Knowing your onions

Onions form the basis of cooking in most countries and I reckon they’re probably the world’s most popular ingredient.

Friday, 28 November 2014

Knowing your onions

Native to Asia, these bulbs grow underground and are used to add depth and flavour to savoury dishes. They are part of the Allium family related to leeks and chives. Dry onions have fresh, juicy flesh, papery skin and a pungent flavour with astringent qualities. These diminish the longer you cook them and they get sweeter, too.

How you cook onions is a really important technique to understand. Depending on the dish you’re creating you need to think about how you want your onions to feature, from caramelising them, to cooking them until they turn a dark brown (not burnt) to give depth and flavour, or nice and chunky so they feature as part of the end dish. Raw, baked, steamed, sautéed, deep fried, you can do it all with onions and how you do it is all very important stuff!

Types of onions

There are hundreds and they all vary in pungency. When you buy them, make sure they are firm and clean without any mould patches or bruising. And, of course, make sure they’re the right one for the dish:

Yellow onions

These tend to be the most commonly used and have a golden skin with a white flesh. Usually hot and pungent. Brown onions - Smaller than the yellow ones and more pungent; perfect for cooking with.

White onions

Fairly large in size with a white, papery skin. They have a strong assertive onion flavour and are good for baking or stuffing.

Spanish onions

The biggest of all of the onions with a brown skin, these are mild and sweet so they’re great for salads.

Red onions

A wonderful dark purple skin with a beautiful white and purple flesh. Milder in taste and taste fab in salsas and in salads.

Salad onions

These are small and white with a long green stem that is used along with the bulb. These are immature onions that are enjoyed before the bulb fully matures. Mild in flavour, they are delicious when used raw in salads (for colour as well as flavour).


Shallots are a subspecies of onion and are much smaller with a very delicate flavour. These are very important in French cooking!

Chopping Onions

We’ve all cried a tear or two over an onion and there are some weird and wonderful ways to try and avoid this. But if you’ve ever wondered why we cry in the first place, then here you go… When you cut an onion you damage the cells, and the onion releases volatile gases, These set off a series of chemical reactions that result in a gas called propanethial S-oxide being released. This gas irritates our eyes and our body reacts by releasing tears to dilute the gas, hence we cry. On the plus side, the more often you chop onions the amount of eye irritation is reduced – so the more you cook the less you’ll sob!

There are plenty of old wive’s tales about how to cut onions so your eyes don’t water, from holding your breath to cutting onions with a spoon in your mouth (seriously!) to even chewing a raw onion while you chop. None of which make any sense to me. Someone told me once to put a lit match in my mouth while cutting but I couldn’t see how setting fire to my eyelashes would help.

chopping-onions blog

Anyway here are a few sensible suggestions that might be more useful:

1. When peeling and chopping the onion, leave the root on. 2. Use a sharp knife to cut – this causes less cell damage so fewer irritants will be released. 3. Once cut, turn the onion over so the flat side sits on the chopping board and once chopped, move the onions into a prep bowl, or to a pan with a lid. 4. Chill your onions as this slows the release of the irritant. If all else fails, invest in some onion goggles

Cooking Onions

Many dishes require onions to be diced, and it’s really important that you chop them all the same size so they cook at the same speed and in the same way. Start by heating your pan and oil on a high heat then add your onions. Make sure you stir them well so they are exposed to the heat evenly. Then after few minutes, the residual water will evaporate and the onions will become translucent. If you’re adding more vegetables then add them at this stage. This gives you a solid base which doesn’t have a strong onion flavour, but will have a nice depth.

For dishes that need a more robust onion kick, like a Jalfrezi or a stir fry, then cut your onions into slices or chunks. Then cook them more quickly on a higher heat so they retain their crispiness and give an even richer onion flavour.

For other dishes where you are looking for a greater depth, then cook the onions low and slow for a long time. Cooking them like this means they lose all of their astringent qualities and become completely caramelised, tender, sweet and delicious.

Indian Cooking

When it comes to Indian cooking it’s all about the onions. These form the basis of your masala sauce and if you take time to cook the onions correctly, then the rest of the dish will just follow easily. So for a great curry follow my three simple rules:

Meat dishes

1. When cooking a meat curry where you are looking for a deep, rich, intense, tomato based sauce the depth will comes from cooking your onions low and slow until they’re a dark drown colour. For dishes such as Thari Wala Chicken or Lamb Bhuna this will ensure that the masala sauce is thick and full of flavour. If you find that your onions are catching on the bottom of the pan then just add a little splash of water and stir. The longer you leave them to cook and brown the darker the coulor of your dish will be so for a really rich dark brown masala, I usually cook the onions for a good 30 minutes.

Onions 2blog

2. When cooking a meat dish with what I would call a white sauce, such as a Chicken Korma one that has a creamy finish and is either yoghurt, cream or coconut based. These sauces are lighter in colour and flavour so the onions need to be chopped much finer and cooked until they only just turn golden.

Vegetables or Lentils

3. These ingredients require an overall lighter flavour where the textures and flavours of the vegetables are more dominant so the base needs to be lighter. Ideally I would only sauté the onions for about 15-20 minutes to soften them until they just begin brown.

Onions 1 blog

Health Benefits

Onions are much more pungent when raw and the volatile oils released from onions are rich in Vitamins B and C, a whole host of minerals such as phosphorus and Magnesium, and they are a great source of folic acid too.

Some of these components are destroyed by heat, so eating raw onions is good for you (but maybe just not on a first date!) Some of us with sensitive tummies can find raw onions difficult to digest - so be aware.

Medicinal Properties

Historically onions were used as a preventative medicine for cholera and the plague. They are also know to have anit-inflammatory and anti-histamine properties too. The Romans used onions to help soothe symptoms of the common cold but more interestingly gladiators would use them as a rub down to tone up their muscles (oohhhh)!
Over the years onions have also been used to help with asthma, the active properties have come from a compound called allyl propyl disulphide. This has similar properties to insulin in that it can also help regulate and balance blood sugar levels but it's always best to see your doctor if you are having any problems related to this.

For more exciting information check out the infographic.

Onion infographic blog

Infographic provided by Hari Ghotra

To embed this infographic in your website, simply copy the code below and paste it into your site:

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