Acorn flour is more complicated than mesquite or beautyberry flour, but still relatively simple. There’s no chemistry or special procedures needed, it can just take a little longer. That’s why it’s good to do in bulk and then store the flour for later use.
Before you do anything else, you have to gather up a bunch of acorns of course. And not all acorns are the same. Some are bigger, some are smaller. Some are sweeter, some are more bitter. Generally, but not always, the bigger the acorn, the less bitter it is (it also has to do with the species of oak tree). It’s this bitterness that we want to get out of the acorns before we make them into flour.
First you’ll want to crack them open and chop the meat up into smaller pieces. Then toss them into the blender, just like making mesquite flour, and grind them up. It helps to add some water to the blender, to ensure they grind up easier. Next take the slurry mix and pour it into a large glass jar; an old pickle jar will do perfectly. This jar is where making acorn flour takes the longest. Let your ground up acorns sit in the jar in your fridge and leach their bitterness into the water. Everyday, pour out the coffee colored water in the jar and re-fill with fresh water from the tap. Give the jar a good shake to mix things back up and stick back in the fridge.
This process, depending on the type of acorns, can take a few days to a week or more. The acorns are done leaching once the flour no longer tastes bitter. Generally, “white” oaks are less bitter and take much less time, while “red” oaks can take much longer. While technically a “white” oak, live oak acorns can be so bitter, as to not be even worth the trouble. We get all our acorns from burr oaks; a moist soil loving “white” oak variety with the biggest acorns you’ll ever see.
After the flour is done leaching, simply pour it through a cheese cloth or other clean rag to squeeze the water out and place in either a dehydrator or on a cookie sheet in the oven at the lowest temp to dry. Once dried, run back through a blender or other grinder to bring to a fine, floury consistency.
Although acorn flour can take some time, acorns are full of protein and healthy oils and fats. Preserving these oils into the final flour, by using this cold-leaching method, allows these oils to act like a binder when making acorn pancakes or pizza or muffins etc.