Growing up, we all learned the four flavors — salty, sweet, sour, and bitter. That’s the way it always was, and that’s the way it was always going to stay. Then, in 1990, umami was officially recognized as the fifth distinct flavor, solidifying the five-taste canon we have today. In 2015, though, whispers of a coming change, that stood to once again upend what we thought we knew, began. The talk centered on a possible sixth flavor being identified with a strange name, oleogustus. So, what’s the status of this new taste, and what exactly is it?

What is Oleogustus?

We’ll start with the easy explanation: what is oleogustus? The translation of the name, chosen by the discoverers from Purdue University in 2015, tells us basically everything we need to know. Oleo comes from Latin meaning oily or fatty, while gustus translates to taste. Together, they mean oily or fatty taste, and that’s exactly what it is. This new taste could be described as a fatty flavor. Now, this isn’t exactly the fatty flavor you’re thinking — the rich, creamy pleasure of a buttery sauce or fatty fried food. That flavor you’re thinking of is actually a mouthfeel as a result of triglycerides in the food that impart to our brains that they’re high in calories. Instead, high concentrations of oleogustus flavor tend to be a bit unpleasant, having a rancid taste at high levels.

Fatty taste was thought to have been a composite of other flavors, often grouped under bitter since bitter is a bit of a catch-all flavoring for unpleasant tastes. Since taste is essentially just a message to our brains about the nutritional value or dangers of a food, oleogustus is similar to the other unpleasant tastes like bitter and sour in that high concentrations of these flavors are meant to act as a warning to our primitive brains to not eat it.

The researchers noted that the fatty taste can taste good in the right amounts, much like how a little bitterness enhances the flavors of wine or dark chocolate.

That isn’t to say oleogustus is completely without value. The researchers noted that the fatty taste can taste good in the right amounts, much like how a little bitterness enhances the flavors of wine or dark chocolate. This is where the balance of flavors becomes important to the tastiness of a dish.

What’s the Science Behind This Discovery?

The characteristics of a primary taste are fairly ill-defined, but generally, they need to fit a few basic criteria.

  • The stimulus (taste) should have a unique chemical structure;
  • The stimulus should interact with a unique receptor;
  • The stimulus should be carried by taste nerves to the central nervous system;
  • The stimulus should have a unique function.

There is also a general agreement that people should be able to distinguish it from other tastes. Prior to the Perdue University study, researchers had been able to identify the chemical criteria of fat, but having test subjects distinguish the taste had eluded them to that point. In order to test for this, the researchers at Perdue University asked the study’s participants to put flavored solutions into taste groups based on similarity. Other factors that could influence the participants’ picks — such as texture, appearance, and smell — were controlled.

The initial overlap between bitter and fatty was explained by the vernacular use of bitter to mean a general unpleasant taste.

While there was some overlap found in groupings of some forms of chemical taste, identified as nonesterified fatty acids and other tastes (specifically bitter), further tests showed a clear distinction between the two. The initial overlap between bitter and fatty was explained by the vernacular use of bitter to mean a general unpleasant taste.

What Now?

This all may leave you with two burning questions: What does this information mean for you, and will we have to start learning six tastes? In terms of officially being considered one of the fundamental tastes, maybe not yet. It can take a long time for a taste to be widely accepted into the group. For example, umami was first discovered in the early 1900s and took nearly a hundred years for it to be officially recognized. While the science may be currently backing idea of a sixth taste, it may still need some time and more research before oleogustus is officially welcomed into the group.

If you understand the workings of a sensory system, you can use them for purpose. — Richard Mattes, Professor of Nutrition Science at Purdue University

It does have promising implications for our understanding of taste and flavor, which can have a wide range of benefits. “If you understand the workings of a sensory system, you can use them for purpose,” said Richard Mattes, a professor of nutrition science at Purdue University, in one of his studies on the subject. “Whether that’s to improve the quality of the food supply, the safety of the food supply, reduction of cardiovascular disease, treat taste disorders, there are any number of possibilities.”

One of the promising outcomes of these findings would be the ability to create imitations of low-fat foods, similar to how we’ve mimicked salt, sugar, and even umami. The current strategy for making low-fat foods has largely been to imitate the mouthfeel of fat, but it has largely been unsuccessful in reflecting the flavor. This is partially why low-fat foods may be unsuccessful in fully replicating (and thus replacing) full-fat foods in a low-fat diet.

● ● ●

As our understanding of taste continues to grow, we can use this to make food taste better and be healthier. While we may not be able to officially add oleogustus to the pantheon of primary tastes yet, it’s an interesting finding that is worth keeping an eye on as we continue to research and learn more.