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Former MythBuster goes on McDonald's french fry fact-finding hunt

Ex "MythBuster" Grant Imahara visits potato supplier Simplot to investigate what McDonald's french fries are actually made from. The list of ingredients might be longer than you expect.

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A potato isn't the only ingredient that makes up a McDonald's french fry. Video screenshot by Bonnie Burton/CNET

Are McDonald's french fries just potatoes or is there more to them? Are the potatoes genetically modified? What kinds of chemicals are used to fry them? Are there really 19 ingredients?

McDonald's hired former to look into common consumer questions about various items on the fast-food chain's menu as part of its campaign, "Our Food. Your Questions."

The promotional campaign -- which began in October 2014 -- promises to inform the public about how McDonald's food is processed, cooked and served. Imahara has already gone behind the scenes at various food-processing plants to find out whether McDonald's uses yoga mats in its McRib sandwiches or pink slime in its burgers and chicken McNuggets.

In this latest video, Imahara takes a look at what goes inside McDonald's french fries by reverse-engineering the process. He starts with a fully cooked french fry and ends his search for answers holding a potato in the middle of a field.

Imahara visits McDonald's USA potato supplier Simplot and chats with production planner Koko Neher, who shows him around the facility. Imahara first gets a glimpse inside the immense freezer tunnel where fully processed french fries are flash-frozen.

But before the fries can be frozen and shipped off, they're dipped in dextrose for color and sodium acid pyrophosphate to "control the graying after freezing," then partially cooked in four different oils: soybean, hydrogenated soybean, canola and corn.

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Imahara explains the 19 ingredients used to make McDonald's french fries. Video screenshot by Bonnie Burton/CNET

Even though the fries are dipped in various ingredients, fried and frozen, Imahara discovers that they do come from real potatoes. McDonald's uses a variety of potatoes, including Ranger Russet, Umatilla Russet, Russet Burbank and Shepody. And according to Neher in the video, McDonald's does not use GMO (genetically modified organism) potatoes for its french fries.

"Potatoes are just like people," Neher tells Imahara in the video. "They come in different shapes and sizes."

But the best part of the behind-the-scenes process is seeing Imahara get excited about the massive potato-cutting machine that looks like a giant wood chipper or an industrial weapon that clearly needs to be featured in a horror film.

"It works similarly to a cannon," Neher explains to Imahara. "We're lining up the potatoes in the tube with high-pressure water and shooting them into the water knife. It's precision cutting."

"That is crazy!" Imahara responds as he holds up the grid of sharp edges that slice the potatoes up to his face. "How fast do they fly through here?"

"Sixty to 70 miles per hour," Neher answers.

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Is this a potato slicer or a prop fit for "Fargo"? Video screenshot by Bonnie Burton/CNET

If watching fast-cutting machines and dextrose dippers isn't interesting enough, at the end of the video, Imahara gets dirty on a farm, literally, digging in the soil for an honest-to-Ronald real potato.

But because McDonald's wanted to make sure skeptics and fans alike got as much information as possible, it made an additional video with Imahara just to explain all 19 ingredients that go into making its french fries.

The list not only includes the potatoes themselves, plus various oils, dextrose and sodium acid pyrophosphate, but also natural beef flavor, hydrolyzed wheat, hydrolyzed milk, citric acid, salt and hydrogenated soybean oil with the antioxidant TBHQ, which "preserves the freshness of the oil."

The longest word on the ingredient list is dimethylpolysiloxane, an anti-foaming agent. "It helps keep the oil from splattering," Imahara says in the video. "It's approved for use in a number of many other very familiar foods."

And the verdict? "So at the end of the day it's not a Franken-fry composed of chemicals," Imahara says.