EP25: Edible acorns – the forgotten food

Acorns are a massive, under-utilised and forgotten food source. Join Robin Harford (your host) and Marcie Mayer (Europe’s foremost acorn food producer), as they explore the edible uses of acorns as a food and in cooking.

Show Notes

Marcie Mayer Oakmeal

About Marcie Lee Mayer

I came to Greece in 1984, when I was 21 years old. I was on a short break from university, and I never went back. It’s been 35 years now in Greece. I’ve gotten involved in all kinds of things. I had a restaurant for 10 years, I was in Athens for 17 years.

I came to live on the island of Kea, which is not far from the mainland, not far from Athens. I came here, as most people do in the beginning, as a weekender with some friends. And I discovered this oak forest on the island, which is very unusual for Greece. They’re not oaks like we’d think of oaks, they’re not terribly large or grand, but it was autumn when I first came to the island, and the trees were in full bloom. And the acorns are absolutely enormous. They’re anywhere from 25 to 45 grammes.

And it was a year when acorns were rolling around the tyres of the cars. So this touched off a childhood memory of mine that I had completely forgotten.

In fourth grade, growing up in Northern California, we learned about traditional foods from the Native Americans in our area, and acorn was their staple food.

And that was always something that fascinated me as a kid. I grew up under two very large oak trees. So I started experimenting, and that’s how this all started.

Transcript of Eating Acorns Episode

Robin Harford: So welcome everybody. This is Robin Harford from EatWeeds.co.uk. I’m absolutely delighted to have Marcie Lee Mayer. And I discovered Marcie by surfing the web and looking at TED.com, one of my favourite places, and I found a video of her talking about edible acorns, and using acorns as food. Marcie, tell us a little bit about how on earth did you get into, one, ending up on a Greek island, and two, getting involved in acorns.

Robin Harford: So I fielded some questions to some customers who bought my Oak Notebook, and we got an awful lot back, actually, more than I imagined. So we’re just going to work our way through these questions. There’s about 30 of them. And they cover from absolute beginners, who don’t know anything but really want to know something, right up to some quite experienced, or very experienced experimental foragers.

Robin Harford: So let me just start the questions for you, Marcie. We’ve got one from Tracy, and it’s a bit of a kind of obvious one, but are acorns really edible, and why do people say they aren’t? What’s the myth and the fear around acorn eating?

Marcie Mayer: Well it’s funny, because it isn’t as obvious as you would think it would be. A lot of us were told as children that acorns are somehow toxic. I’ve heard that from many, many English people, that they were told that. I put a lot of thought into it. I think it was probably the poorest and the most desperate humans that ate acorns after other crops were cultivated, so acorns were part of our diet. Acorns were our staple diet for human beings in many areas of the world. But then as they began cultivating other crops, the acorn was less predominant, and it is labour intensive, and I think somehow it got a stigma as being a poor person’s food. Because there’s no doubt that the last few people and communities that ate acorns regularly were the poorest.

Marcie Mayer: That, together with the fact that acorns were, at some point, were substituted as human food, and they were given to livestock, mostly to pigs. And so they got a stigma as being somehow pig food, you know, only fit for pigs is an expression. That’s pretty much all I can come up with. I mean, yeah, they’ve just slowly but surely were, a stigma was attached to eating acorns. And then that transferred into being thought of that they were toxic.

Robin Harford: I’ve got a questions from Marie. She says, “Can Irish and English oak acorns be used in the same way?” So, in effect, basically, to generalise that question, can all oak acorns be used in the same way?

Marcie Mayer: Right. Yes. I certainly haven’t experimented with all acorns, but I have experimented with many different kinds. There are more than 500 species of oak and yes, they’re all edible, as long as the tannins are leached down to a level which isn’t harmful. The tannins, if they’re left too high, of course they’re going to be harmful to the kidneys. So you know, that is a question that can lead to all kinds of places, but the short answer is yes, all acorns can be eaten.

Marcie Mayer: Now, because it’s a very new field, it will require people in different areas with different trees and different acorns to do their own experimentation and see what works best. I’ve been fortunate enough to work in the Mediterranean, where the weather is excellent, and I’m sure that the techniques that I’ve come up with are not applicable 100% to other places. So it’s still an area that a lot of research is going to be needed.

Robin Harford: Yeah, no, I think one of the things in the beauty and the joys of the current kind of wild food movement is that it is an experiment, and it’s an ongoing experiment. It is a rediscovering of the ways that we might have eaten wild plants in the past. And I do encourage anyone who’s listening to this show to do what Marcie says. We know that all the acorns are edible, all the oaks acorns are edible, so start playing. Now some of them will have high tannin content, some will have low tannin content. I know that, I think, not that I know, I’ve been told that the Holm Oak, the Holly Oak, the evergreen oak, in Britain has the lowest tannin content, but I don’t know about that. Do you know anything about that, Marcie?

Marcie Mayer: Well, a word about tannin. There are many facts, or so called facts, that I found on the internet, which are absolutely across the board wrong. The white oak, we know that oaks are divided into two groups of white oaks and red, or black oaks. And white oaks have generally lower tannin content than red oaks. So it has been assumed, but by people who haven’t actually been on the ground experimenting, that white oaks acorns would be much easier to de-tanninize, if you will, to leach, than red acorns. That isn’t so, because white acorns also have an enzyme that red acorns don’t have, which essentially locks the tannins in. So, even though you have higher levels in the red acorns, you end up being able to leach them out much more quickly. So my experience, my personal experience has been that red acorns I can get leached and ready to go within three or four days, in vats, at the most. And white acorns can take often two or three weeks.

