From Mighty Oaks, by Jeff Dexter
Here in Aiken, we’re halfway through acorn season. The white oak acorns are mostly split and starting to sprout. The red oak acorns, which are later to sprout, are still good for harvesting. The differences in germination time are due to tannin content, which is a factor in both flavor and processing methods.
Though there are many species of oak that produce them, acorns can be divided into two classes.
— White Oak acorns come from trees his leaves’ edges are usually smooth or lobed. The acorns
tend to fall in a short period of time (late August through September), and, soon after falling,
they tend to start sprouting and become unusable. They’re usually smaller and less nutritious,
but do tend to be less bitter and easier to process.
— Red (or Black) Oak acorns come from trees whose leaf edges are usually pointy or spiky. The
acorns tend to fall over a longer period of time, but do not sprout until the following year, which
means they can be collected from early autumn to spring. They’re usually larger and more
nutritious, but tend to be more bitter and take longer to process.
All acorns are edible. They contain complete protein and all of the eight essential amino acids necessary in the human diet. On average 3.5 ounces provides the RDA of protein (6.3%), fats (54.8%), carbs (39%), plus lots of B vitamins and minerals. However all acorns contain tannins and phytic acid which must be removed prior to consumption. Thankfully, soaking them in water will remove these. If acorns are eaten unprocessed, the high level of tannins will bind with nutrients, making them unavailable and can even cause organ damage – especially to the kidneys. Please don’t become overly obsessed with this and think that every particle of it must be removed. We regularly seek out foods and drinks with the astringent and bitter flavors that tannins provide. Think: tea wine coffee and chocolate. Tannins do contain antioxidants and antimicrobial properties and may be useful in the prevention and treatment of cancer.
Gathering acorns
In gathering acorns, you’ll find that most of them you collect will be no good. Do not gather acorns that are green, have their caps attached, or have holes or cracks in them. In addition, any that have black streaks on the shell have probably been infected with a fungus that turns the nut meat black. Lesser infected acorns can be trimmed of this black area. Once collected, dump them into a bucket of water to clean dirt and debris off of them. Remove
all that float. (Note: If the origin is of the white oak variety, this dunking in water may cause them to sprout). Once cleaned, they may be immediately cracked for processing, however, you may find that the nut meat sticks to the shell. Drying them first will shrink and separate the nut meat from the shell, making them much easier to crack. To dry, spread them out in a single layer on some movable surface – canvas, sheet pan, plastic bin cover, whatever — and dry in the sun for a couple of weeks. Take them inside to avoid rain and morning dew. Dried acorns can be stored for many years. To use, the acorns must be cracked and shells removed. This can be done individually with a nutcracker or by deftly hitting each one, point-side down, on a piece of wood, (to keep them from zooming away), or by putting mass amounts of them between sheets of cloth or canvas and pummeling with a flat stone or some similar device. Some acorns have a dark, thin skin on them if this will not remove easily, try soaking the acorns for a few minutes. If no luck, dry these soaked acorns in the sun for one to two hours. Rub a quantity together in your hands. Or you can ignore the skin. Some say it makes no difference
whether it’s there or not.
Processing
With shells removed, the acorns are ready to leach in water to remove tannins. How long does it take? When are they done? The short answer is that they are done when they’re done. Taste a small piece. If it is not bitter or leaves an astringent feel in your mouth, it’s done. It takes as long as it takes — from a few hours to two weeks; much of this depends on the method of leaching, and the size of the acorn pieces. Acorn flour leeches so much more quickly than whole or half pieces. It also depends on the leaching method chosen.
Hot water leaching
Quickest but only larger chunks can be processed. Heat a large amount of water. Put acorns in a smaller pot. Pour a generous amount of boiling water over them. Boil 20 minutes. Pour off water. Replace with fresh boiling water. Repeat until acorns are done. Four times? Eight times? Do not ever let cold water come in contact with the acorns during this process this will bind the tannins into the acorn and they will never be removed. Boiling remove the fats from the acorns and cooks their starches, limiting their use as a binder in baking-type dishes.
Cold water leaching
Slower, but the fat and nutrients are retained. Chop or grind acorns to the size of course kosher salt or larger. Put in bowl. Cover with a generous amount of water. Let’s sit. Water will turn yellow. Poor off water. Replace with more water. Refrigeration not necessary. Change water twice, (or at least once), per day. Four days? Seven days? Depends on the original tannin content. When done, place acorns in a cloth and squeeze water out. Spread on sheet pan 1/4 inch or less thick and dry in the sun. When dry, it can be used as-is or ground into flour.
Random notes
• Generally the larger the cap and proportion to the acorn, the more tannins it will contain.
• Do not pick acorns off of the tree. Green acorns that have fallen may be okay if they turn brown when dried.
• Red oak acorns in their shell are good for 5+ years when stored away from both moisture and temperature extremes.
• White oak acorns should be used soon after gathering.
• Only crack what you can use in a reasonable amount of time.
• Since they oxidize and turn brown after cracking it might be best to drop them in water as you shell them.
• Soaking them in this water overnight may loosen the skins.
• Using a food processor or blender at the start may grind acorns into too fine a powder — difficult to leach without losing content.
• When leaching, adding baking soda to each water-change may help to accelerate the removal of tannins.
• The leaching water may never become completely clear. Use taste to determine when they are done.
• Leaching can be accomplished by putting acorns in the sack and throwing it into a stream. Alternately, a mesh bag placed in the toilet tank, (not the bowl!) will provide regular changes of fresh water.
• When drying acorns/flour after leaching, stir every few hours.It may take up to a day to completely dry.
• Completed acorns/flour have a shelf life of about one week. For longer storage, keep in the fridge or freezer to keep oils from going going rancid.
• Subjecting acorns to temps 150° or above at any point — during storage drying, processing — will cook the starches.
• When cold leaching above 75° the main danger is fermenting acorns. Changing the water two times daily may prevent this. Otherwise leach them in a jar in the fridge.
Now What?
What to do with the acorns and flour after all this work? Boiled, coarsely chopped acorns are good added to holiday stuffing/dressing. Mashed (boiled) acorns with butter make a nice side accent. My finished products wouldn’t make the cover of Bon Appétit, but they contain a complement of carbohydrates, fats, protein and a range of essential nutrients. What do they taste like? The fritters are reminiscent of veggie burgers — or of those wonderful pan scraping we eat when no one’s looking. The butter makes a nice topping on baked winter squash. The flour has a neutral flavor. I made “butter” with grapeseed oil and salt, which brings out the nutty flavor of the acorns. My Fritter was made with garlic, egg white, and baking soda and was fried in oil. Alternately, you can do what squirrels do with some of those acorns. Bury them. Then see what happens.
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