Normally, the chemical mist released when we cut onions – propanethial S-oxide – makes us cry. Now, scientists have discovered a way to minimize these tears. The secrets are the quality of the blade and… calmness.
In the study, recently published in PNAS, it was demonstrated that sharper blades and slower cuts have significantly reduced the amount of onion haze released during preparation, keeping your eyes drier and kitchen surfaces safer.
The research team used a mini guillotine, a high-resolution camera and sensors to carefully track the droplets expelled as the onions were cut, comparing the characteristics of the mist with the sharpness of the knife, the speed of cutting and the force applied.
“We discovered that the speed of the mist that comes out is much higher than the speed of the blade being cut,” the corresponding author of the study, physicist Sunghwan Jung.
Each layer of an onion has an upper skin and a lower skin, and as these layers are ruptured, analysis has shown that there are two resulting effects: an instantaneous explosion of mist and then a slower infiltration of fluids through the layers.
Get a good knife and take it easy
Less sharp knives created substantially more droplets and faster spraysinvestigators discovered.
As they require more force to break the skins, pressure builds up in the onion juices. Faster, more vigorous cuts with a dull blade projected the droplets even further.
The initial ejection of droplets can occur at very high speeds, the observations showed, reaching 40 meters per second – which corresponds to 144 kilometers per hour. It is these droplets that pose the greatest threat to the eyes.
Use sharp blades and smooth cuts keeps the mist of droplets below eye level, concluded the team from Cornell University in the USA.