Marcie Mayer: So again, I’m so glad that you said that. Experiment, play. It’s all about that. I mean, it’s all about just seeing what you can do with something that has been forgotten for a long time. But we know you’re not going to get hurt, as long as you get those acorns tasting to the point where the tannin isn’t so much that it makes your lips pucker.

Robin Harford: Another question for Marie, and a concern of many, many people certainly over here, is oaks are slow growing and, if humans were to start eating them, then the native population might be wiped out. What do you advise to prevent this, specifically in the context of community gathering and harvesting. How do you prevent, the concept of the kind of, the pillager forager, of stripping everything, is kind of a myth. There is no doubt there are certain individuals that do that, because they see dollar signs. But 99% of people that I know are respectful, but it’s a good question, because it’s one that we are, as foragers, challenged by people who just want us to eat food from the supermarket.

Marcie Mayer: Absolutely. No, I think it’s very important for anybody who’s involved in foraging or harvesting of tree crops, to be very aware of all the other species that depend on these acorns, as well as us, if we start eating them more regularly. So that would involve either some kind of replanting programme. Obviously not stripping the trees. It’s not as much of a problem with acorns as you would think, because we leave so many acorns at the tree that we deem inappropriate for flour. But those are perfectly viable as a seed, those will become seedlings. The other thing that happens is, we have an ongoing compost pile with reject acorns and reject acorn caps, and those sprout saplings, which can be easily replanted. We do replant some of them. But a programme could be, so you could be just directly putting acorns back into the ground.

Marcie Mayer: Here, this isn’t really a concept I’ve had to deal with, because I’m working in an ancient oak forest, which has about 200,000 trees. And I really only need about 200 individuals for the business that I’ve built around acorn flour. So there’s really no fear of that here. I can understand, though, in urban or suburban areas, you’d have to be particularly careful to make sure that there are plenty of acorns left for saplings.

Robin Harford: Yeah, so that kind of pops into my mind when I hear you say that, is that actually acorns could actually become a potential cottage industry for rural communities that are basically failing.

Marcie Mayer: Well that’s the idea. You know, nobody’s going to get rich from gathering acorns and processing them. But it can supplement your cupboard, and it can supplement your income in some way. And I think the way to go is that small community cottage industries, exactly. I can’t even imagine how big food could get involved in acorn processing. It’s far too labour intensive.

Robin Harford: Yeah, yeah. A question here from Stephanie, who is a soap maker. And she says, well, firstly, “Can oil be extracted from acorns?” And secondly, “If so, can that oil be used in soap making?” Because she says that many soap making staples have a huge carbon footprint associated with them.

Marcie Mayer: Okay. I’m not a soap maker, so I can’t really speak too much specifically to soap making. Acorns do have oil. Different species have different levels. They’re not very high. Six, seven percent. You’ll read much higher in some literature online, but so far I haven’t found that. Theoretically and experimentally, I have extracted oil. But living in Greece, in a place so inundated with excellent quality olive oil, yeah, I decided that there was no reason for me really to try to extract oil on a large basis from acorns. And also, I like to leave the oil in, as much as I can, in the acorn flour I’m making, because it just makes it more nutritious and more tasty. But it’s not very high in the first place. It’s only about six or seven percent.

Marcie Mayer: I think that for soap making, it would be very interesting to use the caps or the shells ground up as an exfoliant in the soap. And then you would get some of the goodness of the acorn, but without really relying on the oil.

Robin Harford: Yeah, great. Actually that springs to mind, because like you said, you have olive oil dripping everywhere. Whereas in Britain, if the planes stop flying tomorrow, if fuel failed, and there was nothing, we need to be looking for alternative food oils. I mean, acorns obviously very low. Beechnut, huge amounts of oil in there. Anyway, that’s a whole other discussion.

Marcie Mayer: Yeah, you probably need to go towards seed in that case. But yeah, that is a whole other bucket.

Robin Harford: A person called Volk, and his daughter, have two questions. “Can acorns be considered a sweet food? I see mainly medicinal and savoury uses. Are they best in sweet or savoury food? Would they go well with meringues, glazed nuts on festive cake treats, dairy delights, etc.?” And then Volk’s daughter, who I assume is quite young, asks the question, “Is it possible to make acorn soup?” So is it a sweet food or savoury, and can you make soup with it?

Marcie Mayer: Well, acorn can be used in sweet and in savouries. I personally use them in sweets in the beginning much more, before I found savoury uses, but now I use them to make falafel and little meatballs. We’ll talk about that later. I’ve written a book called Eating Acorns, and I’ve included 70 recipes in the book, and only about a quarter of them are for sweets. Most of them are savoury.

Robin Harford: Can I just quickly interject there?

Marcie Mayer: Yes.

Robin Harford: Regarding Marcie’s book, we actually have a bit of a special offer for you, with free posting. So don’t just shoot off, if you’re listening to this, and head to Amazon. We’re going to be providing a special offer for anyone who would like to pick up Marcie’s book and some of her acorn flour.

Robin Harford: Sorry, Marcie, I interrupted you.

