Thursday, 24 October 2013

On Onions

Well, I was cutting up an onion today to make curried eggs for lunch, and I was wondering why onions make you cry. I know that the only way I get relief from my tears is to wear goggles when I cut up onions, and this is not very convenient!

I found, in my travels, why onions make you cry. I also found out some other interesting things, too!

When you cut an onion, you break cells, releasing their contents. Amino acid sulfoxides form sulfenic acids. Enzymes that were kept separate now are free to mix with the sulfenic acids to produce propanethiol S-oxide, a volatile sulfur compound that wafts upward toward your eyes. (I know - I would never have thought of this.) This gas reacts with the water in your tears to form sulfuric acid. The sulfuric acid burns, stimulating your eyes to release more tears to wash the irritant away.

Cooking the onion inactivates the enzyme, so while the smell of cooked onions may be strong, it doesn't burn your eyes. Aside from wearing safety goggles or running a fan, you can keep from crying by refrigerating your onion before cutting it (slows reactions and changes the chemistry inside the onion) or by cutting the onion under water.

Above are the three main colours of the many types of round onions you can get. (Of course, you can have spring onions too.) I actually didn't know you could get white ones!

Further Reading
(I found waaaayyy more information about this subject than I bargained for!! Here are a few of the most interesting pages I found.)

- This page has some basic information about the onion, what to use it with and what to substitute it for.

This page is rather interesting, listing most of the commoner types of onions. And even out of the common ones I found plenty that were new to me!

This Wikipedia page has a lot of interesting onion info.

This page tells you what sort of onion to use when. I found it fascinating.

- For those of you who like the practical side of things, here is a pile of onion recipes. Some of these look really nice!

What have you learnt about onions that you didn't know already?


  1. Breathing through your mouth instead of your nose usually helps

    1. That's a good piece of advice. I must try that. :)


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