Acorn leaching machine

This summer I harvested over 60kg of northern red oak, I've already made maybe a kilo of tasty flour by cold leaching in a mason jar, where you grind the nuts and fill with water and change the water every twelve to 24 hours.

But I'd like to imagine a larger scale operation, where I could pay the people who are already picking nuts for nurseries to give me a portion of their harvests so I can produce larger volumes. I think the key to this will be to have a degree of automatisation.

Nut sorting is an interesting challenge, you have to filter out the bad nuts and then sort the good ones by size. A black walnut producer in my region uses a magic eye for this, but thats pretty expensive. Either I convince him to let me hitchhike on his operation or I use the method I've been using now, where I drop the acorns in water, discard the floaters then visually inspect all the others. It's not too hard and it can be done in front of the tv.

Nut drying is pretty easy, you just need the space to lay them all out and a fan.

Nut cracking is already a solved problem and acorns are much easier to crack then walnuts, though I'll have to find an affordable machine, something like the davebilt should do, if I can find one.

Nut leaching is the longest part. It took me a little longer than two weeks to leach my red oaks (though burr oak can take as little as 3 days). You have to change the water every day, that could be harder with bigger volumes. You also have to keep it cold lest it ferments.

My current idea is to build some kind of vat with a pre-filter at the base, to keep the acorn meat in, and a tannin filter underneath to clean the water, the clean water is then pumped through a refrigerator and finally pumped back onto the acorns. Maybe the acorn vat has an agitator to make sure every surface is exposed to water.

I'm planning to work on a proof of concept this winter, but I'd be interested in hearing any advice, ideas, or if you know of any machines that already do this.

If your well or tap water is cold enough, couldn't that just run slowly through the nut meat to keep it cool and rinse it?  Then you wouldn't need the pumps and refrigeration.  It would consume water but maybe not too much, especially if you can use it for some other use around the place.

With your current plan, I wonder if you can clean the water well enough for it to do a good job in subsequent leaches?

Interesting problem.
Are you sure hot leaching wouldn't be more effective?
Heat is easier/cheaper to generate than cold, and it might be faster as well.
Would charcoal be a good tannin filter?
A repurposed cloths washer might serve part of the process.
It could agitate , rinse and  spin dry the acorns.

Patrick Marchand wrote:
Nut cracking is already a solved problem and acorns are much easier to crack then walnuts, though I'll have to find an affordable machine, something like the davebilt should do, if I can find one.

I have a davebilt nut cracker I bought some years ago and have been happy with it.  I got mine straight from the company.  Looks like the problem right now is that they get more orders than they can keep up with.  At their site is this recent blog post which essentially says, "If you want one get on the waiting list and we'll fill them first come first served."  

This suggests boiling for 15 minutes and then reboil until the water is no longer brown:

"To remove tannic acid, you must leach the acorns with water.  The Indians set the acorns in a basket in a clean fast-flowing stream.  The water rushing through the basket would leach out the tannins in a day or two.  Since most of us do not have a clean fast-flowing stream nearby, we need to boil out the tannins....Toss the nuts into a large pot, and cover them with plenty of water.  Bring to a boil, then boil for about 15 minutes.  The water will turn brown, the color of tea, as the tannic acid is extracted from the kernels.  Throw out the water...and replace it with fresh water.  To save time, have a second pot of water already boiling.  Reboil  the acorns, throwing out the brown water, several times until the water no longer turns brown."

https://www.wildflower.org/expert/show.php?id=2947

There are several suggestions from well know people.

Hot leaching is not an option, it cooks the starch so it doesnt bind as well if you try to use it as a flour, besides, it makes for a much less nutritious end product.

As for the davebilt, I saw one go on ebay, but I didnt manage to win the auction. I'm keeping my eyes open, but I'll probably put myself on the waiting list.

agreed, cold-leaching gives a much better product for more purposes.

at our nut processing facility, we’re borrowing a hazelnut-cracking rig from a local farm that had it made with a grant but doesn’t seem to need it. i’ve been looking for a picture online but haven’t found it. it’s basically a automated davebilt cracker with a built-in adjustable winnowing fan. it’s really nice for acorns.

our best plan for a leaching tank would probably be best inside of a walk-in cooler to really control temperature. you don’t really need to switch out the water as often if it’s continuously recirculating.

you may want to look into raising the pH a bit, too, which really speeds up leaching. i know people who have used actual lye to pretty good effect, but i prefer a bit of wood ash or baking soda.

I read about the effect of lye, does it have any effect on the taste ?

I wonder if the tannins actually saturate the water and if they do, are we really reaching that level when leaching the acorns.

During the holidays, I'll be moving into my new home which has an unheated spot that should always be around 0, it would do great as a walkin cooler. I should be able to do some side by side tests and a water pump isnt too hard to find.

I wonder if this would do the trick: https://www.ebay.ca/itm/225231287993?hash=item3470d4b6b9:g:vM4AAOSwdhxjYD9T&var=524175331961

i couldn’t detect a flavor difference where lye had been used.

i don’t think the water really gets a chance to become really saturated, so to speak, with tannins. i will say though, the nice thing about switching out water is that it’s coloration can give info (without lots of tasting) on how much tannin is left, based on how much the water colors in a day.

that cracker may do the trick. as long as the shells are good and dry, acorns really are pretty easy to crack.

Alicia Bayer makes both hot and cold leach types of flour. Somewhere on the forums she posted what each type is best for making things to eat are. Here's a thread about her book.

Check out the systems that aquarium enthusiasts use for high-volume filtering! I bet it'd be /perfect/ for acorn leeching.

Aquarists already have established that charcoal filters are fantastic for REMOVING TANNINS. That's why they have all sorts of workarounds to avoid using charcoal in their setups when creating environments for fish that need high-tannin water. (Fish which thrive in swamps and very slow-moving rivers often prefer tannin-heavy water, and it's good for their health)

Idea for acorn leaching:

1 big aquarium
The aquarium has a hole on one side for pouring water out when it reaches a certain height, and on the bottom opposite corner, has an inlet tube connected to a water pump.
The water pump pulls clean water from the Sump tank.

When water is pouring out of the high-up aquarium hole, it is directed through several sieves to remove larger particles (like floating acorns and bits of twigs).
The rough-filtered water then flows into the top of the sump tank.
The sump tank is filled with charcoal.
On the other end of the sump tank is a tube, connected to a water pump, which pushes the water which has made it allll the way through the charcoal filters & is now clean - back into the aquarium tank, to be pushed past the acorns again and leech more tannins out.

The water should stay a little cooler than room-temperature, due to evaporative cooling off the top of the aquarium (if it's open-topped). However this means you'd need to regularly add water back into the system.

If you really need it COLD, some sort of refrigeration thing will be needed. Systems like geothermal heating usually use a supercooled liquid (like liquid nitrogen) to cool off air/water for air conditioning.