Onion: how to choose, store, soak and substitute it

Aroma compounds

The volatile molecules behind its aroma. Each one adds a distinct note.

Propanethial S-oxide the lachrymatory factor: sharp, irritating and penetrating note of freshly cut onion
Propanethiol the main odor source: sulfurous, pungent, fresh-cut onion
Dipropyl disulfide mellower cooked-onion aroma with a slightly nutty undertone
Methyl propyl disulfide green, alliaceous note typical of cooked onion and scallion
Dimethylthiophene formed on frying: the characteristic fried, toasted onion aroma

In the kitchen

It is the aromatic base of the sofrito in countless stews, sauces, soups and rice dishes. It is also used raw in salads and fresh sauces, pickled, caramelised or fried as a side. In Chilean cooking it is cut into thin strips (pluma), soaked, for Chilean salad, and finely diced, also soaked, for pebre; finely chopped it holds up the pino filling of empanadas and pastel de choclo; in thick chunks it goes on anticuchos, and in pluma it is sautéed for cazuela. The longer and slower it cooks, the sweeter it becomes.

Season Onions are available all year: storage onions are harvested in late summer and autumn and stored, and in spring and early summer new onions are sold, sweeter and juicier.

Pairs with

Garlic
Tomato
Beef
Potato
Bell pepper
Egg

How to choose, store and substitute it

How to choose it

Choose firm onions that feel heavy for their size, with dry, glossy, crisp skin and a closed, dry neck. Avoid those that are soft when pressed, with marks, mould or green sprouts, and those with a damp neck, which spoil first. New onions, with thin, moister skin, should be used within a few days.

How to store it

Keep them in a cool, dark, ventilated place (a mesh bag or basket, never a plastic bag) and away from potatoes, whose moisture and gases make them sprout: storage onions last 1 to 3 months. Once cut, keep in an airtight container in the fridge for 5 to 7 days. Chopped and frozen it lasts about 3 months, only for cooking, because it loses its texture when thawed.

What to use instead

Shallot: the same amount; it is milder and sweeter, ideal for dressings and sauces.
Leek (white part): one medium leek for each onion, for sofritos and soups.
Spring onion or scallion: for raw dishes; they add freshness without the bite of onion.
Onion powder: 1 tablespoon for each medium onion, only in stews and marinades.

Frequently asked questions about onion

How do you soak sliced onion for Chilean salad?

Cut it into thin lengthwise slices, leave it 10-15 minutes in cold water with a pinch of salt and drain it well. It loses its sharpness and turns crisp and easier to digest without losing flavour: it is the trick behind Chilean salad and pebre. For a milder result, change the water once.

How do I avoid crying when cutting onion?

Chill it 15-30 minutes in the fridge before cutting, use a very sharp knife (a dull edge crushes cells and releases more irritant compounds) and leave the root for last. Cutting near the extractor hood or with a window open also helps.

How do you caramelise onion?

Slice the onion and cook it for 40-45 minutes over low heat in a wide pan with oil or butter and a pinch of salt, stirring now and then; if it sticks, add a splash of water. Do not turn up the heat: it burns and turns bitter instead of browning. It yields about a quarter of the raw volume.

How much does one onion yield?

A medium onion (about 150 g) yields close to 1 cup of chopped onion. For the pino filling of empanadas, plan as much onion as meat: it is what makes it juicy.

Recipes with onion

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