MIT scientists reveal why it’s hard to evenly split Oreo filling between two halves

Researchers at MIT created a 3D-printed device to develop a better understanding of the science behind what happens to the cream filling when you split the two sides of an Oreo cookie. Their device, the Oreometer, uses rubber bands and coins to control the torque applied to each side as a cookie is twisted apart. Adding pennies to one side rotates one of the two chambers and separates the Oreo.

After testing various types of Oreos, the researchers added scientific weight to something that nearly every American over the age of three already knows: the cream filling usually sticks to one side, even with Double and Mega Stuf varieties. Twisting speed mattered, according to the team — if you try to do it quickly, it may take more strain and stress to split a cookie. Curiously, the scientists found that the cream only separated more evenly when testing older boxes of cookies. 

The researchers suspect the Oreo manufacturing process is one reason for the phenomenon. “Videos of the manufacturing process show that they put the first wafer down, then dispense a ball of cream onto that wafer before putting the second wafer on top,” Crystal Owens, an MIT mechanical engineering PhD candidate, said. “Apparently that little time delay may make the cream stick better to the first wafer.”

The team published a paper on their research in the journal Physics of Fluids. As Gizmodo notes, they conducted the experiment as an exercise in rheology, which is the study of how matter flows. 

The researchers determined that, based on how the filling responded to stress, it should be classified as “mushy” instead of brittle, tough or rubbery. They also found that the cream’s failure stress — the force per area needed to deform the filling or make it flow — is around the same as mozzarella cheese and double that of peanut butter and cream cheese.

There could be some other practical benefits of the research. “My 3D printing fluids are in the same class of materials as Oreo cream,” Owens said. “So, this new understanding can help me better design ink when I’m trying to print flexible electronics from a slurry of carbon nanotubes, because they deform in almost exactly the same way.”

In addition, Owens suggested that if the inside of each Oreo half had more texture, it might have a better grip on the cream and the filling would be more even when a cookie’s twisted apart “As they are now, we found there’s no trick to twisting that would split the cream evenly,” Owens added.

If you’d like to try the experiment yourself, you can download the 3D printer files. Just be sure to eat some of the separated Oreos afterward. For science.