Amy Miller runs a chestnut farm and processing cooperative in Carrollton, Ohio. I met her at a nut growers conference last summer and was immediately interested when she said she’s experimenting with using her chestnut processing equipment to make acorn flour.
“At Route 9 Cooperative where I work and I have a farm, we primarily process chestnuts,” Miller said. “And it turns out that a lot of our machines that we have for drying, peeling, and milling chestnuts also work for acorns.”
Miller first started thinking about trying acorn processing when a business reached out saying they wanted to buy and use acorn flour in their products but had nowhere to get it. So that winter, she and a research colleague applied for a grant to experiment with producing their own acorn flour using Route 9’s chestnut processing equipment.
“The way that we process our fresh chestnuts is when they come in from the field, they go through a winnowing machine,” she said. “So it's an air cleaner, which separates any field debris, grasses, small sticks, that sort of thing, from the nuts themselves.”
The same machinery works well for the acorns. Next: the nuts, still in their shells, go through a hot water bath. The point of this is to kill little the worm-like bugs called weevils that can live inside all types of nut species.
“Every nut has its own weevil,” she said. “And weevils are highly specialized, so most weevil species that affect nuts are very species-specific. There are chestnut weevils that affect chestnuts, acorn weevils that affect acorns, filbert weevils that affect filberts or hazelnuts.”
The list goes on. The good news is, the same treatment seems to work to kill both acorn weevils and chestnut weevils.
“That's a very precise temperature of 120 degrees Fahrenheit,” Miller said. “And we typically give the nuts a bath at 120 degrees for 20 minutes.”
Once the weevils are taken care of, the nuts get dried.
“We have forced air dryers,” she said. “This is just kind of like ambient air being blown with a big squirrel cage fan into bins that have perforated bottoms. We're just basically forcing a bunch of air past the acorns. They will dry in those ambient air-drying bins, essentially until we're ready to process them.”
By “process,” Miller means shell them and mill them into flour. This is where the processing starts to diverge for chestnuts versus acorns. One of the biggest differences between the two nuts is that chestnuts are great for both eating fresh and making flour. The higher quality or “grade A” nuts get sold fresh, while the “grade B” nuts go through the drying process and are then milled. But because acorns are high in bitter tannins, they’re not good for fresh eating: you’ll pucker up and spit them out. Instead, these same tannins act as a preservative, allowing acorns to store dried for months or even years without losing quality. Later, they get cracked and made into flour. This flour then needs to be leached—or soaked in water to remove the tannins.
“At the moment, we are just processing the acorns like chestnuts and we’re selling the flour un-leached,” Miller said. “We make sure that folks know that when they get the flour. The acorn flour can be leached at home and there are some really good instructions online for leaching batches of flour at home as you need it.”
Miller gave me a bag of Rt 9’s un-leached acorn flour and I ran water through it at home until I got a flour with a sweet, mild flavor. Route 9 isn’t set up to leach acorns at scale, Amy told me, because their main focus so far has been chestnuts. But experimenting with acorns has been a great way to use the chestnut equipment while it’s idle, once chestnut processing wraps up in December and they’re staring down a long winter.
To learn more about this project:
https://projects.sare.org/information-product/diversified-processing-of-acorns-preliminary-findings/
The Local Food Report is edited by Viki Merrick and produced by Atlantic Public Media in Woods Hole, Massachusetts.
