Onion

I recently learned that “purple” garlic really does taste different to its white counterpart.

It’s a “hardneck” variety, meaning it’s got a wooden stem in its centre: this makes the cloves larger, sweeter, milder, and more evenly-sized.

Which left me wondering ― is there an equivalent rationale behind why some onions are more intense than others?

Anyone who regularly cooks will know that picking your alliums often feels like Russian roulette. The eye-wateringly sharp kinds seem to come out of nowhere, and often appear in the same pack as their less offensive peers.

But why does it happen, and can you tell which onions will make your eyes water before you slice into them?

It’s all down to sulphur

To understand why some onions are more likely to get you to “cry,” we need to look at what causes the reaction.

Per Britannica, onions are excellent at absorbing sulphur as they grow. This is used for amino acids in the bulb.

But when you slice into an onion, its cell walls break down. That allows enzymes to meet sulphur-rich amino acids, creating a chemical known as syn-propanethial-S-oxide (

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