This is a transcript of the Gastropod episode, Green Gold: Our Love Affair with Olive Oil, first released on December 4, 2017. It is provided as a courtesy and may contain errors.

SARAH SCLARSIC: Oh wow. Let me know if I’m like hurting the tree or… It’s really fun. There we go, yeah. It’s very gratifying, like olives just go flying off in all directions at your—at your whim.

CYNTHIA GRABER: You asked for it, we’ve made it. An episode all about olive oil! This is Gastropod, the podcast that looks at food through the lens of science and history. I’m Cynthia Graber.

TWILLEY: And I’m Nicola Twilley. And that was the sound of my friend and Gastropod fan Sarah Sclarsic harvesting olives by combing through the branches using a vibrating electric rake.

ROBIN SLOAN: So maybe, maybe this is like a really deep tissue massage for an olive tree.

TWILLEY: I like it. I was—it feels like you’re stroking it, stroking and tickling.

SLOAN: But kind of rough, right? I mean it’s kind of like MMMGRRR.

TWILLEY: That’s my friend Robin Sloan, co-owner of both the olives and the vibrating rake. Cynthia and I visited the olive grove he leases in the Bay Area to learn what olive oil actually is, and how you make it.

GRABER: But that’s not all we wanted to find out about the green gold this episode. You might have heard that people have been enjoying olive oil for thousands of years. Is it true that ancient Greeks and Romans smeared the stuff all over their bodies?

TWILLEY: And what on earth does extra virgin actually mean? Like how can something be more virginal than a virgin? That doesn’t even make sense.

GRABER: And, something a lot of you wanted to know—is the extra virgin olive oil in your pantry the real deal? That’s what listener Brenda Vest thought after she heard an episode of ours last spring.

BRENDA VEST: I love listening to your podcast and the fake foods one really got to me and I was like oh my God, I hope they do an olive oil one.

TWILLEY: Brenda’s wish was our command. So here we go.

PRE-ROLL

TOM MUELLER: My favorite ones are the thousand year trees, the grandfather trees or grandmother trees, some of which, you know, the Crusaders saw on their way south to the Holy Lands to break some stuff.

GRABER: Tom Mueller wrote the book Extra Virginity: The Sublime and Scandalous World of Olive Oil. These olive trees, they genuinely can live for hundreds, even a thousand years.

TWILLEY: Tom says olive trees are hardcore. You can chop them off at ground level and they’ll spring back. They’ve been growing wild in the Mediterranean for millennia.

MUELLER: The oleaster or wild olive has provided food for people and pre-people for a long, long time. There are olive pits in Neanderthal caves in Gibraltar and leaves and pits in various Paleolithic and Neolithic sites where Homo sapiens was collecting small olives, so the oleaster berries, basically—hunting and gathering berries.

GRABER: The hardy, productive olive tree has long been the focal point of human settlements.

MUELLER: It’s quite inspiring to see these huge ancient braided trunks sometimes with marks of war on them, with ancient fires that they’ve survived.

TWILLEY: We didn’t get to visit any grandfather or grandmother trees this episode, but I’m not complaining, because we did get to go to two olive groves—one in the Old World and one in the New.

ANNA CASAREI: Hello, my name it’s Anna Casarei. I’m growing here in Castello del Trebbio.

GRABER: Anna and her husband own about 10,000 olive trees spreading over the hills in Tuscany, not too far from Florence. We were there on a sunny summer morning. The trees stretched out around us. The leaves were rippling in the breeze.

CASAREI: I think the olive tree, it’s unbelievable because he has some leaves that have a different kind of color, and depending if you have the wind going on. Each time you are looking at the olive tree it changes color. It came from silver to green.

TWILLEY: And then on an equally sunny day at the end of October, we visited a much smaller olive grove—precisely 327 trees. It was near Fremont, just south of San Francisco in California.

SLOAN: I’m Robin Sloan and I’m the co-founder of Fat Gold and I’m a novelist too.

KATHRYN TOMAJAN: I’m Kathryn Tomajan. I’m also the co-founder of Fat Gold and I am an olive oil maker by trade.

TWILLEY: Kathryn first visited this grove as a consultant. She’d been brought in to help its owners make better oil.

TOMAJAN: I was just awestricken, because it was a beautiful time of year and the hills were still green and it was basically the prettiest olive grove I’d seen in my travels, especially in California.

TWILLEY: So when the current owners were getting old and wanted to scale back their workload, Kathryn and Robin decided to lease the grove themselves.

GRABER: Both of the groves we visited have a handful of different kinds of olive trees growing—Tom says there are more than 600 different subspecies of domesticated olives total. Different varieties grow better in different ecosystems, or people choose the subspecies they like based on flavor.

TWILLEY: Kathryn and Anna’s groves have pretty similar varieties.

TOMAJAN: We have six different varieties that are planted here. Most of them are traditional Tuscan varieties and those are Frantoio, Leccino, Maurino, Moraiolo, and Pendolino. And then we also have a sixth called Taggiasca, which is an olive variety that is traditionally from Liguria—the Liguria region of Italy which is on the Mediterranean coast.

TWILLEY: What’s kind of cool is you can really quickly start to tell these different varieties apart in the grove, even if you’ve never really paid attention to the shape of an olive tree before.

