When chefs create a dish, they don’t just think about its flavor. Among the factors they consider, texture plays a huge role. Texture is what makes food appealing or not — think of the difference between a boiled chicken breast and a crispy fried cutlet.

Research recently published in Scientific Reports reveals the extent to which texture can make or break our enjoyment of a food — and how the tongue can feel out those differences in the first place.

"This may have implications for parents of picky eaters, since texture is often a major reason food is rejected."

In the study, Penn State University researchers show that the human mouth is especially sensitive to texture because of its ability to detect differences in pressure.

Researchers used varying textures of chocolate to illustrate this point. A group of 111 volunteer tasters went through two tests: The first group -assessed their tongue’s sensitivity to texture, and the second involved attempts to eat gritty chocolate.

They hypothesized that some people are more sensitive to texture than others, much as some people are more attuned to taste and smell.

“It has been argued that texture is not typically noticed when it is within an acceptable range, but that it is a major factor in rejection if an adverse texture is present,” write the researchers in the study.

In other words, we don’t notice texture often, but when we do, it has a big impact on our eating experience.

“We’ve known for a long time that individual differences in taste and smell can cause differences in liking and food intake — now it looks like the same might be true for texture,” says co-author and food science associate professor John Hayes, Ph.D. “This may have implications for parents of picky eaters since texture is often a major reason food is rejected.”

The researchers found a link between a person's sensitivity to pressure and their ability to discriminate between gritty and fine chocolate. Unsplash / Charisse Kenion

Researchers used a weird device known as Von Frey Hairs — imagine toothbrushes, each with a single bristle of varying thickness — to show that some people are better at discriminating between different amounts of pressure on their tongues. Texture, they explain, all comes down to the interaction of food with the tongue’s mechanoreceptors, which are stimulated by pressure.

Then, they had the volunteer tasters try six different kinds of chocolate, all custom-made in their lab. While the ingredient lists were constant for all types, the size of the particles within each chocolate differed, ranging from 30 to 80 micrometers in diameter (most commercial chocolate, they point out, contains particles with diameters 30 micrometers or less, so it was pretty gritty stuff). They repeated the experiment with two commercially available chocolates: Scharffen Berger Bittersweet Dark (fancy) and ChocoLove Strong Dark (not as fancy).

Von Frey Hairs were used to test a person's ability to discriminate between varying pressures. Nicole Etter/Penn State

Chocolate, as we know it, is a suspension of ground-up cocoa and sugar dispersed in a whole lot of fat, and less expensive types generally have coarser particles than the smoother, more expensive ones. The team hypothesized that the people who were better at detecting differences in the Von Frey Hair test would also be better at distinguishing between the chocolates of varying grittiness. They were mostly right.

People who had “high acuity” in the Von Frey Hair tests on the center of the tongue were significantly better at discriminating between chocolates. The same, however, couldn’t be said for people with high acuity on the lateral edges of their tongues.

These results are some of the first pieces of evidence showing a link between a person’s ability to perceive pressure and their sensitivity to gritty chocolate, a proxy for particle size.

Preference for different textures varies across cultures. In Chinese cuisine, gelatinous and cartilaginous textures are more common than they are in Western cuisine, such as in the chicken feet at center. Unsplash / Van Thanh

It’s useful information for chocolatiers, who probably shouldn’t be scrimping on particle size if they want to keep their customers, but it’s a helpful reminder for food enthusiasts as well. Texture isn’t something we notice often as smell and flavor, but when we do, it’s a big deal, so it’s worth paying attention to. The late, great chef Anthony Bourdain was attuned to these variations in texture and cultural attitudes toward them, noting in a discussion on the gelatinous and cartilaginous textures in China’s cuisine: “That resistance, that boing, that rubberiness, elasticity—it’s kind of the last frontier for Western palates.”

Though individual tongues may be naturally more or less sensitive to textures, it’s worth remembering that our enjoyment of textures remains open to change.

Abstract:

Texture affects liking or rejection of many foods for clinically relevant populations and the general public. Phenotypic differences in chemosensation are well documented and influence food choices, but oral touch perception is less understood. Here, we used chocolate as a model food to explore texture perception, specifically grittiness perception. In Experiment 1, the Just Noticeable Difference (JND) for particle size in melted chocolate was ~5 μm in a particle size range commonly found in commercial chocolates; as expected, the JND increased with particle size, with a Weber Fraction of ~0.17. In Experiment 2, individual differences in touch perception were explored: detection and discrimination thresholds for oral point pressure were determined with Von Frey Hairs. Discrimination thresholds varied across individuals, allowing us to separate participants into high and low sensitivity groups. Across all participants, two solid commercial chocolates (with particle sizes of 19 and 26 μm; i.e., just above the JND) were successfully discriminated in a forced-choice task. However, this was driven entirely by individuals with better oral acuity: 17 of 20 of more acute individuals correctly identified the grittier chocolate versus 12 of 24 less acute individuals. This suggests phenotypic differences in oral somatosensation can influence texture perception of foods.