I use onions in cooking most of the time. However, it can be a very tearful experience, as I am sure you all know! I find red onions seem to catch me out more than most and I can be found sobbing over a Bolognese sauce if I get a really strong one.
So why do onions make us cry? I decided to look into it, after a recent tearful stir fry experience, and discovered something I hadn’t known before – much of it is linked to the sharpness of our knives!
Apparently, chopping onions with a blunt knife makes tears much more likely. When you chop onions with a blunt knife, the blade bruises the surface of the onion rather than slicing straight through. This means enzymes are released that can irritate your eyes. Using a very sharp knife when cutting onions can reduce that as it’ll slice right through, rather than crush the skin.
But what is it in onions that causes our eyes to water? It all starts underground as onions absorb sulphur from the earth. This creates a class of volatile organic molecules and when you push a knife through an onion it crushes the cells and releases amino acid sulfoxides to form sulfenic acids.
These then react with the air to create a volatile sulphur compound that, when it comes into contact with our eyes, creates a burning and stinging feeling. The tears are our eyes trying to wash the acids away. Most of the acidity is concentrated in the onion’s root.
But dry your eyes and try some of these helpful tips the next time you’re making Bolognese or any other onion-based delight.
- Use a sharp knife
As identified above, make sure you use a sharp knife – this will cut through the onion more smoothly and cause less crushing which will release less acid.
- Put it in the fridge/freezer
Try putting the onion in the fridge 30 minutes before chopping it or in the freezer for 10 -15 minutes – the cold will inhibit the release of the gases. But don’t keep them in the fridge all the time as this will soften them and make them go off quicker.
- Open a window
Chop your onions near an open window so the breeze can waft away the acidic fumes – or even a fan or vent if you have one.
- Leave the root
Chop the onion while leaving the root on so as not to release fumes from the most concentrated area.
- Soak it in water
Chop the end off the onion and then put it straight into a bowl of water to soak. The water will draw out the acid making you tear up less when you chop it. However, this could make your onion taste slightly weaker.
And if none of those work… why not treat yourself to some very fetching ‘onion goggles’ now widely available on line!