Making chestnut flour

What is the best approach to making chestnut flour? We are in process of planting a chestnut polyculture orchard. Certainly we will want to process some chestnut flour at the home scale, as one family member has gluten sensitivities and we eat gluten-free at home in consequence. But with around 250 chestnut trees, we could consider making flour at a small commercial scale.

As I understand it, the chestnuts are roasted, then dehydrated, before grinding.

Is there anything special to look out for in a grinder to process chestnuts?
Would a typical home grain grinder be able to handle them? What if we decided to scale up to chestnut flour sales in a few years, what are our options there?

chestnuts kind of turn rock hard when dried. getting them chopped down to smaller, easier-to-grind size pieces before drying is important unless you have a really serious grinder (which i suppose you may get if you want to go to a commercial scale).

in general, stone-burr mills are adequate for chestnuts. there are both home-scale versions and bigger commercial ones.

I did see a video where they were grinding whole chestnuts in Italy but it was in an ancient mill with huge stone wheels. I can't remember if they dried the chestnuts first but I assume so.

For a modern home machine it sounds like the chopping should take place before drying. Thanks for mentioning that, I might have skipped that step. They would probably dry faster and more evenly if pre-chopped anyway.

I have never used a grain mill so maybe this is a kind of dumb question, but everything put into the mill needs to be dry, right? Is it possible to grind fresh or only partly dried material and then finish dehydrating, maybe even re-grinding when fully dry? Might be a solution to the rock-hard problem but I have a feeling this is not how the machines work. I imagine the grinding surfaces would clog pretty quickly with material that is not fully dry?

i know some mills say they work with not-totally-dry things (fresh corn, etc), but i’ve never tried, myself. a friend of mine tried to grind fresh corn with a mill that claimed it would work and he wasn’t happy with the results. higher-quality mills may work better for that.

"As I understand it, the chestnuts are roasted, then dehydrated, before grinding."

To my knowledge, chestnuts are NOT roasted before drying and grinding for flour. I have bought both dried whole chestnuts and chestnut flour in Chinese markets and they were apparently dried and ground raw (judging by color).

"I have never used a grain mill so maybe this is a kind of dumb question, but everything put into the mill needs to be dry, right? Is it possible to grind fresh or only partly dried material and then finish dehydrating, maybe even re-grinding when fully dry? Might be a solution to the rock-hard problem but I have a feeling this is not how the machines work. I imagine the grinding surfaces would clog pretty quickly with material that is not fully dry?"

Depends on the kind of mill you are using.  If you are using a hand mill with metal burrs like the classic Corona Mill, you can grind virtually any material, from fresh chestnuts, oily nuts, partly dry field corn, beans, etc.  That would be a quicker solution to cutting chestnuts into smaller pieces to dry for grinding in a stone (or synthetic stone) burr mill like the KoMo. Stone burrs cannot handle moist grains or oily seeds, not even dry soybeans, as they will clog. After drying fully, the pieces can then be ground easily by the stone burrs.

I would also say chestnuts aren't roasted before drying, based on the ones I've bought. And, yeah, they're super hard.

Do your chestnuts shed the fuzzy brown layer under the shell easily? I soak the chestnuts before blending to make a batter, bypassing the flour part. If I don't pick out most of the brown skin that gets trapped in the chestnut crevices, the batter can be fairly bitter.

There was some good advice on chestnut flour in a recent book I was reading titled “trees of power” by Akiva Silver. He mentioned that he air dries them in an onion sack hanging from a rafter and then grinds them in a mill as needed. It seems pretty simple and I’m a little skeptical but I’m going to give it a shot in future years as my 6 chestnut trees mature. They’re going to make way too much to consume fresh. I think a frozen chestnut butter could also be interesting.

That's great, I'd be happy to skip the roasting step :) And it sounds like there are grinders that can make flour from whole chestnuts so if I don't have to chop them before grinding, there's another step that can be skipped. This is sounding easier!

