If you find yourself crying when chopping onions, physicists have found a possible solution 鈥� but professional chefs probably aren鈥檛 going to like it.
When onions are cut open, they spray a mixture of sulphur-rich compounds into the air, one of which is syn-propanethial-S-oxide, a chemical that triggers the nerves in the eye responsible for producing tears.
at Cornell University in Ithaca, New York, and his colleagues used a high-speed camera to analyse in detail the spray produced when brown onions are cut with blades of varying thicknesses and at different speeds.
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Using a mounted guillotine consisting of a thin steel blade released from above, Jung and his team sliced a quarter of an onion that had been coated in black spray paint, which helped them track how the onion deformed, and watched the particle spray with a high-speed camera. They also used an electron microscope to measure the width of the blade tip, which varied between 5 and 200 millimetres, and changed the height of the blade to adjust the cutting speed, ranging from around 0.4 to 2 metres per second.
The researchers found that sharp blades produced fewer, slower droplets with less energy. When an onion is cut with a dull knife, the blade causes the onion skin to bend, storing elastic energy and building up pressure inside the onion. As a result, when the skin erupts, it does so more explosively, causing some particles to reach speeds of up to 40 metres per second. Once these droplets reach the air, they can fragment, producing more droplets.
A blunt knife can produce as much as 40 times as many droplets as a sharp one, while the fastest speeds produced four times as many particles as the slowest cutting speeds, the team found. Therefore, sharp knives and slow cuts should result in less of the irritating chemicals getting to your eyes 鈥� but Jung and his colleagues didn鈥檛 put this to the test. The team declined to discuss the research with 快猫短视频.
鈥淐utting is a really strange process,鈥� says at the University of Manchester, UK. 鈥淲e cut things with knives every day, but to cut something, you need to go down to the atomic scale.鈥�
鈥淲hether it鈥檚 really going to change much in the kitchen, it鈥檚 not obvious to me it鈥檚 going to be particularly useful,鈥� she says.
arXiv