Marcie Mayer: Oh, thank you. Thank you. And so yeah, Volk’s daughter, sorry, don’t know your name. Acorns are great in soup. I’ve got three recipes in my book. I’ve got an acorn barley stew, an acorn lentil soup, and an acorn split pea curry soup. I use acorns fresh during harvest time. I have acorn chips frozen in the freezer that I pull out and add into soups often. And acorn flour makes a fabulous thickener. It’s a substitute to corn flour. It’s a lot healthier, and it’s a lot tastier. So the sky’s the limit, as far as possibilities of using acorn flour. I think it’s important for people to realise that it’s not about making acorn flour behave like wheat flour. You have to figure out what it’ll do on its own. That’s kind of been my approach to it. It is gluten free, so that means it won’t rise the way wheat flour will. So it has a whole bunch of, it has many qualities, but they’re very different than wheat flour.

Robin Harford: Yeah, I told a friend of mine, who’s a big food prepper, about you and your flour, and he shot me over a recipe for his variant. And I then said, “Would you reckon I could make that, use acorn flour with this?” And he went, “I don’t think this’ll work.” So I completely ignored him. He’s one of my best friends, so I’m allowed to say that.

Marcie Mayer: What is [inaudible 00:16:46].

Robin Harford: And I started experimenting with acorn and, what did I use? Acorn and flaxseed. Literally just that, with a bit of oil and salt. And I’ve ended up making these extraordinary crackers. I’m still experimenting. I’m not quite there yet.

Marcie Mayer: Aren’t they good?

Robin Harford: They were good. One, because they don’t use wheat flour. I mean, I’m completely off grains. I don’t eat any grains, not because I’m Celiac or anything, but just because I’m quite interested how grain culture came about, when nomadic, just to be very clear, nomadic hunter gatherers became pasture-less, settled down, and then we got agriculture. So grains are part of the agricultural civilization.

Marcie Mayer: Right.

Robin Harford: Prior to that, we would have nicked a few little seeds, a few bits of wild wheat or oats that we saw around. But we certainly wouldn’t have eaten them in the quantity we are eating them now. So, your flour is extraordinary, I have to say, and I’ve made a slow cooked venison casserole the other day, and I heaved in lots of the acorn flour. And it just produced this delicious sauce. I mean, absolutely… I mean, you imagine, venison and acorns, I mean it-

Marcie Mayer: I can just imagine them. Those things are made to be together. Acorn and mushroom as well. All the forest foods go so well. But also, many other things. I make an acorn flax cracker as well. I think I’ve got the recipe in the book. And yeah, it’s absolutely wheat free. Some of my recipes do have wheat flour; they’re a combination, because I haven’t set out to write a 100% vegan or 100% acorn cookbook. I tried to include a lot of recipes that would be accessible to many different people. I’m sure the audience here are a little bit more forward thinking and have a lot more information than say, the general audience does, buying cookbooks, so I’m trying to add recipes that also somebody who’s not 100% committed to 100% acorn, would also be able to try.

Robin Harford: Yeah, no, and for me, I encourage not only in my courses, but on my Eat Weeds site, with recipes. I used to, until quite recently, just put suggested instructions. Which the word is, suggested, these are not rules. These are a template that you can either make exactly as the recipe says, or you can expand from and play with. And you said that at the beginning. It’s about experimenting and playing. So it’s great to have recipes, because they are a starting point, but don’t be a slave to them. Just play.

Marcie Mayer: Exactly. The girl that edited my book, she said, you know, I’ve never seen a recipe book so straightforward and so simple, and it’s not very verbose. And it’s like, yeah, well, you know, you just want to get to it. You just want to get an idea that this is how I use it, and it’s really tasty, but you know, you’re free to do something else, if that’s what you’ve got in your cupboard.

Robin Harford: Yeah, absolutely. Okay. Onwards to the next one. Question from Sam. What would your top tips be for someone wanting to try cooking with acorns for the first time?

Marcie Mayer: That’s a great question, and that gets back to, you want to experiment with acorns and see what they’ll do. Now what I’ve found is that they do not have gluten, but they do gel nicely. So if you just take a couple tablespoons of acorn flour with some juice, and you simmer that for a few minutes, and then you pour it into some kind of mould, and you put it in the fridge, you get a really nice smooth jelly. Now you don’t get that with wheat flour. You just get paste with wheat flour, if you did the same thing. So it behaves very, very differently. So I would say, experiment. I think crepes are a first great thing to do with acorns. If you get some acorn flour, or make some acorn flour yourself, just substitute it 100% in your favourite crepe recipe with some eggs and some milk, if you’re not a vegan, and they make sort of a pumpernickel coloured crepe, very dark brown, but very, very tasty, and very aromatic.

Marcie Mayer: If you are a vegan, I actually, on my acorn flour, I have included a very simple, simple vegan crepe recipe, which just makes kind of a crispy crepe that you can wrap anything in.

Robin Harford: Yeah, I was in India in January, and ate from a kind of street food vendor. And they had a flatbread that didn’t have wheat in it, and I have to say, when I was experimenting with the flour and the flaxseed, it reminded me of it. I can’t for the life of me remember the name of the bread, because it certainly, I think it might have been region specific, because we certainly don’t normally get it over here. But I’ll try and dig out the recipe for it and put it up on Eat Weeds in conjunction with your flour, so people can play. But that worked very well. And like you said, it was like a crepe, and it was brown and a bit crispy, but delicious all the same.

Robin Harford: So another question from Sam. He says, “The oak trees in my area are a bit stunted. Is it still worth processing smaller acorns?”

