How to make acorn flour (cold or hot-leached)

This acorn flour article provides all the information you need to know to figure out which oak trees produce the ideal acorns for acorn flour, how to make your own acorn flour, and how to turn acorn flour into delicious food. Read on to find out how to eat acorns as food — including some of our favorite acorn dishes & recipes!

---

 

How (and why) to Make Acorn Flour

 *This is one of our longer blog posts, so we’ve broken it into three sections for your convenience (all on the same page). We invite you to read all three sections, but if you just want to jump right to the part you’re interested in, simply click on the jump link below to skip right to it:

I. The Acorn Story

II. How to Make Acorn Flour and Acorn Grits

III. Acorn Recipes
  

---

Part 1. A brief history about the amazing edible acorn

“Acorns!? Are they even edible?” “Who has the time to make acorn flour?” “Why on earth would anyone want to make or eat acorn flour?” 

These are questions that people might ask you if you tell them you’re going to make acorn flour – or perhaps you’re also asking these questions. As such, we thought we’d start this article by sharing why we invest time into making acorn flour before moving on to the How To and Recipes sections.

If you’re like the average American who watches about 5 hours of television per day (Nielson), you could choose to reallocate a few of those hours towards doing something fun, new, and tasty like making acorn flour (or starting a garden).

Even if you’re not inclined to make your own acorn flour after reading this article, perhaps you’ll understand why someone else might want to. For us, making acorn flour and other garden- or forest-to-table foods provides a personal, visceral connection to a planet and a history we all share—and are stewards of—as human beings.

Who knows… Maybe making acorn flour might even cure you of NDD (Nature Deficit Disorder)!

If nothing else, perhaps you’ll simply look a bit differently at a majestic oak tree next time you spot one, realizing that they’ve been an integral part of the “human food story” for millennia—a story each of our ancestors wrote a few sentences in before passing it on to you.

The Tyrant Farms Acorn Story

Years back, my parents got me “Nature’s Garden: A Guide to Identifying, Harvesting, and Preparing Edible Wild Plants” by Samuel Thayer.

Thayer’s book may well be the best guide available for anyone who wants to learn more about all the delicious native foods that grow not only in the wild, but unbeknownst to us in our own back yards. (We’re all surrounded by edible “weeds.”)

As the son of humanities professors, I grew up with a keen interest in anthropology, archaeology, paleontology, and history, which — combined with The Tyrant’s biology background — catalyzed into our passion for trying to better understand the biosphere we call planet Earth and the edible plants, fungi, and other organisms that have allowed people to thrive here.

Thayer’s book does a brilliant job of going beyond the mechanics of identifying edible foods in the wild. He also connects the reader to the rich history of each of those foods and how they’ve been used throughout human history.

As a reader, you feel as though you’re not just learning plant facts, you’re finding out about a long-lost sibling who was separated from you at birth. You immediately want to find them, connect, and be a part of their life again.

Here are a few excerpts from “Nature’s Garden” that we love:

“Archaeologists tell us that gardening began 5,000 to 11,000 years ago in various parts of the world. This refers to our modern, civilized concept of gardening, which entails removing the native ecosystem and replacing it with a few exotic plants organized in a simple, geometric fashion. People have been tending Nature’s Garden for much, much longer. When Europeans first encountered such landscapes [forest gardens] they did not recognize them for what they were. The idea of working with the inherent tendencies of a natural plant community to produce food was so foreign to the European way of thinking, it was assumed that these people remained hunter-gatherers only through ignorance of the techniques and concepts of plant cultivation… They didn’t just cultivate plants, they cultivated ecosystems, working with the existing plant community. This isn’t agriculture—it is ecoculture.“

Thayer’s book covers a huge range of edible plants, but he holds a special reverence for acorns, which have been a staple crop for human civilizations across the world (in Asia, Europe, and the Americas) for thousands of years:

“There is no food that means more to me than the acorn, for the acorn fulfills both a promise and a fantasy: that the forest will provide for me. When I gaze across the [valley] I see more than scenery. I see thousands of acres of bounty, millions of pounds of delicious food dropped from the crowns of countless trees, waiting to be gathered by eager hands. I see more food than I could ever eat—more than I can even fathom. A wilderness and an orchard in one.”

