As I have talked about in another post, acorns are an attractive source of food if you know how to deal with them. They contain tannic acid that must be leached before eating, as it can cause stomach aches. After processing, there is a wide range of ways to use acorns in our recipes, being baking with their flour the most interesting.
Some acorns may require no more processing than shelling them to eat, as they are low in tannins and it may vary with the different species of oak. However, British native species contain enough tannin and leaching this bitter substance out is indispensable.
Clean and select your acorns
After collecting your acorns, clean the lot up into water, discarding the ones that float. That indicates the presence of nasty maggots and you will notice some of them have black holes.
Supposedly, you are not using all your acorns straight away, so you will need to dry them in the sun. This event is very improbable in British winter, so you can put them in the oven at 150ºF for 15 minutes instead. You don’t need to cook the acorns, just dry them off for storage and make them easier to shell. Put them in different batches if they are too many.
Shell your acorns
The first step in processing acorns is to open them. It is not an easy task and it will be a tiring job dealing with them. The nuts have a shell not very suitable for nutcrackers, so they are best opened with a knife or a hammer, just cracking the shell, not mashing the kernel. Put them into water to prevent oxidising.
Leach your acorns
There are several ways of leaching acorns.
- Boiling acorns in water. As soon as it does, pour the water off into the sink and repeat the process up to five changes of water until it stops turning dark. Boiling the acorns will remove the tannins and bitterness and will make the meat soft and sweet. Some people prefer to boil them with shell in order to not overcook.
When boiling, you are also precooking the starch and boiling off their natural oils, reducing their nutrition. They will be good to cook in the oven as a whole nut to eat as a snack, but the flour will not act as a binder when baking.
- Filling the bowl of acorns with medium hot water. After half an hour, drain the water off and replace the water again. Then, repeat the process as much as it is necessary and the water no longer turns tea coloured. You will not boil the nutrients, but probably you will have to change the water more times.
This method suits baking as long as the temperature is not extremely hot, because the starch will not be cooked and will thicken when baking.
- Grind the acorns into meal, put in water and let it set. Then strain, to add more water again, changing the liquid as much as it is required and the water runs clean. Being cold processed, it is the most suitable for baking and you will not need any extra binder, yet it will be more time consuming.
Dry your acorns
Make sure you dry well after leaching, as acorns are rich in fat and the meal will spoil and get mouldy if left damp for long. Whole acorns can be patted dry on a tea towel, but then roasting brings out the sugars in acorns and helps to preserve them. Make sure you check the acorns in the process, as some may roast faster than others.
Use a jelly bag for the grinded meal and squeeze to get the water out. Dry it in the oven at the very lowest setting for 30 minutes if you don’t have a dehydrator, making sure you stir the meal to prevent top layer to burn.
Grind your meal into flour
The term flour refers to the final product, the finely milled meal of the acorns you want to make now. Once the meal is completely dry, it may be a little coarse. You can put it in a coffee grinder or a food processor and process in batches for about 1 minute, to then remove any big particle with a fine mesh sieve.
Storing your flour
Once your flour is completely done, store it in an airtight jar in the fridge, as the fat and oils will make it rancid otherwise. For long time storage, it is best to put whole acorns and flour vacuum sealed into the freezer.
It can be used as a normal flour to give your bakes a nutty flavour. However, acorn has no gluten, so it is usually mixed half and half with white or wheat flour. It also does not need too much sugar in cakes, as acorn flour increases sweetness when baked.
You can bake whatever you fancy and especially it suits perfect as a substitute for chestnut recipes. From breads, to cakes, cookies, wraps and even pasta, there are no limits. I have already tried an acorn bread and acorn pancakes, which proved to be delicious.