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It is hard to think about the foods we love, or the ones to which we are averse, without considering texture. Would you relish a powdery apple, or congealed oatmeal? Soggy popcorn? You might eat it, sure, but would you enjoy it?
When we describe food to others, texture often holds as much importance as flavor. There is huge variation in the language we use to describe what we eat: crispy, soft, creamy, dry, lumpy, smooth, sticky, chewy, fibrous, crumbly, tough. The possibilities are endless, along with differences in our individual preferences. While the texture of a slippery, un-caramelized mushroom gives my gag reflex a good workout, it might be your bag.
Texture is determined by sensory receptors in the mouth, as well as the noise the food makes as we chew it. However, even though the physical properties of food can be scientifically measured (an area of study known as rheology), texture is a highly subjective concept. In his book Food Texture and Viscosity, Concept and Measurement, the late Dr. Malcolm. C. Bourne, emeritus professor of food science at Cornell University, wrote: “Texture is a human construct.”
Our personal sensitivity to texture is the product of experience and expectation; our individual memory bank of food memories and how things “should” be. “If you are expecting a crunchy Dorito and, when you bite into it, it is just limp, you’ll be upset,” says Dr. Stephanie Bull, a senior lecturer in the Department of Food and Nutritional Science at Reading University. “We have learned experiences of what we expect particular foods to be. We expect certain textures and, if a food matches our expectation, we are happy.”
Perhaps this is why unexpected textures can be so confounding: We have no reference point. Yet, food behaving differently than we expect it to can also be exciting. When I worked at Observer Food Monthly, which appeared in the Guardian newspaper’s Sunday edition, I had the privilege of eating at some very fine restaurants. I remember going to Dinner by Heston Blumenthal and having the infamous, trompe l’oeil Meat Fruit dish: a chicken liver and foie gras parfait set in mandarin orange jelly, resembling a perfect, plump mandarin. My brain told me I was cutting into, and about to eat, a citrus fruit. Instead, I half-chewed a rich, smooth parfait that tasted of Medieval decadence and I wanted to squeal.
How something feels in the mouth is often secondary to flavor when it comes to foods that unsettle us. “Texture seems to be the key sense in determining our food dislikes,” says Dr. Charles Spence, a Professor of Experimental Psychology at Oxford University. He has worked with chefs like Heston Blumenthal and Jozef Youssef to bring elements of sensory science into restaurants. With his team at the Crossmodal Research Laboratory, Spence has developed a line of scientific inquiry called gastrophysics: the study of the variables that affect how we experience food and drink. “It is the science of the perception of food,” he says. He won the Ig Nobel Prize for his 2014 “sonic chip” experiment that, in essence, showed that loud chips taste better. Increasing the volume of the sound of crunch, via headphones, while eating Pringles made participants believe they were 15 percent crunchier and fresher. He has also shown that people give fizzy drinks higher ratings when the sound of the bubbles popping in their mouths is loud and fast.
Spence believes there may be an evolutionary function to enjoying, or disliking, particular textures, that echoes our primitive ancestors’ reliance on foraging the natural world for sustenance. Slimy foods like tapioca, oysters, seaweed, and okra can make some people squeamish, especially if they didn’t grow up eating those foods. “There may be a primitive thing about the state of foods and their likelihood of being safe or nutritious,” says Spence. “Slimy is a texture often associated with foods that have rotted or gone off, so it seems plausible that we might try to avoid them.”
Of course, these textures are celebrated in some cuisines. Deliciousness feels different across the globe. In Japan, for example, there is a term for the texture of prized slimy foods: neba-neba. Some key examples are natto (fermented soybeans), seaweeds, tororo (grated mountain yam), and the glossy-capped nameko mushrooms that are often added to miso soup.
Some globally beloved textures, like crunchiness, may speak to the brain detecting something that will be nutritionally beneficial to the body. “In terms of assessing freshness, the ‘crisp button’ in our brains is one that is meant to be pushed,” the neuroanthropologist and research scientist John. S. Allen writes in his book The Omnivorous Mind: Our Evolving Relationship with Food. He explains how, for our insect-eating ancestors, the crunch of a cricket’s exoskeleton denoted nourishment: “Our preference for crispy may have originated with insects and fullback plant foods, but cooking makes different foods crispy and moved that preference into the centre of our diet.”
It is hard to imagine a texture that invokes as much universal delight as crispiness. “The appeal of crispy food appears, like our inalienable rights to life, liberty, and the pursuit of happiness, to be self-evident. Everybody seems to enjoy crispy food,” Allen writes. Even the word “crispy,” onomatopoetic and evocative of good pie crusts, tempura, French fries, potato chips, and other delights, sells.
Why are crispy and crunchy foods so gratifying? Eating is a multi-sensory experience. One of the key senses is proprioception (also called kinaesthesia); our body's ability to sense movement and location. Proprioceptive sensations are interesting because we are largely unaware of them. They are there in every muscle movement we have: when we unconsciously know how to place one foot in front of the other as we’re walking; when we bring a fork toward our mouth and it doesn’t end up piercing our cheek. The jaw is teeming with proprioceptors, which give the brain a lot of sensory information when we eat. This rich experience can be both stimulating and grounding. For children with sensory processing difficulties, the proprioceptive system can be exercised with crunchy foods that provide a lot of sensory input.
Crunching means making noise inside the mouth, which may also be part of the evolutionary appeal of crunchy foods. “Fresh fruits and vegetables tend to make more noise and preserve more nutrient content, but that wouldn’t explain our desire for snack foods, which also tend to be noisy; chips, cookies, nuts, and so on,” says Spence. He has “yet to prove” the theory, but wonders if crunchy foods are so appealing for modern humans because they often signal a high fat content that our big, energy-hungry brains crave. “The brain loves fat,” he says.
