Anything that contains sufficient fermentable sugars can potentially turn into alcohol. I think some nuts will not be suitable, but chestnut seems to have the appropriate profile to ferment into alcohol, although all the recipes I looked at were with added sugars.
I still wonder if malting nuts would create enough fermentable sugars to turn them in alcohol.
chestnut does seem like the best bet, since it's starchier than just about any other nut. after the nuts fall, starch is gradually converted to simpler sugars, so some storage before trying to ferment them might improve results. I imagine there would still need to be some way to convert more of the starch to something more fermentable, though.
for beer, grains are germinated then dried to make malt. malt is then mashed (heated in water) to activate enzymes in the grain which convert complex sugars into simpler fermentables. something similar might be done with chestnuts. base malts generally have enough enzymes to convert their own sugars and some additional sugars, so using barley malt and chestnuts might do the trick. or malting chestnuts could be attempted, though I would guess that the necessary enzymes are unlikely to be present. enzymes could probably be purchased and added separately.
mold is another possibility for converting sugars as is done with koji for sake, soy sauces, miso, amazake, doboroku, etc. that's probably the route I would explore first. perhaps the simplest would be to purchase some rice koji and incubate it with cooked and coarsely crushed chestnut with a bit of water. in fact, I think I've still got some chestnuts drying out in the refrigerator and I might give this a try.
A chap on another site i belong to malted acorns with some success.
Odd flavour even in whiskey that he made with the 'beer' but technically it worked.
He thinks that his process was imperfect though and that he can get more the the 4% he got from his initial fermentation.
Nuts. An interesting addition, but quite difficult if that is to be your main fermentable. I can see there being a couple of problems as nuts have oils that could ruin head retention, but at the same time they have quite a bit of proteins, so the effect could be more balanced (I simply don't know). I would wager that germinating them is definitely the first step, followed by baking them in the oven. The amount of time in the oven will depend on what kind of flavor you want VS how much sugar you want. If I had enough nuts to try this, I would start out with several pounds of nuts and attempt to germinate them. I don't know how this is done. I've germinated seeds, but not nuts (i know, nuts are seeds, but in my head it seems different). If someone could post a method for that step, then the next would be to roast and boil them. Boiling will help by both dissolving the sugars and processing some of the proteins. Hops will still need to be added as they help to preserve the beer.
If anyone is feeling especially gung ho about using nuts, I'd try shaving off the membrane directly next to the nut (beneath the shell, attached to the meat) and placing it in a solution or sterilized water with sugar (or brown sugar, or just boiled apple juice, or any kind of sugar infused liquid) to try and cultivate some natural yeast. Who knows, could be interesting.
If someone could correct me one way or another on germination, that would be appreciated
Given the high levels of protein and fats found in most nuts, you'd need to jump through quite a few hoops. To remove the fats you'd need to use the left-over pulp from oil production, and the get the right balance of carbs to protein you'd need to add some kind of carbohydrate source, probably cornstarch. You'd need a ratio of at least 3:1 or 4:1 starch to pulp to get a balance comparable to grains and avoid problems like poor extraction of sugars into the mash, or a protein haze after fermentation.
This places quite a lot of restrictions on which nuts you can use, however there are three which are obvious choices. Chestnuts have about the same amount of fat as wheat or barley, and a 28:1 ratio of carbs to protein, so would be the simplest option. Copra meal - the pulp left over after coconut oil production - has a 7:1 ratio of carbs to protein, comparable to that of wheat, so may be worth trying if you can get it. And finally, any tree nuts where the pulp left over from oil production has a flavour that is strong enough not to be drowned out by adding loads of cornstarch to the mash. Walnuts would be my first choice, as long as you can get hold of the pulp.
You could replace the cornstarch with another carbohydrate source as a complimentary flavour, of course. Anyone for walnut and banana beer?
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