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
https://www.cmu.edu/student-affairs/resources/cmu-pantry/shelf-life.pdfhttps://catalog.extension.oregonstate.edu/sites/catalog/files/project/pdf/pnw612.pdf
https://food.unl.edu/free-resource/food-storage
https://www.fao.org/3/au105e/au105e.pdf
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6804776/#:~:text=The%20flow%20properties%20of%20yellow,wt%2Fwt)%20were%20measured.
https://www.gcca.org/resources/industry-topics/what-are-proper-conditions-storing-corn-meal-or-corn-flour
Can’t seem to find any information about long term storage for corn flour. Is corn flour and cornmeal the same thing? Would corn flour be stored the same way?
The main difference between the two is how finely they are milled. The storage for them is essentially the same.
Could you address the storage of the organic masa harina I purchased? I was hoping to store it in mylar w/oxygen absorbers. Only ingredients are corn & a touch of lime. What about vacuum seal bags as well?
Thank you!
Because of how moist cornmeal (and masa harina) can get, I’d just store it in sealed jars, vacuum sealer bags or vacuum sealer jars. It has a really long shelf life even without OAs anyway.
I just read thru your post on popcorn and this post. I have some questions I am hoping you can help me with. I have dent corn berries in 5 gallon buckets with a gama lid that is snug but not tight – Is this a concern? I also packaged back in the day 2 yrs ago some of the remaining corn berries in mylar with oxygen absorbers. Those bage were then pout in a bucket with a gama lid. I just opened that bucket to check the bags and they (mylar bags) are suctioned down pretty tight meaning they are not puffy at all. What would your advice be for those bags? Leave them as is or open them and put them loose in 5 gallon buckets like my other dent corn…or throw them out? Yikes!!!! 🙁
Also would corn flour aka – Unifine corn flour also be a concern?
Thank you!
If you don’t want to throw away the corn, the safest thing to do is make sure you heat the corn to at least 185F for at least 10 min. This is the temperature at which the disease-causing toxin dies (Note that the SPORES need to be heated to higher temps to die, but they don’t make you sick. It’s the toxins they produce which kill you, and those are destroyed at 185F).
So, maybe grind it up into cornflour and make bread? 🙂
https://ucanr.edu/sites/MFPOC/Emergency/Botulism/
https://www.who.int/news-room/fact-sheets/detail/botulism#:~:text=botulinum%20are%20heat%2Dresistant%2C%20the,for%205%20minutes%20or%20longer).
Hi, I stored a few buckets of dried dent corn kernels I purchased, in Mylar bags with O2 absorbers, about 7 months ago. The bags are still vacuum sealed but there is a slightly funny smell to the one I just opened. Is 7 months long enough for botulism to develop? Is the funny smell a sign of botulism or rancidity or something else? I planned to just use it for grinding cornmeal to bake cornbread in my grain mill. How will I know if there is botulism in it? And if there is, will it contaminate my grain mill?
I also have one other bucket that’s been sealed O2-free about for about 3 weeks. Are they all ruined now? What should I do? Would it make sense to open up all the bags and take out the O2 absorbers?
Any help/advice is appreciated, thanks!
Botulism can develop quickly, so you need to be careful with anything you think is contaminated. The good news is that you don’t have to throw away the food. BUT you MUST heat it to kill any botulism toxins which may be present. This requires heating it to a minimum of 185F/85C for at least 5 minutes. To play it safe, disinfect your grain mill after grinding.
We raise our own corn and grind for cornmeal. I sift it thru a sifter. I’ve always stored in the freezer but I’m wondering if it’s safe to store in Mylar bags with oxygen absorbers
Because of the moisture content, you are better off storing it in the freezer. Only store it with O2 absorbers if you are certain it is dry enough.
It’s the baking powder giving off CO2. Mine are doing the same thing. I will however throw mine away as Cornmeal, pancake mixes contain more than 10% moisture and storing long term with O2 absorbers is not recommended. I believe some of the LDS sites explain moisture content of certain dry foods etc when storing long term. Another example, you should not use O2 absorbers with dried fruits unless freeze dried. Just store these without o2 absorbers and rotate.
Botulism likes moisture above 30% but it’s difficult to know what conditions were when I packaged the cornmeal. I purchased 25lbs for $15 at Sams club. Tossing it is worth more than my anxiety of eating it.
Since May I have stored 7 bags of self rising cornmeal mix (5 lb. in each bag) in mylar bags with 500cc oxygen absorbers. I was taking inventory yesterday and noticed that 2 of the bags were puffy and another one looked like it was about to explode. I opened them and they looked perfect and had no smell. To prevent it from happening again I began looking for the cause and found this site. I put the cornmeal mix straight from the store bag into the Mylar bag, added the OA, got all the excess air out, zipped it shut and then heat pressed the top edge closed. I have zero knowledge/experience with botulism so I don’t know if botulism had started growing in the bags or if fermentation had started in the bags. Any ideas on this and how to prevent it from happening again? I threw all 3 bags in the garbage, but would it have been okay to spread the cornmeal mix out in pans and warm it in the oven and rebag it if it was due to fermentation?
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.
Short-term, that should be fine. Long-term, you might have issues because fridges actually have high levels of humidity and the humidity levels can vary quickly (like each time you open the door).
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?
I’d wait for a low-humidity day to package the corn meal and you should be fine. This post has info about how many oxygen absorbers – https://www.primalsurvivor.net/oxygen-absorbers/ Use the same amounts as you would for flour.
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
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!
Can rancid corn meal be restored by baking in an oven? Can it be used to feed chickens?
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/
Would it be safe and effective to add desiccant packs to the bolted cornmeal to help avoid botulism?
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.
What’s the best way to store Maseca corn meal?
I want to know this too!
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
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.
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.
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
Could you vacuum seal it in a mason jar?
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.
Hello,
Can moisture and oxygen absorbers be used for grits in mylar bags?
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.
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.
When do you use heat, before or after you store it?
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.
Freeze drying removes moisture and corn meal is usually full of it. So that should definitely help!
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
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).
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
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.