TOMAJAN: And this is the Maurino, that one looks kind of fuzzy and hairy. I kind of like the way that one looks. And this one here is the Moraiolo, which I think is my favorite.

SLOAN: But it’s like the mopey Moariolo, they’re all so sort of droopy.

TOMAJAN: And then this is the Pendolino and that real bushy, very vigorous one is the Taggiasca.

GRABER: The varieties that both Anna and Kathryn have on their properties, they’ve been growing in the Mediterranean for thousands of years. Olive trees first came to California with the Spanish missionaries in the 1600s.

TOMAJAN: And California had a robust olive canning industry throughout the last century. And then canned olives have kind of fallen out of fashion. And I think probably in the late 80s, early 90s, people started really wanting to plant olives for olive oil, and so this modern era of olive oil production was born in California. And then in the last 20 years, the olive industry has exploded.

TWILLEY: And one of the main reasons behind that explosion is a new way of planting, growing and harvesting olives. It’s called super high density planting, and what it means is the olives are planted really close together in very tight rows and they’re pruned in a particular way so that they can be machine harvested.

GRABER: One of the benefits of this super high density style of planting is that it’s made olive oil economically viable in California. As you all probably know, land is extremely expensive in California, and so is labor.

TOMAJAN: Since then we’ve seen olive productivity explode in California and the industry really being able to make olive oil at an affordable price point for people or for consumers that had never heard of California olive oil before.

TWILLEY: Basically, the way these Californian groves are planted and pruned means you can take a lot of the labor costs out of the equation by using a machine to do the harvesting.

TOMAJAN: And when I say machine harvested, I mean there’s a huge machine that goes over and basically swallows the entire olive tree and has these sort of rubbery fingers that knocks the olives off. And there’s a sort of a catch basin underneath and it goes over an entire row of olives without stopping, harvesting every tree in that row. So it’s actually really interesting and exciting, and I do a lot of work with super high density olives. But you know there’s something pretty special about the traditionally spaced, where they let them grow together to their full maturity and beauty.

GRABER: Kathryn and Robin’s grove has trees more traditionally spaced, wider apart, and it is indeed gorgeous. Plus, they can grow a wider variety of olives with different flavors. Only three varieties currently work well with the super high density system. Nicky, you and I visited it together, but you also got to go help out when they were harvesting the trees, which I unfortunately missed.

TWILLEY: Yes. Turns out that even though I am a Californian now, I am actually very cost-effective labor. Free, in fact. Robin and Kathryn gathered a group of their friends early one Saturday morning to help out.

SLOAN: The olives have been growing on the trees the whole year. As you’ll see when we harvest them, they’re quite dark and they’re already quite oily. Like they are ready—they’re bursting with oil, ready for the oil to be extracted. So here’s the steps of what we’re doing today.

TWILLEY: Step 1: Lay out some nets under the trees to catch the olives.

SLOAN: Here, so let’s go—let’s pull it in as tight as you can.

TWILLEY: Step 2: Fire up the vibrating rakes.

SLOAN: So I think for all the people who are gonna be using the magic wand, the vibrating rake, um, whatever, the vibrators—it’s going to be a learning curve to learn like how we do it. And so we just don’t actually know what the best technique is for getting all the fruit off and kinda like—who knows what it’s gonna be like.

TWILLEY: That’s right, none of us had ever done this before. Not even Kathryn.

SLOAN: Oh my gosh, we’re totally going to try this. So give it a shot, let’s see what happens.

TWILLEY: It was weird and super fun. You just kind of combed the vibrating rake through the branches and the olives started whizzing off in all directions.

GRABER: You said nobody had ever done it before—was there a steep learning curve? Did you watch a video on YouTube or something?

TWILLEY: No instruction needed, we were all just naturals. Honestly, it was like if you’ve ever groomed a pet—you get a feel for how to move the rake through the branches really quickly.

DAFNA KORY: They’re pretty hard.

TWILLEY: A bunch of us held the nets up at the edges, and then others, including a handful of kids, followed behind with buckets, hand harvesting the olives that the rakes had left behind. Some of those olives really didn’t want to leave home.

GRABER: Kathryn and Robin had a great time at their very first olive harvest. But earlier this summer, things were looking a little grim. They had an infestation of the olive farmers’ nemesis, the olive fly.

TOMAJAN: It’s basically a fruit fly that has a very symbiotic relationship with the olives. So they lay their eggs in the olive and the larvae eat their way out, essentially ruining the fruit. So there was a few weeks where we started seeing some damage, some damaged fruit, and I definitely freaked out. I was like, I don’t know, I don’t think this farming thing is for me. It’s like an emotional roller coaster! It’s all these ups and downs!

GRABER: They used a number of organic measures to get rid of olive flies—they even hand-picked contaminated olives to stop the fly from spreading. But there were a few fly-bitten olives left when we visited.

TOMAJAN: If you want to break one of these open just to see the inside and kind of see what it does to the fruit, you can see that—ah, there’s the worm!

GRABER: Oh yeah.

TWILLEY: So gross!

GRABER: There’s the little….

TOMAJAN: It’s very disgusting. So basically most of our effort during the year, with the exception of pruning and harvesting, the third biggest task for us is protecting our fruit from the olive fly.

TWILLEY: I should say here that the entire orchard looked like some kind of ghost orchard art installation. Kathryn and Robin had sprayed the trees with white clay as a coating on the olives to try stop the fly from getting in. And all that clay—I ended up completely coated in it myself when I was harvesting. My hair was a solid clay-particle based structure by the end of the day.

