Despite oak trees are very common in Britain, not many people have considered to use their nuts as an edible resource. They cannot be eaten straight from the tree, as they taste very bitter due to the high content in tannins and therefore are considered poisonous.
However, a bit of processing can reward you with a rich food source that can be ground to make flour which you can use to bake bread, pastries, pancakes and even pasta. Just ensure you have a bucketful to make the process worth the effort.
There are plenty of different techniques and this one is my own, but please experiment and find the way it works best for you.
Once acorns are shelled and skins have been removed, cut in pieces and blitz them into a coarse flour consistency. Leach with cold water to remove the bitter tannins, preserving the starch that will hold the dough together. Follow detailed instructions as previously explained here.
When the leaching process is completed, transfer the flour to a new cheesecloth and strain the water over a colander, letting the acorn meat rest there for a while. This will help preserving the fat and starch content.
Once drained, spread the flour over baking paper and dehydrate it in the oven. You can also use a dehydrator at the lowest temperature, so as not to cook the starch. Higher temperatures will produce a darker flour.
The last step is grinding the flour to a fine powder, using a coffee grinder. The end result should be a thick and powdery consistency, similar to shop bought flour, with no visible pieces of acorns left.
Storage and use
Acorn flour is high in oils and it may go rancid over time, thus carefully storage is necessary. Plastic airtight containers and glass jars are fine, but a brown paper bag will increase its lifespan a little further. Also, storing them in a cool dark place is advisable.
Chestnut and acorn flour are pretty much interchangeable in recipes, but you can find inspiration in Korean cuisine, as they use acorn in many dishes. In some parts of Italy use (or used) this flour to make pasta.
The flour is gluten-free and does not need too much sugar added, as it gets caramelised when it’s baked due to natural sugars. For standard recipes it is advisable mixing with conventional wheat flour in equal measure (and your hard work will stretch further).