I suppose drying in an onion bag could possibly work if you lived in a very dry climate, or maybe hang the bags by the wood stove. There's a heritage nut orchard we visit that has an old drying shed with a wood stove on the ground floor and drying racks stacked above it on an upper floor. There are chestnuts at this orchard but I'm not sure if they were dried in the shed, or if it was just used for their walnuts, hazelnuts, etc.  I can't see how the flavour of any of those nuts would be affected by wood smoke, but I wonder if drying in that way imparts any smokiness to chestnuts? And if so, does that carry over into the flour and is it good (the flour equivalent of smoked paprika?) or bad (I have never heard of smoked flour and maybe there's a reason for that)?

I have a feeling there is going to be some experimentation involved.

In the next year or two we plan to build a couple of solar dehydrators for summer produce and in dry years those could be useful for chestnuts - it will depend very much on the timing of the start of the fall rains versus the chestnut harvest. In a different climate I could see that being a good solution, but here it would not be reliable. Fortunately I have an Excalibur dehydrator which would be enough capacity for now and when all our nut trees start producing (we have planted hazelnuts, English and black walnuts, heartnuts, buartnuts and pecans as well as the chestnuts) it might be smart to copy that old nut drying shed.

My trees are just barely starting to produce, one or two of the 8 or so named varieties have only produced a handful of nuts and those did release the fuzzy brown layer well.  It's early to say whether all varieties will be equally good.  But they are all grafted commercial European or European x Japanese hybrid cultivars and according to the descriptions the ones we have planted should be easy to peel. That is something that has been selected for in the commercially grown cultivars and was one of the characteristics I was looking for in choosing which ones to plant.

I did a really quick web search for 'smoked chestnut flour' and it turns out there really is such a thing and even better, it is a gourmet thing! Check out this web page -

smoked chestnuts

It's worth reading the whole thing, but here's a spoiler:

"Giovanoli’s chestnuts end up on the drying floor of his special chestnut smoking hut, where they are dried in chestnut wood smoke at approx. 60-80°C for 6 weeks. The dried chestnuts have a smoky flavour that goes perfectly with game dishes. In his restaurant in Lenzerheide, gourmet chef Ladurner uses them to make not only bread but also a wonderful smoked chestnut ice cream. "

I want smoked chestnut bread! And I really want smoked chestnut ice cream!

Making flour with the 15 pounds of chestnuts that I harvested in the fall is on my long list of winter projects!
In the past I've roasted and peeled fresh chestnuts, ground them in my Vitamix, then dehydrated and ground again before
storing in an airtight bag in the freezer. It was absolutely incredible mixed with chickpea flour to make soccas.
This time around I plan to score the chestnuts, boil, peel, grind, dehydrate and grind again.

The smoked chestnuts and resulting products sound amazing, perhaps I'll try that one day and make smoked chestnut soccas!

I had to go look up soccas as it was a form of flatbread I haven't encountered but they look delicious.
Now I want smoked chestnut soccas too! :)

my family makes chestnut flour on a very small scale. we've got a lot of trees, but share most of the nuts with friends and wildlife. we make flour with raw, boiled, roasted (in the oven or in a skillet), and smoked chestnuts. they're all good in their own way.

my experience is that the most difficult part of the process by far is peeling the nuts. I've burned my fingers and gotten peel under my nails every fall for years. it's tolerable with friends, but I wouldn't want to do it by myself. I suppose there's a good chance that there's an easier and less painful method that I just haven't stumbled across yet. I have tried a couple models of "chestnut knife" without much luck. could just be user error...

there's an old water powered grist mill near us that I'll take a load of chestnuts to one of these years. just haven't been able to peel enough at one go to make it worthwhile. for now, we use either a home-scale grain mill or a food processor. both work fine. for the mill, we have to either cut the chestnuts into smaller pieces before they dry or break them up with a hammer after they dry. again, both options seem to work fine, though one is a bit more exciting and messy than the other.

one of the ways chestnuts are shelled and de-skinned on a somewhat larger scale…seems a little crazy. they basically fire them out of a little cannon into a thick wooden plate. they hit just hard enough to split the shell and skin, then those bits get blown off with forced air. i saw this at route 9 chestnut cooperative in ohio. they use it on their chestnuts that are destined for flour.

