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There is much more to a pumpkin spice latte than meets the eye. Or, rather, more than what you think is meeting your tongue!

Say you take a big swig of a pumpkin-pie-flavored drink. The drink hits your tongue, and flows over your papillae, the little bumps where your taste buds live. Within each taste bud, special receptor cells bind with the compounds in the drink and send taste information to your brain. Meanwhile, the scent of the latte travels up your nose, where more receptor cells – this time for smells -- tell your brain which chemicals they detect. Those signals, plus other information like the color and texture of your drink, combine to form what your brain interprets as the taste of pumpkin pie in delicious liquid form.

But you haven’t actually consumed any of the spices you’d normally associate with pumpkin spice flavor, like cinnamon, nutmeg, and cloves. Your brain thinks you have, because the drink contained compounds specially designed to trick your brain. That’s the science of synthetic flavoring, and it’s involved in practically every processed food. At some point in your life you’ve eaten something with “natural flavors” or “artificial flavors” listed as ingredients. That means that the food has some added compounds to give it a specific taste.

The science involved can be incredibly complex --and flavorists, the scientists who work with flavor, often have to study for five years or more to get certified by the Society of Flavor Chemists. And that’s after getting a bachelor’s degree in biology, chemistry, or food science -- and usually a master’s degree, too. But this area of specialty has allowed the food industry to become what it is today – where you can make practically anything you want, have it taste like anything you want, and do it all for not very much money.

Whenever you eat anything -- from a fast-food cheeseburger to an apple picked right off the tree -- whatever you’re tasting, your brain is picking it up from the chemicals in your food. People often talk about chemicals as though they’re somehow inherently bad for you, but literally everything in the universe is made of chemicals. Water, the air we breathe, organic broccoli -- everything.

Thing is, it’s often hard to tell what they’ve actually included under the vague heading of natural or artificial flavoring, because the ingredients that make up different tastes are mostly secret, closely guarded by the companies that manufacture them. But, at least in the United States, every chemical in a flavoring has to be on the FDA’s list of compounds it calls Generally Recognized As Safe, or else shown to be safe by whatever company is using it.

For a compound to be considered a natural flavor, it has to start out as part of certain living things, like tree bark, meat, or yeast. But not all living things make the cut -- something that comes from bacteria, for instance, wouldn’t be considered a natural flavor. According to the FDA, artificial flavors are compounds that aren’t made from the living things on their list. Which means artificial flavors are just... every flavor that isn’t a natural flavor.

Isoamyl acetate, for example, is what you’d probably recognize as banana flavor. It’s in actual bananas, so if you extracted some from a banana, that would make it a natural flavor. Or you could just mix amyl alcohol with sulfuric acid and vinegar, and you’d wind up with the artificial version of the very same flavor. Either way, it’s the same compound giving your candy that banana taste -- but since they were made in different ways, they fall into different categories.

Take vanillin, for instance, the compound that gives vanilla its taste and smell and one of the first flavors ever to be made in the lab. Natural vanilla, which comes from the vanilla bean, contains hundreds of chemicals, but the only really important one for taste and smell is an aldehyde called vanillin. Vanillin’s structure makes it an excellent chemical to use as a flavor, because its oxygen atoms help it dissolve in water. Plus, aldehydes usually have strong smells, and vanillin also contains a ring of six carbon atoms, known as a benzene ring, that tends to make chemicals even smellier.

Back in 1874, a group of German scientists figured out what vanillin looked like and started making it out of a chemical in pine bark called coniferin that smells and tastes like cloves. Over the years, vanillin has been made in lots of different ways, like from apple seeds, for example, but these days, it mostly comes from reactions with compounds that start out as petroleum. Vanilla extract from the bean is much harder -- and more expensive -- to produce, and only makes up about one five hundredth of the vanilla used worldwide every year. If that were the only way to get it, the world would have a lot less vanilla-flavored stuff.

Synthetic vanillin, on the other hand, is way cheaper, and can mostly keep up with the demand -- about 10,000 metric tons of it is produced each year. But part of why vanillin is so popular is that it also has lots of non-flavor uses, too, like in reactions used to make certain medicines, or in perfumes. But about three quarters of the artificial vanilla produced in the world is used just for ice cream and as a flavoring for chocolate.

