Cookbook:Acorn

An acorn is the edible nut of the oak tree.

Characteristics
Acorns come in a variety of shapes an sizes, but they have a tough outer shell and a rough "cap" surrounding the nut meat. The meat is mild once processed, but it is full of tannins, bitter, and mildly toxic when raw. The acorns of different species of oak trees will vary in tannin content. Ilex/holm/holly oaks in Western Asia produce relatively sweet acorns. In North America, white oaks are common, and their acorns are milder than those of other endemic varieties like red oak.

Acorns can also vary in fat, protein, and carbohydrate content, all of which will affect the flavor and cooked product. Higher fat content makes for a "moister" acorn and acorn meal, while carbohydrate-rich acorns are drier and make a finer flour.

Selection
Acorns mature over the spring and summer and fall from their trees in the fall. They can be gathered from fall to early spring, but after the fall there is a risk of them molding and/or sprouting. Gather the acorns as soon as they fall, discarding any that have a small hole in the site from oak weevils.

Storage
Freezing is the best way to store acorns, both before and after processing. This keeps them fresh and prevents the oils in them from turning rancid.

Processing
Acorns require significant preparation before they can be consumed.

First drying
Shelling acorns is easier once they are dry. You do this in wide shallow pans or a dehydrator to prevent mold growth. Ensure good air circulation.

Shelling
Shelling can be done with a hammer/mallet or a specialized nutcracker. Rounder acorns should be placed on their flat top, while long acorns should be placed on their sides before hitting with a hammer. Place the acorn meats immediately in water if desired to prevent oxidation.

Leaching
The tannins in acorns can be leached using either a hot or cold method. Hot leaching is faster, but it cooks the starch in the nut, which will affect its binding properties later on.

For hot leaching, place the nuts in a large pot of water. Bring to a boil, then drain and discard the water. Repeat the boiling and draining with fresh water until the nuts are mild enough to eat.

For cold leaching, there are two primary methods. The first involves tying the nuts in a cloth and submerging in a well-cleaned toilet tank (not toilet bowl). Flushing the toilet causes fresh cold water to flow over the acorns, which leaches out the tannins. The second method requires grinding the nuts, transferring to a container, and covering with cold water. Store the container in the fridge, changing the water periodically, until the meal is no longer bitter. Drain and squeeze out all liquid.

Final drying
If present, rub the thin skin off the nuts. Dry the leached acorns, preferably in a dehydrator. If you want to preserve the starch, keep the temperature below 150°F.

Use
Acorns can be eaten whole like other nuts, and when ground can used like other nut meals. Acorn meal contributes fat and protein to baked goods, though it has no gluten. It can also be used to make a porridge, much like cornmeal. Acorn starch jelly is used in Korean cuisine.