Marcie Mayer: Yeah, I mean, I’m sure it’s a little bit more frustrating. It is very satisfying to work with these enormous acorns we have here, and it’s not nearly as much labour. But you know, you’ll have to process some and taste it, and see if it’s worth it to you. You’re the only one that can really answer that question. I’ve tasted wonderful acorns that were small, you know, but they ended up making a fabulous flour. That’s another thing that you see in my book, is I have three different acorn flours on a table, and you can see the different colour. One is almost a brick red, and the other one is a dark beige, and the other one is a creamy colour. So whatever acorns you have are going to be very unique, and you’ll have to find out if it is worth it for you.

Robin Harford: So Andy’s got a bit of a curiosity question. He says, “Why do squirrels bury them? Is it to ensure a steady leaching process to remove the tannins, or are they just being greedy?” Does anyone even know?

Marcie Mayer: Yeah, I can’t speak to that. Definitely that’s not my field of expertise, but it sounds reasonable, you know. It sounds reasonable. Crows, jays, and other birds that have evolved to carry as many as three acorns in their gullet, also bury them, and often forget about them. And I doubt that the birds are burying them for leaching reasons, so who knows?

Robin Harford: Yeah, who knows? One of the great mysteries of life, isn’t it? We’ll get there eventually maybe. And who cares? Does it matter, really?

Marcie Mayer: That’s okay. [inaudible 00:24:04] the answer to that question.

Robin Harford: So Amanda asks, “I would like to know if the edibility extends to all oaks?” We’ve already answered that question. Yes, all oak acorns are edible, providing you process them correctly, which we’re going to be getting on to.

Robin Harford: So Marilyn asks, “What kind of drinks can you make with acorns? Is it just the coffee, or is there anything else?”

Marcie Mayer: Okay, well yeah, the area of Extremadura, which is a peninsula between Spain and Portugal, which has somewhat of an acorn based economy, they do the acorn fed Jamon ham, but they also do some artisanal products, and one of them is an acorn liqueur. It’s very tasty and I believe they just put raw acorn into distilled alcohol and let it soak for many many months. I cheat, and when I leach the acorns, I save some of the water off of the first leach, which is very, very, very dark, almost chocolate brown with tannins. I boil it down into a syrup. And then I add a couple of drops of that into vodka, or the other drink that we drink here in Greece, Raki Tsipouro, and it gives it a really interesting flavour and aroma and colour. Just on a side note, Absolut Vodka actually came out with an oak vodka, which is absolutely delicious, last year.

Robin Harford: Wow. Fascinating.

Marcie Mayer: As for the coffee, I think we’ll talk about that a little bit later, because I think there’s another question about coffee specifically.

Robin Harford: Yeah, okay. Yeah, just something popped in about caution, because you’re using the first soaking, so it’s very, very high tannin content. So, concerning tannin’s impacting kidneys, in a bottle of vodka, say, how many tablespoons would that be? Millilitres, do you think?

Marcie Mayer: One teaspoon in a bottle of vodka.

Robin Harford: One teaspoon. Okay, that’s all right, yeah.

Marcie Mayer: Yeah, so I’m not worried about that, yeah.

Robin Harford: Yeah.

Marcie Mayer: But again, I mean, I wouldn’t drink a bottle of that in a day.

Robin Harford: Well I did in my past. I don’t drink alcohol, so I’ve got a bit of a history with it, which is why I don’t, but hey, any of you that do, and I know a lot of you really like your wild booze, go for it.

Marcie Mayer: I have that recipe in the cookbook. I’ve added something with the acorn vodka, as well as the grubs. When we’re harvesting acorns, some years there’s a certain amount of grubs that come out during the processing, and I found that you can pop them like popcorn, and they’re really, really tasty.

Robin Harford: Wow. Okay. Sorry, vegans, that one’s just made you throw up. But-

Marcie Mayer: I’m sorry.

Robin Harford: I’m big into grubs myself, so that’s interesting that we can eat acorn grubs.

Marcie Mayer: Oh, absolutely. And they’ve been in the acorn their whole lives, eating pure acorn, so they’re so clean. And they are so tasty.

Robin Harford: Wow. So how would you cook the grubs?

Marcie Mayer: I just get a skillet, with a bit of either oil or butter, just a bit though. I saute a garlic clove, just to flavour the skillet a bit. Even a little bit of rock salt can go in there. And then I just throw them in. They just blow up and pop like popped corn.

Robin Harford: I can see Fergus Drennan getting on to this one. His next video on Instagram, it’s going to be him eating acorn grubs.

Marcie Mayer: I love it. I love it.

Robin Harford: [crosstalk 00:27:49] Fergus.

Marcie Mayer: That and acorn vodka, and you should be good to go.

Robin Harford: Excellent. So Tracy says, “What is the modern use of acorns as an alternative food source to compensate for imported foods?” Sorry. “What is the best modern use of acorns?” Well, flour, I suppose, really.

Marcie Mayer: I think it’s the easiest to store. But for the home, for the person who’s doing this at home, I think the easiest way is to process your acorns, either in a granular form or in slices, and then freeze them. Freeze them in portion sizes. And then when you’re cooking, you can just pull a bag out and add it. If you don’t want to go through the entire process of drying it out and milling it, you can cut out two of the steps like that.

Robin Harford: Okay, great. So moving on to the removal of tannins, you’ve got a number of questions. The first one’s from Colin, who says, “What is the best way,” so we’re not talking industrial. We’re not talking at the level you’re doing it. We’re talking for home use, people at home. “What is the best way to remove the tannins? Can we use a stream like our forefathers did?”

