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​The Flavor Brief​

A weekly letter about food, science, and why things taste the way they do

​Read Past Newsletters​

​Season 2 of Flavor Forward is live on YouTube. Watch the premiere here.​

Hi Reader

Pick up a piece of good cheese and eat it slowly. There's something happening in your mouth beyond the salt, beyond the sharpness, beyond the smell. Something harder to name. For most of culinary history, we assumed that something was texture. Scientists assumed the same thing. Then, in 2010, a nutrition researcher at Purdue University named Richard Mattes started asking whether the tongue might actually be tasting the fat itself.

He called the idea oleogustus, from the Latin for oil and taste. Not the richness, not the mouthfeel, not the aroma. The taste.

Most of his colleagues were skeptical. Fat, the thinking went, worked on flavor through two pathways: it dissolved and carried aroma compounds to your nose, and it created the physical sensation of creaminess or coating. That it might also register on the tongue as its own distinct signal was a harder sell.

In 2015, his team published the study that changed the conversation. They gave 102 people cups of solution representing each of the five known tastes, sweet, sour, salty, bitter, and umami, plus one containing fatty acids, with texture, odor, and appearance all controlled so the only variable was taste. People found it easy to identify sweet, salty, and sour easily. The fatty samples were initially grouped with bitter, which makes sense: bitter is the word we reach for when something tastes unpleasant. But when participants were asked to sort bitter, umami, and fatty separately, they could do it. Fat had its own perceptual identity. Something was happening on the tongue that didn't fit any existing category.

Here's the part that surprises most people: oleogustus in its pure, isolated form is not a pleasant taste. It reads closer to rancid. Scientists think it may have evolved, like bitterness, as a warning signal to steer us away from spoiled food. The fat we love in a well-marbled steak or a glossy pan sauce is a whole system working together: aroma, texture, and taste in concert. Pull them apart and the taste component alone is almost unrecognizable.

Since 2015, the receptor biology has become one of the most active areas in taste research. A protein called CD36, found on taste bud cells, appears to be the primary detector for long-chain fatty acids. And it turns out not everyone's CD36 works the same way. A single genetic variant determines how sensitive you are to fat taste. Some people need a much higher concentration of fatty acids before they register anything at all. Others pick it up at very low levels. Researchers have now identified 24 genetic variants across 15 genes linked to how we perceive fat, which begins to explain why two people can eat the same dish and have genuinely different experiences of how rich or how satisfying it feels.

A recent twin study added another wrinkle: how much fat you habitually eat may reshape your sensitivity more than your genes do. Eat a high-fat diet consistently and your threshold shifts. Your tongue, in other words, is not fixed. It adapts.

The most recent frontier involves hormones. Research published in early 2025 found that adiponectin, a hormone tied to metabolism, influences fat taste sensitivity through receptors on taste bud cells, and does so differently depending on sex. The biology keeps getting more complicated. What started as a simple question, can we taste fat, has opened into something much larger about appetite, genetics, hormones, and how the body regulates what we want to eat.

Oleogustus has not yet been officially recognized as the sixth basic taste. The bar is high: a chemical stimulus, specific receptors, a signal to the brain, conscious perception, and measurable physiological effects. The evidence is building on all five counts. It isn't there yet, but it's closer than it has ever been. I even included it as a separate chapter in The Flavor Equation cookbook.

Which brings it back to the kitchen. Because whether or not oleogustus earns its place on the official list, the practical reality is the same: fat is doing something in your mouth beyond coating it. It's signaling. It's part of the taste experience, not just a vehicle for it.

That's the question I wanted to bring into Season 2 of Flavor Forward on YouTube with America's Test Kitchen. Not "fat is flavor" as a chef's shorthand, but what that actually means at the molecular level, and how understanding it changes the decisions you make at the stove. I made duck fat-roasted potatoes and South Indian lemon peanut rice -- chitranna, two dishes that show two different ways fat functions as a flavor tool. If the science above got you thinking, the episode is where it lands in a real kitchen.

Watch: Flavor Forward Season 2, Episode 1

Does Fat Equal Flavor?

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COMING SOON

Fundamentals of Flavor is available for preorder now — this one has been six years in the making and I'm genuinely proud of it. If you've been cooking with me for a while, this book is for you. Preorder Now →

I hope this episode makes you think differently about every fat in your pantry.

Nik