Bitter orange

Their sharp, bitter juice and aromatic peel are best known in marmalade. You can also use the juice in sauces for duck or pork, or whisk it with oil, garlic and herbs for a marinade.

Simmer the whole fruit in water until the peel is tender, often around 1–2 hours; cool, halve and remove the pips, then slice the peel and cook it with the strained cooking liquid and sugar. For a reliable set, bring the mixture to about 104–105 °C.

Yes, but the flesh is much more sour and bitter than a sweet orange, so most people use small amounts of the juice or zest rather than eating one as a snack. Avoid the white pith if you want to reduce bitterness.

Choose firm fruit that feels heavy for its size, with fragrant, unblemished skin. The peel is used as well as the juice, so avoid fruit with mould or damaged, soft patches.

Keep them in a cool, dry place if you will use them within a few days. For longer storage, refrigerate them in a breathable bag; freeze the juice or finely grated zest if you need to keep them longer.

For marmalade or a sauce, combine sweet orange juice and zest with lemon juice to bring back some of the sharpness. It will be less bitter and less aromatic than bitter orange, so it is an approximation rather than an exact swap.

Seville oranges are a well-known type of bitter orange, especially valued for marmalade. The name bitter orange also refers more broadly to the citrus species Citrus aurantium.