snapshots: the blog

Recipe Box: Acorn Flour

Alternative flours have gained a lot of popularity between their usefulness for those who react to gluten and those who just like to experiment. And there are an increasing number available, from oat to rice to almond, and a bunch more. Not only do these flours allow for gluten-less baked goods, but they also have their unique flavors and textures. As this Autumn came into full swing and squirrels began scurrying to collect acorns, I was reminded that acorns have been known to be an energy-rich food source for foragers, and as I researched this I came across a number of sites that discussed making acorn flour!

It is not an overly difficult process, but it is time consuming. Depending on where you live, you might have many varieties of acorns or large quantities of acorns available, or you might have just one oak tree jutting up through cracked cement in front of a friend’s house. In my experimenting, I used around 25-30 acorns to yield just over 1 cup of acorn flour so no matter what your situation you should be able to collect enough acorns to try this out–you just might have to fight off a few squirrels.

After my own experimentation with making acorn flour, I have some tips to share if you would like to attempt this fun and rewarding project.


 The Acorns

One of the major things to consider is the kind(s) of acorns you will use. I would strongly encourage using only white oak acorns, simply because red oak acorns take a whole lot longer to deal with. If you aren’t familiar with the differences between red oaks and white oaks, you can grab a tree-identifying book from the library or use the handy-dandy internet to assist in this process. The most basic means of differentiating is cracking the shell of an acorn and seeing if the nut inside has another layer of “furry” skin–I swear that sounds grosser than it is–which would mean it’s a red oak. To use a red oak acorn, you would need to get that skin off, which is most easily done by boiling the acorn, but for flour it’s best to not heat the acorns (more on this in a bit).

The other important thing when collecting acorns is to check for little holes in the shell. If you see a little hole, leave that on the ground because that means a grub has been there, and that is as gross as it sounds. In general, if your acorn looks funky, don’t risk it.

So seek out your white oak acorns, check them for holes/quality, and crack them open–set them on end like in the photo above and hit the top with a hammer until the shell splits apart. This is the most labor-intensive part of the process, but I thought it was a lot of fun. Especially the quizzical looks from passersby as they watched me collecting squirrel food from the ground.

Leaching the Tannins

The reason people aren’t just walking around gobbling up acorns is because almost all varieties contain too much tannic acid to allow this. Red oak acorns typically have more than white oak acorns, another reason why red oak acorns are not desirable for flour. What is tannic acid (also called tannins)? It was/is used to tan animal hide, and when consumed it will constipate you and prevent your body from absorbing iron. Still stoked to do this? You should be because nature was kind and made tannic acid water soluble  which means we can leach it out.

The fastest way to leach the tannins out of the acorns is to boil them, but this also screws up the natural stick-to-itiveness that exists in acorns that help a little with the lack of gluten in baked goods. This is a good option if you want acorn pieces to include in something else–after boiling, roast them to bring out the natural sugars or candy them for a sweet treat. For flour, we need to cold-water leach the acorns:

  1. Grind/chop the acorns in a food processor until it is as fine as coffee ground for a French press (larger grains).
  2. Line a bowl or bucket with something like a cheese cloth, old kitchen towel, or old pillow case (it will be stained).
  3. Pour in the ground acorn and then pour in enough cold water to saturate the acorn.
  4. Cover and set aside (I kept mine in the fridge to keep cool and out of the way).
  5. Change out the water 2-3 times each day. Do this by squeezing the acorn in the cloth until as dry as possible and dumping the old water out and then returning the acorn/cloth to the the container and filling it with fresh cold water.
  6. If using white oak acorns, this process could take 7-12 days. Once the water is less brown and just kind of cloudy, try tasting a little ground acorn–it should resemble corn meal in texture–to see if you detect the strong bitterness that comes with tannins.

dried ground acorns

Grinding the Flour

Once you’ve leached the tannins out of the acorns, you need to make sure you get the flour completely dry before you do anything else with it. I found a very effective way of doing this was spreading them out on baking sheets and placing in an oven on the “warm” setting with the oven door open for 30 minutes to an hour, occasionally stirring. Then leave it out overnight, covered, to make sure it’s dry.

The next step is further grinding the acorns into a flour, which is difficult/impossible to achieve with an average food processor. If you have a mill, then you’re set to make yourself some flour. If not, you can get very close to the fineness of flour by using a coffee grinder as I did. If you go this route, make sure you thoroughly clean and thoroughly dry the coffee grinder before using it. No moisture is key. Then run the acorn through the grinder a few times until you’re satisfied with the fineness. Store in a sealed container in the fridge, as the flour could possibly become rancid at room temperature after an extended period of time.

And there you have it! It’s a process, but really not super difficult. And if you have kids, they could have a ball collecting the acorns and cracking them open. And when it’s fun, it’s not child labor!

Sources and Further Reading

I owe a lot of my experimentation to a number of others who have gone through the trouble of offering their experience to learn from for people like us:

As far as using the acorn flour in recipes, I found the site Gluten-Free Girl to have a fascinating post about replacing wheat flour gram-for-gram with alternative flours & starches: She says if you replace 1000 grams of wheat flour with 700 grams of alternative flour (such as acorn flour) and 300 grams of starch (such as corn starch or arrowroot), then you’re good to go. While I haven’t tested this extensively, it did work for a muffin recipe. The post I linked to is a bit wordy, so scroll down near the bottom if you just want this info.

If you try this, let me know how it turns out! I’d also love to know what what recipes you use it in. Good luck beating those squirrels to the goods!

acorn flour

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