Making a curry without onion is almost unthinkable. Nearly every curry starts with cooking onions. Some curries have a lot of onions and some have only a small amount of onions. But the onions are always there.
Onions have been grown around the world for thousands of years and their taste varies from sweet to very pungent (Indian curries usually use more pungent onions). And their aroma also varies from almost nothing to a pungency that makes your eyes water.
Why do some onions make your eyes water? It’s because they contain enzymes that begin to break down when you cut the onions. The enzymes create mild acids that are unstable and turn into a gas. The gas contains sulphur and moves through the air and reaches your eyes where it reacts with the water in your eyes to form a mild sulphuric acid. Not surprisingly, the acid irritates the nerves in your eye and makes them sting. The eyes react to the stinging by producing tears that dilute the acid and clean out your eye.
Not all onions are this strong. But if they are, or you cry easily when cutting onions, you can take some avoiding actions. Try cutting the onions under a running tap so that the gas reacts with the tap water and not your eyes. Alternatively, you can cut up the onions in a bowl of water to have the same effect. Most of the enzymes are concentrated in the root of the onion so you could cut off the root last (and under running water).
Once the cooking has started, the eye-watering problem is gone.
But you should take care when cutting up onions so as not to rub your eyes with your fingers because that is really going to hurt. If this happens, wash out your eyes with lots of water.
Onions are a key component of curries. Most recipes start with instructions to heat up the oil, over a medium to high heat, and cook the onions until they are soft (onions soften and have a golden colour when they are cooked but some recipes tell you to keep cooking the onions until they are black and crisp). The onions are often cooked with ginger root and garlic.
After being peeled, onions are usually finely chopped, coarsely chopped or sliced. All things being equal, finely chopped onions take less time to cook than coarsely chopped onions. Curries will be browner and darker the longer the onions are cooked – you should only cook the onions until they are soft (around 10 minutes, depending upon the heat of the oil) unless you are told otherwise.
Deep fried, or blackened, onions are sometimes used as a garnish for curries such as on a Do Piaza (or dopiaza).
And onions are good for you. They contain anti-cholesterol, anti-cancer, antioxidant and anti-inflammatory components that are effective in treating a wide range of diseases such as diabetes, heart disease and even the common cold.
Next time you make a curry, make sure that you have a couple of good onions nearby.