Why do onions make you cry? A botanist explains. Plus all the ways to keep a dry eye
A professor of botany explains why onions make us cry, and we consider some of the ways you can try to stop the tears flowing
Ever been moved to tears while cooking dinner? If not, you are probably not cooking with onions. For most of us, our eyes react this way because of a sophisticated self-protection system in these allium plants.
Jutta Papenbrock, a professor at the Institute for Botany at Leibniz University Hannover, in Germany, explains why cutting onions makes us cry, and ways to prevent it.
Sulphurous, volatile substances are produced when we cut onions, thanks to a reaction between the organic compound isoalliin and the enzyme alliinase, which are contained in onion cells, Papenbrock says. This substance helps protect onions by keeping predators like voles and rats at bay.
The two substances come together when an onion cell is destroyed, releasing a volatile mixture that irritates the eyes, which then produce tears to flush it out.
It is possible to genetically modify onions so that they do not contain these substances. But that also reduces the somewhat pungent flavour that we like in onions, she adds.
Tips to make chopping onions less tearful
To lessen the release of this mixture, use a well-sharpened knife. It will divide the onion flesh, damaging and bruising the least number of cells – considerably reducing the chemical reaction that causes the irritation.