GRABER: This isn’t only a problem in California. The olive fly is a huge threat to groves in Tuscany, too. Anna’s been battling it herself lately. And it’s only getting worse because of climate change. The winters are just too warm—they don’t always get cold enough to kill the flies.

CASAREI: And we are always about two or three percent that it’s nothing. In the last year, we grown up seven, eight percent. And you have to take care. But every year you have more and more. And this is happened because we don’t have any more cold winter. She’s not dying. She’s still there waiting, that the new season came.

GRABER: Anna has her mind on olive flies—she isn’t yet worried about a different disease that’s basically decimated entire regions of southern Italy’s olive trees.

RODRIGO ALMEIDA: Specifically what we’re talking about is the southern region of Apulia, the Cilento area. So this is at the very tip of the heel of the boot, let’s say. So you have areas where you really have no live olive trees anymore.

TWILLEY: That’s Rodrigo Almeida. He’s a professor of environmental science at the University of California Berkeley. And he studies this terrible olive plague. He says millions of Italian olive trees have died.

ALMEIDA: At some point in the past this bacterium that that’s called Xylella fastidiosa was introduced into the region.

GRABER: This Xylella bacteria colonizes the part of the plant called the xylem network. It’s basically the plumbing system for water flow inside the olive tree.

ALMEIDA: So essentially as the bacteria moves and colonizes the plant, it clogs up water flow and the plants are essentially thirsty.

GRABER: So the trees die of thirst.

TWILLEY: The Xylella bacteria is transmitted from tree to tree by insects, while they’re feeding on the water and nutrients that circulate around in the tree. And Rodrigo says that if a mature olive tree gets infected, it can go from healthy to dead in a couple of years.

GRABER: Like Rodrigo says, Xylella was introduced to Italy, it’s not from there originally. Scientists first detected it in 2013 but Rodrigo thinks it got to Italy a couple of decades earlier.

ALMEIDA: So this is another point that’s somewhat controversial but today with the data that we have available, all the data indicate that it originated from Central America.

TWILLEY: In fact, Xylella is widespread in Central America and South America, where it infects coffee plants and citrus. In Brazil, it got to a point where something like six million citrus trees were getting infected and destroyed each year. In North America, in California, Xylella infects grape vines.

GRABER: There are grape vines in southern Italy, too, but they haven’t been destroyed by Xylella. And Kathryn and Robin’s olives in California so far are safe. Why is that? Well, it turns out that different strains of Xylella attack different plants. So far, scientists aren’t seeing a lot of—oh, the grape vine Xylella just jumped to the olive tree! But that’s not 100% failsafe, because the Xylella from Central America that came to Italy didn’t start on an olive tree. So… it’s complicated. But it’s dangerous.

TWILLEY: Xylella is a pretty common plant disease, and like most plant diseases, you have some tools to stop it from spreading. The main one is quarantine. This is where growers cut down infected trees but also all the other nearby trees that might also have been exposed even if they aren’t showing symptoms yet. It’s a “better safe than sorry” approach.

GRABER: The authorities in Italy and the EU called for just this approach—cut down infected trees and the trees surrounding them to be safe. But southern Italians were unwilling to chop down their beloved trees.

TWILLEY: These olive groves go back centuries. They define the landscape, the culture, the food—everything. So that was one problem.

GRABER: Another challenge was the fact that there was a big social media campaign to undermine the science.

ALMEIDA: You have a very challenging situation at the moment for example, where you had scientists working on the epidemic being investigated by a local prosecutor, possibly being charged for being responsible for the epidemic. You have people who do not believe in science, for example they don’t believe that Xylella fastidiosa is a bacterium. They don’t believe that it’s present there. They think it’s a hoax. They think that the Mafia is behind it. There are several different conspiracy theories and this sort of narrative permeated through the local population or at least sections of the local population. And you ended up with a situation where politicians were not willing to do what was supposed to be done and make difficult decisions. And as a consequence the epidemic has spread.

GRABER: Xylella has since been found in Spain and France, too. Honestly, this all makes me a little panicky. I think a full third of my diet must be made up of olive oil. How worried should I really be?

ALMEIDA: I think people are right to be anxious. It’s not the end of olive oil production in Europe. It’s clear that if it’s in specific circumstances like in southern Italy, if the conditions are just right you can have a devastating epidemic.

TWILLEY: Scientists are working to breed Xylella resistant olive tree varieties; they’re figuring out new ways to control the insects that spread the Xylella, and the EU has cracked down on Italy to make sure people do enforce the quarantine.

ALMEIDA: My understanding is that there’s been a little bit of a shift here where the local government is complying with the recommendations a little bit more.

GRABER: All my digits are crossed. I can’t imagine Italy without olive oil, or my life without all the olive oil possible.

TWILLEY: You and me both. But Cynthia, we’ve been talking about olives for a few minutes now, but we have yet to even get into what olive oil is. And I know this sounds like a stupid thing to ask—like of course we know what olive oil is, it’s oil from an olive.

GRABER: But we figured we should ask the expert—that’s author Tom Mueller—we should ask him what it is. Just to be sure.

MID-ROLL

MUELLER: An olive is a drupe, technically speaking. A seed fruit like a plum or a cherry. And so olive oil or what you extract from the olive is quite literally fruit juice.