Oak Tree Species and the Best Edible Acorns

There are hundreds of oak species worldwide, and about 90 species found in North America alone. (It’s easy to find good oak tree ID guides for whatever region you live in like this oak trees of the eastern US guide).

Each species of oak tree produces different sizes, shapes, and flavors of nuts which also have different nutrient content and levels of “tannins.” High tannin content is what makes acorns unpalatable/inedible before leaching. (Tannins are quite common in plants — they’re what make coffee bitter and apples tart.)

Tannin is actually good for you in small amounts due to its antioxidant properties. However, in large amounts (such as unleached acorns) tannins can be a toxin and an antinutrient. That’s why hot or cold leaching acorns to drastically reduce their tannin content is necessary prior to eating them.

Which oak trees have the highest and lowest tannin content? 

According to Thayer, who seems to have eaten virtually every species of acorn on earth, acorns’ tannin content ranges broadly by oak species. For instance, the red oak species Q. agrifolia has a tannin content as high as 20.3% (Koenig and Heck, 1988). On the opposite end of the spectrum, the white oak species Q. ilex has a tannin content of 0.4% (Mazueles Vela et al., 1967).

This variability in tannin content makes providing precise instructions for how long to leach acorns before eating them very difficult. The answer depends on the type of acorn used. 

Oak trees as part of a “forest garden”

After reading about acorns in Nature’s Garden, The Tyrant and I began looking at the three huge white oak trees growing in our yard in a different light… 

They’re no longer irritating trees that block some of the sunlight from our garden before dropping trash nuts all over our yard in the fall. They’re now welcome, integral participants in our edible forest garden (along with our hickory nuts and chestnuts).

This was a fundamental mind shift in the way we viewed a garden, and also facilitated our interest in the philosophy of permaculture.

Thankfully, our white oak trees also happen to produce some of the largest, tastiest acorns of all oak varieties. The first fall after reading Thayer’s book, we collected about a gallon of fallen acorns from our driveway and garden, and made a small “test batch” of acorn flour using a fast, hot leaching method to remove the tannins.

Once our acorn flour was produced, we made acorn fritters, and were delighted by their deliciously rich and nutty flavor. We brought the remaining acorn flour with us to a family Thanksgiving getaway in Asheville, NC and it was a huge hit. Everyone demanded a second round of acorn pancakes at breakfast, and our small supply of acorn flour soon disappeared! 

Every fall since, we happily gather ever-greater amounts of acorns to process into acorn flour, then share much of this free forest bounty with our family during holiday meals or as gifts.

We’ve also been fortunate enough to find nearby groves of burr oaks (Quercus macrocarpa), who produce the largest acorns we’ve ever seen. (See above picture.) The giant nuts of a burr oak put our white oak acorns to shame in a size comparison. 

Interesting Acorn Facts & Figures

We’ve been amazed by the size and quantity of acorns that a single oak tree can produce. We’ve also been amazed by all the facts and figures we’ve learned about oak trees and their potential to produce huge quantities of food for people (or livestock). 

Here are some acorn facts you might also find interesting: 

a. How long can oak trees live and how many pounds of acorns can they produce? 

The average oak tree initiates acorn production around its 25th year. It will continue to increase acorn production for the next 75 years of its life before plateauing around year 100 at an average of about 2,500 acorns per year (that’s equal to somewhere between 500 – 1,000 pounds of acorns depending on the variety of oak).

Incredibly, the average natural lifespan of a white oak is 550 years old! Some trees live to be thousands of years old, like this magnificent 2,000 year old giant Coast Live Oak tree in California or this 1,500 year old “Angel Oak” tree that we used to live near in Charleston, SC. Wow!