Marcie Mayer: Well, our forefathers had cleaner streams than we do. So you have to be really careful about anything you do in any stream. You have to know exactly what’s going on upstream, and that’s almost impossible during this day and age. So that’s a whole different, that’s something I can’t really speak to. You’ll have to use your judgement . Hypothetically speaking, yes, you can put them in a net bag, either in or out of the shell, and have them in running water. The easiest way to do it at home, I think, is shell them and put them in vats of water. The water does not need to be moving. The tannin that’s coming out of the acorns basically keeps the water fresh. You won’t get mould growth, or anything like that. So if you change the water once a day, or change a quarter of the water once a day, that should be sufficient.

Marcie Mayer: I’ve also found that, no matter how dark the water’s getting from the leaching process, the acorns continue to leach, even in very dark water. So it’s a misconcept that you have to just keep changing the water. I don’t change the water much at all.

Robin Harford: Really? So I mean, the way that I’ve leached in the past is to put them in a bucket with the shells on, pour hot water on, wait 24 hours, then shell them, then put them back into the bucket. And for the next five or so days, pour hot water on in the morning, strain it off the next day, more hot water. So I don’t actually need to do that. I can just keep them in the bucket in cold water.

Marcie Mayer: You don’t want to put hot water on acorns, ever, in any state. It really saps them of their nutrients, and it also kind of slows down the leaching process. So, if you’re in a hurry, and you came in from outdoors with a bucket of acorns, and you wanted to cook them that moment, then yes, you could do some boiling water leaches and get them edible within a half hour. But you would never, if you are going to use hot water, you need to continue with hot water. As you pour off one load of water and add another one, you need to add hot water. Otherwise, if you go from hot to cold and back again, you’re essentially locking the tannins in.

Robin Harford: Oh, okay.

Marcie Mayer: And as far as, yeah, you need to get them out of their shells, probably, before you start the leaching process. Otherwise, you’re just leaching the shells for no reason. You’re just adding time to the process.

Robin Harford: So by that you mean actually shell them before you use the cold water leaching method, as well as the hot water leaching method?

Marcie Mayer: I would never use hot water on acorns in any-

Robin Harford: No, but what you just said about if you’re in a hurry?

Marcie Mayer: Right, yes. So basically, yeah, you want to take the shells off. In order to get the shells off, you might leave them to dry outside in the sun or in the air and then, as they dry out a bit in their shells, there’s a bit of space between the shell and the nut itself, and they’re easier to crack open.

Robin Harford: Okay, so I think the question’s coming on later, but I’m going to ask it now. Do the acorns have to be brown, or can we gather them when they’re green?

Marcie Mayer: I would only ever gather green acorns. So, as they ripen and they become brown, there’s just more and more chance that they’re going to be infested by something. There’s many different things that can get at your acorns. So I prefer to net the trees, and this is the way that it’s traditionally been done in Greece for centuries. Net the trees, and then you tap at the branches, and the acorns fall out green. And those green acorns are brought to a specific place where insects can’t get at them, where they can naturally dry out, ripen and dry out, but off of the tree.

Robin Harford: So when you dry them out, I’m just saying for people who’ve never done this before, you put them in a single level. So like, lay them on a drying sheet in a container. You don’t put them in a bag and just let them sit, because that’s going to create moisture and mould, I would imagine.

Marcie Mayer: They need to be left out. It’s possible, either on a wooden deck, where that can absorb some moisture, or on a rack that’s above ground. And then they need to be covered up in the evening, if there’s a lot of precipitation. So that’s-

Robin Harford: What’s precipitation mean?

Marcie Mayer: If there’s a lot of moisture in the air. So I have a specific table, which is 50 square metres of space, that I dry. It’s above ground, so there’s no problem with rodents, and that helps me to dry them in the sun, without having any problems with infestation or rodent.

Robin Harford: So to get, say, 500 grammes of acorn flour, how many kilos of acorns would you need to gather?

Marcie Mayer: It’s about one to four. So about two kilos for 500 grammes. You lose a lot of weight as the acorn dries out, so you lose moisture. You lose a lot of weight with the shell, you know, 20, 25% with the shell. You lose some with an acorn that’s not suitable, that has to be discarded. So it’s about one to four, which is why it’s expensive. Acorn flour is going to remain expensive until we can get the process, until we can get the quantities a little bit higher than they are now.

Robin Harford: Okay. So we’re going to get into the nutrition of why use it. But there’s another question here from Fergus, who I mentioned before. “If leaching in streams and rivers,” which obviously we don’t really advise, because of what you’ve just said about there’s no wild water anymore, “do you do that with the shells on or off?” So you’ve said you do it with them off.

Marcie Mayer: Yes. And I have, Fergus, I think, was also interested in leaching acorns in the sea, and I have tried that. In that case, I put them in their shells, because I felt they would need the protection, you know. So I put them in net bags in their shells, and I hung them off of buoys someways out, in a clean part of the sea. Well, the sea’s very clean here, but in a place where I knew boats wouldn’t be passing and things. Excellent results. Amazing results. I liked the way the salt tasted as well in the nut. But, because I have a business based on acorn flour, there was no way that I could certify sea-leached acorn flour, because their main question is, what sea? Where? How can we regulate this? So, but for somebody who’s doing this near the sea, I think it’s a great idea. And if they’re in the shell, you won’t have to worry about some sea creatures eating them.

Robin Harford: Yeah, so how long would you leave them in the ocean, in the sea for?