GRABER: That is not the answer we were expecting!

TWILLEY: But why would the juice of a fruit be so oily? Plum juice is not oily. Cherry juice is not oily.

GRABER: Tom says it’s all because of what the olive seed needs to grow.

MUELLER: It is a nectar that produces magnificent compost, ideal compost for the olive seed especially when added to a dab of bird droppings. And since then it’s become the ideal nectar for the classical world in terms of bodily beautification, skin health, food obviously, fuel for lamps and furnaces, lubricant for machines, softener for fabrics—and we’re talking the Greco-Roman world but also well before.

TWILLEY: Tom told us that the olive was likely first domesticated around 4000 B.C. in the eastern Mediterranean.

MUELLER: And by about 1000 to 1500 B.C., it was industrial. And there are huge presses found in Ekron in Israel with huge logs for lever arms that could produce something on the order of a million liters a year.

GRABER: The people who lived around the Mediterranean used olive oil for food, of course, but as Tom said, that’s not all. By the time of the Greek and Roman empires, olive oil was thoroughly integrated into all areas of life.

TWILLEY: First of all, Tom says, olive oil was the greatest renewable energy source in antiquity. It burnt super hot and it contained two times the energy of carbon. But people weren’t just burning it. They weren’t even just eating it. They were in fact rubbing it all over their bodies.

MUELLER: I mean the idea of having… doing sports or bathing in the classical civilized manner was unthinkable without olive oil and its various extracts. You know, olive oil was also used in the home as soap and as a base for perfumes and to be used against hair loss and stomach aches. And as a religious offering—little vials of olive oil are found in various shrines around the Mediterranean.

GRABER: Olive oil was such a great base for perfume because it kind of melts into the skin and leaves this lovely shine. It’s not dry, like the alcohol-based perfumes you can buy today. And of course it contributes its own olivey scent to the mix. I use olive oil as an all over moisturizer, and my partner Tim says it leaves a delicate scent of dinner.

TWILLEY: Cynthia, you and Tim are not the first to have noticed olive oil’s miraculous beautifying powers. After Odysseus got shipwrecked in The Odyssey, he slathers himself in olive oil and poof, suddenly he’s as handsome as a god.

GRABER: The prophet Mohammed was said to have used so much olive oil on his body that even his shawl was drenched in it.

TWILLEY: But like I said, people weren’t just rubbing themselves in olive oil in ancient world—they burned it for light, they used it for frying…

MUELLER: As a preservative, which is still very popular today. Under oil—you know, your tuna under oil keeps better. As a contraceptive, I’m not sure how that went, but it was a major, major part. And as an aphrodisiac. Again, I can’t vouch for the active ingredient but it was certainly mentioned by Greco-Roman writers.

GRABER: In the ancient world olive oil was as valuable as petroleum—rock oil—is today. There were wars fought over it.

MUELLER: Huge fortunes were amassed with olive oil. Emperors like Trajan and Hadrian were the scions of these flourishing olive oil dynasties in Spain and North Africa. A bit like sheikhs in the Middle East today with petroleum. So it was an empire builder and a source of enormous wealth as well as the definition, one of the definitions of culture. And also again, the Romans in their militaristic way, when the Roman legions would go to far flung lands they would plant vines and they would try to plant some olive trees. And if it didn’t work out they would certainly have a lot of imports of olive oil, because to be the master race in their sense you really had to do civilized things and that involves olive oil.

TWILLEY: Olive oil has always been popular in the Mediterranean. Other cultures had other fats: butter, coconut oil, sesame oil, ghee, lard, et cetera. But then, just a few decades ago, a doctor called Ancel Keys, who we’ve talked about on this podcast before…

GRABER: He starred in our butter episode as the man who villainized our favorite spread.

TWILLEY: He did a big study looking at what made the difference between countries where people had more heart attacks versus countries where people had fewer. And his findings became popularized as the Mediterranean diet. Keys published a book on the Mediterranean diet in 1980, extolling the virtues of olive oil and lots of vegetables as a way to avoid heart disease.

GRABER: This dietary advice took a while to catch on, but by the 90s, olive oil had started to become super popular throughout the world, not just in the Mediterranean. One quick note—there are lots of flaws with Keys’ research, and other fats are not necessarily evil. That said, olive oil is high in antioxidants. And it’s delicious.

TWILLEY: It is delicious. But here’s the thing: we tasted a ripe olive straight off the tree in Kathryn and Robin’s grove, and it was rank.

GRABER: Oh my god that’s disgusting. Wow, it’s like bitter and like…

TOMAJAN: Astringent. Yeah.

TWILLEY: Like very drying, like your entire mouth is dried out. And then some. For a while.

GRABER: Wow it’s really gross. Can you imagine that people who are like, this tastes disgusting! Let’s put it in salt and see what happens and maybe it’s going to be delicious. Salt because that’s how you cure an olive and invent table olives for snacking.

TOMAJAN: I just can’t—I just have no idea how anybody… I always have these like fascinations like, how did anybody decide that coffee could be, coffee beans could be turned into coffee. Same with olives. I have no idea. I mean, they taste not good off of there but it’s… there is something that happens in the mill. And it’s all a little bit mysterious to me still because I’m not like a chemist or a biologist, but there’s enzymatic reactions that happen in the crushing process that release those aromas. That’s why you don’t taste—they don’t taste good off the tree but with some enzyme action that happens in the mill with a little bit of you know crushing and agitation. I don’t know—it becomes perfume.

