Acorns contain a lot of tannins, which gives them a bitter taste. Before eating, they need to be specially prepared to remove the tannins. Red oak acorns have the highest tannin content while white oak acorns have the lowest.
When gathering acorns, select fat ones that have no wormholes. They should be yellowish, not black and dusty. When you get home, spread the acorns in a single layer on baking sheets and cook them in the lowest temperature of your oven for a hour. The dry heat of the oven will cure them and kill any larvae or insects inside. To leach out the tannins, follow these steps:
1. Pop the caps off and crack the shells. The acorn meats should be yellow, not black.
2. After shelling the meats, add them to a food processor and pulse until you have a coarse meal.
3. Place the meal in a bowl and add enough boiling water to cover, and let stand for a hour.
4. Drain the water and add clean hot water. Stand another hour.
5. Repeat steps 3 and 4 until the bitter taste is removed from the meats enough to your liking. The meal should taste nutty, like hazelnuts or sunflower seeds.
Place the wet meal in a cheesecloth and strain out the water. Spread it on a cookie sheet and dehydrate it in your oven at the lowest setting, stirring often to prevent the meal from scorching.
Since acorn meats are fatty, they can mold and turn rancid. You can store extra portions of meal in the freezer or refrigerator in an airtight bag or jar. The dry meal will last a week or so, stored in an airtight jar in your refrigerator.