For many of us, acorns are a big pest with very few uses. They rain down upon everything in sight, cluttering up driveways and gutters, drumming on tin roofs and hitting unsuspecting visitors on the head. However, for foraging types such as I, they represent a valuable food source.
In the North East US, the first acorns to begin dropping are from the White Oak group (which includes Chestnut oaks). These nuts are often bright green or yellow when they fall, quickly turning brown. They are usually elongated with a rounded base. Unlike the Black oak group (which includes the common Red Oak), these acorns will germinate the same year that they fall, so that there is a very limited window in which to collect and process them, before they either sprout or rot.
Gathering acorns requires a lot of stretching and bending, and is great exercise. I sometimes get quite pooped after an hour or so of these aerobic workouts. Not only that, but I carry a bag with me that gets heavier and heavier as the harvest goes along.
In the beginning of the season they are quite sparse, but as we get further into the fall they become increasingly more abundant, until a bag of acorns can be collected in a very short time.
Within the next couple of weeks after the White oaks acorns begin dropping, the Red Oaks and their kin will begin to drop their fruit. There isn’t the same urgency with these nuts, as they remain on the ground for many months, germinating in the spring.
If you are gathering either type, be choosy about what you put into your gathering bag. You should look for large, solid, heavy nuts, without firmly attached caps. If they have a tiny hole, leave them behind, as they have been invaded by maggots. There’s no point in carrying back several pounds of acorns, only to throw half of them away.
If you are planning to make acorn flour, it is good to be aware that 2 1/2 pounds (about a kilo) of acorns will yield one cup of flour, so gather at least 10 lb (4 or 5 kilos) of nuts. I generally end up with around 100lb each year. That’s a lot of shelling!.
When it comes to shelling your acorns, be aware that White and Black oak varieties require different techniques. The White Oak shells are thinner and more flexible and cannot be cracked with the blow of a mallet. These shells need to be sliced with a sturdy knife longways, then the nuts can be pried out of the shells.
With the harder Black oak shells a blow with a hard object (like a hammer or mallet) will split them, revealing the nut meat. Some folks will leave them to dry out on a rack for a couple of months, so that they are easier to shell. At this time a whole bunch of them can be put into a canvas bag and beaten with a mallet, then sorted out and separated into nut meats and shells.
Once you have removed white oak nut meats from their shells, they should be immediately put into a container of water to stop them from oxidizing and turning brown. This is not necessary with the Black oak group.
Acorns are high in tannins, making them difficult to eat and somewhat toxic. This can be remedied by a process called leeching. For this part you will need a food processor, or a means of grinding them into a fine grit and some large jars (1/2 gal or larger).
After checking your shelled acorns to remove any shell fragments or bad nutmeats (black bits) place the nut pieces into a food processor and grind them fine. Adding some water may help with this. Pour the grits unto a large jar until it is half full. Top the jar up with water and let sit. You should pour off and replace the water 3 to 4 times a day until the grits no longer have that bitter tannic taste (about 5-7 days).
At this point, I dry my grits and keep them in the freezer, only taking them out as I need them. To turn them into flour, I grind them in a coffee mill. Some folks recommend keeping them moist and grinding them for immediate use, to retain their nutritional goodness, but this makes storage problematic.
If you plan on storing your acorns for future use, dehydrate them by laying them out on a well ventilated drying rack in a single layer, to avoid molding. After several months, they can be stored together in a squirrel-proof container. Make sure that it isn’t airtight, as they still could mold (I use canvas rice bags).
Acorn flour can be used in any of your regular recipes, but needs be mixed with at least 60 percent regular flour, otherwise it gets too crumbly. Even one third acorn flour will make a huge difference to the taste and texture of your pastry, not to mention its nutritional value. I find that acorn pastries are not only flaky and delicious, but acorn pastry is much more predictable than regular pastry and doesn’t need to be kept cold in the same way.
Once you begin baking with acorn flour, you'll wonder why you ever did it any other way!