GRABER: Nicky, you got a chance not just to pick olives and get clay in your hair, but to see Kathryn and Robin milling their olives for the very first time! I’m jealous.

TWILLEY: You should be jealous—it was awesome. Although we had to leave while everyone else was drinking post-harvest beers, and race down the peninsula to the nearest olive mill that was small enough to process our tiny harvest.

TWILLEY: The team at the mill dumped the olives into a giant bin, and then Kathryn hit the magic button. The olives started moving up a conveyor belt and then they fell into a bubble bath.

TOMAJAN: There they go! The olives are getting cleaned up with a little water.

TWILLEY: And then they get pulled up into the crusher. And that’s where things start smelling good.

TOMAJAN: So we’ve got ground up olives here in what we call the malaxer. It’s kind of like, imagine a KitchenAid mixer where you’re mixing it up. And this malaxation process allows the cell walls of the olive to break down and the microscopic droplets of oil to coalesce together and that’s what the malaxer is for.

TWILLEY: But it smells so freaking amazing.

TOMAJAN: Smell it, right? You can smell the olives, yeah. It’s one of my favorite smells in the world.

TWILLEY: The crushed up olives had to stay in the malaxer until Jeff, the guy who runs the mill, started seeing oil.

JEFF: So you see the shininess? For those of you on radio: It’s shiny.

TWILLEY: At this point the paste gets pumped into the decanter, which is a centrifuge that separates the olive skin and flesh from the oil and water. And then, the final step, the oil and water—the olive juice!—that goes into another centrifuge that separates them and spits out a stream of water and a stream of oil.

TOMAJAN: There is it! First oil!

GRABER: Kathryn and Robin are currently bottling up their oil. We have details on how you can get it at gastropod.com. And if you want to hear what Kathryn thought of her very first taste of her very first oil? Listen all the way through the credits.

TWILLEY: Turns out that our crew of a dozen complete novices picked over 1,000 pounds of olives from 32 trees that day. Which made 15 gallons of oil, or more than 100 bottles’ worth. And I slept like a baby that night.

GRABER: At this point, most people would mix their oils into blends. Kathryn actually plans to keep her different olive varieties separate from one another—single varietal olive oils. And that’s one of the ways you can really taste the difference among different oils, based on the olive variety. We did a tasting of Anna’s oils in Tuscany.

CASAREI: Sit down, relax. I’m going to serve you two different varieties. Don’t smile because you feel—to taste, to taste oil, you have to keep the oil in your mouth and take in air through the teeth.

TWILLEY: That sound—that sound has a name. I’m going to let Tom say it, because my Italian is terrible.

MUELLER: Strippaggio, or stripping. It’s slurping essentially, you slurp. Drawing in air in the corners of your mouth which aerosolizes the oil and makes the aromas go back into your nasal passages. And it allows you to—I mean, it’s amazing. If you put olive oil in your mouth and you taste it and you swallow it and then you do it again, the same oil, and you do this slurping, which sounds something like this.

GRABER: Then you can really get a sense of all the different aromatics and flavors in the oil. It sounds weird, literally, and it feels weird. But it works.

CASAREI: Here is, it’s a 2016, as I told you, was a warm climate. The flavor, it’s not so intensive. But today I smell—of course I smell olives. I smell the leaves.

GRABER: So of course we gave it a try, too. SLURP. Don’t choke on it! Careful there! It has like a pepper. Not the like, sear the back of your throat but like a peppery vegetal—I mean, it’s really strong, I love it.

TWILLEY: Very peppery. How was our technique?

CASAREI: You see, when you start to—it mean the technique it works. So the fact that you were choking was a good thing.

GRABER: The choking response doesn’t just mean that you’re tasting it correctly. Another reason you might be coughing is because of that peppery note. Which is also good. The more peppery the olive oil is, the most polyphenols it has. Those peppery polyphenols are what many scientists think are awesome for your health.

TWILLEY: Anna’s oil was delicious, unsurprisingly. And very peppery, as you heard. We choked. But then she gave us the final sample. Her own oil, but so old it had gone rancid.

GRABER: I’m afraid to drink this. Do we have to? Oh no. Just as expected, it tasted disgusting. Old, stale, musty. I had to immediately take a taste of her fresh oil to clean my mouth of the flavor.

CASAREI: Honestly, I make this oil because when we have a tasting I have to show them, because it’s happened that when I gave them my rancid oil that was the old oil, they say it was good.

TWILLEY: This is what originally inspired Kathryn to get in the olive oil game herself—a professor made her taste some rancid olive oil as part of an international food studies class.

TOMAJAN: And he poured us all a little tasting cup full of olive oil. And he said tell me what you think of this olive oil. So we all tasted it. And all the Americans were like, Yep that tastes like olive oil. And he’s like, Great, that’s rancid. And I was like what? I’ve been eating rancid olive oil my whole life and I didn’t even know it. Like, foodie extraordinaire did not—like, knows nothing about olive oil clearly. So really what emerged from that experience was consumer rage.

GRABER: Anna and Kathryn’s point is—many Americans and northern Europeans kind of like rancid oil because that’s what we think olive oil is supposed to taste like. Because a lot of the oil that’s sold as lovely extra virgin olive oil? It’s not.

