How to Store Cornmeal Long-Term and Does Cornmeal Go Bad?


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Last Updated: February 7, 2022

Cornmeal is one of the best staples to keep stored.  However, there is a lot of confusion about cornmeal shelf life and whether it’s okay to store it long-term.

Here I will cover everything you need to know about shelf life, which types of cornmeal last longest, storage methods, and more.

Cornmeal Shelf Life

Cornmeal will generally last 6 to 12 months when stored at room temperature in its original packaging.  In an air-tight container stored in a cool, dark, and dry place, cornmeal can last even longer than this.

When stored with oxygen absorbers in Mylar bags, cornmeal can last over 10 years.  However, the shelf life ultimately depends on a lot of factors like the type of cornmeal and storage conditions.

Which Type of Cornmeal Lasts Longest?

By definition, cornmeal is just dried corn kernels that have been ground up.  Cornmeal is then broken down into types based on its fineness and whether it has been bolted or not.  As a general rule, bolted cornflour will last the longest.

Bolted vs. Unbolted Cornmeal

Bolted cornmeal: (aka degerminated cornmeal) means the ground corn kernels went through a sieve.  The sieve removes pieces of the hull and germ, both of which contain oils.

Unbolted cornmeal: (also called water-ground, stone-ground, or old-fashioned) will still contain hull and germ.

Almost all commercially sold corn flour today is bolted.

When nutrition is your primary concern, unbolted cornmeal is healthier.  But the oils in unbolted cornmeal will cause it to go rancid fairly quickly.

Going rancid doesn’t happen overnight: the cornmeal will gradually start tasting bitter and stale.  It might still be safe to eat after 6 months but won’t be pleasant to eat.

Grind Fineness

When a grain is finely ground, more of its surface is exposed to oxygen and will start to go bad faster.  Thus, you’d expect whole corn kernels to last the longest, followed by grits, polenta, and cornflour.

However, this isn’t always true with cornmeal.  The reason is that coarsely-ground cornmeal usually still contains oil-rich pieces of the germ and hull.  Even though it has less surface area, grits will still go bad faster than corn flour because of the extra oils.

Top Tip: When in doubt, look at the nutrition label of the cornmeal.  The lower the fat content, the longer the cornmeal will last.

Best Ways to Store Cornmeal

Freezer

Shelf Life: Indefinitely

The best way to store cornmeal is in the freezer.  It will last indefinitely this way.  However, be cautious when removing cornmeal from the freezer: moisture will start to form in the bag.  The pockets of moisture can cause the cornmeal to get moldy very quickly.

Air-Tight Containers

Shelf Life: 1-2 years

Storing cornmeal in air-tight containers such as mason jars or good plastic containers will help increase shelf life. The container will prevent oxygenation and also help keep pests out (moths particularly love cornmeal).

Cornmeal can even last several years like this so long as the temperature and humidity are low. Be sure to keep the containers away from sources of heat like water heaters or stoves.

Note that pest eggs are sometimes already in the cornmeal when you buy it.  When they hatch in a few weeks or months, you’ll see their larvae crawling around inside the container.  Learn more about how to prevent pantry pests.

Oxygen Absorbers

Shelf Life: 5-10+ years

The oxygen absorbers are little packets of iron that grab onto oxygen molecules.  When you up an OA in a sealed, air-tight container, it creates an oxygen-free storage environment.  The food will last longer because oxidization can’t occur.  Mold, bacteria, and pests also won’t be able to survive without oxygen, so the cornmeal stays safe to eat.

You can use oxygen absorbers in mason jars or even some food-grade buckets.  However, Mylar bags are generally considered to be most reliable for long-term food storage.

Read more about how to pack food in Mylar bags and how to use oxygen absorbers here.

Warning: Cornmeal, Botulism and Oxygen Absorbers

Most bacteria cannot survive without oxygen.  Botulism is an exception. It survives in oxygen-free environments.  However, it does require moisture to survive, which is why it’s safe to use oxygen absorbers for dry foods but not wet foods.

I mention this because corn kernels and cornmeal are often very moist. When stored in an air-tight container with oxygen absorbers, it could cause botulism.

A few Primal Survivor readers have even written saying that they saw signs of botulism in their bags of whole corn kernels (though not cornmeal): the bags were puffy and bulging.

Botulism requires a moisture level of 35% to grow.  Because it is such a big deal though, you generally shouldn’t store anything with more than 10% moisture in an oxygen-free environment.

Typical moisture levels of cornmeal are around 14%.  Corn flour tends to have less moisture at around 8-10%.

To play it safe when packaging corn kernels or cornmeal with oxygen absorbers, only package it on low-humidity days. You might even want to dry it out a bit in the oven first (and then let it come to room temperature before packing).

Related: How to store cornstarch

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Leave a comment

  1. Hello I have stored cornmeal in mylar bags With oxygen absorbers but the mylar bags have swelled up like a balloon any ideas?

    Thank you

    Reply
    • Do not eat it! As I talked about in the botulism section, cornmeal is often really wet. It could be swelling because of botulism growing in it.

