Creative Sustenance

Culinary and other adventures in foraging, gardening, urban farming and more, in Wisconsin and the Midwest.

Acorn flour

I've always been fascinated by acorns, ever since I was a little kid. I loved the Looney Tunes cartoons with Mac and Tosh, the Goofy Gophers, and the two rodents' obsessive desire to collect truckloads of acorns while outwitting loggers or Elmer Fudd. When hunting or hiking through the woods I would, and often still do, invariably come home with a pocket full of the smooth-shelled little nuts, just for the pleasure of examining and admiring their symmetrical beauty.


I tried eating them several times as a youngster, figuring that if the squirrels loved them they must be good. But whenever I cracked them open and chewed the hard nuts inside I found that their flavor ranged from barely palatable to only okay, and ultimately deemed that while they must be edible on some level they were probably a food that only squirrels could truly appreciate.  

Then, as a teenager I read Euell Gibbons. That changed everything. Gibbon's brief chapter, and the first food-specific chapter in his Stalking the Wild Asparagus, was about acorns and their use as a reliable food source both historically and presently. He even compared them favorably with candied chestnuts when prepared in a similar manner. All I needed to do, according to Gibbons, was learn and practice the process of leaching with water the bitter tannins from the acorn nutmeats. Badaboom badabing, acorn hurdle solved!

I don't use acorns much as whole or pieced nuts, but more often like to make flour from them. So that's what we'll look at in this post. I've used both hot water and cold water leaching methods to process acorns. They both work, and they both yield different results as far as flavor, color and texture of the finished product is concerned. The best and most thorough discussion I've ever seen on the leaching process is found in Sam Thayer's excellent book, Nature's Garden. Thayer explains in detail several leaching techniques, as well as the entire operation of processing acorns, from collection to shelling to grinding to leaching and more. But his discussion on identifying and delineating good, worthy acorns from bad, weevil infested acorns is what I found most impressive. The man has collected, processed and eaten many hundreds of pounds of acorns in his life, and his knowledge on the subject is unsurpassed. 

Here's how I processed a few pounds of acorns into flour recently.

1. Sort and clean. Upon returning home after collecting the acorns I placed them in a sink full of cold water and swished them around. This serves to clean them and to further separate sound acorns from damaged acorns. Acorns that are weevil damaged will float, and you can easily skim those from the water and dispose of them (see images below of damaged acorns, but we'll talk more in depth about weevils and other acorn and oak issues in a future article). The ones that sink are not all necessarily weevil or otherwise damage free, but the ones that float surely are damaged, So, by skimming the floaters you've effectively eliminated the sure losers right away. And don't wait to do this; do it while your acorns are freshly collected. If you let them sit around for a week before getting to them the good ones will begin to dry a bit, and as they dry they become more buoyant, and some that are good may float along with the ones that are damaged, making the float test imprecise.

Acorns with weevil exit holes. These acorns are no good.

2. Shell and dry. I only collected a few pounds of acorns on this outing so I decided to shell them immediately and then dry the nutmeats. You could also dry the nuts in the shell, and then shell them later at your convenience. I just had the time and inclination to do everything right away with this batch. Once the nuts dry they have a long shelf life as most nuts do (I've still got dried butternuts in the shell from last year to get to). 

There are several of ways to shell acorns. To crack the shells you can use a nutcracker, or place them in a cloth bag or under a towel and hit them with a hammer, or ""peel" them with a knife if the shells haven't dried out and are still pliable. Thayer has a very interesting shelling method he calls "the towel method", which makes use of, yes, a towel and a "stomper", a 5'- or 6'-long smooth pestle-shaped heavy piece of wood. I won't describe his process here, but encourage you to purchase his book so you can read about it yourself. Whatever method you choose to remove the shells from the nutmeats is fine. I've used them all and they all work to one degree or another. With this small batch I chose to peel them with a knife because the shells were pliable enough and I could do it while sitting and watching a football game on TV (and the Packers now I feel like I have to shell acorns during every game).

I would take an acorn and, with small sharp knife in my right hand, would make two or three quick, shallow vertical cuts into the shell from top to bottom of the acorn by rocking or arcing the knife edge with some pressure along the surface of the shell, effectively creating one or two elliptical or teardrop shaped patterns in the shell. Then, using the edge of the knife or a fingernail I'd pry or peel the little teardrop of shell from its place, trying to bring the inner "bark" or lining of the shell with it. Once that first piece was removed it was a simple matter to pop the rest of the shell off the nutmeat. This sounds more involved than it really is, but once you get into the rhythm of it it takes just a few seconds to shell each nut.

