The Scientific Reason Why McDonald’s Fries Are So Good

You're not the only one who can't stop eating them. Ever wondered why?

A large order of French Fries and drink are photographed at a McDonald's restaurantGene J. Puskar/AP/REX/Shutterstock

Everyone knows what it’s like to eat McDonald’s french fries.

As you pick up the box, you get a whiff of that unmistakable frying oil scent, reminiscent of drive-thru windows and fast-food counters. You grip that iconic red box with the famous arches on the front, holding a generous handful of stiff golden sticks. Then you take the first bite and hear that satisfying crunch through the crispy outer layer, with the salt so discernible you can feel it leaping onto your tongue. And then the fluffy, soft inside: some magical combination of potato that manages to taste a million times better than the raw starch. They’re warm and satisfying, and you polish them off one by one. Before you know it, the whole box is gone. Craving fast food right now? We’ve got you covered.

It makes you wonder: What do they put in McDonald’s fries to make you eat your way to the bottom of the carton? As it turns out, it’s not just one thing—it’s a spellbinding combination of things, creating a taste experience unlike any other fast-food chain’s. To make it easier to digest, we’ve broken the secret McDonald’s recipe into three components.

The Smell

Scientists believe our sense of smell might be responsible for up to 90 percent of perceived flavor. If you ever doubt this statistic, just think about how unappetizing food seems when you have a cold and your nose is blocked. Without that delicious aroma, McDonald’s french fries wouldn’t taste as good. This smell—and the taste that comes with it—is almost exclusively from the oil in which the fries are cooked.

Like most fried foods, McDonald’s fries are cooked in vegetable oil. To mimic the chain’s original oil blend, which was mostly beef tallow, the oil is laced with chemical flavoring to replicate that mouthwatering smell. In other words, the delicious scent we know and love is actually the smell of potatoes cooked in beef fat, an aroma so powerful it makes the fries seem even tastier!

The Taste

The smell might get you to take that first bite, but it’s the taste that brings you back for more. While homemade french fries don’t require much more than salt, potatoes and oil (unless you want to get fancy with seasonings), McDonald’s has mastered the art of combining a boatload of ingredients to bring that treasured sensation to the finished product. The main players? Salt, sugar, and fat.

Including one or two of those in a recipe makes it good, but having all three sends it over the top. In the food industry, the perfect equilibrium of these ingredients is known as the “bliss point,” and Michael Moss’ Pulitzer Prize-winning book Salt Sugar Fat: How the Food Giants Hooked Us explains that processed-food manufacturers invest lots of money finding it. Eating those tasty McDonald’s fries even releases dopamine in your brain, the neurotransmitter that triggers feelings of pleasure. So how does McDonald’s do it? In addition to frying and seasoning the fries, McDonald’s coats them in dextrose, a form a sugar. So the fries have the big three—salt, sugar and fat.

The Crunch…

…or, more specifically, the mouthfeel. That’s the way something feels as you eat it. How hard is it to break with your teeth? What’s the texture feel like on your tongue? Everyone judges mouthfeel differently, but McDonald’s has clearly found one that appeals to most of us.

So where does that tantalizing mouthfeel come from? It’s not from a special fryer—almost every fast-food restaurant employs a similar machine to deep-fry food. The McDonald’s difference may be a secret ingredient denoted online only as “natural and artificial flavoring.” Maybe that’s what separates McDonald’s fries from others in the fast-food industry.

When you put all those sensory details together, it’s no mystery why these fries are addictive. We like to say the same thing about our favorite Parmesan garlic fries—even without added chemicals or artificial flavoring! If you ever get tired of fries, switch up your order with the Mcdonald’s secret menu.

Here’s how to open a ketchup packet so you can dip your fries at the drive-thru without a mess.

Want to learn more secrets about your favorite hangouts? We dug up the real meaning behind Starbucks’ name, and it’s probably not what you’d think!

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