Oak trees may substantially vary their acorn output each year as a natural defense against animals (squirrels) and insects (weevils) that eat their acorns. This is why Native Americans who used acorns as staple crops stored up to two years of acorn nuts or flour as insurance against low acorn production years.

Every year since we’ve been in our house at Tyrant Farms, our white oak trees have produced different quantities of acorns. Usually, one of the trees will produce a huge crop, while the other two produce a lower yield for a year, each alternating their production based on some unknown biological mechanism.

During peak years, we can easily fill a five gallon bucket with white acorns in about an hour in our backyard — without putting much of a dent in the acorns piled on the ground.

For reference, five gallons of fresh acorns produces about 12-18 pounds of dried, shelled nutmeat, which ultimately breaks down to about eight calorie-days for an average person.

That means a single oak tree that produces 1,000 pounds of acorns could technically provide 2 people with all the food/calories they’d need for an entire year.

It’s easy to see how — especially when incorporating other native foods — entire villages relied on acorns from a grove of well-tended oak trees as their staple crop.

b. Acorns are extraordinarily nutritious…  

Even though levels of nutrients vary greatly between oak subspecies, they all produce exceptionally nutritious nuts.

The process of “hot leaching” removes a lot of the water soluble vitamins and nutrients from the acorns, but not the fat soluble ones. “Cold leaching” removes fewer nutrients, but is more time-intensive. 

The general nutrition facts (Sources: USDA, 2008 and Mason, 1992) shows that acorns are:

• 50-90 percent complex carbohydrate;
• 5-30 percent fat (the healthy monounsatured and polyunsatured fats);
• 5-8 percent protein;
• contain all the essential amino acids;
• are very high in Vitamins B6, Potassium Manganese, and Copper;
• are a good source of a laundry list of other vitamins and nutrients.

Also, oak trees require no human input to grow and produce a yield. No fertilizer, pesticides, or water.

Native American populations who relied on acorns would boost yields by doing yearly controlled light burns under their favorite oak trees to kill the weevil larvae and provide a fertilizer boost to the tree from the burned organic matter.

We’d be willing to bet they also added some of their own fertilizer as well, such as “liquid gold.” (Ha.)

Another interesting benefit of using acorns and other perennial trees as food crops: an average hardwood tree (such as an oak) can absorb as much as 48 pounds of carbon dioxide per year and can sequester 1 ton of carbon dioxide by the time it reaches 40 years old!

Interestingly, oaks are just one type of tree that produce a nutritionally balanced staple crop via their nut fruit. Chestnuts are another species that has been similarly utilized around the world, and their nuts are even easier to process into useable food (no leaching required), but that’s a story for another day…

Why Should You Care That Oak Trees Produce Healthy, Delicious Edible Acorns?

All of this information might make a person ask: why did we decide to build the foundation of our entire food system on wheat, corn, soy, and other annual plants that require huge amounts of edible forests to be cleared and massive human inputs during planting, growing, harvesting, and distribution.

Millions of pounds of synthetic fertilizers, pesticides, fossil fuels, and water are used during this process.

If someone tells you that the only way we can possibly feed the 7.5+ billion people on planet Earth is by continuing to poison our air, water, and soil growing chemically-intensive monocultures, just smile and know that they might be well-intentioned, but their perspective is based on a fundamentally misinformed, historically narrow understanding of the available alternatives. Many of these alternatives have already been tested and proven safe & sustainable for thousands of years by millions of people across multiple civilizations, and could be scaled up to meet our food needs today.

If a person is only aware of salt and pepper, asking them how best to “spice up dinner” isn’t going to yield a very flavorful meal.

As the late American philosopher Alan Bloom said:

“We need history, not to tell us what happened or to explain the past, but to make the past alive so that it can explain us and make a future possible.”

We don’t believe that humans should return to “living in tepees,” and we’re certainly not Luddites. Yes, we’re actually quite fond of technology (as you might have guessed by the fact that we designed and built this website ourselves, shoot and edit all of our own pictures, use smartphones, etc).

