Thus, it is always wise to refrigerate an opened jar of miso rather than keeping it out in the open. The warm temperatures of the normal settings will hasten the contamination process. The miso paste will soon be riddled with tiny microbial contaminants.  

The taste and color of a miso paste can be marginally altered when it is stored for a prolonged time period. However, this has no bearing on the safety and usability of the product. It can still be consumed without any health-related reservations and concerns.


Originally, miso was used exclusively by the Japanese monarchy. Today, the miso paste has become a culinary gem for commoners. The vivacity of the ingredient allows it to be used in dishes for a prolonged period of time to enhance their flavors and improve their tastes.

Refrigerating the paste after use helps boost the shelf life of the product. When you purchase an unopened jar, it is advisable to store it in the freezer until you are ready to unseal it. Sealed jars of miso can also be stored in cool cupboards, away from sunlight. However, once the seal is broken, it is prudent to refrigerate the jar in order to enjoy the tasteful paste for a long period of time.


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Hi! I'm Nidhi.

Here at the EHL, it's all about delicious, easy recipes for casual entertaining. So come and join me at the beach, relax and enjoy the food.


  1. The fact that miso can last over 20 years is impressive, but it’s important to ensure proper storage for this longevity.

    1. It’s hard to believe, but the facts don’t lie. Miso can last an incredibly long time if stored properly.

  2. The science behind miso’s longevity is truly fascinating. I’ll cherish my miso paste even more now.

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