Back to the Basics: Acorn Flour

There was a time when the Californian diet was dependent on acorns. Some native groups consumed acorns as up to 50% of their daily caloric intake. Besides being plentiful and rather easy to harvest, acorns are *delicious*. So why do people look at me like I’m a maniac when I tell them that I am cooking with locally harvested home-ground acorn flour?

Well, because the American industrial food machine doesn’t want you to know that you don’t need their corn. Foraging is for people who can’t afford supermarkets, didn’t you know?
Truly, after experimenting a bit with acorn flour and acorn meal, I find it incredible that this remarkably rich, hearty, flavorful (not to mention nutritionally sound) food is not a staple of our diet even to this day. So here I go on to my soapbox again…
You don’t have to buy into the industry’s game. There are plenty of incredible native edibles that are right in front of you. They are rich with history, and full of the flavor of the land we live on. When harvested respectfully, there is no damage to the plants (or the wildlife that depend on them – squirrels never gave up on acorns even when they fell out of favor with us lame-o humans).
This post will never be long enough for me to impart all of the wonderful history and information I’ve run into while researching acorns and their use as a food source in California (and the rest of the world). There are many websites and books that have fascinating and useful information about gathering acorns and cooking with them, and I suggest that you check them out.
One book that has EXTENSIVE information about types of oaks and their various acorns (including taste descriptions and ease of harvest) is Nature’s Garden by Samuel Thayer. Most of his book is focused on the Eastern and Central parts of the US, and many of the plants he discusses don’t grow ’round here. Still, a must-read for any foraging enthusiast.
In the meantime, here’s the basics you’ll need to know, and a recipe that is sure to win over even the staunchest of acorn adversaries. Enjoy!

To harvest the acorns:
Wild food gathering is all about trying to get the most food for the least amount of effort (anyone who has spent 4 hours hunched over a bowl of elderberries picking out stems and bugs can attest to the trials and tribulations of foraging). Because of this, choose the largest acorns when you are planning your harvest. They will yield the most flour for the least amount of time spent gathering and shucking.
In this area, the most time-and-energy efficient acorns are black oaks, tan bark oaks, and valley oaks. Locally (California Bay Area), the valley oaks seem to be the way to go, but any large acorns will do if you have access to them.
Acorns ripen in the fall. Once they are brown and on the ground, though, it is generally too late – they are easily infested with mold, rot, and weevils, or have already begun to sprout. The best time to harvest is when they are just beginning to brown but are still ON THE TREE. At this time, many of them will still be green. That’s OK. The acorn should pop easily out of the cap without breaking it, should feel heavy for its size, and should be free of holes.
(A note on holes, weevils, and rotty-spots: just cut them out. Don’t waste all the good meat just because a bug snacked 1/10 of its mass – that’s silly.)
Gather more acorns than you think you need. You will be glad you did.
Acorn meat is best when fresh, and will discolor quickly when husked. You should shell your acorns the same day you pick them, and drop the shelled meats directly into a bowl of cold water to prevent browning. As long as you keep them in water, these will keep for a couple of days this way (you know, if you are like me and trying to fit foraging in with a couple of jobs, a backyard farm, and a supposed social life). Just make sure all the nut meats are covered.
To leach the tannins:
Place the husked acorn meats into a blender (rumor has it that a food processor will work, but the blender does a fine job of pulsing the meats into a fine powder and the meats don’t damage the blender’s sturdier blades). Cover with just enough water to come to the top of the meats, and blend until the meal is the consistency you want.
At our house we like to do some of our acorns as coarse ground meal (to be used like corn meal, steel-cut oats, or polenta), and some finely ground for baking into yeast-leavened breads, tortillas, and cakes.

Pour the blended acorn meal and water into large jars and add more water until the solids are no more than 30% of the mix. Set the jars in a cool place and do not move them for several hours. This will allow the meal to settle to the bottom of the jar and the tannin-rich water to separate out. Let the meal leach for about 12 hours.
To change the water, carefully pour off the water in the jar, making sure to reserve the fine silt-like flour that will collect on top of the coarser meal. Don’t worry about pouring off ALL the water – just get out the stuff that doesn’t have any acorn meal in it. Then re-fill to the same ratio (one part meal to 2 or 3 parts water) and mix everything up to re-distribute the meal in the water.
Allow this to settle for 12 hours and repeat the draining and re-filling process. Do this twice a day for about 5 days. Ten changes of water ought to be enough to leach all the tannins out of most acorns, but the best way to tell is by taste (you will also notice that the rinse water will go from brown and cloudy to nearly clear as the tannins are removed). Once the meal is sweet and nutty (and doesn’t make you make the raw-olive face), the leaching is complete.
DO NOT OVER-LEACH!!! If you do, the delicious complexity of the acorn flavor will wash away leaving you with a bland paste that is perfectly fine to use as flour, but is certainly nothing to write home about. Taste the meal each time you drain it (*ahem*…after about 6-8 rinses; no point in being a masochist or anything). Make sure you get the bitter tannins out, but then stop. The sweet, nutty flavors of the acorn are worth saving.
To store the meal:
Strain the acorn meal through a few layers of cheesecloth draped into a colander, and squeeze until the meal is mostly dry (it won’t really get dry without intentional dehydration). At this point it can be packed into freezer-safe storage containers (we use gallon capacity zip-top “freezer” bags because they can be flattened and stacked easily).

To dry-store your acorn flour, you will need to completely dry it – I have heard of people using their dehydrators (with the fine sheets for making fruit leathers in the trays), baking the meal in the oven (be careful not to burn it!), and letting it dry on sheets in the sun and then breaking up the clumps in a food processor or through a sieve. I’m sure any of these methods work well, but it seems unnecessary unless freezer space is at a premium in your house. Freezing the meal assures that it will not become moldy or rancid (acorns have a medium-high fat content and spoil easily), and keeps a lovely light color to the flour.

Acorn meal can be substituted 1:1 for corn meal in nearly any recipe, and will provide a deep, nutty, earthy flavor with which corn can never hope to compete. It can be mixed into bread doughs where it will supply ample texture and color without setting off the moisture levels in the dough. Coarsely ground or chopped, it can replace nuts in many recipes (I am planning a fall pie crust based on coarse acorn nut meal and spices and filled with a winter squash custard).

Rumor has it that they can compete with (and sometimes even surpass) olives for the amount of oil that can be pressed from them – another experiment to try very soon!
Tomorrow I will post my recipe for acorn bread, which is an easy and VERY tasty introduction to the world of cooking with/eating acorns. Until then…get yourself a basket and start harvesting!
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