MUELLER: Olive oil fraud is enormously widespread today and there are two different kinds. Like in politics or in finance, there is the illegal fraud… you know, the favorite way of doing fraud is simply to sell something which isn’t extra virgin as extra virgin and pocket the differential. You know, you can get away with putting really bad olive oil from olives into a bottle of extra virgin sometimes mixed with extra virgin to give it a little more pizzazz and sometimes just sold as is.

TWILLEY: Bad olive oil is called lampante, officially speaking—meaning it’s only fit for use for lighting a lamp. Lampante oil will typically be made from olives that have fallen from the tree rather than being freshly picked. They might have already fermented, which fermentation is often associated with great flavors but definitely not in the case of olive oil.

GRABER: To make this bad oil remotely palatable, the fakers do something called deodorization. They clean the oil of the nasty overtones by heating it to about 40 to 60 degrees Celsius. It’s tasteless at this point, but deodorization also removes any of the healthful compounds. You’re left with just the fat.

MUELLER: You can also mix it with even cheaper vegetable oils, you know soybean, sunflower, and so on. So that’s the illegal fraud. That’s fraud fraud. Then there’s legal fraud, where you have a label which says “the ancient millstones” or you know some Italian sounding name, which has absolutely nothing to do with Italy. You know, the olives were grown somewhere in southern Spain or North Africa. And then you know, sold as fake Italian.

TWILLEY: For a lot more money. Then there’s a product called “extra light olive oil.” That’s actually illegal in Europe, but you can buy it in the States. It sounds like low-calorie olive oil, right?

MUELLER: But guess what? It’s the same 120 calories per tablespoon as all the others. It just doesn’t have any flavor and it doesn’t have any color. Because it has been processed in a refiner. It’s been refined. It sounds so good except that it just means devoid of good stuff. You know, it’s an open swindle. So those are the legal frauds.

GRABER: Not only is this extra light olive oil fraudulent, but it’s tasteless, and, once again, not good for you. By making it “extra light,” the companies first of all are probably using crap oil to start with. And then, like Tom says, they’re removing any of the beneficial compounds.

TWILLEY: So how common is olive oil fraud—both the fraud fraud and the legal fraud? The truth is, it’s hard to know. Unsurprisingly, most of it goes undetected. In 2010, UC Davis did a survey of 14 different brands of imported extra virgin olive oils on California supermarket shelves, and they found that more than two thirds of them were actually not extra virgin quality at all.

GRABER: In February of this year, Italian authorities arrested 33 suspects from a Calabrian mafia clan. They were, among other things, allegedly exporting fake extra virgin olive oil. They were importing super low grade crap oil, cleaning it with chemical solvents, and labeling it as extra virgin and exporting it to the U.S. There’s a lot of money to be made in this: high quality olive oil can sell for $50 a gallon, while the fake stuff costs only $7 to make. Tom Mueller told us that the profit margin can be higher than selling cocaine.

TWILLEY: Olive oil fraud is not a new problem. As we discussed in our episode on food fraud last spring, people have been faking food as long they’ve been buying and selling it.

MUELLER: You know the oldest mention of olive oil in writing is on cuneiform tablets from the 24th century B.C. in the kingdom of Ebla. And those tablets mention the king’s olive oil investigators going around to the mills to make sure those olive oil millers weren’t getting up to their usual tricks. So you already have an oil fraud squad. So clearly this is an ancient problem.

GRABER: Tom loves telling the story of Monte Testaccio in Rome. It’s a hill of potsherds left over from the Roman empire. And there are fragments of writing on those pieces of terracotta.

MUELLER: And if you piece those together you will see that the writing outside the amphorae that were used to import olive oil to Rome mention who grew the olives, where those olives were milled—in Spain, North Africa, or wherever it was. How much it weighed when it was put on the ship, how much it weighed when it was taken off the ship at the port of Rome.

TWILLEY: The Romans didn’t just do this for fun. And it wasn’t just bureaucratic OCD, either.

MUELLER: They did it because there was an enormous fraud problem and the way to stop the fraud is to keep very careful tabs on who’s doing what and how much stuff weighs, where it’s coming from, what the names of the people are, so that if there is a problem—if you open an amphora and you say this smells funny, who made this? You can go back up the supply chain, find the person and probably in Roman times cut both their feet off and ask them not to do it again.

TWILLEY: Nowadays olive oil fraudsters that are caught tend to get huge fines and or jail sentences instead, but you get the picture.

GRABER: So we’ve told you that a lot of what is sold as extra virgin is not actually extra virgin. But back to a question we posed earlier in the episode: What the hell is extra virgin?

MUELLER: Right. So this virgin oil is olive oil produced by mechanical means, i.e. grinding and pressing or spinning out the oil.

TWILLEY: So that’s virgin oil. And there are three grades of virgin oils: Extra Virgin, Virgin, and Lampante. So even the stuff that is unfit for human consumption—that is only supposed to be used for fuel—that is still virgin.

MUELLER: Extra virgin is the highest quality grade of virgin oils. So that’s Virgin Virgin. That’s why I chose the title Extra Virginity because it’s such a complete joke. I mean the title itself tells you what a joke it is. It’s like extra dead or semi-pregnant. I mean it doesn’t make any sense at all.

