Citrus fruits belong to the family of Rutaceae, subfamily Aurantioideae. The family of citrus fruits is made of three genuses: Citrus, Fortunella and Poncirus Trifoliata. Despite the genus of citrus fruits is made of three genders only and eighteen defined species, there are many natural mutations. For this reason citrus fruits are very common in the world, with which have also been created many hybrids. According to a botanical point of view, the fruit is a hesperidium, that is a berry with a pulp divided in segments containing seeds. The pulp of citrus fruits contain cellulose, whereas the juice contains carbohydrates, citric and tartaric acid, proteins, ashes, vitamin C, lipids, carotenoids and chlorophyll.

 The homeland of the Citrus genus is China and India, Poncirus is from Korea and China, whereas Fortunella is from China. China and other neighboring regions are the territories from which citrus fruits have been originated, it is right in these regions we can find the first written evidences about citrus fruits. From the far east, citrus fruits begin to spread in the neighboring countries and arrive to India, Indochina and the islands of Southern Chinese Sea, the Philippines sea and the Indian ocean. From China citrus fruits also arrive to Japan: the modern satsuma mandarin, making 80% of this country's production, derives from Chinese guanxi. It seems this mandarin has been imported in Japan in 1500 and it quickly adapted to the new soil therefore becoming a typical product.

 The first written information about citrus fruits in India dates back to the times of the first written forms of Sanskrit, the Indo-European language imported from Aryans between 2000 and 1000 BC. In Sanskrit, citron and lemon are translated with the same word jambila: this term is found for the first time in the Vajasaneyi samhita, written around 800 BC. As in Sanskrit do not exist ancient words to refer to orange, this support the hypothesis it was imported in India from China about 2000 years ago, probably by the migrations from Yunnan to the Brahmaputra valley. It is known people from India had cultural and commercial contacts with the people of Mesopotamia, the land between the Tigris and Euphrates rivers. Despite the climate was not suited for the cultivation of citrus fruits, the skill of Mesopotamian agriculturists was successful in overcoming this limitation.

The most common varieties of citrus fruits: orange and lemon

 It is very likely the cultivation of citrus fruits made its way from India to Afghanistan and Pakistan, from here it spread in the west. Another evidence of the “migration” of citrus fruits to the west is offered by Jewish sacred books: the frequency with which the citron plant is mentioned suggests the Jews knew citrus fruits, or at least citron, before the Christian era. In Greece the citron plant is mentioned in many documents. In some papyri citron is mentioned with the word kitron, in other documents of the sixth century, such as the ones of Galen, it is used the term kitrion or kitreos. Theophrastus (372-287 BC) in his book “Historia plantarum”, describes the citron plant by specifying it was a plant common in Persia and in the land of Media. Another evidence is found in a book dated back to 200 AD, “Deipnosophistae” written by Athenaeus, in which it is said Juba, king of Mauritania, in his “History of Libya” mentioned this fruit and said it was called “Esperya apple” by Libyans. According to these evidences, it seems Greeks did not know any citrus fruits but citron, although the expedition of Alexander reached Punjab (India) and botanists also took part to the expeditions.

 Ancient Romans called citron malus medica first, then citrus. The first mention in Latin literature dates back to the second century BC by Cloanzio Vero, followed one century later by botanist Opium who mentioned it in its book “de Silvestris Arboribus”. Theocritus from Syracuse, who lived in the second century BC, did not mention it. In the Middle Age, during the first crusades, French saw for the first time citrus fruits and therefore introduced them in their homeland. Also the maritime republics contributed to the spreading of citrus fruits. In the twelfth, thirteenth and fourteenth centuries citrus fruits were common all over Italy, Spain and South France. It is believed sweet orange was not introduced in Europe by Arabs or by maritime republics: it probably were Portuguese to introduce it in the Old Continent. In fact, one of the first names used for sweet orange was “Portugal”. During Renaissance citrus fruits were spread and known everywhere: this is also proven by the many written documents, as well as being depicted in many paintings.

 In Italy the best climate for the cultivation of citrus fruits is in the south. In central and northern regions became common the custom of planting them in earthenware vases, which could be exposed to the sun during summertime and during wintertime moved in a place sheltered from the cold. This technique of cultivating citrus fruits also spread in France, and it was then adopted by Germans, Belgians and Dutch as well. At the end of 1700s citrus fruits were known in America too, introduced by Europeans during the colonization of the continent. As time passed by, new varieties of citrus fruits were discovered, including bergamot, grapefruit and Mediterranean mandarin, clementine and tangerine. In particular, bergamot was probably originated by a spontaneous hybridization, whereas grapefruit was discovered in the Barbados Island and was described in 1750 by Griffiths Hughes, whereas in 1789 Patrick Browne described the grapefruit discovered in Jamaica, and both them called it the “forbidden fruit”.

