Untreated, a piece of dry kibble is largely flavorless. Made of various meals and fats and blended with wheat and soy grains to offer balanced nutrition for an animal’s body, it would fail to stir the interest of most domesticated pets. Dogs might eat it without enthusiasm; cats would let it grow stale on the floor. Indifferent to grains, they need some extra incentive to empty their bowls.

That’s where Nancy Rawson, Ph.D. comes in. The Associate Director of the Monell Chemical Senses Center in Philadelphia, Rawson is an expert in tastes and flavors relating to research palatants—additives that give bland foods their taste appeal—for both humans and animals alike.

“[Food companies] want to bring the pet to the bowl,” Rawson tells mental_floss. “Dog food companies are good at formulation, but look elsewhere for their flavor systems.”

A large part of the work of places pet food companies consult with--one, AFB International, was where Rawson worked from 2010 to 2016--is focused on developing coatings that will make pets enthusiastic. For cats, the results of a hit recipe might mean whining and weaving in between their owner's feet until dinner is served. For dogs, it might entail getting so excited that they eat too quickly and bring the food right back up.

“I wouldn’t say puke is a good sign,” Rawson says. “But it can mean dogs really like the food.”

iStock

After subsisting on table scraps or the carcasses of dead livestock for thousands of years, domesticated dogs and cats started enjoying commercially produced canned food beginning in the 1920s. (Dog biscuits were invented in England in the mid-19th century, but only found favor in wealthier families.) The first canned food was Ken-L-Ration; those who opened a tin were likely to find wet food consisting largely of horse meat.

The demand for ready-to-serve dog food—cats were a minority interest for the companies at that time—grew so much that the Chappel brothers, owners of Ken-L-Ration, started breeding and slaughtering up to 50,000 horses a year for the purpose of putting their remains in cans. Horse meat became a less common ingredient by the 1940s, replaced with other kinds of meat, but with the outbreak of World War II, the rationing of both meat and tin meant that wet food in general grew scarce. Pet owners turned instead to the enormous stacks of dry kibble, which had first gone on sale in 1928 in 100-pound bags.

It was breakfast cereal that ushered in the modern age of marketable chow. In 1950, Ralston-Purina, which made both pet food and human-grade foods, developed an extrusion process in which they could shape their grains into air-puffed shapes that would hold up to submersion in milk. Purina’s dog food division took notice, spent three years tinkering with the extrusion machine, and then released Purina Dog Chow in 1957 to great acclaim. Easier to digest, with a fatty coating and texture made possible by extrusion, it marked the first time food companies treated a dog’s palate as worthy of consideration.

iStock

With $22 billion in sales in 2014, pet food companies are using some exacting science and research to make sure their kibble is worth binging on. For that, they outsource to companies like AFB and Kemin, home to flavor experts who develop the palatants designed to appeal to a pet's appetite.

Because canines and felines are non-verbal, Rawson is an expert on using bowl tests to assess the appeal of various dry food palatants—made from chemical blends, soy, corn, and animal organs blended into powder or liquid form [PDF]—using bowl tests. (Wet food, while it can contain palatants, is often flavorful enough on its own.) Animals at AFB are presented with two different meals and measured on criteria such as how quickly they come to the bowl, which bowl they indulge in first, how long they take to empty it, whether they stop and come back, and in some cases, how much time they spend with their nose buried in food relative to how long the food was available. This metric, for dogs, is called the Nose in Bowl, or NIB, test [PDF].

“You kind of have to treat them like babies,” Rawson says. “They can’t respond in words, so you pay attention to their behaviors.”

Cats, Rawson says, are reliable addicts for polyphosphates, an additive that she likens to the salt humans pour over their food. Cats also prefer the easy breakage of X-shaped kibble over other shapes, meaning that fun extrusions aren’t just for human amusement. “Cats don’t have molars, so different shapes break into different sizes more easily.” X-shaped pellets are easier for them to chew.

Dogs, on the other hand, aren't nearly as choosy. “We did a study and found that dogs will eat the largest size of kibble, regardless of breed,” Rawson says. A more important goal in designing dog food, both in terms of palatants and food density, is cleaning the dog's teeth, as well as slowing them down so they don't eat too much at once.

“Dogs are pleasers,” she says. “They’ll eat a bowl of rocks if their owner puts it down in front of them. The palatants act as more of a preservative for the food.”

And while dogs focus on smell, the aroma coming from an open bag isn't strictly for them. When owners open a chicken or fish-flavored meal, Rawson says, a lot of that smell and presentation is meant as much for the human as their pet. If AFB indulged only in what drove dogs crazy, like compounds given off by decomposing protein, their owner would never buy a second bag.

“When you open a bag of chicken kibble, you want it to smell like chicken. The job of the palatants companies is, in a way, to serve two masters.”

iStock

For pet food experts like Rawson, how food exits an animal is almost as important as how well it’s enjoyed on the way in. Dyed food, while festive for owners, turned out not to be such a good idea when your cat barfs up a rainbow on the carpet.

Palatants can also incorporate stool-hardening agents to make clean-up easier. Ever wonder what makes certain chow puppy-appropriate? Aside from calories, it’s partially an ability to reduce loose stools in younger dogs. Companies are "always trying to optimize stool volume,” she says. Reducing odor is also key, and certain formulations can do a better job of that than others.

Recently, the pet food conglomerates have been eyeing the growing demand for food that resembles human-grade servings. Purina now offers premium meals containing rotisserie chicken and filet mignon and employs a full-time pet food chef.

For Rawson, the movement into food that could conceivably co-exist on both a dog’s and owner’s plate isn't one worth embracing. “One of the fundamental problems is one of sustainability,” she says. “We’re diverting millions of tons of chicken meat into pet food that could be going to humans. Pets evolved eating guts. That’s what we should be using.”