Marcie Mayer: I’d probably leave them at least a week. Again, that’s going to depend on the acorn and how long it takes. White acorns, which are more common in Great Britain, tend to take about a week in water.

Robin Harford: Okay. So just to clarify with the leaching. There’s no need to kind of put a slit in the shell, or anything like that, before you leach. You just put them in whole?

Marcie Mayer: Again, we’re talking about in the sea. Otherwise, if you’re leaching them at home, fresh water. I say, get the shells off. Get the shells off, discard them, use them as mulch. But yeah, you’re just adding more tannin into the process. You can eliminate that from the beginning, and that’s one step in the right direction.

Robin Harford: So if you are leaching them in the shell in the sea, you don’t need to put a slit in them-

Marcie Mayer: I don’t think so. No, no.

Robin Harford: Okay, great. Okay, can acorns be stored unprocessed-

Marcie Mayer: Yes, yes.

Robin Harford: After leaching, I’m assuming that says, that means.

Marcie Mayer: Well, no, acorns should be stored unleached. That’s the secret, because the tannin is a natural preservative. So the secret to storing acorns long term, is to get them very, very dry, so they rattle like beads in the shells. And then store them in the shells somewhere in a place where rodents and insects can’t get at them. Everything will try to get them in storage. They smell so good. Everything will try to break into your storage and steal your acorns. So I’ve tried everything. I’ve even sealed them in bags, which I didn’t like. But I had these plastic bags that are reusable. But if they’re in the shell, and they’re hard like beads, they have a much, much higher chance of being okay for a very long time.

Robin Harford: So once they’re really dry, like you say, they’re rattling around like a bead, could they be stored in like a big five litre, five gallon buckets, with an air tight lid?

Marcie Mayer: Absolutely. That the best way. A nice stainless steel vat, with a tight lid and a big, big mouth at the bottom, that you could just open up and pour them into a bucket, that’s the ideal.

Robin Harford: Wonderful. Debbie asked, “Are damaged acorns still okay?”

Marcie Mayer: No. It depends what they’re damaged with. I mean, the grubs will go in and out, and they’ll leave a nice channel through the acorn, but by the time they’ve been processed, they’re rinsed so many times, that doesn’t really bother me. There are also very small moth-like creatures. I’m not exactly sure what they are, what the name is, that will come in and bore through the acorns and turn acorns that are in storage, even if they’ve been dried properly, that turn them into dust within days.

Robin Harford: Wow.

Marcie Mayer: Yeah. But no, if an acorn doesn’t look good, you don’t want to eat it. That’s what I always tell the people that are helping me sort. Just imagine, this is food, and if it doesn’t look like something you want to eat, then throw it away.

Robin Harford: Yeah, I find that actually quite a lot on my day courses, when we go gathering, is that we’re so programmed by supermarket food. So in botany there’s this term, plant blindness, which is why people don’t see plants, they just see a green wall, a green haze. And it’s almost like there’s a, almost supermarket blindness, in the sense that when people have gone out gathering, they will bring back food that basically should have come out the bottom of a compost bin. And I say to people, would you really genuinely want to eat this? And why go for brown, mottled, old plant matter, when there’s fresh, young, vibrant, greenness. But people’s cognitive filters literally can’t see. They are plant blind. They can’t see the different between a healthy plant and one that should be in the compost bin.

Marcie Mayer: Interesting.

Robin Harford: And foraging does retrain you in your kind of perceptions of being able to discern healthy versus kind of definitely gone past it’s best to pick date.

Robin Harford: Okay, we’ve got a question here from Theresa, or Teresa. She says, “Can I roast and eat acorns roasted in aluminium foil in a fire? Will the roasting take the tannins out?”

Marcie Mayer: Not if they’re in aluminium foil, but if you put them in their shells in the ashes of a nice fire, in the coals, that is one method of leaching acorns. I don’t have personal experience with that, but I have talked to lots of the old-timers here on the island that ate acorns during the second world war and the civil war after that, here in Greece. And the way that they generally ate them was by putting them in the ashes in the fireplace and getting rid of some of the tannins like that.

Marcie Mayer: I’ve also found, I know it’s going to probably make a lot of people’s head spin here, but microwaving acorns also leaches the tannins out very quickly. I don’t use a microwave. I don’t own a microwave. But I did do some experimentation with it, and it’s quite interesting how easy it is to get the tannins out with a microwave.

Robin Harford: How long would you be microwaving them for, and what kind of temperature? Can you remember?

Marcie Mayer: Yeah, of course. It’s called microwave-aided extraction. It’s in my book.

Robin Harford: All right, okay.

Marcie Mayer: And you basically rinse them out like normal. Leach them like normal. And then the wet mash, you put on a paper towel in the microwave for about 30 or 40 seconds, and then you break it up a little bit, turn it over, another 30, 40 seconds, and that’s it. It’s ready to go.

Robin Harford: Wow, that’s pretty quick.

Marcie Mayer: That’s really quick.

Robin Harford: Okay, so, question from Fiona. “How do I make coffee with acorns?”

Marcie Mayer: Well, that’s an interesting question, because what they call acorn coffee, I would never call coffee. It’s good, but it’s not coffee. And I think it did more to ruin the reputation of acorns than to help it when people started being aware of acorn coffee. And I guess, during the World War II, again, they used acorns as a substitute for coffee. I’d call it an infusion. I’d call it a tea. But it really doesn’t taste like coffee. All you do is brew some acorn flour in a hot cup of water.

