Harvesting and Processing Acorns


by June Jacobson

A basket of Acorns ready to be processed

“Is it worth it?”

Every Fall I answer this question about gathering and processing acorns. My answer is always “yes!”, especially if you find joy in the hunt for wild foods and the experimental path to self-sufficiency. It also helps if you don’t expect perfect results every time, as wild foods can be wonderfully unpredictable. Below you’ll find a tutorial on identifying, harvesting, storing and cold-water processing white oak acorns.

If you would like, you can skip right to How to Cold Water Process Acorns

Identifying acorns

White Oaks

The Oak genus, Quercus, belongs to the Beech Family. There are many different species in this genus, but they are generally divided into three groups: White, Red and Black. Acorns can vary widely in sweetness, nuttiness, and especially Tannic Acid from group, species and even from tree to tree. Tannic Acid (also referred to as tannins) is what makes the nut bitter and astringent before processing and the reason we don’t eat most acorns raw.

The Tannic Acid in the acorns can be so strong that some people question “Are acorns edible?” Of course! Some acorns can be so naturally low in Tannic Acid that they can be eaten without processing, but most will need to have some of the tannins leached out.

Here in the Pacific Northwest, I encourage folks who are trying acorns for the first time to look for white oak species because they generally have less tannin. That means when you’re looking at an oak tree, make sure its leaves have rounded lobes instead of pointy lobes. Leaves with pointy lobes will belong to the red or black oak species.

rounded lobed leaves are from White Oaks

Since the Willamette Valley in Oregon used to be Oak Savannah, I can find Oregon White Oak, Quercus Garryana, scattered about in parks, along roadsides or even large stands in farm fields. But there are some 600 species of white oaks, so have fun hunting!

Harvesting Acorns

If you’re like me, all year long you’ve identified or made friends with trees on your daily commutes, on special trips to the in-laws who live across the Willamette Valley, or while strolling through city streets. You’ve seen those rounded lobes and you’ve made a mental note to come visit those trees again in the Fall, when acorns start dropping. It helps to visit these trees after a strong rain or wind storm in October and November, as this can produce a windfall.

My harvesting style depends on how much time I have. Given enough time, I’ll check each acorn for weevil holes before tossing them into my bag. Less time, I toss them all in the bag and sort through them when I get them home.

Storing Whole Acorns

Sometimes you’ll have to wait before processing the stash of acorns you’ve collected. You want to prevent them from sweating and molding, and to be able to easily check them for weevil holes once in awhile.

Acorn weevil

We need to get them into a place where they will breathe and dry out. I like to spread them across a sheet on the floor. Every so often I’ll roll them over to see if new weevil larvae have bored out through the shells and are rolling around on the sheet. Don’t be alarmed, just pick up the little white buggers and toss them into the yard, toilet, or whatever floats your boat.

When I can’t process acorns right away, I like to use them when the nut has been dried to the point of being rubbery and pliable, but not rock hard. When they’re still pliable, the thin tannic sheath that covers the nut is easier to remove with my bare hands. When you dry the nuts than this, you have to use other methods. You can crack the shell and test a nut every once in awhile to determine when you’ve reached this point.

When they’re dry inside, throw them into a breathable sack and hang them in a dry, cool and ventilated place. Depending on the tannin in the nut, many sources say they can be preserved for up to two years

How to Cold Water Process Acorns

The goal: remove most or all tannins from the acorn meat with least amount of energy consumption and maximum retention of fats and nutrients

What you’ll need:

  • nut crackers
  • cutting board and knife OR food processor,
  • jars
  • water

Step #1: Crack the shells and remove the nuts

Hammer Stone

Depending on the white oak, your acorns could have very thin shells or thick hard shells. Different tools work better for different shells. Here are a few tools I have used: hammer stone on a cutting board, good quality nut crackers (the painted Christmas kind usually lose their head with the first nut), hammer and a towel on a cutting board.

My favorite method is using a smooth, rounded rock that fits into the palm of my hand called a hammer stone. I lay the acorn down on the shallow mortar made by a friend of mine or a cutting board and I bop it. This works great for the skinny, thin shelled acorns that seem to just bend with the nut crackers.

Step #2: Inspect the nuts, taste test and toss them into a bowl of cold water

A fresh nut should be a golden brown color, although it may change to a more gray brown as it dries. If you see a little pink hue on parts of your nut, it means it is starting to germinate, and getting ready to sprout. That is okay. In fact, some folks are starting to use sprouted acorns in recipes. They claim that the nuts are sweeter and easier to digest since the nut starches have started to turn into sugars. Taste test a nut so that you know what you’re starting with. You’ll be taste testing throughout and it helps to know what progress you’re making.

Throw your nuts into a bowl of water after removing the shell. Fresh or lightly dried nuts may start to change color the longer they sit out, much like a cut potato will darken. The darker brown lines and color change is caused by exposure to the air and can ultimately affect the flavor if left to dry out too long outside the shell.

Step #3: Make a course meal

Once you’ve shelled the nuts you want to chop them on a cutting board with a knife into a coarse meal. If you have a food processor, drain them and process them for just a second or two. The larger you chop or process, the longer it takes to remove the tannins.

Step #4: Start your water bath

Acorn meal in water bathFill jar(s) half way with acorn meal and the rest of the way with water. Let jars sit on the kitchen counter, but drain the meal and change the water daily or even twice a day (jar on the left). I usually keep my first and second changes of water. They’re always dark brown and highly tannic, (jar on the right). I’ve used it as an anti-fungal foot wash with great success, but I’ve heard folks have used it to make a natural shampoo and tanning solution for animals hides as well.

Step #5 Taste test and toss in the fridge

After a few days of changing the water and noticing the color fade to lighter shades of brown or dark yellow, I taste a nut. If I deem it good enough, (IE, enough of the astringent taste is gone that I find it tasty) I’m done. If it’s not, but getting close, I change the water again and then stick it in the fridge. I figure that the less tannins there are to keep bacterial growth down, the better the odds are that something unwelcome could grow. In the fridge it goes and I keep changing the water until it’s clear or the nuts no longer taste tannic. This can take a few days or a couple weeks depending on the nuts.

Step #6: Decide what to do with the meal

Since you’ve cold processed your meal, the gluten-like nut starches, fats and much of the nutrition is still in great shape. I do a few thing with my drained meal. I’ll use it immediately to make a Sweet Acorn Porridge, in a Spiced Apple and Acorn Quick Bread, or in Curry Squash and Acorn Ravioli. If I’d like to preserve it for later use, I dry it in my dehydrator as is, or process it into a finer meal and then dry it. It’s easier to grind into a flour in my coffee grinder when it’s fine.

I hope to post a few recipes soon. I’ll update this post when I do.

Notes on Processing

I’ve just covered one of my methods of cold water processing. It’s clearly for those who are not in a hurry! If you’re ready to process your acorns and want to eat a meal at the end of the day, I recommend trying hot water processing. I’ll post an article on hot water processing acorns soon.

Talk a couple of friends or family members into coming over, throw in a movie or favorite series or just catch up while sitting around the kitchen. It’s one of my favorite weekends spent with students at Trackers, as we all tell stories and get to know each other better. The productive socializing culminates in a delicious meal, so you can’t beat it!

Well, that’s it! Are you ready to cold process your acorns now? If you have any questions, drop me a note and I’ll see if I can help! Happy acorn hunting!”