Why Flour Goes Bad
Flour is considered a non-perishable food. However, if you don’t store flour properly, it will go bad. Here’s what you need to know about flour storage and the best options, including for long-term storage.
Just like any dry food, flour can go bad if it is exposed to oxygen, light, moisture, or insects. If you just leave a bag of flour in your pantry, here are some of the problems which can occur that will make the flour go bad.
Mold: Humidity or temperature fluctuations can cause flour to absorb moisture and eventually start to get moldy. You’ll be able to smell the mold before you actually see it.
Oxidation: Oxidation occurs when oxygen from the air interacts with nutrients in the flour, causing them to break down. This is particularly a problem with whole-grain flours. Oxidation will cause the natural oils in the whole-grains to go rancid.
Insects: Even if you store your flour in air-tight containers, you can still get insects like weevils or moths.
How is that possible?
Because flour often already has insect eggs in it when you buy it. It can take weeks or months for them to hatch depending on the conditions. Once they do hatch though, you have an infestation which is very hard to get rid of.
Absorbing Smells: Flour can act like a sponge and absorb the smells of whatever is near it. Have onions next to your flour? Then the cake you make with it will have an oniony smell too. You especially don’t’ want to store flour (or any other food, for that matter!) near chemicals like cleaning products.
Below are several flour storage methods. If you want to store flour long-term (over 3 months), then the best method is Mylar bags with oxygen absorbers. No other method is truly reliable for long-term flour storage.
Shelf Life: Approximately 6-10 months
In its original paper package, flour usually won’t last more than 6 months. If you remove it from the package and put it into an air-tight container, it can last much longer.
One potential problem is that there might already be insect eggs in the flour when you get it. It can take weeks or even months for the eggs to hatch. When they do, you will have a nasty infestation which is hard to get rid of. Thus it’s smart to take steps to kill insect eggs in the flour before storage, such as by freezing or microwaving it first.
Shelf Life: Indefinitely
If you have room in your freezer, freezing flour is a great way to store it. It will last forever in the freezer, though you should have a plan in case power outages occur.
To use, remove flour from the freezer and let it get to room temperature. Note that flour can absorb moisture due to condensation while you bring it to room temperature. To prevent moist flour, keep the flour in its sealed container – the condensation will collect on the container instead of getting into the flour.
If the flour gets damp, you can spread it out on a baking sheet and heat it in the oven at about 200F. If the flour is very damp, you might need to heat for up to an hour to get it dry. After drying it, sift it to remove any clumps.
Shelf Life: 1-2 years
The vacuum sealing process removes air from the packaging. The bags are not completely leak-proof; air and humidity will eventually seep through. However, the reduced amount of air means flour stored this way will last much longer.
Vacuum sealing also keeps insects from getting into your flour. It will NOT kill insect eggs which are already in the flour though. That’s why many people first take steps to kill insects in dry food before storage.
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To store flour with vacuum sealing:
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Shelf Life: 5+ years
Oxygen absorbers are little packets of iron which trap oxygen. If you place OA packets into a good-grade plastic container with flour, it will absorb the oxygen in the container and prevent spoilage from oxygenation. The lack of oxygen also means that insect eggs can’t hatch.
The problem is that most storage containers are not truly air-tight and will eventually leak. This includes recycled soda bottles as well as food buckets.
Buckets with gasket lids (see on Amazon) are usually better at preventing air leakage, so are a decent option if you need to store a large amount of flour.
Canning jars also tend to be very reliable and you’ll know the oxygen absorbers have worked because the lid will look “sucked down.” Just be careful to store jars somewhere cool and dark, as heat and light can also cause spoilage.
Read about oxygen absorbers here.
Shelf Life: 10+ years
If you want to store flour for months, years, or even decades, the best solution is to use oxygen absorbers in sealed Mylar bags.
Mylar bags are made from a metal-like material which is impervious to moisture and oxygen. By sealing flour in Mylar bags with oxygen absorbers, the flour is completely safe from light, moisture and oxygen. Even insect eggs can’t hatch because there isn’t oxygen in the packaging.
When stored this way, white flour can last 10-15 years. Whole-wheat flour can last approximately 10 years this way.
Read about how to store food in Mylar bags.
Dry canning is a process where dry foods like flour are put into canning jars with lids and then heated in the oven. The heat is thought to sterilize the food and create a seal. Even though canning jars are used, dry canning is NOT the same as water bath canning.
As warned about by NM State University, there are a lot of potential problems with dry canning.
Because of these issues, Mylar bags with oxygen absorbers are the only acceptable method for storing flour long-term.
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So I put my flour in a big trash bag and froze it for about a week. Then I let it sit out on the counter to come back to room temperature. After than I placed the flour in brown paper bags. Taped them shut. Then vacuum sealed those. I did throw in an oxygen absorber between the brown paper sack and the plastic bag. Not sure if I should have put it in the flour. But it sealed everything well and I have a pound of flour vacuum sealed in each bag. Could you guess that would lengthen the time more than 2 years?
Your flour should last quite a long time like that. 🙂 Obviously I can’t say exactly how long it will last because some things – like if you live somewhere very hot and humid — will decrease shelf life. You should really look into Mylar bags + OAs though. I find it to be less work than dealing with freezing staples, but that’s just my opinion.
Can I put the flower in the microwave and how long before I put it in a Mylar bag
What about non -wheat flours? Do they have the insect egg problem too?
Yes they do! Almost any grain will or can have insect eggs. However, I personally haven’t noticed the problem with cornmeal/polenta as much. It might be because that is usually packaged in plastic whereas many other flours are in paper bags which can easily be penetrated by insects.
This information was extremely helpful for beginners. Thanks
I like your site. Good content. Not to wordy. Friendly yet concise. Ty.
Why thank you 😀
I put my flour in ziploc bags with oxygen absorbers in each bag, I plan to put the bags in a 5 gallon bucket, the ziploc bags are not full, how do I know if the oxygen absorbers are working?
Ziploc bags actually aren’t completely airtight. Air leaks in through the seal and through tiny holes in the plastic bag itself. After putting an oxygen absorber into them, the bag might look “sucked down” a bit. But, over time, the air will leak bag into the bag. I know sealing them can seem intimidating, but Mylar bags + oxygen absorbers really are the best way to go for long-term storage of dry goods.
I need help. I have new jars and lids to put flour, oatmeal, rice dry goods in.
Lots on internet about dry canning that isn’t safe. Should I put flour in
Freezer to kill bugs first for say 3 days let it dry out for 3 days in its bag
Or plastic bag. Then put it in dry sterilized jars and lids. It is hard to find oxygen
Absorbers in stores. I don’t have vacuum sealer machine would buy if I could
Find it. Even though I don’t have oxygen absorbers or vacuum sealer can
I put flour ( oatmeal ,rice) in jars and how long would it last??
If I find a vacuum sealer machine some people say to put a coffee filter on
Top of flour so flour doesn’t break the machine with flour dust.
I would very much appreciate your help. Best wishes
Go to amazon to find both Mylar bags and oxygen absorbers. You can seal the bags after placing them in a bucket (fill the bags after they are in the bucket) by using a flat iron that women use for their hair or even a regular iron by placing a board across the bucket, fold the bag over the board and then iron It on a heat that won’t melt the bag. Make sure you use enough of the O2 absorbers for the size of bag you are using. Look on YouTube for aid in doing all of this.
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