CAMBRIDGE, Mass. — Oreo fans all have their own methods when it comes to dunking and eating the popular snack, but they all share one common problem — no one can get the cream on both sides when they twist the cookie open! Now, MIT engineers are taking on this challenge to see if science can figure out how to perform the perfect twist.
“There’s the fascinating problem of trying to get the cream to distribute evenly between the two wafers, which turns out to be really hard,” says Max Fan, an undergraduate in MIT’s Department of Mechanical Engineering, in a university release.
Although twisting the famous cookie open may seem like a kid’s game, scientists say it’s actually a great test of rheology — the science of how non-Newtonian materials flow when something twists, presses, or stresses them.
Unfortunately, their results so far show this may be a puzzle that has no solution! Aside from older boxes of Oreo cookies, the team found there wasn’t a single variety of Oreo that split with the cream on both wafers. It didn’t matter how much stuffing there was or what kind of wafer the Oreo had, study authors couldn’t find a way to twist a fresh Oreo open and get the cream to evenly break on both sides.
Is it the factory’s fault?
The team also measured the torque it takes to twist open the Oreo. The study finds it takes the same amount of force as turning a doorknob and about a tenth of the torque necessary to twist open a bottlecap.
As for the cream itself, the MIT engineers say its “failure stress” is about twice that of cream cheese and peanut butter. This measurement refers to the amount of force it takes to get the cream to flow or deform. Interestingly, Oreo cream has the same failure stress as mozzarella cheese and researchers classify its texture as “mushy,” rather than brittle, tough, or rubbery.
So, what’s the deal? Why won’t this cream ever split evenly? It turns out the actual manufacturing process may play a role.
“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,” says Crystal Owens, an MIT mechanical engineering PhD candidate who studies the properties of complex fluids. “Apparently that little time delay may make the cream stick better to the first wafer.”
Entering the ‘Oreometer’
This experiment didn’t just feature a bunch of scientists sitting at a table twisting Oreos and dunking them in milk. Researchers actually created a 3D-printable “Oreometer” — a device that grips the cookie while the weight from pennies and rubber bands control the twisting force.
The team went through nearly 20 boxes of Oreos, using regular, Double Stuf, and Mega Stuf cookies, as well as regular, dark chocolate, and “golden” wafer flavors. No matter the flavor, the machine could not get a single fresh Oreo to separate evenly.
“We had expected an effect based on size,” Owens says. “If there was more cream between layers, it should be easier to deform. But that’s not actually the case.”
Interestingly, researchers also found that the cookie’s position in the box also affected which wafer the cream stuck to. Oreo cream tended to stick to the inward-facing wafer, with wafers on the left side of the box leaving the cream on the right wafer and vice versa.
Again, the team believes the distribution of these snacks plays a role in how the cookie crumbles. Factors like heating and jostling during transport may cause the cream to peel away from one wafer and stick to the other. Owens notes that their findings may actually help scientists working with complex fluid materials.
“My 3D printing fluids are in the same class of materials as Oreo cream,” she adds. “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.”
Redesigning the Oreo?
So, it is really impossible to perfectly twist an Oreo and get cream on both wafers? Yes and no. Study authors believe a more textured Oreo wafer might grip the cream better, creating a more even split when you twist the cookie open.
“As they are now, we found there’s no trick to twisting that would split the cream evenly,” Owens concludes.
The findings are published in the journal Physics of Fluids.