The Acorn Files ~ How to Cold Leach Acorns

For the past several years, acorns primary harvested from the Northern Red Oak have become an important part of our families diet. Harvested in the fall, we scrambled at various locations, filling as many basket loads as we can before winter sets in. In a good year, we will collect over 100 pounds, providing us with enough mass to enjoy this wild food a few times a week. Unlike most nuts, the high levels of tannins do not allow humans to simply eat them out of the shell as you might with a pecan, walnut, or Brazil nut. Although some species of oaks provide less tannic acorns, all must be properly prepared before consuming. 

Cold or Hot leaching are two methods utilized around the globe to turn acorns into an edible food. Leaching refers to drawing out the tannins through either hot or cold water. While both methods have their pros and cons, I mostly process acorns using the cold leaching method. Although the process can take a week, there is little work involved each day. 

Photo by Frank Giglio

How To Cold Leach Acorns

Step 1. ~ Get Crackin

Assuming your acorns have been collected and dried, its now time to open them up. The fastest method is seen above, using the DaveBilt #43 cracker. You can also pick up a set of the Drosselmeyer crackers which you can find online for under $40.00. If you don't own one nor wish to purchase more equipment, a rock or a hammer and a sturdy board will do the trick. Fun to do with family or friends so load up a Netflix movie and get to it. You'll want a minimum of 1 quart of shelled acorns to make a batch of flour. 

Sorting through cracked acorns, removing the nutmeat from shells.

As you crack the acorns, separate the nut meat from the shells, discarding any nuts that are moldy or blackened internally. Cover your acorns and their shells with water is a great way to float most of the shell fragments but is not recommended if you planning to dry mill your acorns into flour. Although i use a blender to grind my acorns, I prefer to keep the product dry through the shelling process. If you need to take a break, place your shelled nuts in the fridge or freezer to help prevent them from oxidizing. 

Step 2. ~ Time To Grind

In order to properly leach the tannins out of the acorns, we need to create as much surface area as possible, so grinding is essential. While a mortar and pestle will do the work, you will likely lose steam or interest before you can grind up enough acorns to make a batch of flour. Having sufficient equipment for this step is crucial, but with that being said, indigenous groups from around the globe consumed a lot of acorns with no modern equipment, so it can be done.  

Because I don't own a grain mill, I use my Vita-Mix and implement an old "raw food days" technique of making "nut milk". I place about 4-5 cups of shelled acorns into my blender and pour water to the top of the pitcher. Secure the lid and blend on high until you can see that the acorns are well ground and mealy in texture. You really don't want any chunks here as they will not leach properly. 

Blended acorns and starchy water. 

Place a bowl in your sink with a strainer possibly lined with cheesecloth. I use large brewing strainers that fit over the Vita-Mix pitcher and allow me to easily pour the contents into the strainer bag. I secure the top of the strainer bag with a half hitch knot or rubber band and place it in the bowl. I run cold water over the bag for a few minutes and squeeze out the milky starch. The liquid can be saved if you wish to make your own acorn starch, but that's another post. 

First day of soaking. Notice the white colored water with starch still present. 

First day of soaking. Notice the white colored water with starch still present. 

Step 3. ~ Soak, Drain, Soak, Repeat

Depending on what species of oak you are gathering acorns from the actual leaching process can take up to 1.5 weeks to complete. I leave my bowl just off to the side of my sink and change the water as many times as I think about during the day. No going overboard here, but a few times a day will help speed things along. There are slow drip methods like using a heavy duty strainer bag or a slow drip from a faucet that can be implemented and speed things up. As the leaching nears completion, you will see the water change to a pinkish hue as seen below. Continue, tasting after 6/7 days until no bitterness is detected on the tongue. 

Cold leached acorns near completion. Notice the pink hue of the soaking water, an indicator you are close to finished leaching. 

Once the acorns are free of bitter flavors, you are ready to utilize them. The wet mass is what I call acorn meal and can be added to a variety of recipes at this point. For extended shelf life, you will want to dry your acorn meal, ultimately turning it into flour. Use a dehydrator or the lowest setting in your oven to dry the acorn meal fully. Once dry, you can re-mill or blend into a flour. You will want to store your finished acorn flour in the fridge until ready to use.