Along with a little learned knowledge over the years I’ve pulled from a number of sources for this bit on acorns as they summed up beautifully the information at hand. As always, references are down below. If you are like me then you parents probably didn’t understand the potential value of this little nut; which in my opinion is right up there with cattails as a survival food; or a sustainable additive to your diet.
The acorn, or oak nut, is the nut of the. It usually contains a single seed (rarely two seeds), enclosed in a tough, leathery shell, and borne in a cup-shaped cupule. Acorns vary from 1–6 cm long and 0.8–4 cm broad. Acorns take between about 6 and 24 months (depending on the species) to mature. People can and do still eat acorns, though they require a certain amount of preparation in order to be palatable.
Oak trees begin to produce acorns at about 20 years old but usually the first full crop won’t happen until the tree is about 50. The average 100-year old oak produces about 2,200 acorns per season. Only one in 10,000 will become a tree.
Acorns provide several notable benefits to those who eat them. Like most nuts, they are a dense food. They are not as high in fat as some other nuts, however, but are heavily fortified with complex carbohydrates and contain many vitamins and minerals. Some studies even show them to have properties that may help control blood sugar levels.
The acorn is an extremely abundant nut, but most people rarely consider it as a potential source of food. For some, this may be because of the strong flavor, while others tend to associate them with the food of squirrels and other rodents. Some cuisines have relied on acorns as a staple for centuries, however, and survivalists often praise them for being easy to find and dense in calories.
Acorns served an important role in early human history and were a source of food for many cultures around the world. Despite this history, acorns rarely form a large part of modern diets and are not currently cultivated on scales approaching that of many other nuts. However, if properly prepared (by selecting high-quality specimens and leaching out the bitter tannins in water), acorn meal can be used in some recipes calling for grain flours. Varieties of oak differ in the amount of tannin in their acorns. In some cultures where acorns once constituted a dietary staple, they have largely been replaced by grains and are now typically considered a relatively unimportant food, except in some Native American and Korean communities.
Oaks fall into two large categories, those that fruit in one season, white oaks; and those that fruit after two seasons, the black oaks and the red oaks. The latter category is often more bitter than the former. The first category have leaves with round lobes and no prickles at the end of the leaves. The black and red oaks have prickles at the end of their leaves. They also have scales on the cups of the acorns, hair inside the caps, and a sheath around the nut (which always throws a color even when the tannin is leached out.) Sometimes those in the first category don’t need any leaching, or very little. The rest always do. But first, separate the acorns.
It isn’t the best idea to eat acorns straight off the ground, the way a chipmunk might. Raw acorns contain high concentrations of tannic acid, so their taste is bitter, and they can be toxic to humans if eaten in large quantities. Even the animals that eat acorns raw often find the tannins to be irritating; for this reason, few animals eat acorns exclusively, and some acorn-eaters allow the nuts to soak in water before they consume them. On the other hand, raw acorns can be stored for months without spoiling; this dramatically increases their value as a food resource.
To separate acorns dump them into water and remove the ones that float. Take the ones that sink and dry them in a frying pan on the stove or in the oven at 150F or less for 15 minutes, preheated. Or put them in the sun for a few days. You don’t want to cook them yet, just dry them off and shrink the nut inside making them a little easier to shell. The yield, not counting bad acorns, is 2:1. Two gallons of usable acorns in the shell will yield a gallon of nutmeat. We must leach out the tannic acid it can damage our kidneys, and regardless, most unleached acorns are too bitter to eat without leaching.
After separating acorns we must shell the nuts and leaching out the tannins that make them bitter and nauseating. You could crack them one by one with pliers or smash them individually with a rock, but the native folks of this land figured out a much better technique: mass breakage.
Simply set out 20-30 acorns on a hard flat surface and smash them all at once with a wide heavy object. Use a sidewalk and a cinderblock in urban environments. Use two big flat rocks in your back yard or in the wild. Whichever “tools” you have at your disposal, you can smash the nuts open in one or two strokes and save yourself a lot of time.
