Orange (fruit)

Botanical information and terminology

All citrus trees belong to the single genus Citrus and remain almost entirely interfertile. This includes grapefruits, lemons, limes, oranges, and various other types and hybrids. As the interfertility of oranges and other citrus has produced numerous hybrids and cultivars, and bud mutations have also been selected, their taxonomy is fairly controversial, confusing or inconsistent. The fruit of any citrus tree is considered a hesperidium, a kind of modified berry; it is covered by a rind originated by a rugged thickening of the ovary wall.

Different names have been given to the many varieties of the genus. Orange applies primarily to the sweet orange – Citrus sinensis (L.) Osbeck. The orange tree is an evergreen, flowering tree, with an average height of 9 to 10 m (30 to 33 ft), although some very old specimens can reach 15 m (49 ft). Its oval leaves, alternately arranged, are 4 to 10 cm (1.6 to 3.9 in) long and have crenulate margins. Although the sweet orange presents different sizes and shapes varying from spherical to oblong, it generally has ten segments (carpels) inside, and contains up to six seeds (or pips) and a porous white tissue – called pith or, more properly, mesocarp or albedo—lines its rind. When unripe, the fruit is green. The grainy irregular rind of the ripe fruit can range from bright orange to yellow-orange, but frequently retains green patches or, under warm climate conditions, remains entirely green. Like all other citrus fruits, the sweet orange is non-climacteric. The Citrus sinensis is subdivided into four classes with distinct characteristics: common oranges, blood or pigmented oranges, navel oranges, and acidless oranges.

Other citrus groups also known as oranges are:

An enormous number of cultivars have, like the sweet orange, a mix of pomelo and mandarin ancestry. Some cultivars are mandarin-pomelo hybrids, bred from the same parents as the sweet orange (e.g. the tangor and ponkan tangerine). Other cultivars are sweet orange x mandarin hybrids (e.g. clementines). Mandarin traits generally include being smaller and oblate, easier to peel, and less acidic. Pomelo traits include a thick white albedo (rind pith, mesocarp) that is more closely attached to the segments.

Orange trees generally are grafted. The bottom of the tree, including the roots and trunk, is called rootstock, while the fruit-bearing top has two different names: budwood (when referring to the process of grafting) and scion (when mentioning the variety of orange).

Etymology

The word orange derives from the Sanskrit word for "orange tree" (नारङ्ग nāraṅga), which is probably of Dravidian origin. The Sanskrit word reached European languages through Persian نارنگ (nārang) and its Arabic derivative نارنج (nāranj).

The word entered Late Middle English in the fourteenth century via Old French orenge (in the phrase pomme d'orenge). The French word, in turn, comes from Old Provençal auranja, based on Arabic nāranj. In several languages, the initial n present in earlier forms of the word dropped off because it may have been mistaken as part of an indefinite article ending in an n sound—in French, for example, une norenge may have been heard as une orenge. This linguistic change is called juncture loss. The color was named after the fruit, and the first recorded use of orange as a color name in English was in 1512.

As Portuguese merchants were presumably the first to introduce the sweet orange to some regions of Europe, in several modern Indo-European languages the fruit has been named after them. Some examples are Albanian portokall, Bulgarian портокал (portokal), Greek πορτοκάλι (portokali), Macedonian portokal, Persian پرتقال (porteghal), Turkish portakal and Romanian portocală. Related names can be found in other languages, such as Arabic البرتقال (bourtouqal), Georgian ფორთოხალი (p'ort'oxali), Turkish portakal and Amharic birtukan. Also, in some of the Italian regional languages (e.g. Neapolitan), an orange is portogallo or purtuallo, literally "(the) Portuguese (one)", in contrast to the Italian arancia.

In other Indo-European languages, the words for orange allude to the eastern origin of the fruit and can be translated literally as "apple from China". Some examples are Low German Apfelsine, Dutch appelsien and sinaasappel, Swedish apelsin, and Norwegian appelsin. A similar case is Puerto Rican Spanish china.

Various Slavic languages use the variants pomaranč (Slovak), pomeranč (Czech), pomaranča (Slovene), and pomarańcza (Polish), all from Old French pomme d'orenge.

