Earlier this autumn, I wrote a few posts on Instagram (@mallorylodonnell) about processing acorns using the hot-water leaching method. I felt they were worth repeating on here, especially as a mild season has meant there are still viable acorns out there to collect. In any case, here is my hot-water method for leaching acorns of their tannins.
First, you must collect your acorns. Choose freshly-dropped acorns that look clean and feel firm and heavy for their size. Avoid acorns with one or more of the following characteristics : a white patina, green or yellow coloring, caps still attached, holes (caused by the exit, not entrance, of a grub), or excessive dark or bright coloration. Sprouted acorns are perfectly acceptable. While there is a definite variance in bitterness between white oak group and red oak group acorns, the most important concern for collecting acorns is their freshness and quality. Size matters too – bigger acorns mean less work. For to be sure, there is much work ahead. First wash the acorns, then cover them with water – those that float are to be discarded.
The second step is shelling the acorns. I am completely convinced I have the best method for doing this. I heat up a cast iron pan with one layer of acorns until they are fairly warm and starting to discolor (from brown to an orange-brown). Then I remove the pan from the heat and crush each acorn the way I would a fat clove of garlic, with the base of my hand pushing down on the base of my knife pushing down on an acorn. The acorn will split naturally in two, and if you’ve steamed it enough in the cast iron pan the dark brown film (like the skin of an almond) around the acorn will come off with the shell. Discard or cut the bad bits off of any imperfect acorns such as those with small holes or black spots. Acorns can also be shelled after being briefly blanched in boiling water or even without any preparation, but I find mine to be the easiest and fastest method.
The third step is leaching the acorns. This is necessary to remove tannins from the acorns for both health and flavor considerations. There are hot and cold methods, we will cover the hot one here.
Fill your largest pot with water and bring to a boil. At the same time bring a smaller pot to a boil. I usually fill the second pot about halfway. Add your viable, peeled acorns (steps 1 and 2) to the second pot and boil until the water becomes quite dark (Euell Gibbons says “tea-colored” but think black tea). Drain the acorns. Do not wash the acorns or clean them with cold water, but you can let them sit between rounds of boiling. Put the drained acorns in the now empty second pot and add some boiling water from the large first pot. I try not to use a huge quantity of water for each round of this, maybe twice as much as the amount of acorns. Repeat this process until the acorns are a chocolate brown and have no bitterness in their taste. I usually find this takes around 3-5 changes of water for sweeter acorns and usually a few more for the bitterest ones. Generally speaking white oaks and live oaks are sweeter, red and black oaks more bitter.
Once the acorns are leached, you may chop or use whole in any way you would use nuts. Bear in mind, they contain less oil than tree nuts, so they will be somewhat drier and crumblier. You can also grind them to a meal (or flour, if you will) and mix with other meals or flours in baked goods (remembering that acorn meal will have no gluten). The whole or chopped nuts or flour can also be roasted or sun dried, the acorns will turn nearly black if one does this.
I encourage everyone who is interested in wild food to prepare acorns. It is hard work but absolutely worth it. While preparing them you may wish to consider the many generations of humanity for whom this was a necessary activity – acorns were a staple food long before cultivated rice and wheat. But most of all they taste great and have a flavor which has no real substitute.