Safe processing of old acorns

November 30, 2011 3:35 PM

Wild foods filter: have these old acorns been processed enough to be safe to eat?

For a class project, my daughter wanted to bring in pancakes made from acorn flour she processed herself. She left this to nearly the last minute, and spent an hour collecting a bag of very muddy, oldish looking acorns. After sorting, she had about a pound of viable (though not exactly fresh) acorns.

She opened them, threw out those that were spoiled/dark/wormy (there were a lot of these), and put the okay-looking nutmeats in to soak overnight. She then ground them in a food processor, and has put the resulting mush through three boiling-water washes. The mush is going to be dried in a 200 degree oven for an hour and then mixed with water and salt to make some (very small) pancakes.

My question is: Does this sound like enough processing to be safe? I really don't want her to inadvertently sicken an entire class.

posted by apparently to food & drink (12 answers total)

I am not an expert on acorn preparation, but I think you should scuttle this project.

This link has details on acorn preparation. Apparently, the boiling process to remove tannins should take about 3 hours(you boil the acorns over and over until the water becomes clear). In addition, before boiling the acorns, the above url recommends heating the acorns in an oven before boling them.

Given the dangers of excess tannin consumption(kidney failure) and the fact we are talking about children, I think 'better safe than sorry' is the operative cliche.
posted by satori_movement at 3:50 PM on November 30, 2011 [3 favorites]

Did she at least shell them before she ground them up?
posted by Think_Long at 3:51 PM on November 30, 2011

Taste some. If it tasted slightly bitter but nutty, they're ok. If you're immediate thought is "Gah! I'm going to get that Kid Charlemagne asshole for tricking me into putting this into my mouth." then they need to soak more.
posted by Kid Charlemagne at 3:51 PM on November 30, 2011

Here's one article describing an indigenous way of preparing acorns in California that requires 8+ hours of "leaching" in water to remove tannins.

Another article suggests that they will taste bitter if tannins are present, but sweet if tannins have been removed.

But I tend to go with satori_movement: if you don't know for sure, don't feed it to kids.
posted by LobsterMitten at 3:53 PM on November 30, 2011

Tannins can cause kidney damage if they are not removed from acorn flour. Definitely DO NOT let anyone eat these pancakes.
posted by candasartan at 4:05 PM on November 30, 2011 [2 favorites]

Don't do it. Let her make something else known to be safe to eat that fits with the theme of the project. Hickory nuts are good, plus natural and wild, and we used to eat them right off the ground, just crack the shell and pick out the meat. Acorns flour could make kids sick, don't risk it. If the idea is making a flour, there are many other grains and things that can be ground and are safe.
posted by mermayd at 4:20 PM on November 30, 2011

The taste (bitterness) will tell you. If they're questionable at all, go down to your local (?) international store that sells Korean foodstuffs: I had Korean neighbors in college who made a dessert paste and noodles with the stuff. That way you could say "this is how we prepared it, see here? But since we're not 100% sure these acorns are safe to eat, we also brought some commercial acorn flour you can taste, and here we made these pancakes with them!"
posted by introp at 4:36 PM on November 30, 2011 [4 favorites]

Although she was pretty careful (she did shell them, and leached for almost 30 hours all told), after reading through the replies I am still going to have her play it safe; it's just not worth the risk. She can bring in her product, and her very thorough report. I love the idea of going to the Korean market, but sadly we're out of time on that. Thanks!
posted by apparently at 8:04 PM on November 30, 2011

Holy Dihydrogen Monoxide Batman!*

The oral LD50 (fatal dose, 50%) for tannic acid in rats is 2260 mg/kg (milligrams per kilogram of body weight). It's even higher in rabbits. Compare this to the 3000 mg/kg oral LD50 for sodium chloride (yes, that sodium chloride).** It is generally recognized as safe by the FDA and is routinely used as a food additive. Conveniently, there is an automatic safety check in place here because tannic acid tastes vile in relatively low concentrations.