Marcie Mayer: I have a product that I call NUT-Ac, it’s kind of a cheeky name, it’s from nut and acorn, NUT-Ac. And it’s acorn flour, 45%, Demerara sugar, and very high quality cocoa. And it’s just a powdered drink, like an Ovaltine type drink, that you take one heaping tablespoon in a hot cup of milk or water or nut milk. And you get kind of a, it’s thicker than coffee, that’s why I wouldn’t call acorn coffee, coffee, because it has more of a thick texture and consistency than coffee does. But very, very filling, and very, very nutritive.

Robin Harford: So we would most probably call that word silky? It has a silky texture to it?

Marcie Mayer: Yeah, that’s good. But in answer to the actual question, how to make acorn coffee. You just take one of those paper filters, put a couple heaping teaspoons of acorn flour into the filter, and strain some hot water over it. And you’ll get a hot, dark beverage. If you’re using acorn flour, then you won’t have any fear of tannic poisoning. If you did that with fresh acorns, you’d just be drinking straight tannin, which isn’t a good idea.

Robin Harford: Yeah. Have you tried roasting the flour, or baking the flour first, before you put it into the coffee filter? Have you noticed any difference there?

Marcie Mayer: I have, and it’s definitely much tastier.

Robin Harford: Okay, great, yep. So Deb’s asked, “Over the past couple of years, I have noticed disfigured acorns on trees. Why is this happening?”

Marcie Mayer: I should know the answer to this question, but I don’t.

Robin Harford: Okay. Is it some from a gall, I think, isn’t it?

Marcie Mayer: It’s probably gall and weather, and/or weather. It’s not, I don’t think it has anything to do with anything inherently wrong with the tree. It’s conditions.

Robin Harford: Yeah. Question here from me that says, “How long will acorn flour keep, and what is the best way to store it?” We’ve discussed storing acorns, but the actual flour itself. You know, when I buy flour from you, is that going to last six months before it goes rancid, or what?

Marcie Mayer: No, it’ll last up to two years, if you keep it in a cool dry place, it’ll last up to two years. There’s no question about that. Of course, if it gets too hot, or if it gets in direct sunlight, it’ll shorten the life. But you want to keep it in an airtight bag in a dark cupboard, and it should be fine for a long time. Or I also keep my flour in the freezer. After this much work, before it’s actually become flour, there’s so much work involved that, by the time I get it to the flour state, I freeze it in very large bags before it gets individually packed and sold. But that’s because we have walk-in freezers here anyway for the production line. If I didn’t have walk-in freezers, that would be a different story.

Robin Harford: Yeah. On to the nutritional aspects of using acorns. What is their nutrition? I mean, are they high protein, high carb? Are they high protein, low carb? High carb, low protein? What about the minerals, etc.? Can you just give us kind of an overview on the nutrient density of this pretty extraordinary food.

Marcie Mayer: Absolutely. They’re not particularly high protein, any more than any other nut. They’re lower protein than almonds and walnuts, but they are high carb. They’re extremely high in trace minerals, in magnesium and potassium, and in polyphenols. I just gave a TED Talk recently, a few months ago, which you can find on YouTube. And in the TED Talk, I say that. A lot of people know that polyphenols a good thing, but they’re not quite sure what it is. Basically, those are antioxidant cells that go after, they search for and go after, sick cells, cancer cells, and they eat them. They eradicate them. So you want a diet rich in polyphenols, and they’re harder and harder to find in this processed world. And acorns are extraordinarily high in them. Anybody who has analysed my acorn flour has been very surprised by that.

Robin Harford: Are polyphenols the same thing you get in things like bilberries and blueberries?

Marcie Mayer: Exactly. And goji, and yes, exactly.

Robin Harford: Okay. So one of the things that I found delightful in your book was a thing that you call, it’s not the community activities… And so I always say on my courses, and when I talk to people, that foraging can be a solo practise, kind of a meditation and just time out for yourself. But ultimately we did it as groups, in tribes and bands. And you have this wonderful concept called Sorting Sundays which, could you just tell us a little bit more about that? Because I think if communities locally around Britain, and I really encourage anyone who listens to this, don’t wait for someone else to do stuff for you. You’ve got to just go out and make it happen yourself. And I just envisioned, when I saw that word, Sorting Sundays, you know, can you imagine if the shops weren’t open on Sundays, and we got together as communities and went acorn gathering. And then we dried and processed it. It just seemed really delightful, actually. I’m just old school, really, I think.

Robin Harford: But what is Sorting Sundays? What do you do? What do you get up to?

Marcie Mayer: It is delightful. It’s a way that a lot of people can get involved as well, that don’t have the time to come out with us and actually do the harvesting. So, during the month of October, I invite volunteers to come and help harvest. And that involves, you know, six to seven hours of work per day. We net the trees and whack the acorns out. And a lot of hauling. It’s hard work. But we have a work exchange. You stay here for free in a very, very luxurious guest house, and you get all your food. So you have no expenses while you’re here. I have hundreds of applications every year, and so it gets filled up quite quickly. And volunteers have the day off on Sunday, and that was, I found, a good chance to kind of get ahead of the game, because the acorns that are coming in, we’re collecting both the caps and the acorns.

Marcie Mayer: Anybody who wants to see what that looks like can see on our site. They’re very, very large acorns, and very, very large caps. And the caps are exported for the leather tanning industry. It’s a whole separate thing. So they need to be separated. Plus, of course, the acorns that are damaged need to be separated out. And it’s just a labour intensive thing that needs lots of hands, and it’s a lot of fun. So anybody who wants to come on Sunday can come help us sort. And everybody gets, you know, acorn cookies. And it is all about community, and the big changes that need to happen in this transition time are going to happen in very small groups. It’s going to start in groups of three, four, five, ten people.

