Lemon juice

A medium lemon usually yields about 30–45 ml, or 2–3 tablespoons. Roll it firmly on the worktop before cutting, then squeeze; warming it briefly in your hands can help if it is cold.

Add it near the end of cooking, especially to sauces and soups. Prolonged boiling can make the flavour harsh; lemon zest added at the end gives a fragrant citrus note without needing more juice.

Keep it covered in the fridge and use it within a few days for the freshest flavour. For longer storage, freeze it in an ice-cube tray, then transfer the cubes to a sealed container.

Yes. Freeze it in small portions, such as tablespoon-sized amounts, so you can thaw only what you need for dressings, baking or drinks. Add frozen cubes straight to a pan when cooking.

Usually, yes: use the same amount in dressings, marinades and drinks. Lime tastes more floral and can be sharper, so taste the finished dish before adding more.

It lifts the flavour of fish, roast chicken, lentil soup, hummus and leafy salads. For a simple dressing, whisk it with olive oil, mustard and a little salt.

In dishes such as ceviche, the acid firms and changes the colour of the fish, but it does not reliably kill harmful germs or parasites. Use fish intended for raw or lightly cured preparations, keep it chilled, and cook it fully if you need a reliably cooked dish.