Does Corn Masa Expire?

In this brief guide, we will answer the query, “Does Corn Masa Expire?” and will discuss some signs to detect spoiled Corn Masa.

Does Corn Masa Expire?

Yes, corn masa can expire. Fresh masa de maiz, also known as masa preparada, may be kept in the refrigerator for up to three days. In a cold, dark location such as a pantry, masa harina, also known as maize flour or as Maseca, lasts between 9 and 12 months. They should be thrown away if they’ve passed their expiration dates.

In some Latin American countries, tortillas alone can provide up to 70% of total caloric and up to 50% of total daily protein, calcium, iron, and zinc intake (1).

What exactly is corn masa?

Corn masa is produced by simulating, on an industrial scale, the ancient Aztec art of cooking and processing corn with lime. Whole corn is boiled and/or cooked with 120 to 300% water and 0.1 to 5.0% lime (on an original corn mass basis) for 0.25 to 3.0 h at 80 to 100°C, and is then steeped for up to 24 h between 40 and 100°C. This process, called nixtamalization, can be either a batch or a continuous process, depending on production equipment and procedures implemented, and is highly dependent on corn hybrids, temperatures, times, and lime concentrations used. During nixtamalization, physical, structural, and chemical changes occur inside the corn kernels (1).

Not to be confused with the Maseca brand of maize flour bags usually referred to as masa harina or cornflour. Masa preparada, or ready-made dough produced from corn masa and either lard or water, is the other name for this kind of prepared dough created from corn masa. However, it may also be prepared using hominy, which is a dried maize kernel steeped in lime syrup (the mineral, not the fruit).

Regardless of how it’s made, corn masa is used to create corn tortillas, tamales, and a slew of other Mexican sweets. If you’re fortunate enough to get fresh corn masa, you may find it in both coarse and smooth ground forms. For tortillas, you want smooth ground, while for tamales, you want coarse ground.

For how long does masa remain usable?

Dry corn masa flour has longer shelf-life than wet masa as well as greater convenience in home and commercial preparation. Typical dry masa flour has 10-12% moisture and is stable against microbial growth; however, it is highly susceptible to the development of off-flavors and odors usually associated with lipid oxidation of unsaturated fatty acids. Major factors that affect lipid oxidation of foods include the presence of catalysts, light, oxygen concentration, water activity, and temperature. Exposure to high temperature during storage and distribution would likely increase the reaction rate. Therefore, the storage temperature could be managed to extend the shelf-life of dry corn masa (2).

Refrigerated fresh corn masa keeps for three days, due to the high moisture content, differently from dry corn masa, which is stable at room temperature for many months. After three days, trash it after keeping it well-covered. Make your masa de maiz at room temperature if you plan on using it to make tortillas. When the weather is warm, the tortillas are less likely to split and break. Processing of refrigerated processed foods of extended durability generally combines mild heat treatment and subsequent storage at temperatures of 4–7°C, providing shelf-life ranging from a few days to 3 months (3).

Keeping your masa for tortillas at room temperature has the drawback of necessitating its disposal after 12 hours. Keep the masa covered in a Tupperware container or wrapped in saran wrap, whichever you prefer.

Maseca flour shelf life

Maseca is a well-known brand of masa harina, the primary ingredient in corn masa. Maseca flour is available at the grocery store in the same plastic bags as other flours, and it may be stored in the pantry with other flours. A plus is that Maseca is more durable than wheat or other kinds of flour.

Corn flour or masa harina, regardless of brand, should last at least nine months and, in most instances, up to twelve months. Maseca, for example. Just be sure to keep your flour in a cold, dark location, like the pantry, to prevent mold growth. Dry corn flour tends to gain moisture from the environment and increased moisture leads to its deterioration and mold growth (4). Use a container with a cover to keep it fresh longer and keep pests away. White flour and maize flour should not be stored in the refrigerator because they may get too wet and develop mold. Whole wheat flour can be stored in the refrigerator. However, studies show that the shelf-life of Maseca dry corn masa flour was 24 wk (6 mo)when stored at 25°C. Each 10°C increase in storage temperature reduced the shelf-life of dry corn masa flour by almost one-half (2).

The “best before” date is usually printed on the bag of flour. While an expiry date indicates that the product has gone bad after that date, this signifies just that it tastes better while it’s still fresh. However, you should attempt to utilize your Maseca within a year after opening it.

If the cornflour is bad or ruined, how can you tell?

The main problem with maize flour/masa harina isn’t typically the age of the product; rather, it’s bugged. Weevils, to be exact. 1 will often lay eggs in a sack of flour or grain. After then, those pesky aphids spread throughout your pantry, eating everything in their path.

If that occurs, you may put the bag in the freezer to put an end to the infestation, but you should simply throw it away. Once you’ve done that, do a thorough purge of your pantry. Toss anything that seems infected from an open bag or package. Make sure no eggs are hidden on the shelf by using a spray cleaner and cleaning the shelves carefully.

In addition, insects are believed to influence fungal growth in stored grains and grain products by increasing seed damage and moisture content via feeding and by carrying microflora within their gut which is viable after excretion (5).

The major factor in consumer acceptance of tortillas are the texture and the handling properties of the product. Right after baking, tortillas are soft and pliable and can easily be rolled or folded without cracking. As the tortillas begin to stale, they undergo changes that result in a more firm, rigid tortilla that will easily crack when rolled or folded (6).

To determine whether corn tortillas are rotten, look for any of the following signs:

  • If stored properly, corn tortillas will last in a pantry for 7-10 days and the refrigerator for 6-8 weeks before going bad. For a shelf life of 6-8 months, place them in the freezer. Freezing the tortilla is the only way to extend the shelf life without adding other ingredients to the tortilla. However, according to the USDA, unopened tortillas can stay at room temperature for 25-45 days. 
  • Mold stains are the most obvious indication of a poor tortilla (7).

Not the same as brown or black markings on certain tortillas left by the griddle. As a result, pay close attention. If you detect even a speck of mold, throw away the whole box since mold spores will have spread throughout the tortillas even if they aren’t yet visible.

Corn tortillas, how long do they keep their freshness?

Corn tortillas, in contrast to their wheat counterparts, don’t keep for extended periods.

Having said that, this does not imply that they go bad. However, they soon develop a robust exterior and leathery hide. The reason for this is because I don’t purchase corn tortillas from the grocery store unless they make them fresh every day in that particular shop.

Make them yourself if you can’t find a nice local restaurant where you can purchase fresh ones. Rick Bayless is my favorite Mexican chef, even though he is not Mexican. See how he makes fresh corn tortillas the easy way. 


In this brief guide, we answered the query, “Does Corn Masa Expire?” and discussed some signs to detect spoiled Corn Masa.

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Rosentrater, Kurt A. Properties of corn masa processing byproducts. 2003 ASAE Annual Meeting. American Society of Agricultural and Biological Engineers, 2003.


Vidal-Quintanar, Reyna Luz. Lipid oxidation in dry corn masa flour and strategies to improve shelf-life. Iowa State University, 1993.


Rajkovic, Andreja, et al. Prevalence and characterisation of Bacillus cereus in vacuum packed potato puree. Int j food sci technol, 2006, 41, 878-884.


Deepa, C., and H. Umesh Hebbar. Effect of micronization of maize grains on shelf‐life of flour. J Food Process Preserv, 2017, 41, e13195.


Weber, Rebecca J. Shelf life extension of corn tortillas. 2008. Kansas State University.  


McCurdy, Sandra M., Joey D. Peutz, and Grace Wittman. Storing food for safety and quality. 2009. Oregon State University.