GRABER: But there are a number of hoops olive oil has to jump through to be legally called extra virgin. First of all, it has to pass a number of chemical tests. Listener Brenda Vest is the one who wanted us to do this episode.

TWILLEY: And Brenda’s job is to perform these chemical tests on the olive oil that her company imports. She has a lab near the port of Baltimore. And we gave her a quick call to find out how she does what she does.

VEST: So let’s say that a container comes in. So there’s a 6000 gallon flexi-bag that arrived at our facility. So the initial quick testing that takes about fifteen minutes where we test free fatty acids, peroxide content, and these are quick titrations that we do in-house.

GRABER: Brenda is checking to make sure that the imported olive oil is not cut with seed oil. Or cheaper pomace oil. They check to make sure it hasn’t been exposed to too much heat and light—this breaks down the oil into other chemicals that Brenda can test for.

VEST: So yeah, overall the process can take from fifteen minutes to three days.

TWILLEY: So far so good, right? Except not, because A) Tom told us that the FDA doesn’t actually require any testing on imported olive oil. So while Brenda’s company is going above and beyond, lots of other suppliers aren’t.

GRABER: And B) this is going to be even more disappointing to hear—these tests are just not enough on their own.

MUELLER: Oil that just passes the chemical tests you wouldn’t touch with a bargepole, you wouldn’t get it near your mouth, but it’s still technically extra virgin.

TWILLEY: But wait. All is not lost. To be labeled extra virgin, olive oil shouldn’t just pass the chemical tests. There’s another more challenging hurdle.

MUELLER: It should be able to pass a taste test or a sensory test where seventeen specifically defined, legally defined flaws can be identified.

TOMAJAN: So I have been trained now to identify all of the flavor defects and flaws that can arise in olive oil—including rancidity, I’m proud to say.

TWILLEY: That’s right: the Kathryn who tasted rancid olive oil and loved it is no more. The Kathryn of today serves on California Olive Oil’s Tasting Council. It’s a third-party group that certifies all California-based olive oil.

GRABER: Every California producer sends their oil to the California Olive Oil Tasting Council. First it has to pass the chemical analysis—low acidity, specific peroxide values, all the types of tests that Brenda does. But then it’s time for the tasting.

TOMAJAN: And we blind taste it, we taste it in these little blue glasses so we can’t see the color because color is not an indicator of quality. And we smell it and we taste it and we are trained to taste for very specific flaws that can appear in olive oil. Rancidity is one. Fustiness is another, which is actually a form of fermentation. Wininess or vinegar is another one that’s also a form of fermentation. Grubby is another one.

TWILLEY: Grubby in this case doesn’t mean dirty, it means there were too many bugs in the olives—like that pesky olive fly.

TOMAJAN: And there’s a few others that we’re trained to detect. And so if the producers’ oil pass both the chemical analysis and the sensory evaluation, they get a seal that says their oil is extra virgin.

MUELLER: A skilled taste panel is an unbelievably sensitive quality judge. And you can game the chemistry but you can’t game the sensory panel, if they are well-trained. It’s just that there aren’t very many of those.

TWILLEY: So at this point, you might be thinking well crap, how am I supposed to know if the olive oil on my kitchen counter is really extra virgin? I’m not trained like Kathryn, but I want to make sure I’m getting the good stuff. Agh!

GRABER: Don’t worry, we’re not going to leave you on a depressing note—there are a number of things you can do to make sure you’re buying real extra virgin olive oil. The first is to look for some kind of third party verification.

TWILLEY: California is ahead of the game here because of its third party testing. Australia is too.

TOMAJAN: If you’re in California look for the California Olive Oil Council seal. If you’re buying oils from somewhere else, look for some third party seal: a DOP or an AOC kind of certification from Europe is a great indicator.

GRABER: In fact, if I have to grab olive oil quickly at the store, I’ll look for California olive oil. And the California Olive Oil certification seal. It’s a good shortcut guarantee of quality.

TWILLEY: But that’s not to say that you can’t buy amazing imported oil too. You just have to do some homework. Like Kathryn says, look for an AOC or DOP seal. Tom recommends using Google Maps to see if there are actually any olive trees at the location where the olive oil says it was made.

GRABER: Or you can buy from someone you trust. I usually get my oil from a store that imports bulk olive oil directly from a farm in Italy. That said, I wouldn’t buy just any oil at a random grocery store where the label says it’s Italian. That is the most likely to be fraudulent.

TWILLEY: One reliable tell that you’re dealing with decent oil is that the bottle will have a harvest date on it. Because good olive oil producers know that freshness is king.

TOMAJAN: If you don’t see a harvest date on the bottle, I would recommend not buying that because the producer’s obviously not proud enough to put the harvest date on the bottle.

GRABER: You want to find one that’s been harvested probably no more than around a year ago. The olive oil is not getting any better as it ages. Remember, it’s fruit juice!

TWILLEY: And that leads us to our next recommendation, which all our experts share: if you buy good olive oil, use it up! Quickly! Literally, the chemical defects that Brenda is testing for are what is happening to your oil as it sits on your counter getting old.

MUELLER: It breaks my heart—I don’t give olive oil as gifts anymore because so many times I’ve given a gift of olive oil, a really good bottle of olive oil, and said, Here, you know this is the real stuff. And they say, Oh, that’s great. And I go to their house a year later and it’s still there collecting dust. And I say, So what’s the story here. And they say, Well, we’re waiting for a special occasion. And it’s ugh, it’s heartbreaking because this is not a special occasion food. This is—I mean this is everyday food. And even if it’s very expensive, it’s something that you use on a daily basis and it should be in the middle of the table.

GRABER: Now you know how to buy oil, and you know how quickly you need to use it. You have great olive oil on your shelf. Time for something fun! Enjoying it.

TWILLEY: The cool thing is that extra virgin olive oil that passes the sensory panel can still taste wildly different, based on where the olives were grown, the climate and time of year, the type of olive, and how they were processed.

MUELLER: You can get fresh cut grass, you can get tomato leaf, you can get green almond nuttiness. Even kiwi flavors.

GRABER: Anna told us a story about an olive oil from Sicily that had an incredible scent of tomatoes. It wasn’t infused with tomatoes, it just literally smelled like tomatoes. So she decided to use it to play a trick on her kids.

CASAREI: I give them two piece of pizza and I tell them, Which one you like more? One with our Tuscany blend and one with this variety from Sicilia, that smell tomato. And they say Mom, the tomato of this pizza much better. I say, exactly the same.

GRABER: The kids thought that one piece of pizza tasted better because it had more tomatoe-y tomatoes. But the tomatoes were the same, it was just the oil that was different.

TWILLEY: And this is where you get to have fun with your olive oil—mixing up the pairings. A softer Ligurian oil is often better with fish, a peppery Tuscan oil stands up to beans. Those are geographical differences, but you can also find single variety olive oils—so an olive oil made only from Frantoio olives, for example, or Arbequina. And those bring different flavors to the olive oil party too.

GRABER: If you have different oils that you want to try side by side, to really appreciate the differences, Tom has a simple recommendation. Mashed potatoes.

MUELLER: Take mashed potatoes and have three different, really different olive oils and try one of each. Just mashed potatoes and put, while it’s still steaming, really good olive oil on there and make a little reservoir in the middle and fill it with olive oil and put your face over it before you eat it and smell. I mean it’s quite—it begins to be, you know, wine tasting without the posing and the terminology. Because you really smell it, you put your snout over it and you smell it and it really is special.

TWILLEY: Special, but maybe not as instantly compelling as Kathryn’s recommendation.

TOMAJAN: You can make a chocolate cake, an olive oil chocolate cake, you could drizzle chocolate ice cream with olive oil and a couple of grains of sea salt is lovely. I just find chocolate and a really robust olive oil just pushes all my buttons.

GRABER: Warning: if you are hungry right now, we are not done listing insanely delicious ways to consume olive oil.

MUELLER: You know, start off with vegetables. Start off with whatever vegetables you like and put some on there and then, put it down and put some more on there. I mean put a lot on there. It has to be dripping with olive oil. And I challenge people not to find it vastly better.

TWILLEY: This has been the Italian trick to make vegetables delicious for centuries.

MUELLER: Some English travelers in Florence in the late 16th century marveled at the amount of vegetables these Tuscans ate. And they said, You know, really they can only choke it down by putting this olive oil on it. That’s the only way that I can understand their ability to eat so many vegetables.

GRABER: I happen to love vegetables and don’t have to choke them down. But I agree that they taste even better with a really healthy glug of olive oil poured on them right before you eat them. This is what Kathryn and Tom are telling you to do—it’s something that’s not super common in America. Pour olive oil on after you’re done cooking. Use it on vegetables. Drizzle it on your soups. It can make food sparkle.

TWILLEY: But none of these delicious serving suggestions is what Kathryn and Robin said when we asked them how they were going to enjoy their very first oil.

TOMAJAN: I know what your answer would be.

SLOAN: What’s my answer?

TOMAJAN: Just give him a loaf of bread.

SLOAN: Yeah, like little pita breads. Yeah, I toast them up, dip ‘em—I’m a big dipper, big olive oil dipper.

TOMAJAN: I love a super simple pot of beans. Super plain, not spiced up any, just simple. For our first crush, I want the pot of beans drizzled with a lot of freshly-made olive oil.

GRABER: Thanks so much to Anna Casadei in Tuscany and to Toni Mazzaglia who introduced us to her. Take Toni’s food tours—tasteflorence.com.

TWILLEY: Thanks also to Kathryn Tomajan and Robin Sloan. You can find out more about their first harvest and how to get hold of it at gastropod.com, where we have links to all the books and papers and olive groves we mention this episode. Not to mention video of the vibrating rakes.

GRABER: Thanks to Tom Mueller, author of Extra Virginity. And Rodrigo Almeida at UC Berkeley.

TWILLEY: And a huge thanks to listener Brenda Vest! We love our listeners and we love your suggestions and we love it even more when you take part in our shareathon. Gastropod.com/share. It’s only running through the end of the year so get in there now!

GRABER: We promised you one last moment from our visit to Kathryn and Robin’s olive grove: Their first taste of their first oil.

TWILLEY: What are you thinking?

TOMAJAN: Mmm! Oh yeah, it’s quite robust because it’s so fresh. So I’m getting a really nice bitterness and pungency and some… it’s quite grassy but also kind of—a few other descriptors I might use is like a green almond, which is a really particular descriptor for olive oil, which is really nice. I don’t know what else. It’s just—it’s good. I’m really happy with it! We will put this in a bottle and love it.