I processed a couple kgs of chestnuts last autumn by grinding them while fresh with my trusty Corona mill, then drying the flour in the dehydrator. I use the flour in baking and in soups. Seems to be keeping well stored in a plastic bucket with a tight-fitting lid.

Andrea Locke wrote:
There's a heritage nut orchard we visit that has an old drying shed with a wood stove on the ground floor and drying racks stacked above it on an upper floor. There are chestnuts at this orchard but I'm not sure if they were dried in the shed, or if it was just used for their walnuts, hazelnuts, etc.  I can't see how the flavour of any of those nuts would be affected by wood smoke, but I wonder if drying in that way imparts any smokiness to chestnuts? And if so, does that carry over into the flour and is it good (the flour equivalent of smoked paprika?) or bad (I have never heard of smoked flour and maybe there's a reason for that)?

There wouldn't be any flavor of wood smoke on what is dried in such a shed. the wood stove must be vented with pipe going outside, just as in a house, so there will be only heat, not smoke.

Margo Michaels wrote:Making flour with the 15 pounds of chestnuts that I harvested in the fall is on my long list of winter projects!
In the past I've roasted and peeled fresh chestnuts, ground them in my Vitamix, then dehydrated and ground again before
storing in an airtight bag in the freezer. It was absolutely incredible mixed with chickpea flour to make soccas.
This time around I plan to score the chestnuts, boil, peel, grind, dehydrate and grind again.

The smoked chestnuts and resulting products sound amazing, perhaps I'll try that one day and make smoked chestnut soccas!

Can you describe what soccas are and perhaps a recipe?

Freyda Black wrote:

Andrea Locke wrote:
There's a heritage nut orchard we visit that has an old drying shed with a wood stove on the ground floor and drying racks stacked above it on an upper floor. There are chestnuts at this orchard but I'm not sure if they were dried in the shed, or if it was just used for their walnuts, hazelnuts, etc.  I can't see how the flavour of any of those nuts would be affected by wood smoke, but I wonder if drying in that way imparts any smokiness to chestnuts? And if so, does that carry over into the flour and is it good (the flour equivalent of smoked paprika?) or bad (I have never heard of smoked flour and maybe there's a reason for that)?

There wouldn't be any flavor of wood smoke on what is dried in such a shed. the wood stove must be vented with pipe going outside, just as in a house, so there will be only heat, not smoke.

I have been watching Youtube videos of chestnut processing in Italy and in at least two of those, the heat/smoke source was an open wood fire like a campfire on the lower floor of a very ancient stone building. Chestnuts were placed over the fire on an upper floor. I don't know how the smoke exited the building.
So that was interesting to see. The more 'modern' (100 year old) drying shed system I mentioned that we've seen here in BC is based on a wood stove with a pipe such as you suggest, but apparently a smokehouse with direct exposure to wood smoke is a viable alternative. I assume this must be the origin of the artisanal 'smoked flour' that I found mentioned online after writing the first post quoted above.

Chestnut harvest is huge this year. Not only numerous, but also very large nuts. Roasted some in my oven with the residual heat after bread baking (it's a Rofco with stones, so retains heat very long). Nuts came out dry. Used a hand powered meat grinder (tre spade) to grind into smaller pieces, this worked quite well.

The result is great for use in stews and soups et cetera, but it's not yet flour. I guess I'll be milling it into flour at some point.

For now I've only removed the outer shell, not the inner. Do people also remove the inner shell for processing into flour?