You must leach the tannic acid, or tannins, before eating acorns.

How to Leach Acorns

by Amelia Allonsy

While most commonly associated with foraging squirrels, acorns from oak trees (Quercus spp.) can also be consumed by humans. Oak trees, hardy in U.S. Department of Agriculture plant hardiness zones 3 through 10, drop their fruits -- acorns -- throughout fall. You can eat the meat plain or grind it into flour. Before consuming acorns, however, leaching is required to remove the toxic tannic acid from the meat. Native Americans placed baskets of acorns in fast-moving streams for several days, but you can leach the tannins in boiling water.

1 Gather only brown or tan acorns after they drop from the tree. Gather acorns only from trees in which you know no pesticides were used.

2 Crack the acorns to separate the shells from the meat or seed kernel inside. Use a nutcracker or hammer to crush the shells. You can discard the shells in your compost pile or use them as mulch around plants. Rub the soft nuts between your fingers to remove the corky skin from the nut meat. Chop the nut meat into fine pieces.

3 Bring two large pots of water to a boil on your stove. The volume of water in each pot should be roughly twice the volume of acorns.

4 Add the acorns to one of the pots of boiling water. Boil for 15 minutes, stirring occasionally, until the water turns dark brown as a result of the tannins in the water.

5 Pour the acorns and boiling water into a colander to drain the dark brown water. Rinse the acorns. Refill the pot with fresh water and return it to the cooktop to boil.

6 Add the acorns to the second pot of boiling water. Boil for about 15 minutes. Check the color of the water to see if it has turned brown, indicating a strong presence of tannic acid in the acorns. Drain the water and rinse the acorns. Refill the second pot with water and bring it to a boil if the water was dark brown and the acorns require further leaching.

7 Continue boiling the acorns in 15-minute increments until the water remains clear at the end of a 15-minute cycle of boiling the acorns. This process can take up to two hours, depending on the level of tannic acid in the acorns. Always be bringing another pot of water to a boil while boiling the acorns in the second pot. While a second pot is optional, having one heating up while boiling the acorns in the other makes the leaching process much faster.

Items you will need

  • Nutcracker or hammer
  • 2 pots
  • Colander

Tip

  • Generally, white oak acorns contain less tannic acid than black oak and red oak acorns and might need to be boiled through only one cycle. Additionally, acorns with larger caps contain more tannic acid. The most important thing to pay attention to is the color of the water as you leach the tannins from the acorns. If the water runs clear after completing a cycle of boiling for 15 minutes -- whether it be after the second or seventh boiling cycle -- the acorns are safe to eat. White oak (Quercus alba) and black oak (Quercus velutina) grow in USDA zones 3 through 9, while red oak (Quercus rubra)grows in USDA zones 4 through 8.

Photo Credits

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