Simple tricks to avoid onion tears backed by science

Chopping onions without shedding tears is unbelievable, and most people hate cutting onions just for this one reason, but why does this happen? Well, researchers at Cornell University have recently discovered the science behind onion tears and revealed simple and effective ways to prevent them.

Cutting an onion is a pain for most people, and this majorly because onions release a chemical irritant called syn-propanethial-S-oxide when cut. This volatile compound then spreads in the air and becomes airborne and irritates the eyes, causing tears. Cornell researchers also found that using high-speed cameras and computer modeling to study the exact mechanism of how this tear-inducing mist is released from onions.

As per the team, it was found that as a knife presses into an onion, internal pressure builds up within the onion layers. Once the knife pierces the onion’s tough outer skin, a sudden high-speed mist of tiny droplets is sprayed out, followed by slower droplets. This mist travels at speeds ranging from 11 to 89 miles per hour, far faster than the blade itself moves.

Sharpness of the blade and how fast you cut significantly affect how many tear-causing droplets fly out. Duller blades bend the onion layers before cutting, causing increased internal pressure and a more powerful spray of irritants. Faster cutting speeds also eject more droplets. The Cornell study showed that sharper blades and slower, controlled cuts greatly reduce the number and speed of these irritating droplets.

To minimize onion tears, Cornell researchers advise using a very sharp knife and cutting the onion slowly and steadily. This approach keeps the internal pressure low and reduces the mist sprayed into the air. Another technique they discovered is to coat the onion with cooking oil before slicing, which can trap much of the mist and prevent it from reaching your eyes.

Apart from reducing tears, using sharp knives and careful cutting also helps limit the spread of any harmful bacteria stored on the onion's surface. This finding emphasizes safer food preparation in addition to making the chopping experience tear-free.