A person can use an ax to cut wood to warm their family, or use that same technology to murder someone else’s family. Similarly, advanced technologies used for the wrong reasons with little regard for human history and the biological systems that sustain all life on earth can lead to frightening outcomes whose ripple effects will be felt for multiple generations.

As such, The Tyrant and I can’t look at our modern industrialized food system and call it “progress,” if that system is guiding civilization down the wrong path for the wrong reasons. We can’t poison ourselves to health (although we’ve gotten very good at treating symptoms of diseases we create), nor will consumers make good long-term decisions if all of the negative outcomes are externalized and hidden from view.

At our core, The Tyrant and I are optimistic realists who are thrilled about the new food movement that we see bubbling up around the world and in our own back yard. This is a movement that recognizes that food production impacts everything: its foundational to every civilization past, present, and future—and it can’t be made of cards that are pieced together atop quicksand.

We believe we’re at a critical juncture in human history: we can redesign our foundational “roots” in order to create healthier & wealthier people and communities that actually improve the health of the biosphere we inherited from our ancestors (regenerative impact). OR we can ignore the consequences for “staying the wrong course,” shamefully burdening future generations with the problems we could have chosen to fix in our day.

The baton is in our hands. Nobody else if going to run the sow for us. We have every resource we need to make the words on this screen “flesh,” except for the collective willpower necessary to trigger a deep, enduring societal response to make it happen (governments, businesses, nonprofits, families & individuals, and institutions of faith all have a role to play).

Let’s combine the lessons of history, biology, and technology to grow and distribute whole regeneratively produced foods hyper-locally, thereby building a better food foundation for America while also providing a food paradigm worthy of exporting to the developing world.

Who knows, perhaps the roots of this new food future can be found in something that’s been with us since our beginnings: the majestic oak tree.

---

Part II. DIY: How to Make Acorn Flour and Acorn “Grits”

We’ve been making acorn flour each fall for about a decade now.

It seems that almost everyone who writes about making acorn flour has a slightly different way of doing it, largely depending on what processing equipment they have available and what type of acorns they’re working with.

This section is intended as a very general DIY guide that you can modify as-needed. Be creative and experiment with different methods as you see fit!

Items You’ll Need to Make Acorn Flour

• At least 1 gallon of large freshly fallen acorns. (Any less and it’s really not going to be worth your effort.)
• Cooking sheets, old screens, or an electric dehydrator for drying acorns. (We have a 9-Tray Excalibur Dehydrator that we use almost every week for one reason or another, and it’s a great resource to have for making acorn flour as well.)
• Instrument to crack acorns. Either: 1) a mallet or hammer and towel, OR 2) a Davebilt #43 Nutcracker (we highly recommended a Davebilt since this device will save you a ton of time cracking acorns and other nuts);
• Something to grind nuts, either: 1) a flourmill or cornmeal grinder, 2) a high quality food processor, 3) a potato masher. (We use a food processor and a potato masher in this DIY, but option #1 would be great if you have it available.)
• A sifter or pasta strainer.

Instructions: How to Make Acorn Flour

Step 1: Find at least one gallon of recently fallen LARGE acorns

If you read the information from “Part 1. Our Acorn Story,” you already know that every species of oak produces acorns of different sizes, shapes, flavors, nutrient, and tannin content.

From our research, the most important factor for selecting which acorns to make acorn flour with should be based almost exclusively on the size of the acorn. The bigger the better.

The reason: all acorns can produce good acorn flour, but the smaller acorns just aren’t worth the effort.

Likewise, if you’re going to go through the effort of making your own acorn flour, we recommend getting at least 1 gallon of them so that you get enough flour to reward yourself for the effort.

Step 2: Crack the acorns

We gave ourselves a Davebilt #43 Nutcracker as a gift years back, and we couldn’t live without it. Our Davebilt can crunch through acorn shells faster than a hot knife through butter.