Robin Harford: Yeah, I agree. And it’d be lovely to have a celebration and acorn festival every year around Britain, the harvest time. You mentioned October. I’ve seen deliciously huge acorns recently, and we’re only kind of, where are we now, we’re in the mid-September. So kind of like mid, onwards. So when do you start gathering and harvesting? Is it done in December or-

Marcie Mayer: It’s variable, but we could start, we have started at the end of September but, you know, the more years I do this, the better I get at it, and the shorter the gathering season actually is. So what used to take me six weeks to gather, now takes me ten days. First of all, I also am interacting with trees regularly, so I know what to expect, and many different factors. Just a word about the acorn festival. I have hosted an acorn festival, this will be the ninth year. It started out as just a group of friends, literally ten people I think we were at the first one. And now we have hundreds of people, and it’s advertised on the radio here in Greece, and people come over for the day. And it’s a very simple grassroots festival. It’s not at all fancy. It’s just about celebrating the trees and the people that live around the trees, and the acorns, and we do games for kids. It’s kind of a cultural indoctrination, if you will, because the idea just is to celebrate this thing and make it fun.

Robin Harford: Yeah. Wonderful. So obviously you just keep gathering your acorns while they’re green. And when they start going brown, that’s when it’s finished.

Marcie Mayer: Well, yes, if I’m very short on acorn, we continue until they’re brown, which involves a lot more sorting, because by the time they hit the ground, they get infested by beetles. The other thing is, you don’t want to collect the very first acorns that fall, because in the beginning of the season, you’ll get one fall of acorns, and they’ll be quite brown as well, early on, and those will surely be infested. And that is why they’ve fallen so early. You ignore those, leave those for the wildlife. And then you net over them, basically, and collect the other ones. The other thing is, the acorns at the top of a tree, on the crown of a tree, will definitely be the least infested, if you’ve got an infestation problem.

Robin Harford: Yeah. So we don’t send our kids up chimneys anymore. We’re going to be sending them up oak trees.

Marcie Mayer: Climbing trees is very good.

Robin Harford: If you are interested in getting a copy of Marcie’s book, which I highly recommend. She is so knowledgeable, one of the top people in Europe who has worked and processed and worked with acorns, as she has already said, for a very, very long time. You can pick up a copy of her book. You can get a bag of acorn flour, cold pressed. You get a fruit chew, and you get free shipping. And shipping is expensive, normally. So if you go to EatWeeds.co.uk./oakmeal, oak, and then meal, as in a meal that you sit down and eat, you’ll find the link to the offer. There’s a coupon code that you need to use, which is just simply Eat Weeds.

Robin Harford: Yeah, is there anything else, Marcie, that you would like to share with the listeners about acorns, oak, anything inspirational, anything that we haven’t covered?

Marcie Mayer: Well, one thing that I think is very interesting, and I think the more people that know about eating acorns, the more likely this information will get into the right hands, is that with their tannins intact, in their shells, acorns can stay a viable food source for up to a decade in storage. And this could have some really very important benefits for places that are experiencing famine or war zones, refugee areas. Because here in Greece, I’m very aware of what’s happening east of us, in the eastern Mediterranean, where there are many, many dense oak forests, and really nobody’s aware that they can be eating the fruit of the oak.

Robin Harford: So it’s been wonderful having you on. You’ve been very, very generous with sharing your knowledge. And all the links to reach out and connect with Marcie will be in the show notes in the podcast section on EatWeeds.co.uk, including the special offer. So, once again, really great to have you. What time of year is your festival, if people wanted to come over? Because I’m certainly intrigued to actually come over.

Marcie Mayer: The festival will be, we have a three day weekend at the end of October in Greece every year, and it’s a time when people who have second homes come here to kind of close the homes up for the winter. So we’ve got an audience, as well as, of course, our local stakeholders. So it’ll be on Sunday, the 27th of October. And it’s during the day. It starts out at 11 in the morning with an oak walk with myself and a professor from one of the universities here in Greece who is an expert, a European recognised expert on oak trees. And so we’re going to have a couple hour oak walk with whoever wants to come along and learn a little bit more. And then the party starts. Oak foods, and live music, and some local producers, and just kind of a fun, grassroots party.

Robin Harford: Wonderful. Nothing, I love grassroots gatherings and festivals. They are the best, like you say, there’s nothing fancy about them. It’s the people, and the practises that we happen to be doing.

Marcie Mayer: Thank you for having me. It’s been a real pleasure. Thank you very much.

Robin Harford: Ah, it’s been a joy. So will the festival be on in 2020 as well?

Marcie Mayer: Ah, yes, I assume so, yeah. We’ve been hosting it for nine years now.

Robin Harford: Great. So is there somewhere on your website that people can sign up to a mailing list, and that kind of thing, to be kept up to date?

Marcie Mayer: There is. There’s an easy way to contact me through the site. So the Oakmeal site is the best way to contact me.

Robin Harford: Great. Okay. Links in the show notes. So thanks again. Cheerio, Marcie.

Marcie Mayer: Thank you.


  1. Squirrels bury acorns because they don’t sleep through all winter in one long run, they wake up every few weeks to eat something. That’s why they have up to 30 different places to bury their food supply for wintertime.

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