Another old-timey artificial flavor is grape, in the form of a compound known as methyl anthranilate. As far back as the late 1800s, methyl anthranilate was identified as an important part of the scent of orange blossoms, and was used in perfumes. And scientists already knew how to make it -- one way involved combining methyl alcohol and anthranilic acid, a type of acid with one of those smelly benzene rings.

By the early twentieth century, the chemical’s popularity made it easy for food chemists to get their hands on it. That’s when they realized that it kind of smelled -- and tasted -- like grapes. Which makes sense, because methyl anthranilate actually is in some grapes! It’s mainly found just one kind of grape -- concord grapes, a variety that’s specific to North America and today is typically used in grape juice. Even though people eat many other varieties of table grapes, methyl anthranilate has still come to mean “grape” flavor to a lot of us, especially in the U.S. That’s why grape-flavored foods... don’t really taste that much like the grapes that most people buy in the store. Food scientists have an official term for the unique, concord-y flavor imparted by methyl anthranilate. They call it foxiness. I guess there’s just no better way to describe it.

Not all flavors have to be as specific as vanilla or grape. Just like if you wanted your food to be saltier, you’d add salt, if you wanted to give your food a kick of umami, a more savory taste, you’d add monosodium glutamate. Good ol’ MSG. That’s what it’s for.

Lots of glutamates show up naturally in things we eat. They’re amino acids, and you’ll find them in most protein-rich foods, from meat to milk to eggs. Monosodium glutamate is the synthesized version, and it’s usually made by fermenting bacteria so that they excrete it. It’s often added to food to make it taste more meaty, and it’s usually the secret to making a veggie burger taste even the tiniest bit like meat.

A lot of people claim that MSG gives them headaches, or that they’re sensitive to it in some way. And MSG is closely related to glutamic acid, an amino acid that acts as a neurotransmitter in lots of animals, including humans. So researchers figured there could be a connection, and kept doing studies to try and learn more about these reactions... but so far they’re coming up empty.

Some studies have shown that when mice are injected with very high amounts of MSG, they die. But scientists have reason to believe that humans and mice handle glutamates differently -- and besides, anything can become toxic when you put enough of it in your body, even water. Studies that try to directly measure reactions to MSG have had trouble finding anything reliable.

In 2000, for instance, researchers tested 103 people who said they were sensitive to the compound. Some people did experience symptoms, but not consistently. Instead, researchers think that people might be sensitive to other ingredients in foods that also happen to contain MSG -- a condition that’s been named Chinese Restaurant Syndrome. So your veggie burgers are probably fine.

The flavors we’ve talked about so far turn out to be relatively simple to synthesize: one molecule, and you’ve got it. But other tastes are a lot more complicated -- you need more than one compound to capture the nuances of pizza, for instance. Or the experience of eating pumpkin pie. That’s why flavorists develop flavor packs, tailored combinations of compounds that food companies can use to make foods taste like whatever they want. Designing a flavor pack goes beyond just combining all the right flavors -- scientists have to consider things like whether one taste will dominate the others, or if the compounds will be used in a food, like bread, where they’ll need to be protected from heat during cooking.

Usually, pumpkin spice lattes aren’t actually meant to taste like pumpkin -- they’re just supposed to taste like the spices you might find in a pumpkin pie. So the flavorists are going for hints of things like cinnamon, cloves, ginger, and nutmeg. But if you tried to actually put those spices in your latte, you’d probably find that it tasted more like chai tea, and not really like pumpkin spice at all. That’s because when you eat a pumpkin pie, the spices have gone through the oven, changing their chemistry.

The pumpkin spice flavor pack accounts for those changes, using synthetic compounds that highlight the strongest notes of pumpkin spice flavors -- once the pie’s out of the oven, that is. It’s not quite the same as eating a slice of that pie, but your latte can use the science of flavor to trick your brain into thinking that you might be drinking a slice of pumpkin pie.

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