Processing Acorns: Step by Step
Acorns are one of the signatures of autumn, all the essence of the mighty oak is distilled into the humble Acorn. The sun and the rain and the moon and all the elements and forces of nature flow through the veins of the oak tree to produce the seed, the progeny. The very future of the oak trees is bound up in each tiny Acorn. According to Genesis 1:11,12 every Acorn is designed and programmed from the beginning of creation to yield fruits according to its kind, whose seed is in itself, on the earth.
Acorns have largely fallen into disuse by humans as a food, much less as a staple food. Acorns used to be such an important crop that whole cultures were centered around them, especially the many Indian tribes in California. Today few people have ever even tasted an Acorn, much less eaten a hot, buttered Acorn muffin, though many are dimly aware that they are supposed to be edible. Perhaps this is because they are intensely bitter when eaten fresh out of the shell, unlike the wild Black Walnuts and Hickory Nuts which still have faithful people willing to go to great pains to extract their sweet, flavorful nutmeats. Acorns require an extra processing step to leach out the bitter tannins that make them unpalatable in the raw.
Or perhaps it is because acorns have such a high content of fats and carbohydrates, undesirable traits in today’s culture, but of paramount importance in primitive societies for sustenance. 100 grams of acorn flour (roughly one cup) contains a whopping 500 calories, 30 grams of fat, and 54 grams of carbohydrate. They also rate pretty high for vitamins and minerals in a nutritional profile, truly a survival food of high degree.
Step One: Harvesting the Acorns
I harvest Acorns every year, usually in mid- to late September. The best places to harvest them are in grassy parks, mowed lawns or waysides as it is very difficult to gather them in the undergrowth of the woods or tall grass meadows. Oak trees seems to have a cycle of production, so that the oak that yielded heavily one year might be dry for the next few years. This can make it tricky to find a good spot as Acorn harvest tends to move around and be somewhat hit or miss from year to year. When I happen upon an especially good year for Acorns and an easy harvesting spot, I try to really stock up.
Harvesting is as simple as picking up the acorns off the ground and putting them into a bucket. I try to get the fresh fallen Acorns early in the season, before they have started to get weathered or buried in leaf fall. Sometimes they are green when they fall, sometimes brown, either way is fine for collecting. Acorn flour yield is roughly 2:1, so two gallon buckets of whole acorns will yield close to 1 gallon of acorn flour.
All Acorns are edible, but some varieties are larger than others and some contain less tannic acid so are much easier to process. Oaks are divided into two main families—red oaks and white oaks. Red oak leaves have pointed tips and white oaks have more rounded lobes on their leaves. I tend to harvest according to availability more than variety.
Step Two: Baking the Whole Acorns on Cookie Sheets
When I bring the Acorns home, I don’t always have time to shell them right away so I might need to store them. The problem with this is that there is a certain little moth that lays its eggs inside the Acorns and if I wait too long, the larva will have hatched and eaten some of the nutmeats. In order to kill these eggs, spread the acorns (whole, in the shell) on cookie sheets and roast them in the oven at 250° for 20-30 minutes. This will allow for a few days before further processing, but for longkeeping, it is necessary to dehydrate them to avoid mold (I learned this the hard way!). This step should be done within 24 hours of harvesting the acorns.
Step Three: Shelling the Acorns
Shelling the acorns is the most difficult step. I used to crack each acorn by hand with a nutcracker and it was a very time-consuming with low yields. I have since developed my own technique for cracking large quantities of acorns in relatively short order. Dehydrating the acorns thoroughly helps to make their shells more brittle and makes the nuts come loose from the shells easier. I have learned that dehydrating them is essential in efficient shelling techniques.
Cracking the shells: If you are serious about acorn processing and will likely be harvesting for years to come, you may wish to invest in a special nutcracking device that shells acorns like nobody's business, hands-down the best (and only) acorn shelling tool on the market. This device will cost about 140$ with shipping, but can be used with pecans, English walnuts, hazelnuts and other softer-shelled nuts. Davebuilt Nutcracker
Otherwise: Using a heavy-bottomed stock pot or 5-gallon bucket or other large vessel, put about a 3” layer of acorns in the bottom and pound them to break open as many shells as you can. I use a round piece of firewood, a large stone would work also. Don’t pound so hard that you crush all the nutmeats.
Have another large vessel ready to sift the cracked acorns into. Place a piece of ½” mesh hardware cloth over the vessel and pour the acorns on top of it. Run your hands over the acorns to help them fall through the mesh. Don’t worry about pieces of shell falling into the vessel--these will be winnowed out later. You may need to push some of the larger nutmeats through the screen. There will probably be several uncracked acorns in the mix. Return them to the crushing operation. I always have some that I end up cracking by hand, but otherwise this is a pretty efficient process.
Winnowing: You should now have a bowl or bucket full of nutmeats mixed in with lots of shell bits and debris. Set up a fan on a chair outdoors (or wait for a very windy day). Place an empty vessel below the fan and slowly pour the acorns into the vessel. The shells should blow away, while the nutmeats fall into the empty vessel. This may need to be repeated several times to get them really clean. Some larger shells may need to be picked out by hand.
Step Four: Leaching the Acorns
Once they are shelled, you need to leach the bitter tannins out. There are two techniques for leaching—a hot water leaching or a cold water leaching. Each method yields a different product. I prefer the hot water leaching. This is accomplished by simply boiling the acorns.
Put the acorns in a cooking pot and cover with about twice as much water. Bring them to a full boil, and boil them for about 5-10 minutes. Then pour off the dark, muddy, bitter water and add more water. Repeat this process up to 5 or 6 times until the Acorns taste mild and palatable.
Step Five: Dehydrating the Leached Acorns
Rinse the acorns and then spread them out on clean bath towels to absorb as much water as possible to aid in the drying process. You must get the acorns perfectly dry to store them or to grind them into flour. I have a dehydrator that I use for this step, but it only holds a gallon or so at a time, so I spread them out on a clean tarp or sheet in a dry place while they are waiting their turn in the dehydrator and I do them in batches. You could also spread them on cookie sheets in a low oven, being careful not to burn them. I’ve had trouble keeping the squirrels and other critters away when I sun-dry them, besides the temperamental fall weather. Whatever works to get them dehydrated!
At this point the acorns are ready for long storage or to grind into flour. I like to keep about half of my harvest as whole dried acorns to experiment with other ways to cook acorns (such as acorn burgers, acorn chili, acorn hotdishes, etc.)
Step Six: Grinding the Flour
The next step is to grind the shelled, leached, dehydrated acorns into acorn flour. I do not have an electric grain mill, but if I did, that is what I would use. I have a hand cranked corn mill that I bought in Mexico for grinding corn. Once the acorns are ground, I sift them through a mesh strainer to sift out any larger crunchy particles. I then use a small electric coffee mill to get the flour really fine, and also to grind those larger particles. I usually do this last step right in small batches right before baking.
This flour can be stored in glass jars until ready to use. I’ve never had it get rancid even when stored at room temperature for long periods of time.
Acorn flour is very much like cornmeal in texture, rather than a fine flour. Therefore, when I bake with it I like to use my favorite cornmeal recipes and substitute Acorn flour. It makes wonderful Acorn cornbread, muffins, and pancakes.