It's impossible to split Oreo cream filling evenly between both wafers, study finds

There's no way to twist open an Oreo and get an equal amount of frosting on both cookie wafers, says Crystal Owens.

And she should know. Owens and her team at the Massachusetts Institute of Technology (MIT) tested just about every variety of the classic cookie in a laboratory in search of that perfectly precise twist — all to no avail. 

"I thought there must be some perfect method of twisting to make this happen, because it works for other fluids," Owens, a PhD candidate in mechanical engineering at MIT, told As It Happens guest host Dave Seglins.

"But what we found out is essentially that Oreo cream is stronger than it is sticky. So when we twist it perfectly, instead of splitting in the middle, it just delaminates from one of the wafers, and so you end up with one wafer with no cream and one wafer with all the cream."

The findings were published in the journal Kitchen Flows, a special issue of the journal Physics of Fluids.

Chasing a childhood dream

Owens has been chasing that perfect twist since childhood, which is what inspired her to pursue this research.

"I've found that some people really like the taste of Oreo cream, but I personally like eating Oreos where I get a little bit of cream and a little bit of wafer in each bite," she said. "What I want to do is I want to twist the Oreos open so that I get a little bit of cream on both wafers."

She hypothesized that, under the right conditions, she could make it happen. 

It wasn't just wishful thinking. Her particular field of expertise led her to believe it could be achieved. 

Owens describes her work as "studying the fluid mechanics of fluids that people don't consider fluids." 

"People think of Oreos, and they don't think it's a fluid. But that's part of our study as we showed that it has fluid properties," she said.

"The wafers are solid, but the cream is actually a yield-stress fluid, similar to toothpaste or something that you can actually reliably squeeze out of a tube."

Owens often tests other yield-stress fluids using an instrument called a rheometer. First you place the substance on the machine's base. Then a parallel plate is lowered onto the test material, essentially sandwiching it — not unlike an Oreo. 

Then, the top plate twists — kind of like opening an Oreo — as the machine's sensors measure the torque, or rotational force, required to twist it open.

With other yield-stress liquids, like 3D-printer ink, it's possible to achieve even distribution, Owens said.

Not so for the stubborn Oreo. The filling always ends up mostly on one side or another, even under what Owens calls "perfect conditions." This means using fresh Oreos from a newly opened box stored at just the right temperature. 

"The best we could do was basically the opposite of what we wanted," she said.

(If you think you can do better, the team has shared instructions for a 3D-printable "Oreometer" — a cookie-specific rheometer that uses pennies and rubber bands to control the twist.)

The researchers also measured how the cream cookie crumbles — specifically after dipping it in milk. They tested the Oreos in one per cent milk for five seconds, and found that one minute later the wafers would fall apart — even if they were no longer submerged in the milk.

"This is a challenge that I had growing up," Owens said. "I distinctly remember losing many pieces of Oreos to my cup of milk."

Even though Owens' study did not yield the results she'd hoped for, she says the findings haven't diminished her love of Oreos. She and her team had to eat many of the imperfect cookies that weren't up to laboratory standards.

"We try to be environmentally responsible. We can't just throw them away," she said. "About half of any box was donated to our break room."

Somehow, she's all the more excited to eat them now. "The more I learn about how to use them, the more fun they are to eat."

Nor have the results diminished her passion for fluid dynamics as it applies to food. She's already mulling a study on how to create an ice cream that doesn't drip in the summer.

"I am maybe one of the world's first cookie scientists," she said, calling her particular field of study Oreology. "May there be many more."

Written by Sheena Goodyear. Interview produced by Aloysius Wong.