However, if you don’t have a fancy Davebilt nut-cracker, a simple mallet or hammer will work.

Put rows of acorns on a towel, fold the towel over on top of the acorns and work your way down the rows, cracking each set of acorns with your hammer or mallet as you go.

Our white acorns typically have a think skin called a “testa” on them that will need to be removed next. We used to try to separate the acorn shells and skins from our acorn nuts at this point, but realized this was costing us a lot of unnecessary time and aggravation. So, do NOT separate the shells, skins, and nuts during this step.

You WILL want to remove any rotten or weevil-infested acorns that you crack open during this step. 

Step 3: Dry Your Acorns, Shells, Skins & All

Take your cracked acorns — shells, skins, and nuts —and either:

1. put your acorns on sheets to dry in the sun, or
2. stick them in a dehydrator.

The purpose of this step is to dry everything out, which will cause the acorn nutmeat to shrink, and their shells and skins to separate from the meats with minimal human effort required. 

Step 4: Separate the acorn skin and shells from the nut meats (aka acorn “testa”)

Once you’ve dried your acorns, removing the shells and skins is simple.

Simply rub them in your fingers and the shells and skins will slide right off. Next, put all of your clean, dried acorn nuts in a bowl. Compost the skins and shells.

Once you’re done with this step, you should have a bowl of clean acorn nut meats with no shells or skins. Now it’s time to remove the tannins by leaching your acorns.

Step 5: Leach your acorns to remove tannins

You can choose to either cold leach or hot leach your acorns to remove their tannins. There are pros and cons to both methods… 

Hot leaching acorns pros and cons:

Pros: Hot leaching acorns is much faster than cold-leaching. Depending on the tannin content of your acorns, the process may take anywhere from 2 to 6 hours.  

Cons: Hot leaching acorns is more energy- and water-intensive process since you’ll be boiling a lot of water on your stove. You’ll also need to plan to spend several hours watching and tending to your acorns as you boil and dump the water. Another downside: hot leaching removes some of the water-soluble vitamins and “sticky” properties of the final acorn flour. 

Cold leaching acorns pros and cons: 

Pros: Cold leaching acorns makes for (in our opinion) a better-flavored final product. It also provides for a more nutrient-dense final product that has some of the nice “sticky” properties of bread flour.

Note that cold leached acorn flour is NOT nearly as sticky as wheat flour though. (Yes, acorn flour is completely gluten-free in case you have sensitivities.)

Cons: Cold leaching acorns takes a long time. Completion time will vary by the tannin content of acorn species and your setup, but plan for 7-14 days minimum. Granted, you’re not actively tending the acorns over this time period. 

How to hot leach acorns: 

To hot leach your acorns, add them to a large pot and fill the pot with water. Bring the water to a low boil. Keep in mind that the acorns will expand as they take on water, so don’t overfill your pot.  

Let the acorns lightly boil for about 30 minutes, then strain them in a colander to remove all the water. Repeat this process and taste a small piece of acorn after each cycle. 

There is no way to know exactly how many flushes of boiling water it will take to remove enough tannins from your particular variety of acorns. (Ours usually take about 5-6 cycles.) Once the acorns no longer have a bitter taste, they’re done.

There are some interesting uses for acorn tannin water if you don’t want to toss it down the drain: some people freeze them into ice cubes for use on poison ivy rashes, some use them for tanning leather, and others have even used it as a coffee substitute (like the Confederate Army during the Civil War). 

How to cold leach acorns: 

There is no single right way to cold leach acorns. Here are three possible methods (we’ve only done the last two methods since we don’t have a clean running stream):

1. Stream leaching 

For instance, if you live next to a running stream with clean, uncontaminated water, you’ve got the perfect setup. Simply put your acorn nuts into a mesh bag(s) and tie them into a secure position in the middle of the running water. 

After a week, take a small nibble of an acorn to see if it’s still bitter. Leave the acorns in the stream until they no longer have a bitter flavor. 

