Anyone who spends a lot of time in the kitchen knows what it's like to bring yourself to tears while chopping onions. To avoid that burning sensation, several creative kitchen hacks have been used, from chopping onions under running water to chilling them in the refrigerator. But according to science, there may be an even simpler answer to this culinary inconvenience.
new study published in Proceedings of the National Academies of Sciences suggested that the key to keeping your eyes dry when handling onions is to cut them slowly with a sharpened knife. This method, which researchers have found suppresses the chemical chain reaction that normally makes us cry, could make cooking with onions less of a heartbreaking nightmare.
Why onions make us cry
When onions make our eyes water, it's just a way of telling us that we don't really want to eat them. This biochemical defense mechanism is triggered when onions absorb sulfur from the soil as they grow, storing it as a compound called 1-propenyl-L-cysteine sulfoxide.
When onions are cut with a knife, this compound reacts with enzymes to form propanethial S-oxide, an irritating chemical also known as a tear factor. The chemical is released in a high-velocity spray of tiny droplets that bombard our eyes and react with their moisture to form sulfuric acid, which damages our tear glands.
At this point, tears begin to flow, trying to wash away the acid from our eyes. However, the amount of acid is so small that it is not harmful, but simply irritating.
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Pressure Spray
Researchers involved in the new study delved deeper into the mechanism that releases droplets from onions, aiming to see what factors influence their effects on our eyes.
To test this, they set up a guillotine-style tool to cut onions and filmed the process with high-speed cameras. Using a simple computer model, the researchers were able to observe what happens when a knife is pressed into an onion; At this point, pressure increases within the layers of the onion, each containing a tougher outer layer (epidermis) and a softer inner layer (mesophyll).
There is then a tension zone within the onion layer where droplets begin to form. Once the knife finally pierces the outer shell, these droplets are thrown out at a speed of 5 to 40 meters per second. The researchers were surprised to see how quickly the spray sprayed during the experiments.
“We found that the speed of mist release is much faster compared to the cutting speed of the blade,” said senior author Sunghwan Jung, a professor of biological and environmental engineering at Cornell University, in his paper. press release.
Preventing Pathogens in the Kitchen
Based on their testing, the researchers confirmed that sharper blades minimized the number of droplets released by the bulb, as well as reducing their speed and kinetic energy.
Blade sharpness and cutting technique are critical factors in safely handling fruits and vegetables that may contain foodborne pathogens such as Salmonella. This is especially true for onions, as their mist can easily spread bacteria around the kitchen.
“Let's say you have pathogens on the very top layer of the onion,” Jung said. “If you cut this onion, these pathogens can be encapsulated in droplets, where they can then spread.”
There are several other solutions that can reduce or even eliminate the droplets that cause tearing. Researchers suggest that coating onions in vegetable oil may help prevent fog from getting into your eyes. If you don't want to cry, cooking with sweeter onions that have less sulfur is also an option.
Some scientists have even abandoned the idea of genetically modifying onions to suppress an enzyme called tear factor synthase, potentially allowing “no tears” onion.
This article does not contain medical advice and should be used for informational purposes only.
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