      Reply
  2. Thank you for informative article. I purchased 4 containers of cornmeal and then decided to put it them in the freezer before storing in a Mylar bag. Is that ok to do or will moisture be a problem from the transfer of containers and temperature?
    Thanks

    Reply
    • Just let it “sweat” off any moisture and stabilize before putting it in the Mylar bag. Ideally, you should always pack foods in Mylar on a low-humidity day or have your dehumidifier or AC going (especially if you live somewhere humid like Florida).

      Reply
  3. Any idea about whether freeze drying will increase storage life? I was given 2 bags of corn meal and I would like to save this longterm. I ran it through my freeze dryer and then packaged in mylar bags with an oxygen absorber.

    Reply
  4. Botulism isn’t the actual problem.
    It is the toxins that are created when the bacteria morfes into a spore.

    Heat kills the toxins, 10 minutes at at least 90 degrees Celsius.

    The bulging In packages can be fermentation too, yeasts will give off a lot of gas.

    Reply
    • Yes. You just put the moisture absorber on the BOTTOM and the oxygen absorber on the top. It’s probably not necessary to do both though.

      Reply
    • You could: mason jars (vacuum sealed or not) fall into the air-tight containers category. But it’s not really a great solution for long-term storage. Jars easily break during natural disasters like hurricanes and earthquakes. And you can’t store too much food in a mason jar anyway.

      Reply
  5. How about #10 cans that are 27-1/2 years old??? No signs of swelling nor rust. Top and bottom of can surfaces are drawn in; no buckling or distortion. Has been in a cool protected humidity controlled environment (my home, A/C). Thanks.

    Reply
    • Since it isn’t a disaster situation right now and cornmeal is really cheap, I personally wouldn’t eat it (if it was freeze-dried berries, that would be another story!). It is *probably* okay to eat. I would cook or bake the hell out of it before eating though. That would kill any botulism toxins in the food:

      “Botulism spores die at 250 F. Botulisum toxin that is the cause of the disease dies at 185 F (below boiling) or boiling for 10min.” (https://ucanr.edu/sites/MFPOC/Emergency/Botulism/)

      “Though spores of C. botulinum are heat-resistant, the toxin produced by bacteria growing out of the spores under anaerobic conditions is destroyed by boiling (for example, at internal temperature greater than 85 °C for 5 minutes or longer).”https://www.who.int/news-room/fact-sheets/detail/botulism

      Reply
  6. I stored dent corn in plastic vacuum bags two years ago, without oxygen absorbers. A couple of the bags have a white powdery substance in them. Is it OK to grind and use this dent corn for corn bread?
    Thank you for any information you can render,
    Joe

    Reply
    • My guess is that the powdery substance is from moths. It might be their frass (poop), shell casings or just crumbs from the corn breaking apart as they eat it. It is safe to eat (I do it all the time) but still kind of gross to think about.

      Reply
    • I wouldn’t rely on desiccants to prevent botulism. It would be safer to dry out the cornmeal in the oven first. Or just store without OAs and rotate through it somewhat regularly. Personally, I don’t store any cornmeal, but I’m not the biggest fan of cornmeal products anyway.

      Reply
    • Baking won’t restore it. The heat might actually make the bad taste more pronounced. The good news is that there aren’t any immediate dangers of eating rancid foods — though long-term it might increase the chances of certain cancers, etc. It’s your call whethery you’d want to give this to chickens. If the chickens are going to be on your dinner table soon anyway, I guess the cancer risk isn’t a big issue 😀

      This post talks more in detail about whether you can cook spoiled food: https://www.primalsurvivor.net/spoiled-food/

      Reply
  7. I am new to long term storage. Froze flour for about 2 weeks. Took out and put in Mylar Bags with absorbers. There was moisture in the outside of bags going from freezer to the Mylar Bags. Now I am wondering if I should have let them come to room temp prior to putting them in the bags. Do I need to redo these?
    Thank you

    Reply
    • To play it safe, I would redo them. Cornmeal can get moisture pockets pretty easily. You don’t need to freeze foods before storing them if you are using OAs though!

      Reply
  8. I bought 5# of Pioneer enriched yellow corn meal at the store. Can I put this to store in a Mylar bag for long term? If so how much oxygen absorbers should I put and what is the shelf life?

    Reply
  9. Thanks for the excellent info. I didn’t realize there were different kinds of cornmeal before reading this blog. I had recently sealed 12 lbs of Bob’s Red Mill stone-ground (unbolted) cornmeal in mylar bags with OA’s. Even after reading this blog I’m still wondering if I should keep it in my long term storage? What’s the shelf life that I can expect with the mylar bags & OA’s?

    Reply
  10. Love the post of storing flour and also on cornmeal.
    I’m wondering about storing the packets of cornmeal mix in the fridge. They are not in paper but in a waxy/plastic bag. I have several and planned to keep in the small spare fridge that is in the garage.

    Thanks for all the articles.

    Reply

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