Late last November, (2023) I spent three fruitful and enjoyable days in Pennsylvania at a silvopasture workshop. As it happened, one of our stops was at a chestnut farm, Castanea, doing much that we’re also hoping to do: growing chestnuts in their silvopasture to take advantage of multiple sheep-chestnut benefits; and processing their nuts in a small-farm facility. I thought what they are doing is a great example of a simple, low-cost way to process chestnuts at the small-farm scale, so here is a description of what they do – to the extent that I understood it. Digging back into my notes I found some gaps, which were filled with some Internet research, so this write-up includes some examples from other farms as well.
Very generally, processing chestnuts involves a number of chestnut-specific steps (they are not like walnuts or pecans or almonds or hazelnuts). As with other nuts, you have to separate debris and bad nuts from the harvest, but then the process diverges. Chestnuts have to be heated to kill weevil eggs; the nuts need to be sanitized in a food grade water and hydrogen peroxide solution; and sorted by size, although not necessarily in that order. These steps are included in each of the (few!) online descriptions of chestnut processing, except sanitizing the nuts, which is sometimes skipped. Below is what Castanea Farm does, with some excursions and comments along the way about alternative processes. I have taken the liberty of using images from other websites, always providing a link to the original. Although this description is of one small farm processing its own chestnuts, I think it's also relevant to a small cooperative model with multiple farms sharing the equipment.
1.Get the right container for your nuts. If your chestnuts come in out of the field in buckets, you’ll need to transfer them into a container that can drain water because three of the steps involve dunking the chestnuts. You can use a picking crate if you’re doing batches of around 30 pounds, or if you’re processing much larger quantities, use large produce crates about a cubic yard.
2.Separate debris and bad nuts. Dunk the crate into a first tank, which has clean, cold water. Debris and bad nuts (with weevils in them) will float to the top. Scoop these all off to the side and lift your container back out of the water. Now you have clean, mostly good nuts. Castanea farm had a system where you could kind of pour the debris out of the crate. They also had a hook hanging from the ceiling with a swivel so that you could lift the chestnut crate out of the water and swivel it over to the next tank. Nice!
Large tote full of chestnuts lifed by machine to be dunked into hot water bath. Screenshot image from youtube video "Bringing Back the Chestnuts: Chestnut Processing" by Virginia FAIRS
3. Kill weevil eggs. A second tank at Castanea Farms is filled with hot water at 120 degrees F. The picking crate with the chestnuts is dunked in this water for 20 minutes to kill any live weevil eggs. At Castanea, the water is heated with a regular water heater and put into the tank; with a small immersion device used to keep the water up to temperature. The mobile chestnut processor developed by the Penn State College of Agricultural Services uses a large 275 or 330 gallon water tote, but I thought that the energy use for heating the water with this system would be quite enormous.
Hot water tank and hot water heater at Castanea Farms. Screenshot image from video made by bctv.org available on the Castanea Farms website under "Chestnuts"
Water heating system developed by Penn State with a large water tote. Screenshot image taken from YouTube video "Chestnut Mobile Sorting Unit Part 1" on Sara Lingenfelder's channel.
4. Sanitize the nuts. The third tank at Castanea has water with a food safe hydrogen peroxide solution (how much HP is that per gallon of water?). The nuts go in there to kill any remaining pathogen spores that might be on the surface of the nut.
5. .Air dry the nuts. Let the nuts sit in a shallow container (the picking crate if that’s what you’re using) overnight to air-dry.
Sanitizing tank at Castanea farms. Screenshot image from video made by bctv.org available on Castanea Farms website under “Chestnuts”
6. Sort the nuts. The most involved piece of equipment at Castanea farms is the size sorter. When the nuts are dry, they go through a sorting bin so they are separated by size – small (<7/8”), medium (1”), large (1.25”), and jumbo. Castanea has a nice sorter made by Charles Edwards of North Carolina. I like on Edwards machine that the holes that the chestnuts fall through are closely spaced. That said, you can’t find them anymore (you can find the patent for the Edwards pecan cracker online though!).
In all processing information that I found, the chestnuts were dry when going through the sorter; some folks, like on the Penn State and the Virginia FAIRS videos, sort the chestnuts before all the dunking. I think that Castanea does it the other way around because they use water to separate the debris and bad nuts from the good ones and at that point, the nuts are wet anyway.
You can’t buy the Edwards sorter off the shelf, so people make the sorters. The Penn State website has detailed instructions online, which you can access with this link. I found another description of making one yourself in this Farmshow article, “Chestnut Orchard Up and Running”
Chesnut size sorter made by Bill and LInda Black, featured in article in Farm Show, 2012 - Volume #36, Issue #4, Page #08, "Chestnut Orchard Up And Running".
7.Cure the nuts. After the sanitation, Castanea then cures the sorted nuts for three days - in the open containers again (I imagine this is somewhat temperature dependent).
8. Quality control nuts. Finally, all the nuts are inspected for quality. I saw one video with a slow conveyor belt that has the nuts rolling down it and workers sorting through the nuts as they come by. I believe Castanea Farms spreads them out on a screen table and manually checks them that way.
Quality control of the chestnuts. Screenshot image from youtube video "Bringing Back the Chestnuts: Chestnut Processing" by Virginia FAIRS