How Long Does Cornstarch Last (And Why)?

Exact Answer: Forever

Cornstarch, or also known as corn flour and masa flour is an example of a carbohydrate that is extracted from the endosperm of corn. Though it has many purposes in cooking, the major purpose of cornstarch is to thicken any type of curry.



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Apart from the purpose of thickening the curry, cornstarch is also used as an anti-caking agent in powdered sugar to make ingredients such as icing and confectioner’s sugar. 

How Long Does Cornstarch Last

How Long Does Cornstarch Last?

Packaging of the cornstarchTime
Airtight packagingForever
Loose packaging (exposed to moisture)2 days to 4 days

The shelf life of cornstarch is indefinite when stored properly. But when not stored as per its proper storage conditions, it can make the shelf life of the cornstarch to get reduced to a significant extent.

The proper storage conditions to store cornstarch is to store them in a container and away from moisture. Though the best way to store cornstarch is to store them in an airtight container, it can still last indefinitely when stored in a normal glass container or plastic container as well.

The biggest enemy of cornstarch is moisture. That is to say that if the cornstarch gets exposed to moisture for longer than a certain duration, it will go bad in a significantly less time than its average shelf life.

Thus, it is always recommended to store cornstarch in a glass container or plastic container, and strictly away from moisture. If exposed to moisture for not a very long duration, the cornstarch is still good for use.

On average, if cornstarch becomes exposed to only a very small amount of moisture, then it will only result in clumping of cornstarch. In other words, only several clumps of cornstarch would be formed varying in size.

If so happens, the cornstarch is still good to use. One can physically crush the clumps using hands and make them turn back into powdery form. After doing that, you can just make cornstarch dry on its own and it will become completely edible once again.

While on the other hand, if the cornstarch becomes exposed to more amount of moisture, then it will result in bacterial growth over the cornstarch.  In this case, cornstarch lasts for about a minimum of 2 days to a maximum of 4 days.

It can be easily identified with a look of small blackish-blue colored dots over the cornstarch powder. If so happens, the cornstarch becomes completely inedible to eat and must not be consumed in any case. If consumed, it can result in severe health issues such as food poisoning.

Why Does Cornstarch Last That Long?

The major reason why the shelf life of the cornstarch when kept in airtight packaging is longer than the shelf life of the corn in the fridge when kept in loose packaging is because of its exposure to moisture.

The most prominent factor which plays a vital role in the decaying of the cornstarch is its exposure to moisture. When cornstarch is exposed to moisture, the shelf life of that decreases to a significant extent making it rot faster than its actual shelf life. 

The reason behind why the shelf life of the cornstarch is shorter when stored in loose packaging is because when stored in such a way the cornstarch can freely get exposed to the atmosphere, and consequently the moisture present in the air as well.

Exposure to moisture makes the organic matter grow over cornstarch which makes it unfit for consumption.

While on the other hand, when the corn in the fridge is stored in airtight packaging, it is not able to interact with the moisture present. As a result, the shelf life of the cornstarch stored in airtight packaging is long.


Cornstarch can readily absorb moisture, thus it must be carefully stored away from moisture especially in cases of humid temperature. Apart from that, high temperatures can also affect the shelf life of cornstarch.

Thus, it is always recommended to store moisture in a cool and dry place. For more exact storage conditions for cornstarch, it is generally mentioned in the packages of cornstarch. The best place to store cornstarch is in a glass or plastic container in the pantry.


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