Texture is the final frontier of food science
Many food aversions are not about taste but texture. Compared to our rich vocabulary for foods’ flavour, the culinary glossary for food tactility is thin. A lemon, for example, might be described as acidic, tangy, citrusy, or sour—but how does that lemon feel? As eaters, we tend to downplay texture’s importance.
A 2002 study in the Journal of Sensory Studies found that texture lagged behind taste and smell—and only occasionally beat out temperature—in terms of the perceived impact on flavour.
But you only have to look at pasta to see how strongly texture impacts our perception of taste. We’ll eat macaroni and cheese in the form of spirals, shells and noodles, but spaghetti mixed with fluorescent “cheese” powder seems anathema—it’s the texture that makes the difference.
For the longest time, food scientists downplayed texture’s importance as well. “When I was a student pursuing a degree in food science, I was taught that flavour was a combination of mainly taste and smell,” recalls Jeannine Delwiche, one of the authors of the 2002 study.
But how a food feels affects our enjoyment of the thing. There is, of course, the actual texture of the food, which scientists call rheology. Rheology focuses on consistency and flow.
For example, it’s fairly evident that cotton candy has a different texture than plain sugar, even though sugar is its only ingredient. But the perception of a food’s rheology—what scientists call psychorheology—is another thing entirely.
If you’ve ever wondered why sour candy always seems to come coated in rough sugar, the reason is simple: We perceive rougher foods as being more sour.
Psychorheology is why we like gummy bears in solid but not liquid form, why we enjoy carbonated soda but balk at its flavour when it goes flat. It’s why we perceive gelato as creamier than ice cream—even though the latter has more fat.
Texture is an important indicator of a food’s fat content. If we can figure out how to trick our tongues into sensing more fat than is actually present in a food, we can increase satiation while decreasing a food’s calorie count.
That’s why some researchers are finally turning their attention to these taste-making sensations.
Chewing the fat
Since the emergence of the “obesity epidemic,” the food industry has found itself under pressure to deliver healthier foods.
Early on, they dealt with the pressure simply by removing whatever ingredient was currently in contention. An obsession with low-calorie foods lead to the rise of artificial sweeteners, while the low-fat fad of the ’80s stripped foods of their richness but packed them with as much as 20 percent more sugar. The resurgence of low-carb diets in the ’90s made sugar passé, so fat and artificial sweeteners were back on the menu.
But these days, we want it all: People look for foods with moderate amounts of fat, little to no added sugar, and whole, “natural” ingredients—but with the same flavour as the fatty, sugary, artificially-flavoured stuff they grew up with.
Companies are responding to this consumer chatter by offering products like reduced-salt potato chips. But once they’re on the shelves, “Nobody buys it,” said Simon Harrison, a researcher at Commonwealth Scientific and Industrial Research Organisation (CSIR).
“Because when you’re going to buy chips, you’re going to go for the yummy ones, not the ones that are salt reduced.”
A low-salt, low-fat potato chip with all the flavour of the ones we go for now would obviously be a huge coup. But the key to creating such a chip might not have anything to do with flavour.
“Texture is a hugely important to what we do,” said Kristopher Bronner. Bronner is a co-founder of the candy company UnReal, along with his brother and his dad.
“My parents are huge health nuts,” said Bronner. One Halloween, his younger brother Nicky—upset at having his Halloween candy taken away—exclaimed, “Why does something I love have to be so bad for me?” And thus UnReal was born.
The Bronners take some of our beloved favourites—M&M’s, Reese’s Peanut Butter Cups—and reimagine them with at least 30 percent less sugar and 60 percent more protein, all without leaning on artificial sweeteners. That means paying attention to every detail, including texture.
Take their rumination on the peanut butter cup, for instance: should it be one solid piece of chocolate with peanut butter filling pumped in, or should it be made in three layers? This apparently has a huge impact on how customers perceive the finished product.
Harrison is trying to systematise what the Bronners are learning by trial-and-error.
The computational fluid dynamics researcher and his team use computers to see how liquids behave (how the water in a tsunami acts when it hits a city, for example). He was initially brought on to model how the Australian Olympic diving team moves through the air and hits the water in order to help reduce injury and improve performance.
CSIR is public-private partnership, and both the Australian government and the Australian food industry were facing complementary problems: how can the government improve eating habits to enhance public health, and how can companies can make healthy foods the public wants to eat?
To solve that problem, they turned to Harrison, who put his biomechanics background to another use—modelling what happens to food when it enters our mouths.
Harrison uses modified versions of the same models his team uses to predict tsunamis to make computer models of the mouth. The models represent all of the aspects of anatomy—the shape of the teeth, the gums, the palate, the cheek, and the throat—and how it all moves when eating a given substance.
“We take our best available representation of the food structure, previous knowledge of how the structure relates to the mechanics of the food, how sticky is it, how strong is it, if you crush it, how many pieces does it break into it,” said Harrison.
The tsunami inside our mouths
A lot happens inside of our mouths between the first bite and the final swallow. The tongue may gently nudge the morsel towards the central incisors—whether to the left or on the right is a matter of unconscious preference—to break food down to even smaller pieces.
The pieces may linger there, or get shunted to the back molars, or the tongue may shift them wholly to the other side. Alternatively, pieces may rest chipmunk-style in the cheek sacs along both sides of the mouth while the molars get to work.
Or, depending on the person and the food, the piece may linger on the tongue, where salivary acids let it soften a bit before chewing even begins.
Food sensory researchers from The Understanding & Insight Group, a consortium of scientists from the US and New Zealand, break these chewing preferences into four categories.
Chewers prefer foods that can be chewed for a long time, like gummy candy. Crunchers prefer foods that respond with a resounding crunch, like potato chips. Suckers prefer foods, like hard candy, that dissolve slowly over time. And smooshers, the laziest of all eaters, prefer soft creamy foods that spread across the mouth with minimal effort—like puddings.
Modeling this turbulent behaviour isn’t easy—traditional imaging devices don’t work so well when the subject is moving—but it’s important.
“Where we put food in our mouth will affect our perception of its texture,” says Harrison.
The way our mouths interact with foods affects how enjoyable we find different formulations of ingredients. Adults, for example, enjoy a complex textural experience, which is why many chocolate bars come with nuts—the texture just adds a certain something…..
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