The researchers glued a wide variety of Oreos to the top and bottom plates of an instrument known as a rheometer and applied varying degrees of torque and angular rotation, noting the values that successfully twisted each cookie apart. They plugged the measurements into equations to calculate the cream’s viscoelasticity, or flowability. For each experiment, they also noted the filling’s “post-mortem distribution,” or where it ended up on the opened cookie.
The torque required to open an Oreo, they found, is similar to that required to turn a doorknob and about 1/10th what’s needed to twist off a bottle cap. The cream’s failure stress—the force required to get it to deform—is twice that of cream cheese and peanut butter, and about the same as for mozzarella. And neither the flavor nor the amount of stuffing mattered: the cream stuck to one wafer about 80% of the time.
The manufacturing process may be to blame, says Owens: “They put the first wafer down, then dispense a ball of cream onto that wafer before putting the second wafer on top. Apparently that little time delay may make the cream stick better to the first wafer.”
Owens, who regularly uses a rheometer to test materials such as 3D-printable inks, thinks the understanding gained from the properties of Oreo filling could potentially be applied to the design of other materials.
