Why You Shouldn’t Can Flour

This can be a dangerous way to process flour.

Of all the things you can buy, getting goods in bulk is always the cheapest. But, what do you do with such large quantities of food, obtained at a great price? Well, when it comes to flour, some people are canning it. Yes, you read that right. But, this method is far from safe for a couple of reasons. Read on to find out how to safely store dry goods bought in bulk.

50 lb sack of flour
Via/ Flickr

Obviously getting flour wet isn’t an ideal preservation technique and that’s why some folks have been dry canning flour in the oven. What does this entail? After canning jars have been sterilized, they are filled to the top with flour and then baked at 250˚ degrees. Then sterilized lids are placed on top while the jars are still hot.

If you’ve never heard of this before and you’re wondering why then it could be because this is a very controversial method for preserving dry goods. Many canning jar manufacturers advise that their jars not be used in this manner. Another concern is that there is no way to verify if foods inside the jars have surpassed 250˚, thereby killing insect eggs, mold spores, and bacteria (including botulism).

box of large canning jars
Via/ Flickr

One risk with oven canning is that you may presume your flour is safe for years to come, even longer than flour that hasn’t been canned. In reality, this might not be the case and your flour should be used in a timely manner as per the package best by date.

So, how did the dry oven method of canning gain popularity if it isn’t safe? According to the USDA, in 1905 an article in the Farmers’ Bulletin touted oven canning as a superior method of preservation. But, even as early as World War I, it was not deemed as safe as steam or pressure canning. However, the dry oven method has still been used all this time because it is easier and cooler for the cook. In modern times usually only dry foods have been canned this way, but even that is not advisable anymore.

So, how do you preserve bulk quantities of ingredients like flour, pasta, powdered cheese, cereals, or powdered milk? The simplest way, if you have the room, is to freeze these foods in sealed jars. Freezing kills insect eggs and some bacteria, and the tight seal on the jars keeps out moisture. While freezing doesn’t kill botulism, the lack of moisture in dry goods means the environment is not suitable for the organism.

vintage flour canister
Via/ Flickr

Though freezing doesn’t kill all bacteria, those that survive are instead rendered incapacitated until the food is thawed. Presumably at that point you will cook the food and the heat will actually kill any remaining bacteria or spores.

Dry goods can also be vacuum sealed, but the benefit to using a vacuum sealer appliance is debatable in this instance. According to the National Center for Home Food Preservation, traditional methods of storing dry goods should result in a long shelf life, although vacuum seal appliances can be used to seal up portions of dry goods that will be used in one go. Open vacuum packs are at risk of spoilage and are no longer preserved.

dry goods in airtight containers
Via/ Flickr

Shelf stable dry goods should be kept free from moisture and away from light, preferably in sealed containers. Freezing can increase the life and safety of ingredients like flour, but oven canning is not a safe solution for preserving even dry goods.

The bottom line is that if you’ve bought a large container of flour then good old freezing or jar storage in the cupboard are still the best ways to ensure a long shelf life.