Why do onions make you cry? The answer is they contain an enzyme which, when released into the air, creates a chemical compound that irritates your eyes and makes them water.
There are two approaches to preventing the tears; you can either protect your eyes, or try to minimise the amount of enzyme released into the air – or, of course, both.
If you wear contact lenses, these will really help protect your eyes from the fumes – just don’t rub your eyes while you are preparing onions (or any food, for that matter). Glasses unfortunately won’t give the same level of protection as the air can still get to your eyes, although a COVID face shield may help.
Buy your onions fresh; older or more pungent onions will release stronger fumes than younger, fresher onions.
Store your onions in the fridge, or chill them for about an hour before you want to chop them. Onions release the enzyme more slowly when cold than at room temperature.
Once the onion has been cut, try to keep the cut side down against your chopping board as much as possible; this will reduce contact with the air around it. This is usually the safest way to prepare fruit and vegetables anyway, as having the flat, cut side down provides a more stable base than the curved or rounded side.
Don’t cut through the root until the last minute; this is where the highest levels of enzyme are. (The root can also be useful in helping to hold the onion together while you chop, see below.)
Work near an open window if you can, or if you have an extractor fan, turn it to high to remove the fumes.
To minimise the release of fumes in the first place, it’s important to use a suitable, sharp knife; this will give a clean cut and not a ragged, torn cut which will cause more damage the flesh of the onion and so release more of the enzyme into the air.
Place the onion on a chopping board and cut the top off; do not cut off the root end as we are going to use this to hold the onion together as you cut.
Cut the onion in half from the top down to, and through, the root and peel away the outer skin.
Place the halved onion flat side down on your chopping board; this will keep it stable and easier to chop.
Keeping your fingers clear, point the tip of the knife towards the root end and make smooth vertical cuts downwards through the onion, slicing from the tip towards – but NOT through – the root. (You can make several horizontal cuts first, angling the knife slightly downwards and slicing from the tip towards the root, but this requires more control to do safely and isn’t necessary unless you need perfect, even dice.)
Now turn the onion so that the top end is nearest to your knife and, cutting across the top of the onion and moving towards the root end, slice downwards smoothly; you may need to hold the onion together as you finish cutting but remember to keep your fingers well away from the blade. The onion should fall into small, evenly-sized pieces.
You will be left with the bottom, root section of the onion; put this flat side down on the board and then chop up and down carefully around it to remove the remaining edible onion, discarding the root.
So how did you do? Tag us on Instagram @paudinpro and show us your new chopping skills!