Acorns as Food

Acorns served an important role in early human history and were a source of food for many cultures around the world.^[16] For instance, the Ancient Greek lower classes and the Japanese (during the Jōmon period)^[17] would eat acorns, especially in times of famine.^{[citation needed]} In ancient Iberia they were a staple food, according to Strabo. Despite this history, acorns rarely form a large part of modern diets and are not currently cultivated on scales approaching that of many other nuts. However, if properly prepared (by selecting high-quality specimens and leaching out the bitter tannins in water), acorn meal can be used in some recipes calling for grain flours. In antiquity, Pliny the Elder noted that acorn flour could be used to make bread.^[18] Varieties of oak differ in the amount of tannin in their acorns. Varieties preferred by American Indians such as Quercus kelloggii (California black oak) may be easier to prepare or more palatable.^[19]

In Korea, an edible jelly named dotorimuk is made from acorns, and dotori guksu are Korean noodles made from acorn flour or starch. In the 17th century, a juice extracted from acorns was administered to habitual drunkards to cure them of their condition or else to give them the strength to resist another bout of drinking.^{[citation needed]}

Acorns have frequently been used as a coffee substitute, particularly when coffee was unavailable or rationed. The Confederates in the American Civil War and Germans during World War II (when it was called Ersatz coffee), which were cut off from coffee supplies by Union and Allied blockades respectively, are particularly notable past instances of this use of acorns.

https://en.m.wikipedia.org/wiki/Acorn