 The family of citrus fruits is vast and includes tens of varieties, many of them are used for nutritional purposes as well as in the cosmetic industry, others, which are not considered edible, are used by the cosmetic industry only because of their essential oils. Following is a list of the most important citrus fruits varieties, their use and properties.

• Sweet Orange - it is an evergreen tree coming from China and Japan, it was introduced in Italy by Arabs in the fourteenth century. Sweet orange contains citric acid, sugar, vitamins and mineral salts, it is used for the production of marmalade, juices, essences and perfumes. There is also a red variety, less and less common because of the preference of consumers for the seedless varieties. The essence of orange blossoms is very expensive and used for the production of perfumes
• Bitter Orange - the fruit of this variety is not edible and it is mainly used for the production of marmalade's, whereas leaves and flowers are used for the extraction of the essential oil
• Bergamot - it is believed it is a natural hybrid of bitter orange. From bergamot it is obtained an essential oil highly regarded by the industry of perfumes, used as a base for the preparation of the eau de cologne. The best quality oil is obtained by the plants cultivated along the coast of Calabria (Italy) as from these fruits can be obtained a percentage of esters of 35-45%
• Citron - of Persian origin, the fruit of the citron can even weigh one kilogram (about 2.2 pounds), it is used for the production of candied fruits, to obtain the essence used for the production of perfumes, in medicine and in the industry of liquors
• Chinotto - cultivated in the Mediterranean areas, it has an aspect similar to orange with a basically bitter taste and a weight of 40-50 grams. It is used industrially for the preparation of candies and beverages, usually colored with caramel (this explains the color of the chinotto beverage)
• Lemon - it is an evergreen tree, characterized by oval shaped leaves and yellow colored fruits. Lemon is the most important citrus fruit, both for direct consumption, as well as for industrial purposes. The juice of the fruit, rich in citric acid and vitamin C, is used as astringent, antiscorbutic and thirst quencher. Lemon is also used by the liquor and cosmetic industry. Also the industry of soap makes use of lemon derivatives. In past times, lemon juice was used as antihemorragic and disinfectant, and sailors used it as a remedy for scurvy (lack of vitamin C) during their long journeys
• Lime - because of its susceptibility to cold, lime is mainly cultivated in tropical and sub-tropical areas. Fruits have a small size and very acid, are used for the preparation of juices and cocktails. Lime is also used by the cosmetics and soap industry. Being an evergreen plant, lime is also used as an ornamental plant which, in favorable conditions, blossoms all year long
• Kumquat - fruit having little commercial importance, of small size and with a sweet skin which, as opposed to the other varieties of citrus fruits, is edible. Because of this characteristic, it is mainly used for the production of candied fruits
• Pomelo - it is cultivated in Thailand only and has no commercial or industrial use, it is used locally for the preparation of homemade jams
• Mandarin - it is an evergreen bush from China, the fruit is similar to orange but with a smaller size. The juice of the fruit, rich in vitamin C, is used by the liquor industry. Its importance is now declining because of clementine, which has less calories and is more appreciated by consumers
• Clementine - it is a natural hybrid from Tunisia and, just like the other citrus fruits, it is rich in vitamin C
• Grapefruit - it is a tree having a fruit similar to lemon, of yellow color, coming from India, rich in vitamin C and fibers. In the 1990s in the United States, it has been obtained pink grapefruit, a hybrid obtained by the orange, rich in vitamin C and vitamin A. It is very important according to an industrial and commercial point of view, because it is consumed fresh and used for the preparation of juices and beverages. Pink varieties are used for fresh consumption only, as carotenoids contained in the fruit have some problems in the preparation of juices

 Arabs discovered the extraction technique for essential oils, however the industrial production of perfumes with extracts of the skin of fruits and petals of flowers was invented by Italians. Naples and Sicily developed these techniques and from here started the fashion of exotic perfumes, which then spread all over Europe. According to a nutritional and dietetic point of view, citrus fruits have a fundamental importance in the diet of the Mediterranean area which is also the main area of production and consumption. In order to get the maximum benefits from citrus fruits juices, it is always advisable to consume them soon after their preparation, because vitamin C, when in contact with oxygen, light and heat, gets rapidly spoiled.