There are nearly as many ways to leach acorns as there are opinions about acorns. The temperature at which you process the acorns at any point is critical. Boiling water or roasting over 165º F precooks the starch in the acorn. Cold processing and low temperatures under 150 F does not cook the starch. Cold-water leached acorn meal thickens when cooked, hot-water leached acorn meal does not thicken or act as a binder (like eggs or gluten) when cooked. Your final use of the acorns should factor in how you will process them. If you are going to leach and roast whole for snacking then boiling is fine. If you are going to use the acorn for flour it should be cold processed, or you will have to add a binder.
Soaking in warm water – Next, separate out all the shell fragments and place the nut meat pieces in pot of warm water. Soak them in warm water for a few hours, then pour off the water. Do a taste test. If the acorns are still too bitter, soak them in warm water for a few more hours. This water bath leaches out the tannic acid, which causes nausea and digestive distress when consumed. Repeat this until they are palatable. For ideas on what to do with the leftover tannic acid, click here.
Soaking in cold water – You could also do a leaching process in moving water with a cloth bag. Clean socks or pillow cases are great, if you have them. Tightly woven baskets are the traditional method of straining them. Immerse the nuts in a running stream and secure them so they don’t wash away. Let the water flow through them for a few days, and you’re ready to move to the next step.
Boiling – The boiling process requires two pots of boiling water. Put the acorns in one pot of already boiling water until the water darkens. Pour off the water and put the hot acorns in the other pot of boiling water while you reheat the first pot with fresh water to boiling. You keep putting the acorns in new boiling water until the water runs clear. Putting boiled acorns into cold water will bind the tannins to the acorn and they will stay bitter. So always move them from one boiling bath to another. Putting acorns in cold water and bringing the water to a boil will also bind the tannin. So it is either use all cold water and a long soaking or all boiling water and just a few hours of cooking.
You can also grind the acorns in a lot of water to a fine meal, let it set, then strain. I add more water to the meal, let set and strain. I do that until the water is clear or the meal not bitter. That takes a few days to a week. Then I dry it in the sun, unless there are squirrels about, then in a slow oven (under 150º F.) I end up with a meal or flour, depending on the grind, that will not crumble when cooked.
Another way is to put the shelled acorns in water in a blender or food processor and blend them into a milk-like slurry. Put that slurry in a fine mesh bag and then massage that under running water like a faucet. It works very quickly but of course some meal and oil is lost in the process. But it turns hours of leaching into minutes. Of course, leaching them in an unpolluted stream is the easiest way but you can also arrange for a container to leak slowly. Simply put a cloth on the bottom to hold the meal in and fill the container when it is empty, or run the faucet slowly to maintain the leaching. Another ways is to clean out the tank on your toilet and put the shelled acorns in a mesh bag in there. Every flush will remove tannic water and bring in fresh.
Many Native Americans preferred bitter acorns to sweet ones because they stored better. If after leaching there is just a hint of bitterness that can sometimes be removed by soaking the acorns in milk for a while. The protein in the milk will bind with the tannin in the acorns and can be poured off, if there is just a little. To get oil from the cold-leached acorns, boil them. The oil will rise to the top of the water. Also, charred acorns can be used as a substitute for coffee but really nothing is a substitute for coffee.
Whole leached acorns can be roasted for an hour at 350º F, coarsely ground leached acorns slightly less time. They can then be eaten or ground into non-binding flour. To make a flour out of your whole or coarsely ground acorns, toss them in a blender or food processor. Strain the results through a strainer to take out the larger pieces then reduce them as well. Acorn flour has no gluten so it is usually mixed 50/50 with wheat flour. Since acorn flour is high in oil it needs to be stored carefully and not allowed to go rancid. Remember cold processed acorn flour has more binding capacity than heat processed acorn flour.