Citrus fruits belong to the family Rutaceae, and the fruits belonging to the genera Citrus, Fortunella, Poncirus and their intergeneric hybrids are collectively known as citrus. The fruit of citrus is a type of berry, and the ripe skin contains two pigments, xanthophyll and carotene, which are responsible for their characteristic colour. The skins also contain oils which are often used in perfumes. The white pith of citrus fruits, known as albedo, is also a rich source of pectin, and that is why the skins readily form jams. Citrus comes from South East Asia, and has been cultivated in China for thousands of years. It is thought that Arab traders brought the fruit to the Middle East and Palestine and it reached Europe by the year 1480. Through colonization citrus spread to North America, the Caribbean and to Southern Africa. Citrus species hybridize easily, and some popular varieties such as grapefruit have only appeared in relatively recent times. The bitter taste of the grapefruit is due to the compound naringin, a flavone glycoside. Some common varieties of citrus include grapefruit, lemon, lime, orange, kumquat and mandarin, including tangerines.
Citrus fruit is known for its high vitamin C-content, but citrus also contains substantial amounts of vitamin A, and they are an excellent source of the mineral calcium. Most of the genera yield essential oils, and citrus has medicinal properties. Citrus is one of the few groups of fruits with established cancer-preventive properties, and the compounds associated with this phenomenon are the flavonoids, glucarates, carotenoids, coumarins, limolene, mono- and tri-terpenes and phenolic acids.82,85
Oranges (Citrus sinensis)
The sweet orange is native to China, and important cultivars include navels, blood oranges
and valencias. The sweet orange is used mainly for its juice, but it is delicious on its own.
Lemons (Citrus limon)
Lemons are used particularly for their juice and in food preparation. It is important to note that lemons and limes are alkaline forming fruits in spite of their acid taste, as citric acid is a weak organic acid that is readily broken down in the body. Lemons can be used in cooking and to replace vinegar in salad dressings and spicy preserves.
Mandarins and Tangerines
Mandarins probably originate from India, and are appealing because of their loose skin. Hybridization with pomelo has produced tangelos which are very aromatic and have a rich fruity taste.