During the shelling process you will also inevitably find acorns that are black and damaged that you didn't discover earlier. Just toss them out. Once all of the acorns are shelled you need to check them over again for any bits of shell or chaff that may be hanging around. It's not a bad idea to give them another wash in the sink. You can grab a handful of the nutmeats and rub them between your palms underwater. This will also help to loosen and remove some of the testa, a brown skin like that which covers peanuts, that may be attached to the nutmeat. 

Once you've got everything shelled and cleaned the tough manual labor part of the process is over. Drain the nuts in a colander and lay them out on towels or on baking sheets to dry a bit. I wanted to hurry the process along so I dried them by placing them in the oven at the lowest setting and with the door ajar. They darkened a bit while in the oven, but that's okay. You can now let them dry completely and store them in an airtight container, or proceed with the next steps straight away.

Shelled acorns drying.

3. Chop and grind. Acorn nuts are hard, too hard to grind as larger pieces in a countertop coffee grinder. I know this because I burned one out trying to do just that. With the small quantity I had on this day I simply roughly chopped the acorns with a chef's knife as I might chop walnuts and then, once I had more or less uniformly small pieces, used a food processor to further pulverize them. Add enough water to the chopped acorns in the food processor to help chop them up. You probably won't be able to get acorns small enough with a food processor to qualify as flour, but you can get them pretty small, like grits or course corn meal in consistency. That's okay because they're now small enough for a coffee grinder to handle them, and certainly small enough to make using a mortar and pestle less taxing.

Acorn grits.

4. Leaching. I now had a pail full of gritty acorn slurry. I could strain and dry it, and then grind it even more finely before leaching. Leaching smaller particles is more efficient for removing tannins; larger particles require more leaching time. But I chose to begin the leaching process with this grittier quantity and then grind it into flour afterward. 

The method I generally use for cold leaching is an old one: simply immerse the thing to be leached in numerous changes of water. When camping once I filled a cloth bag with acorn nutmeats and tied it to a stick in the shallow water of the lake we were camping near. Here at home I just use a giant glass jar.

  • Place the acorn flour or grits into the jar no more than a third of the way up.
  • Fill the jar with cold water and give it a good stir.
  • Let it sit in the fridge for several hours or even a day at a time.
  • Drain or decant the water from the particulates that settle on the bottom.
  • Repeat, over and over and over, until the nuts no longer taste bitter.

One of my acorn leaching jars.

I let this batch leach for a week-and-a-half. The color of the water is not an indicator of when the process is complete (it won't become clear); you have to use taste as your guide. Be patient...this is simple and doesn't require much interference on your part, it's just very time consuming.

Once the acorns lose their bitterness, you'll want to squeeze out as much water as you possibly can. Set a strainer or colander over a bowl, line it with cheesecloth or a tea towel, scoop in a softball-size blob of acorn mush, bring the corners of the cloth together and begin twisting it to tighten the ball more and more. Squeeze the ball with your hands as hard as you can to get as much moisture out as possible. When you remove the acorn mush from the cloth it will be like a ball of sandy clay if it's gritty to begin with. Repeat with all of the acorn mush. 

Straining and squeezing after leaching.

NOTE: The moisture that you wring from the acorn mash can be used if you wish. It's not quite the same as the leaching water drained from the jar each day. It's a little more milky, so to speak, and it's got some flavor and nutrients. I used this particular acorn milk to poach a chicken in that I used in a mushroom and chicken potpie.

Ball of clay-like acorn flour. 

5. Dry. Next, I spread the acorn grits onto a couple of baking sheets, breaking up the bigger clumps with a fork, and again set them in the oven at its lowest setting and with the door ajar, stirring occasionally, until they were completely dry. 

6. Grind into flour. Now I had a good quantity of dry, tan-colored acorn grits, the consistency of sand. A coffee grinder could handle these particles pretty easily, and in no time at all I ground everything into fine flour. Store the acorn flour in a dry container or sack as you would any flour. You can use acorn flour like you might any non-wheat grain or nut flour. Add it to recipes for breads, pastas, gravies and so on. Among other things, I'll be using it to make pie crusts for meat and mushroom pies I have on our Thanksgiving menu. We'll share those recipes with you when we make them.

One jar of finished acorn flour.

I'd wager that there are oak trees near where you live, maybe even in your own yard. Why let the squirrels have all of those tasty acorns. With the quantity of acorns that an oak tree can produce, chances are that there are enough for both you and the squirrels to enjoy.


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