We get jars of 750 ml and fill them up to the ‘break of the neck’ with flour. We knock them on a surface, or press the flour with a spoon or the palm of the hand to pack it tight. We then place the jars in the oven of the wood burner or the electric cooker for one and a half hours at 90o C. Next, wearing kitchen gloves to avoid burning our hands, we take the jars out one by one and close them securely with new sterilized lids. (We sterilize lids by placing them in boiling water for 15 minutes.)
When the jars have cooled down, we store them in a cool shady place. Our flour can be preserved in this way for many years.
Heat treatment can also be done in a microwave oven at 500w for 5 minutes, although we do not recommend the use of one.
You must remember that by heat treatment, some of the nutrients of the flour are destroyed. Heat shall also destroy gluten (a wheat protein) and our flour will lose some elasticity, but we should keep in mind that this way is good for long term storage. Furthermore, flour should be protected from light, so we have to keep our jars in a dark closet. Finally, before securing them, we can place laurel leaves on top of the flour.
In case hour flour is infested by insects, we pass it through the sieve, and any small critters shall remain in the sieve. We can then heat the flour in a pan in the oven at 90o C for one and a half hours to kill any remaining insects or their eggs.