The Cook’s ABC – Know your onions

By Alan Lugton, Cookery Manager

There is a lot to say on the beneficial health properties of the simple onion, as well as its many applications in the kitchen, improving the flavours of your favourite meals.

Though it has to be said, they are a complete nightmare to prepare when in a rush, often leaving hapless cooks wandering blindly around the kitchen in tears. Have no fear – knowing your enemy can help you beat it, and in no time you will be chopping onions like a pro.

Cry me a river

So what is it about the onion that actually causes us to open the floodgates whenever we are cutting them? I always like to compare the layers of an onion to layers of bubble wrap, with each bubble (or cell) filled with evil eye burning acid – it helps when thinking about the processes I am going to go through with you.

The cells don’t actually hold burning acid in them, but instead enzymes and amino acids which, when released into the air as fine mist, react together to produce ‘Syn-Propanethial-S-oxide’, a volatile gas which reacts with the eye, causing stinging.

That’s the sciencey bit over, so what can we do to make chopping onions less painful? We can generally approach this in two ways, either by:

  1. blocking the gas from reaching our eyes, or
  2. reducing and limiting the gas that comes out of the onion

The first is easy – wear goggles, not very convenient though. Glasses will have some effect but as it’s the gas that causes the stinging, not the mist directly, some of it will find a way around.

The second point has been the subject of much discussion over the years and has produced some interesting solutions of which only a few are credible. I have listed these at the botton of the blog, however I want to focus on the correct technique for preparing an onion to chop first, as many of the other tips won’t work as well, if you haven’t got the basics.

How to prepare an onion

First peel the skin off…

The outer layers of the onion are leathery and/or brittle as all the chemicals have started to dry out and are essentially inactive. So peeling the skin and outer layers won’t set you off.

The best way to do this is to use a small paring knife to lift the skin at the top of the onion, then pinching it between the blade and your thumb peel the skin down to the root.  Don’t be tempted to cut the top off as this will release the chemicals inside.

Once all the skin is peeled off – trim the root, being careful not to cut into the flesh – you will now have a nice peeled onion ready to chop. Because the inner flesh has not been cut – it can sit there without making you cry, until you are ready to cut it up.

A word on knives – If I can take you back to the bubble wrap metaphor – if you were to pop one of those bubbles – the chemicals inside would spray everywhere – however if you slice through them with a sharp knife they just stay there and slowly drain out.

Using a blunt knife is a bit like popping those bubbles, so always use as sharp a knife as you can get so we can slice through them effortlessly. A word of caution though if you do use a really sharp knife and then try to cut through an unpeeled onion, you are effectively wrapping a piece of tough skin around your blade and you will again end up squashing those bubbles rather than cutting them.

A word on technique – Good slicing or chopping requires the blade of the knife to run across the onion, from heel to tip, while applying pressure. If you place the blade on top of the onion and just push down you will just squeeze and pop the cells and release lots of chemicals. This is also the same reason why you should never double chop – once your onion is chopped or sliced – put it aside. With double chopping you will cut the onions on the top of the pile – but not before the flesh below gets squeezed to bursting point and once again the tears will rain down.

Once you have these essential elements in place then we can look at these final tips.

 Top tips for tear free chopping

  1. Cool your onions – whether it is straight from the fridge, running underwater or even from the freezer cooling an onion works, as it makes the chemicals slightly more viscose and reduces any fine mist and slows production of the volatile gas.
  2. Use a sharp Knife – See above
  3. Use good knife techniques – See above
  4. Keep your onion face down – When making the initial slices to half or quarter the onion, keep the exposed side towards the board. this will reduce chemicals rising into the air.
  5. Cut fast and safe – The quicker you get this over and done with the less chance you have of getting it in your eyes but dont go fatser than your skills allow.
  6. Never double chop – Remember the bubble wrap? Double chopping is like stomping all over it with boots on.

Other things that might be worth a try:

  1. Cut onions near a steam (draws the vapours away from you)
  2. Whistle while you work – (blows vapours away)
  3. Breathe through you mouth – and while you’re at it, stick your tongue out as the vapours will be drawn here first and avoid the eyes.

Warning: the last three tips will make you look rediculous – but less so than wearing goggles.

That is all!

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