The significant danger of eating these pancakes (assuming they don't taste vile, see above) is that a child who has a tree nut allergy, but doesn't think of it as such, might not realize that acorn flour pancakes would be just the thing to give them a lovely case of anaphylaxis.

The significant danger in not eating these pancakes is teaching children the lesson that, "While primitive peoples did exactly this thing for millennia, you are not competent to soak nutmeats in water until they no long taste vile. The world is far too complex and dangerous for the likes of you to hope to control even the smallest little part of it and only our beloved and omnibenovolent corporate gods are capable turning plant matter into food that is mostly melamine free and you should go watch TV or play video games instead. Holy, holy, holy! Amen."

I mean seriously, I did this very thing using a recipe in the Boy's Life (the Boy Scout's monthly magazine) one Saturday morning when I was like 11.

*Technically the IUPAC term for water is "Oxidane", which sounds so much scarier, don't you think? Either way, the "di-" part is redundant. It's Iron (III) Oxide, not Diiron Trioxide.

**Do not be lured into thinking that LD50 data is always comparable species to species. Rabbits and humans, for example, can tolerate far less endotoxin by injection than rats and some things are uniquely toxic to some species. But it's a handy check when you don't have any historic data (or FDA GRAS status) to go on.
posted by Kid Charlemagne at 2:46 AM on December 1, 2011 [4 favorites]

I'm with Kid Charlemagne -- go by taste and add disclaimer before serving (for tree nut allergy/wild food squeamish).

Additionally here are some other acorn recipes -- http://hungerandthirstforlife.blogspot.com/2011/11/wild-things-round-up-acorn.html

And a writeup of how other folks around the world use acorns -- http://honest-food.net/2010/01/03/acorn-cake-and-acorns-around-the-world/

As an extra experiment, perhaps gather some more acorns and process them in a different way and see if there is a flavor difference. Serve the better flavored food.
posted by countrymod at 6:42 AM on December 1, 2011

For the record, I am pretty firmly in the "let them experiment" camp -- my kids are free to forage wild oniongrass, dandelion, hickory and beech nuts. If this was early in the season and she had collected a pile of beautiful fresh acorns, I would have trusted the processing instructions and let her go in with her pancakes and a nut allergy warning. My chief concern here was the age and condition of the acorns. It's sorta late in the season here, and more than half of the acorns she collected were flat-out disgusting: rotted, squirming with insect larvae, moldy. We threw out those that were obviously a problem, but it got me wondering if there were some invisible-to-the-naked eye nasties in the acorns she did use, and I was worried that the standard tannin-removal process would not be enough to render those sorts of spores/toxins harmless.

We are definitely going to try again when fresh acorns come into season next year. The flour she did make smells crazy delicious. Thanks for the additional recipes!
posted by apparently at 6:59 AM on December 1, 2011 [1 favorite]

Just wanted to chime back in and say, from what OP originally wrote, it wasn't clear how long the acorns had been leached. So answerers were assuming, reasonably, they might not have been leached long enough.

I don't think anyone here is saying "while primitive peoples did exactly this thing for millennia, you are not competent" etc. I think we were saying, given only the info posted in the question, it wasn't clear whether the procedure followed was enough to remove the tannins. Also, with a lot of things primitive peoples did for millennia, they were doing it in cultures that had a ton of hard-won expertise about which nuts to use (eg what time of year to collect them, how wormy could they be), what to look for to tell when they were done leaching (how exactly should they taste), etc. So it would be a poor rule to say "primitive peoples did it, so we can just follow our instincts and it will be safe". If someone doesn't have a trustworthy source of info on wild foods, eg which berries or mushrooms are ok to eat, it's not paranoid to say "err on the side of caution." From the initial question it wasn't clear what sources of info OP was relying on.

For the record, I fully agree that kids should learn about wild foods and native practices in a hands-on way. OP, I think it's fantastic that you're encouraging her to try making acorn flour and to know about where food comes from etc. I remember vividly being that age and reading a book about native life and wanting to make acorn flour, but just never having the gumption to go through all the work - so hats off to your kiddo for doing it.
posted by LobsterMitten at 12:11 PM on December 1, 2011