As I write, I am eating from a bag of chipotle-flavored tortilla chips. My skull rattles as I move the crisp shards around my molars. The flavor never weakens. After swallowing one, I’m ready for another, reaching into the bag in a trance-like state. Then the bag is mysteriously empty. I am greedy, but this would not happen with a bag of spinach. I notice how the flavor keeps singing. “The sound of crispy foods seems to make flavor last longer as we eat them,” Bull explains. When we hear what we’re eating, the entire process is more stimulating. We want more. “The force you put into your jaw is fed back to the brain, along with the sound of chewing and the vibrations of the skull. This feedback loop stops you becoming habituated to the texture.”
Bull notes that some people with auditory loss “report texture as being less intense,” but also that, even with age-related decline in dental health or ability to swallow, the feedback systems that can detect texture “are still in place.” When eating function deteriorates in elderly people, it can be necessary to introduce a texture-modified diet of soft foods, often in puréed form. A purée does not emit much sound in the mouth, which may impact satisfaction.
At the root of our enjoyment with crispy, crunchy, or chewy textures is the simple fact that chewing itself is pleasurable. “Chewing is an enjoyable sensory experience that gives great satisfaction. It is one of the few sensory pleasures that lasts from the cradle to the grave,” Bourne wrote in Food Texture and Viscosity, Concept and Measurement. Chewing increases blood flow to the brain. More blood means more oxygen and energy, which makes the brain perform better. A large Swedish study in 2012 found that elderly people who could chew hard foods had lower risk of cognitive impairment.
It is a cruel trick of nature that our ability to appreciate texture may not decline along with our physical ability to eat. In 2016, a group of Japanese researchers investigated whether the perceived sensations of nursing care foods could be changed by providing auditory feedback. Thirty adults took part in the experiment. For half the participants, researchers used an electromyogram (EMG)—an instrument that records the electrical activity of muscles—to detect activity in the masseter (the prominent muscle of the jaw) and played crunchy chewing sounds while they ate. Participants were asked to rate the taste, texture, and feelings associated with the puréed food. For those who had been played the chewing sounds, the food was perceived as “rougher” and having “a greater number of ingredients” than it was by those who ate normally, and the former group also rated their satisfaction as greater. Considering this effect, a tool for helping people on soft diets enjoy their food more could be a kind addition to elderly care.
Although food with one-note texture can quickly become boring, our preferences may be cultural. Some cuisines put particular textures at center-stage. In East and Southeast Asian food traditions, chewiness is highly appreciated. (In Taiwan, the springy, elastic texture is known as “Q”; equally cherished as al dente to Italians.) Think sticky rice; mochi; udon noodles; tapioca balls in boba tea; tripe or tendon dishes. In many cuisines around the world, creating texture differences in dishes is important. The north Indian dish of tarka dal involves whole spices like mustard and cumin seeds being fried in a liberal amount of oil or ghee, to be drizzled over the dhal before serving. In Japan, crunchy preserved vegetables (tsukemono) are a common accompaniment to meals—particularly rice dishes. Tender Mexican tacos al pastor come with firm, finely diced raw white onion, while soft, rich carnitas are anointed with crisp, pink pickled onions. Even the West’s love of chips and dip speaks to the inherent satisfaction of contrasting textures on the palate.
The pleasure of crispy, crunchy textures may be universal, but certain textures remain polarizing. Tripe is a popular dish in continental Europe, Central and South America, and many Asian countries, but people who hate it really hate it; unable to get past the slippery-yet-tough mouthfeel. For me, the texture isn’t the problem; the honeycomb appearance, however, triggers my trypophobia and is a psychological barrier. When I spoke to Spence, he mentioned jellyfish as an ingredient scientists are encouraging more people to get behind, given concerns over the depleting resources of our seas. Jellyfish are abundant and murderous. Large blooms have shut down nuclear power stations. They are highly sustainable: Even if you remove one jellyfish from the sea, new ones will keep being born because they spawn from polyp colonies attached to the ocean floor. But could the texture ever have mass appeal to those who didn’t grow up with it?
Jellyfish is popular across Asia, particularly in China, Korea, Taiwan, Vietnam, and Japan. It’s often sold dehydrated, then marinated and served cold in refreshing, spicy salads. With little inherent flavour, it serves as a vehicle to whatever seasonings are added. “Jellyfish has no taste—it is pure texture,” says Spence. Unsurprisingly, he conducted an experiment in 2019 that showed how “multi-sensory experience design” may nudge people toward sustainable ingredients they are not accustomed to. Spence worked with chef Josef Youssef, who created a cold cucumber gazpacho dish that was muddled with marinated jellyfish. The dish was placed on a table that had an underwater scene mapped onto it as crunching noises were played to diners through headphones. The response from diners was “uniformly positive,” according to the study’s conclusion.
Overcoming texture aversions may be key as we have to adapt our diets to being led by more sustainable ingredients. We need to eat less meat and more vegetables to mitigate climate change. If you are averse to certain vegetable textures, slow, steady exposure might help. But while the pandemic continues, with life feeling up-in-the-air for so many of us, it is important that we hang onto the pleasure of food—of which texture is key. Enjoy the sonic assault from your bag of chips. Savor the crisp skin of a baked potato. Notice the sensory overload of a crunchy, juicy pear. The world may feel in flux, but a good, noisy chomp is one of the simplest grounding tools we have.
