Physicists conducted a serious scientific study and found that two factors can help reduce eye irritation. These are slow movements while cutting onions and using knives that are as sharp as your skills and sharpening stone allow, writes Independent.
Scientists explained that people cry when cutting onions because a chemical reaction occurs in the eyes. Onions contain volatile liquid compounds - syn-propanethial-S-oxide. It is released into the air during the cutting of this vegetable and activates nerve endings in the cornea.
The study, published in the journal PNAS, discusses an assessment of the factors that led to the release of various volumes of liquid in the form of aerosols during onion cutting.
In the study, scientists cut onions using a special guillotine that could be equipped with different types of blades, and also coated pieces of onion with paint to better observe the cutting process.
In each trial, the scientists varied the size of the knife, its sharpness, and the speed of cutting, as well as used a microscope to carefully measure the knives before use.
Videos recorded during the study showed the difference in the amount of onion juice released - a measure of the degree of eye irritation that each chopped onion could cause.
The researchers found that the spraying of aerosols was related to the sharpness of the knife and the speed at which each knife movement cut the onion: the sharper the knife and the slower it moves, the less onion juice is sprayed.
"Faster or dull blades significantly increase both the amount and energy of the ejected droplets," the authors of the study wrote.
They explained that dull knives seemed to press down on the onion, causing its layers to bend inward and then spring back, pushing juice into the air. When juice droplets were tossed into the air, they broke into smaller droplets and released even more pungent compounds. And faster cutting, the researchers found, leads to greater juice leakage. As a result, this leads to greater eye irritation.
"Keep your knives sharp and cut carefully to minimize splatter," the authors of the study advise.
Will cooling the onion help protect the eyes?
The scientists also decided to test the common belief that cooling onions before cutting reduces eye irritation. They cooled the onions at a temperature of 1 degree Celsius for 12 hours and compared the results with samples at room temperature. The researchers found no "significant difference between the two conditions."
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