Seville orange

The Seville orange is a hybrid of Citrus maxima (pomelo) and Citrus reticulata (mandarin), originating in Southeast Asia, likely in the region of southern China or Indochina. It spread along trade routes to the Middle East and Mediterranean, reaching Spain by the 10th century, where it became naturalized, especially around Seville. The tree is evergreen, with glossy leaves and fragrant white flowers, and bears fruit that is round to slightly oblate, with a thick, rough, deep-orange rind. The pulp is acidic and bitter due to compounds like naringin and neohesperidin, which are not found in sweet oranges. The fruit matures in winter and is harvested from December to February, a timing that aligns with marmalade-making season.

The Seville orange is the gold standard for marmalade, as its high pectin content ensures a firm set without added pectin, and its sharp flavor balances sugar. In Spain, the fruit is used to make mermelada de naranja amarga, and the peel is candied for confections. The juice and peel are also key ingredients in liqueurs such as Cointreau, Grand Marnier, and curaçao, where the bitter oils impart complexity. Beyond marmalade, the fruit is used in savory dishes, like the Pato a la naranja (duck à l'orange), and in marinades. The essential oil from the peel, known as neroli when distilled from flowers, is used in perfumery and flavorings. The dried peel is a common spice in Asian cuisines, and the fruit is used to make bitter orange sauce in British cooking.

In traditional medicine, Seville orange has been used for centuries to treat digestive issues, insomnia, and skin conditions, with the peel containing synephrine, a compound similar to ephedrine. Modern research has explored its potential for weight loss and athletic performance, but clinical evidence is limited, and high doses can cause cardiovascular side effects. The fruit is also a symbol of Seville, where orange trees line the streets, and the city's annual orange harvest is donated to marmalade producers. In the UK, Seville oranges are a seasonal import, with a short window in January, and are often sold specifically for marmalade-making. The bitter orange is also used in religious and cultural rituals, such as in the Jewish festival of Sukkot, where the etrog (a citron) is used, but the Seville orange is sometimes substituted in some traditions.

Beyond marmalade, the Seville orange has niche uses: its wood is used for fine carpentry, and the flowers are a source of neroli oil, which is more expensive than the fruit's peel oil. The fruit is also used in traditional Chinese medicine as zhi shi and zhi ke, for digestive disorders. In the 18th century, the Seville orange was used as a rootstock for sweet orange cultivation, and it remains a common rootstock today due to its disease resistance. The bitter orange is also the parent of many hybrid citrus varieties, including the bergamot orange, which is used in Earl Grey tea. A little-known fact: the Seville orange is not actually native to Seville; it was introduced by the Moors, and the name is a misnomer. Additionally, the peel contains a compound called auraptene, which has shown anti-cancer properties in animal studies, though human research is pending.

Naringin

A flavonoid glycoside that gives bitter taste to citrus peels.

Synephrine

An alkaloid found in bitter orange, used in weight-loss supplements.

Neroli

Essential oil distilled from orange blossoms, used in perfumery.

Pectin

A natural gelling agent found in fruit, used to set jams and marmalades.