Every wonder why oranges, lemons, and limes spray a small mist when you peel them? That’s the question researchers at the University of Central Florida have been asking for the past eight years. They believe that a better understanding of orange peels may lead to better asthma inhalers—or an improvement on any mechanical tool that needs to quickly disperse contents into the air.
A citrus rind is made up of two layers: one thick and spongy, and the other firm and thin. Assistant professor Andrew Dickerson says the spongy material surrounds the oil, and when the peel is bent, that thicker material pushes against the oil, which in turn pressurizes the fluid. “The stiff outer layer holds the pressurized fluid back until—pop!” That’s when oil droplets escape through the rind’s tiny pores.
Dickerson and his team have been recording slow-motion video of oranges and limes being squeezed to watch the explosion of these oil droplets close-up. “When the citrus is squeezed, these jet streams are about the size of a human hair, and the oil breaks up very quickly,” said Dickerson.
That’s because the pores are jagged and quasi-elliptical-shaped, and therefore cause the oils to break up into little drops a lot quicker than if they were circular. Dickerson says the oils reach speeds of 22.5 miles per hour over the distance of one millimeter or less, accelerating 1,000 times faster than a rocket going into space. That’s why when someone peels an orange, you can smell it so quickly.
Dickerson says he’s still in the early stages of his research, but envisions taking the concept of a quick spritz from an orange peel and applying it to a one-time asthma inhaler that could release medication very quickly.
Watch the video above to see the slow-motion close-ups of a jet stream of oil escaping an orange rind.