Experiments in eating acorns (part 1): tutorial on how to make acorn flour

I’m fascinated by the oak tree and acorns. There’s something mystical about a tiny humble nut turning into a huge tree in the silence of time. For the past few years, in the fall, I like to pick acorns and experiment with turning them into human-edible foods. Why? Think zombie apocalypse! I will be a valuable member to any band of survivors and sure to last till season 8! Hehehehe!

That aside, I enjoy the process. Come November/December, and it’s the frenzied holiday shopping season. Picking acorns and processing them takes me away from all that and it teaches me to be more appreciative of the nature around me. It’s a lot of fun to forage and to add value to something that people generally don’t think much of. The first time I processed acorns, it was a kitchen disaster… but I managed to make a small batch of very basic granola and it was immensely rewarding. I’ve fine-tuned some of the steps and I think I’ve gotten a little better since. So in this post, I’ll provide a tutorial on acorn processing and in a subsequent post, will share some recipes. I use whatever device I have at home for this, and it is adequate for small-scale production.

Finding the right nut!

This is one of the most fun for me. Finding the right oak tree! This will open up a whole new realm of awareness for you. You’ll be walking around your neighborhood far more mindful of the type of trees and leaves that surround you. White oaks work the best. Acorns contain bitter tannins and white oaks generally are less tannic than the red oaks. You could use red oaks, but it will take a long time to get rid of the bitterness, particularly using the cold leaching method, which I prefer. In this part of the US, with humid and warmer climate, red oaks predominate over white oaks.

[Side note: I think the high tannin in red oaks prevents them from germinating too early in the season. Up North, I notice a lot more white oaks… maybe the colder weather means we don’t want the tannins delaying germination when Spring finally comes. But I’m no botanist. This is based on a vague recollection of something I think I read. So the relation between tannin content, weather, and germination needs to be verified]

The best way to tell the difference between a red and white oak is to look at the leaves. Red oaks have veins that go all the way out and are spiky. White oaks have rounded smooth leaf lobes (Figure 1). Also crushing the acorn, you can guesstimate the tannin content by the color. Yellowish reddish colored nut meat indicates higher tannins.

Figure 1. White oak with smooth rounded leaf on the left and red out with spiky leaf on the right

Once you’ve found your tree, gather. It’s best to collect early in the season when some of the fallen acorns are still green. But even the brown ones are good for eating. Collect more nuts than you think you’ll need. Because depending on the tree, 30–50% of the acorns may have to be thrown away because of the acorn weevil. As you gain more experience, you’ll be able to tell which acorns have good nut meat by the weight and shell color. And if you see a tiny hole, it means there’s a tiny weevil grub inside feasting on the nut. But you don’t have to worry too much about it yet since there is a follow-up selection method.

Acorn selection and freezing

Once you’ve gather enough, you’ll need to wash the acorns. During the washing process, you’ll notice that some acorns float up and some sink. Discard the floaters… those are probably not much good and probably has acorn weevil. Once acorns are collected, washed, and selected, I usually like to freeze them. It’s a good way to store them till you have time to take on the more labor-intensive task of shelling. Also, it seems like freezing the nuts make it easier to shell and remove the inner coat from the nut. Under the hard shell, there is a coat that can stick to the nut. That eventually comes off during the leaching process, but best to remove them during the shelling.

Cold leaching and making flour

1) Shelling: First step is to thaw the acorns and then remove to shell. I don’t use anything fancy. Just a simple nutcracker (Figure 2). This cheap little device has worked pretty well for me.

Figure 2. My nut cracker cracks the nut

2) Mushing: Once I have a nice pile, I use a normal blender to make acorn mush. Just add water and blend.

3) Leaching: Now you’re done with the laborious part. Now to remove the bitter tannins. I prefer cold leaching although hot leaching is an alternative. Cold leaching takes time but it’s a fairly passive process and all you have to do is change out the water. I like to put the blended acorn slush into a big container (like a cooking pot or something), then fill it up with water and let it sit in the fridge. Along with the main pot of acorn mush, I also like to aliquot a small amount of the mush into a transparent glass jar (a used pickle or olive jar is what I use) and this pretty much functions as visual indicator of where I am with the tannin content (Figure 3). It’s also fun to see the acorn butter at the bottom of the jar (Figure 3). The first day, the water looks dark and during the first 3 days or so, I may change out the water twice a day. Eventually the water begins to clear and once a day suffices. To change out water, I simply pour out the old water and refill and shake well and put in back in the fridge. Don’t worry about getting rid of all the old water… you don’t want to be losing too much of your hard-earned acorn meat every time you do this… simply decant and refill. Along with the water color, you can do a taste-test. Day 1, it’ll be very bitter. For this batch, by day 8, the water looked clear and the meat lost its bitterness.

Figure 3. Top left is day 1. Bottom left is around day 7 or 8 and the water has become lighter. On the right, there is the acorn butter that has solidified at 4 degrees C, and settled on the bottom

[Side note: Hot leaching is a faster alternative. It involves boiling the acorn and pouring out the water and repeating few times. Instead of days, you could be done in a day. But the acorn flour is of lower quality, in my opinion, and you also end up losing the butter and that’s sad]

4) Drying out: After the final decant, transfer the acorn into a cheesecloth over a colander. Make sure to scrape the butter and add that as well. Squeeze out the liquid. This year, I squeezed out the liquid in the morning, placed the acorn mush on a cookie sheet and spread them out (Figure 4) and left it on my kitchen table and went to work. Then in the evening, I dehydrated the mush in my oven. Set the oven to the lowest temperature (mine is 170 degrees F). Place the acorn mush that’s been spread out on a cookie sheet in the oven. The first 30–40 mins, I had the over door close so there’s enough heat to evaporate the water. After that, I spread the acorn mush around, and placed it back in the oven, but kept the oven door cracked open a bit so the acorn does not bake and burn. Just keep an eye on it. You just want the water to evaporate and the mush to dehydrate. If you have a dehydrator, that’ll work great! I don’t.

Figure 4. Acorn mush ready to be dehydrated

5) Grinding the flour: Once it’s dry, you got acorn meal. If you want to make acorn falafel, leave some of the meal. For making flour, you have to grind.  I use a coffee grinder and since I use an old coffee grinder, my flour tends to be bit gritty and more like  masa or corn flour (Figure 5). It won’t be as refined as the white flour you get at the store. But I don’t mind that since this is home-made flour and not processed as much, and that’s the whole point.

Figure 5. My flour grinding set up; pretty self-explanatory on what you need to do

And that’s it! You got acorn flour (Figure 6). I usually refrigerate it and start baking within a few days!!

Figure 6. Acorn flour! The product of all your hard work. Notice that it has a naturally brown color and unrefined texture.

In an upcoming post, I’ll share a few recipes. The falafel uses acron mush/meal.

[please excuse typos and errors; not proofread and author makes lots of typos]


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