2. Toilet leaching (yes, seriously!)

No, you’re not going to use the toilet bowl! You’re going to use the tank. Fill a mesh bag with acorns and place it in the back tank on your toilet. Not too tight because the acorns will expand. 

Each time you flush your toilet, a new round of clean water comes in and the tannin water flushes out. Take a small nibble of an acorn after about 7 days to see if they’re still bitter. Remove once acorns are no longer bitter. 

3. Container leaching

Place your acorns plus fresh cold water into a large food-grade container (preferably glass or ceramic). A minimum of twice each day, stir the acorns then strain them. Dump the water and repeat. 

There is a risk of contamination with this method if you’re not very careful about regularly changing out your water 2+ times per day. After 7 days, take a nibble of an acorn to test for bitterness. Once bitterness is gone, you’re done. 

Note: For all three options above, breaking your acorn nut meat into smaller pieces will speed up the cold leaching process. However, it is more difficult to keep small pieces inside a mesh bag. 

Step 6: Mash and Dry Your Leached Acorns

Regardless of whether you hot or cold leached your acorns, your next step is to mash and dry them. 

Once your acorns are leached and cooled down to the point that they won’t burn you, place 2-3 cups of acorns at a time into a large mixing bowl.

Use a potato masher to mash the acorns into a moist yet powdery texture by pressing down then turning with the masher. There should be almost no visible pieces of acorns left when you’re done with this step.

Another option is to put the acorns into a food processor with just enough water for the processor to blend the mixture into a fine pulp. After mashing or blending, spoon your mashed acorns onto baking sheets or dehydrating racks to prep for drying. 

You can either oven bake on the lowest temperature possible or use a dehydrator. If using a dehydrator, you’ll want to first put down parchment paper over your dehydrator sheets to make sure none of the acorn mash falls through the small openings as it dries.

Make sure your acorns are completely dried out before proceeding to the next step. Any moisture in your acorn flour could cause it to go bad quickly when stored.

As mentioned, we use a 9-Tray Excalibur Dehydrator for this step (pictured below).

Step 7: Grind Into Acorn Flour, Sift Out “Acorn Grits”

Last step! Once your acorn mush has completely dried out, place batches of it into a food processor and grind it on the highest setting possible for 1-2 minutes. Stir and repeat until completely powderized.

Next, place a colander/pasta strainer in or over a large bowl (as pictured above). Pour your acorn powder into the colander and sift.

The finely ground acorn flour will sift through into the bowl. The small chunks of acorns, i.e. “acorn grits,” will remain in the colander.

Storing acorn flour

Store your acorn flour in an airtight container in a dry cupboard, a fridge, or a freezer. Given the varying fat content in different types of acorns, there’s no way to say for certain how long your acorn flour will last before going bad. We’ve had acorn flour last for up to two years.

The higher the fat content, the shorter the shelf life. If you have way more flour than you can eat in the next six months, you may want to store it in a freezer to extend its life. The same goes for your acorn grits.

Congratulations! You’ve now made your own acorn flour! This delicious and wholesome staple food has nourished people for thousands of years, and now it can be part of your food story as well. 

Part III. Acorn recipes & acorn dishes

Now that you’ve made your acorn flour, the fun part begins: eating acorns as food. 

Acorn flour is much thicker, sweeter, and heavier than regular wheat flour. The closest texture equivalent we can think of is bean (legume) flour.

Since acorn flour doesn’t have gluten in it, it will not stick together as well as wheat flour (even cold leached acorn flour), so treat it accordingly when cooking. There are countless ways you can use your acorn flour and acorn grits, so explore and experiment!

In case you’re wondering: are there any recipes for acorns? the answer is: yes. To help you get started, we’ve added some simple acorn recipes (below) that we enjoy:

Acorn flour & American persimmon cookies (click for recipe)

Acorn flour crepes – sweet or savory (click for recipe)

Hot-brewed acorn & yaupon holly – is this caffeinated native drink better than coffee? 

Other simple acorn recipes you can make from acorn flour: