The Fat Gold Guide
to Extra Virgin Olive Oil
Welcome! This guide opens with an olive oil primer. If you’re already familiar with the basics, you might be more interested in our tour of a running olive mill. There’s lots to explore, and you are definitely encouraged to jump around.
This is a living document, constantly being updated. If you’re wondering about anything not covered below, don’t hesitate to drop us a line at robin@fat.gold.
Thanks for reading!
Understanding olive oil
The essentials
What is olive oil?
Olive oil is best understood as the fresh fruit juice of the olive. It doesn’t taste sweet like other fruit juices, but just like other fruit juices, it’s intensely flavorful as well as perishable. Thinking “olive oil is the juice of the olive” puts your head in the right place for the rest of the story.
What’s an olive, then?
An olive is a drupe, or stone fruit, with a fleshy exterior surrounding a single pit. (Other examples of drupes are almonds, apricots, cherries, and plums.)
Every olive is composed of solid matter—skin, flesh, pit—along with water and, of course, oil. The ratio between them differs depending on the olive variety; table olives have been bred for flesh, while oil olives are the opposite.
But, even our favorites for Fat Gold are relatively stingy: at most, an olive is around 20% oil.
What’s “extra virgin”?
“Extra virgin” is a quality standard. It means an olive oil (a) has no chemical or sensory defects, and, in addition, (b) offers some amount of fruity flavor. The standard also requires that the olives weren’t processed with chemicals or extreme heat.
This standard isn’t a destination, but a starting point. Sometimes, the way people use the term “extra virgin olive oil,” it sounds as if those oils are all the same, and that’s definitely not the case. Some are bold and peppery, others mild and fruity; some are packed full of antioxidant biophenols, others have hardly any; some are fresh from the most recent harvest, others have been sitting on the shelf for years!
There are grades of olive oil beside extra virgin, and many have practical applications. For example, virgin olive oil barely misses the mark for extra virgin; it might have a small defect, while remaining perfectly palatable and, just as important, extremely nutritious.
Here’s a “family tree” of olive oil grades:
Olive oil | Olive pomace oil | |||||
Unrefined olive oil | Refined olive oil | Blended olive oil | Crude olive pomace oil | Refined olive pomace oil | ||
Extra virgin | Virgin | Lampante |
A few notable definitions:
Refined olive oil has been treated with extreme heat and/or chemicals, stripping out all its flavors and antioxidant biophenols. This kind of oil is basically equivalent to any other refined oil—like canola oil—regardless of source.
Olive pomace oil is produced by sending the solid waste from an olive mill back through the mill, a second time. To learn more about pomace, you can read up on the milling process.
Lampante is a fun term for the oil deemed unfit for consumption, and relegated, in the old days, to lamp fuel.
Here are the grades of olive oil you’ll find stocked at the grocery store:
Extra virgin | Virgin | Olive oil Pure olive oil Light olive oil Extra light olive oil |
No defects Fruitiness > 0.0 |
Some defects Fruitiness > 0.0 |
Blend of refined olive oil with with virgin or extra virgin olive oil |
As you can see, extra virgin olive oil is the good stuff, free from any defects, while virgin olive oil might have some defects, but still has that olive-y goodness—the flavors and biophenols.
All the other phrases you might encounter on labels—pure olive oil, light olive oil, extra light olive oil, to name a few—are suspect. They indicate you’re probably looking at refined olive oil.
Extra virgin certification
To earn the designation “extra virgin,” olive oil can’t have any chemical or sensory defects. But how are these defects detected?
The production of olive oil is a relatively simple process, but there’s a lot that can go wrong, and when it does, the evidence is there in the chemistry of the oil, and also in its flavor. Certification is therefore a two-pronged process.
The chemical test
As soon as our oil is milled, we send a sample to a lab for a standard battery of tests. Here’s an example of a lab report for one of our oils from several years ago:
Here’s a breakdown of the lines on the lab report:
Test | What went wrong? |
---|---|
Peroxide Value (PV) | The oil oxidized. |
Free Fatty Acids (FFA) | The fruit was damaged; it might have been crushed or bruised. |
UV Absorbance (K232) | The oil oxidized or was refined. |
UV Absorbance (K272) | The fruit oxidized or went rancid. |
UV Absorbance (Delta K) | There was refined oil detected in the sample. |
Total Phenol | (This one doesn’t measure a problem. Instead, we are looking for a big number!) |
Of particular note are the peroxide value, which is associated with oxidation—the result of exposure to heat, light, and oxygen over time—and the total phenol level, which isn’t part of the extra virgin standard, but is important to olive oil’s flavor and health benefits. (You can read more about biophenols to find out why.)
The sensory test
At the same time, we dispatch another sample to a sensory panel, a group of trained tasters who taste each oil blind, using an exacting protocol, and identify defects that the lab can’t pick up.
Fat Gold’s majority owner, Kathryn, has served on one of these taste panels. Here’s an example of a flaw Kathryn might detect:
If olives sit too long after harvesting, they can begin to ferment before milling. When you’re harvesting grapes to make wine, fermentation is what you want; when you’re harvesting olives to make oil, it is absolutely not. Fermented olives produce oil with an unpleasant flavor. Chemical tests can’t pick it up, but trained tasters can. This defect is called fusty. Sometimes it’s subtle; other times, it’s overwhelming. In either case, if the sensory panel catches it, this flaw will disqualify your olive oil from extra virgin status.
If your olive oil passes both the chemical and sensory tests, you’re allowed to market it as “extra virgin” in the state of California. In many cases, the sensory panel also provides a mark you can display on your label: a seal of approval for discriminating customers.
What if an oil doesn’t pass these tests?
This happened to us a couple years ago; it was a big batch of frantoio that had suffered a milling mishap. The oil wasn’t extra virgin, but it was still really good, perfectly tasty and unquestionably nutritious. We donated it to a food bank here in the East Bay, where it was used in food preparation.
Tasting olive oil
Here’s how to taste olive oil like a pro on a sensory panel.
Grab a small cup or glass and pour out a little bit of the oil. Warm it up in your hands; even a few extra degrees of heat will send volatile molecules flying into the air. (The sensory panels use warming mats; they aim to taste the oil at 82 degrees F. Note that you’d never store it at that temperature!)
Now, smell it. Extra virgin olive oil has tons of aroma, and you can pick up a lot of information right here. You might smell things as various as green banana, tomato leaf, or fresh-cut grass.
Finally, take a sip. Slurp in a bit of air at the same time. Swallow.
There are three things you’re looking for in an extra virgin olive oil, all in balance:
Fruitiness. Olives are a fruit, and you can smell the evidence in well-made extra virgin olive oils. Here are some broad families of aromas and flavors you might identify:
- Green or herbaceous: fresh-cut grass, artichoke, green tea, tomato leaf, green almond, pine, mint
- Fruity: tomato, apricot, cherry, apple, citrus, guava, avocado
- Nutty or spiced: cinnamon, black pepper
- Floral: jasmine, lilac
- Others: hay, straw, wood
Bitterness. If you ever nibble an olive straight off the tree, you will discover that they are very, very bitter. Some of that bitterness makes it way into the oil.
Pungency. This is the spicy sensation that you might feel at the back of your throat. It’s not spicy like a chile pepper; more like ginger or radish.
That last sensation is caused by biophenols. In non-virgin oils, the refining process has stripped them out, but extra virgin olive oil has them in abundance. We explore biophenols elsewhere; the thing to know right now is, you can taste them! It’s the biophenols that produce the burn at the back of your throat.
Of course, you might also taste flaws. Here are some of the most common, each with its source:
The global olive
There are many different olive varieties, some of them traditionally associated with different regions. Just for starters:
Name of variety | Associated with | Usually tastes |
---|---|---|
Frantoio | Italy | bold and peppery |
Picual | Spain | herbaceous and fruity |
Mission | California | Usually eaten as a table olive! But, its oil is delicious: bitter and herbaceous. |
That’s just a tiny sample; other varieties to watch out for are picudo, arbequina, hojiblanca, leccino, maurino, moraiolo, taggiasca, koroneiki… the list goes on and on and on.
So why are different varieties associated with different regions?
Part of the story is environmental. For example, some places freeze, and only certain olive varieties can withstand that. But that’s not the whole story. Were Italian and Spanish tastes also different? And, if so, did their tastes inform a cuisine that demanded a particular kind of olive oil… or did the olive oil come first, and help form the cuisine?
It’s difficult to find answers to these questions. Italy’s olive oil is bitter; Spain’s is fruity; and those traditions—those expectations—run deep. One of the exciting things about olive oil in California is that there aren’t really any expectations—not yet. So, we can pick and choose, sample and select.
That’s not to say we don’t have a lot to learn from Italy and Spain, not to mention Greece, Tunisia, and Turkey. But, untethered from tradition, we also have unique opportunities to explore and inquire.
Understanding biophenols
Biophenols are the complex organic compounds—a whole bouqet of them, some unique to olives, like oleocanthol—that produce the burn at the back of your throat when you taste extra virgin olive oil. They also produce powerful effects in your body.
These compounds are, even after decades of study, rather mysterious; scientists don’t know how exactly they interact with each other, or exactly how they act on the body. But, at this point, there is a strong consensus that they DO act, and powerfully. We’ll discuss that below.
It’s important to say: ONLY virgin olive oil has biophenols. If it doesn’t say “virgin” or “extra virgin” on the label, then the oil inside is refined, which means these compounds have been stripped away.
Even extra virgin olive oil loses its biophenols over time. They are antioxidants, which means they prevent the chemical process of oxidation. They’ll happily do that for your body, but, until they’re consumed, they do it for the oil, too! When extra virgin olive oil is exposed to heat, light, and air, its biophenols “sacrifice themselves” to protect it.
Biophenol levels are measured in milligrams per kilogram; a level in the 100s would be considered low, while levels over 300 are considered high.
Extra virgin olive oils go even higher—Fat Gold has milled some with more than 600 mg/kg—but, as the biophenol level increases, there’s a risk the oil will be unbalanced: all burn and no fruit, a pungent medicine.
Olive oil in the body
Extra virgin olive oil has tremendous, broad-spectrum health benefits. We tend to be cautious here, because the mechanisms aren’t totally understood… but, at this point, there is no debating that the benefits are real, and, in some cases, profound.
One of our favorite sources is Dr. Mary Flynn, an associate professor of medicine at Brown University. In presentations, she often shows a slide listing the health benefits that have been demonstrated in peer-reviewed studies.
Extra virgin olive oil has been demonstrated to:
- decrease blood pressure
- increase HDL (“good”) cholesterol
- decrease the oxidation of LDL (“bad”) cholesterol
- decrease blood clotting
- decrease inflammation
- decrease the level of insulin in the blood
- decrease blood glucose
These benefits have consequences for health and longevity.
In early 2022, a group of researchers at Harvard’s T. H. Chan School of Public Health published a study looking at the diets of a very large cohort (~60,000 women, ~30,000 men) over nearly three decades, 1990-2018, along with their health outcomes.
Higher olive oil intake was associated with:
- 19% lower risk of cardiovascular disease mortality
- 17% lower risk of cancer mortality
- 29% lower risk of neurodegenerative disease mortality
- 18% lower risk of respiratory disease mortality
The Harvard study also includes this diagram, which is both a helpful overview of the potential mechanisms for olive oil’s health benefits AND a reminder that we don’t know exactly how it works:
It’s worth dwelling for a moment on the “healthy gut microbiota” cell included above. As we are all waking up to the importance of the gut microbiome for overall health, researchers are learning olive oil has a role to play. Here’s a passage from a study published in December 2021:
Extra-virgin olive oil affects the gut microbiota by reducing the abundance of pathogenic bacteria, stimulating the growth of beneficial bacteria, and increasing the production of microbially produced short-chain fatty acids (SCFAs), which exert a wide range of anti-inflammatory effects […]
As the research piles up, study after study, an overwhelming consensus emerges: extra virgin olive oil is really good for the human body, in almost every way you can imagine.
It’s almost preposterous that this substance, with all these benefits, also tastes delicious, and makes other things taste delicious. There’s literally no downside. Now that American culture has mostly recovered from the catastrophic anti-fat propaganda of the 1980s and 1990s, we can glug freely and, if we’re lucky, live a little longer, too.
Producing olive oil
Here, we’ll detail each step in the process of making olive oil. Remember: it’s fruit juice! So, you need to grow the fruit, harvest it, and squeeze it. Simple, right? Let’s begin.
Growing olives
One of the most important characteristics of an olive grove is the density of its planting.
At one end of the spectrum, there’s traditional spacing. This is your postcard grove on a scraggly hillside with a view of the Mediterranean. Before modern irrigation and fertilization, if your trees were planted too close together, they’d compete for water and nutrients. So, in a traditional grove, the gnarly old trees are spaced wide, 30 feet or so; they’ve been there a thousand years; your goats frolic among them.
Next, there’s medium density. Here, your trees are arranged in a wide-spaced grid, with about 18 feet between them. The small grove we managed in Sunol, California was planted in this way:
It’s nice! Olive trees can thrive in mediocre soil on rough terrain. Therefore, traditional or medium-density planting can be a way to get something good from challenging land, or even a hillside, that might not otherwise be productive.
Next: move the trees a little closer together, 8 feet or so, and you have high density. Here, the trees begin to resemble a single long hedgerow:
Finally, there’s super high density. Here, your trees are planted in very tight rows; they truly look like long hedges.
The upside is that you pack in much more fruit per acre, which means more oil per acre. Also, you can harvest the olives mechanically, with huge, over-the-row harvesters that swallow the trees, knocking the olives from their branches and catching them before they hit the ground. People often think of machines as being designed to fit a particular task, but in this case, it’s the other way around: these groves are designed to fit the machine!
For all these reasons, super high density planting has been key to the growth of California’s olive oil industry. But there are downsides, too:
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This style of cultivation is stressful on the trees, and diseases spread more easily through the grove.
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There are only a few olive varieties that flourish when planted this way: arbequina, arbosana, and koroneiki. So, when you find a bottle of California extra virgin olive oil on the shelf in a grocery store, odds are good it’s one (or a blend) of these varieties.
Harvesting olives
Olives can be harvested many different ways; here at Fat Gold, we’ve tried most of them. The choice depends on the kind of planting (described above), the farm’s own infrastructure, and the availability of skilled harvesting help.
You can harvest olives with
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your hands, using small plastic rakes to pull the olives off the branches onto fine mesh nets laid below.
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powered rakes, which have long, vibrating tines that reach in and knock the olives from the branches.
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pistachio shakers, which we’ll show you below.
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over-the-row harvesters, which can only be used in high-density groves.
Here’s Robin with one of the powered rakes. Watch your fingers!
Here’s a glimpse of the pistachio shaker, a clever, two-part machine that surrounds a tree and… shakes the hell out of it!
The olives come rocketing off, collected by a broad conveyor belt, dropped into a bin:
Regardless of how the olives are harvested, the moment they come off the tree, the clock starts ticking. It is an olive oil maker’s responsibility to keep them cool—so they don’t start to ferment—and keep them moving. The sooner you can get your olives into the mill, the better.
Milling olives
In the old days—the very old days—olives were crushed under a stone wheel, and the resulting paste pressed between woven mats; this is the etymology of the term “cold-pressed.” Here’s a rendering of those mats, circa 1600:
Olive oil hasn’t been produced in this way since the mid-20th century, when mechanical crushers and centrifuges took over. Although the image of a stone wheel is evocative, we don’t think there’s any reason to lament the passing of these tools: modern olive oil has better taste, healthier properties, and a longer shelf life than anything produced in centuries past.
(One of the implications of this evolution: “cold-pressed” isn’t really a meaningful term anymore.)
Now, we’ll walk you through a modern mill visually.
These snapshots were all captured at Frantoio Grove, the terrific olive oil maker in San Martin where Fat Gold has milled our olives many times. For reference, this mill would be considered small; there are others where each of the machines you see below is the size of a large truck.
First, the olives are washed, cleaning off any dirt as well as loose leaves.
Sometimes we stand and watch them go—our last glimpse of the olives we worked so hard to harvest!
Next, the olives go into the crusher.
Olive oil makers use a couple different versions of this machine, and the choice between them has an outsized impact on the characteristics of the finished oil. Even though this crushing step is very brief, a large fraction of an olive oil’s aromas are created in this moment: a kind of Big Bang.
Today, most modern mills use hammer crushers, which smash the olives against a stainless steel grid. The friction of the hammers raises the temperature of the olives 8-10 degrees F; this burst of heat kicks off enzymatic reactions inside the pits that, in certain olive varieties, produces undesirable flavors and aromas.
There’s a newer kind of crusher that uses slicing blades rather than smashing hammers. This gentler treatment produces less heat, so there’s less danger of those unwanted enzymatic reactions kicking off, and less danger of unpleasant bitterness.
The crusher shown here uses hammers, smashing the olives against a fine steel grate; all of this is hidden inside the machine’s sturdy enclosure:
The crusher produces a paste that flows into the malaxer. This is a crucial step in the process. In the malaxer, oil droplets coalesce, and other compounds leach out of the olive flesh, into that oil: aroma volatiles, flavor compounds… and biophenols!
Control is crucial. The paste can stay in the malaxer anywhere from five minutes to an hour, at anywhere from 67 to 80 degrees F. If you malax too little, you leave most of the oil behind, and the oil you do get isn’t very flavorful; malax too much, and you “cook” the oil, possibly ruining it before it’s even emerged from the mill.
After the paste has spent some time in the malaxer, and the oil particles have begun to coalesce, it’s sent onward to the decanter. This is a centrifuge, which does That Thing Centrifuges Do: separate components of a mixture with different densities, using centrifugal force to push them to different regions of the giant spinning mass.
Out of the decanter, the solid part of the paste—called the pomace—flows one way (exiting the mill) and the liquid flows another. This offers the first glimpse of the oil. The friction in the centrifuge heats it up; if you’re milling right, this is the hottest the oil will ever be in its whole lifetime.
The liquid that emerges from the decanter still has a lot of water in it, so it’s helpful if it can flow next into a separator, another centrifuge, this one oriented vertically, that spins twice as fast as the decanter and pulls the oil away from the water. This is similar to a machine used in the dairy industry to separate milk from cream.
The separator offers the first opportunity to sneak a taste… and we always take it.
Filtering olive oil
Olive oil comes out of the centrifuge cloudy—the oil is mixed with water, and tiny particles of olive flesh, too. As an olive oil maker, you can either wait for that haze to settle, pulled down by gravity, and then pump the clear oil off the top—a process known as racking—or you can send the oil through a filter to get it crystal-clear immediately.
Racking takes time, but customers want fresh oil immediately, so, olive oil makers have traditionally sold some of their oil still hazy. Italians call this offering olio nuovo, new oil, a term that’s now commonly used in California, too. Olio nuovo tends to feel a little heavier in the mouth. (For the beer drinkers: it’s like a hazy IPA.) And, because those tiny particles of flesh and water are eager to start fermenting, it’s much more perishable than racked or filtered oil. You’ve got to use olio nuovo quickly.
Another approach is more direct, and much faster, than racking. When you filter your oil, you run it through a series of dense cellulose plates. They catch the olive bits and, most importantly, absorb the water. The olive oil that emerges is clear and brilliant.
The filter is a relatively new addition to California olive oil production. The series of cellulose plates looks like this:
The filter’s effect is immediately visible. Here’s Kathryn with a sample of oil, directly before and after filtering:
We’ve heard that Italian olive oil makers call their filtered olive oil brillante, and looking at this oil, you can see why:
Using olive oil
Storing olive oil
Here’s the bargain you strike with a maker of extra virgin olive oil: they pledge that their product is pristine; from that point onward, the responsibility to keep it tasty, and healthy, is yours.
As an olive oil consumer, your enemy is rancidity.
Waking up to rancidity
This was Kathryn’s gateway into olive oil.
She was studying at the University of Gastronomic Sciences in Northern Italy, where she dug deep into the production and consumption of wine, beer, cheese, chocolate, coffee, charcuterie… and, of course, extra virgin olive oil.
During a field trip to visit the Tuscan olive oil maker Frantoio Franci, Giorgio Franci offered Kathryn and her classmates a taste. “Oh, yes,” the Americans all said, nodding, “tastes like olive oil.”
“Well,” Franci replied, “that’s rancid olive oil.” These were burgeoning master eaters—really, food experts already—and they hadn’t been able to tell the difference. Kathryn was mortified; so mortified, in fact, that she spent the rest of the year focused on olive oil, and eventually wrote her master’s thesis about its production.
Like Kathryn and her classmates, you’ve imbibed rancid olive oil without realizing it. You’ve probably consumed a lot of rancid fat in many forms, unfortunately. Once you learn to taste it, you’ll find it often in bags of chips and boxes of crackers.
Rancid oil tastes oilier than fresh oil. It coats your mouth and lingers, rather than finishing cleanly. Its smell is a giveaway: something like plastic, even crayons. If you’ve ever eaten a spoiled nut, that’s also a good comparison.
What is rancidity?
As olive oil is exposed to air, heat, and light, its long fatty acid chains break apart and the oil begins to oxidize, creating peroxides. Over time, these peroxides break down into little molecular shards that don’t smell or taste good. That’s how fresh olive oil turns rancid.
The remedy is clear.
- Oxygen is bad, so: always put the cap back on your olive oil.
- Heat is bad, so: don’t store any olive oil in direct sunlight or near your stovetop.
- Light is bad, so: always buy olive oil packaged in very dark glass or, even better, an opaque tin.
Occasionally, you’ll find olive oil in a plastic container; these are opaque, which is good, but plastic breathes, which is bad. Opaque glass or tin are the best storage options.
None of this will save your olive oil in the long run. Rancidity is the fate that awaits even the best of the best, stored in pristine conditions. So, there’s an additional principle that applies to the care of extra virgin olive oil:
- Time is bad, so: use it up!
How much time do I have?
It depends on the oil: how it was made, how it was stored by its maker, and the level of biophenols (which slowly declines over time, as these antioxidants sacrifice themselves to stave off rancidity).
Here’s a very general guide:
Before opening, high-quality extra virgin olive oil will be good for at least two years after its production.
After opening, high-quality extra virgin olive oil will be good for three months in its container—assuming you follow the guidelines above.
Cooking with olive oil
We have a stockpile of recipes and ideas over here!
What about the smoke point?
This is probably the most common objection to cooking with olive oil: the idea that it can’t handle the heat, and above 400 degrees F will start to burn, producing smoke, along with bad flavors and unhealthy compounds.
But… a lot of people (including the authors of this guide) cook every night with extra virgin olive oil… and they will confirm that this is not actually an issue.
First: just because you’re cooking a dish in an oven set to 400 degrees F doesn’t mean every molecule in the dish reaches 400 degrees. If that was the case, your dinner would scald you every night! In practice, the olive oil coating your food rarely reaches its smoke point.
Second: quality matters. Olive oil that’s not extra virgin, low on biophenols, and/or stored carelessly will smoke and degrade much more readily than a high-quality extra virgin olive oil.
And the smoke point is not always synonymous with degradation; all smoke points are not made equal. A lab in Australia reports (PDF):
Extra virgin olive oil (EVOO) and other common cooking oils were heated up to [460 degrees F] and exposed to [350 degrees F] for 6 hours, with samples assessed at various times, testing smoke point, oxidative stability, free fatty acids, polar compounds, fatty acid profiles and UV coefficients. EVOO yielded low levels of polar compounds and oxidative byproducts, in contrast to the high levels of byproducts generated for oils such as canola oil.
Translation: extra virgin olive oil produced less unhealthy gunk than canola oil at the same temperature, all the way up through both of their smoke points.
Are there a few cooking scenarios where an oil other than extra virgin olive oil is a better choice? Sure. But those are rare and specific.
Outside those exceptions, extra virgin olive oil should be your everyday cooking oil, whether you’re baking or roasting or frying. Olive oil tastes better than refined cooking oils, and it brings a whole host of health benefits to every dish. Those health benefits are reduced when the oil is heated, yes—but not eliminated. Food absorbs the olive oil, before and during cooking, so plenty of those biophenols get soaked up and delivered to your body.
Put simply: extra virgin olive oil is too good not to cook with.
The end, for now
That concludes the Fat Gold Guide to Extra Virgin Olive Oil! Whether you read this document straight through or treated it more like a buffet, we hope you feel a little more knowledgeable and confident now than when you started.
This is a living document, constantly being updated. If you’ve spotted any errors or omissions, please let us know at robin@fat.gold.
If you take away only a few things, let them be these:
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Extra virgin olive oil is the fresh juice of the olive, as flavorful and perishable as that implies.
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Extra virgin olive oil’s health benefits are profound, and the fact that it also tastes so good—and makes everything else taste so good—is almost absurd.
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Extra virgin olive oil is not for hoarding: use it up!
–Robin, Kathryn, and Bryan