Common oranges

Common oranges (also called "white", "round", or "blond" oranges) constitute about two-thirds of all the orange production. The majority of this crop is used mostly for juice extraction.

Valencia

The Valencia orange is a late-season fruit, and therefore a popular variety when navel oranges are out of season. This is why an anthropomorphic orange was chosen as the mascot for the 1982 FIFA World Cup, held in Spain. The mascot was named Naranjito ("little orange") and wore the colors of the Spanish national football team.

Hart's Tardiff Valencia

Thomas Rivers, an English nurseryman, imported this variety from the Azores Islands and catalogued it in 1865 under the name Excelsior. Around 1870, he provided trees to S. B. Parsons, a Long Island nurseryman, who in turn sold them to E. H. Hart of Federal Point, Florida.

Hamlin

This cultivar was discovered by A. G. Hamlin near Glenwood, Florida, in 1879. The fruit is small, smooth, not highly colored, and juicy, with a pale yellow colored juice, especially in fruits that come from lemon rootstock. The fruit may be seedless, or may contain a number of small seeds. The tree is high-yielding and cold-tolerant and it produces good quality fruit, which is harvested from October to December. It thrives in humid subtropical climates. In cooler, more arid areas, the trees produce edible fruit, but too small for commercial use.

Trees from groves in hammocks or areas covered with pine forest are budded on sour orange trees, a method that gives a high solids content. On sand, they are grafted on rough lemon rootstock. The Hamlin orange is one of the most popular juice oranges in Florida and replaces the Parson Brown variety as the principal early-season juice orange. This cultivar is now the leading early orange in Florida and, possibly, in the rest of the world.

Other varieties of common oranges

Navel oranges

Navel oranges are characterized by the growth of a second fruit at the apex, which protrudes slightly and resembles a human navel. They are primarily grown for human consumption for various reasons: their thicker skin makes them easy to peel, they are less juicy and their bitterness – a result of the high concentrations of limonin and other limonoids – renders them less suitable for juice. Their widespread distribution and long growing season have made navel oranges very popular. In the United States, they are available from November to April, with peak supplies in January, February, and March.

According to a 1917 study by Palemon Dorsett, Archibald Dixon Shamel and Wilson Popenoe of the United States Department of Agriculture (USDA), a single mutation in a Selecta orange tree planted on the grounds of a monastery near Bahia, Brazil, probably yielded the first navel orange between 1810 and 1820. Nevertheless, a researcher at the University of California, Riverside, has suggested that the parent variety was more likely the Portuguese navel orange (Umbigo), described by Antoine Risso and Pierre Antoine Poiteau in their book Histoire naturelle des orangers ("Natural History of Orange Trees", 1818–1822). The mutation caused the orange to develop a second fruit at its base, opposite the stem, embedded within the peel of the primary orange. Navel oranges were introduced in Australia in 1824 and in Florida in 1835. In 1870, twelve cuttings of the original tree were transplanted to Riverside, California, where the fruit became known as "Washington". This cultivar was very successful, and rapidly spread to other countries. Because the mutation left the fruit seedless and, therefore, sterile, the only method to cultivate navel oranges was to graft cuttings onto other varieties of citrus trees. The California Citrus State Historic Park and the Orcutt Ranch Horticulture Center preserve the history of navel oranges in Riverside.

Today, navel oranges continue to be propagated through cutting and grafting. This does not allow for the usual selective breeding methodologies, and so all navel oranges can be considered fruits from that single, nearly two-hundred-year-old tree: they have exactly the same genetic make-up as the original tree and are, therefore, clones. This case is similar to that of the common yellow seedless banana, the Cavendish, or that of the Granny Smith apple. On rare occasions, however, further mutations can lead to new varieties.

Cara cara navels

Cara cara oranges (also called "red navel") are a type of navel orange grown mainly in Venezuela, South Africa and in California's San Joaquin Valley. They are sweet and comparatively low in acid, with a bright orange rind similar to that of other navels, but their flesh is distinctively pinkish red. It is believed that they have originated as a cross between the Washington navel and the Brazilian Bahia navel, and they were discovered at the Hacienda Cara Cara in Valencia, Venezuela, in 1976.

South African cara caras are ready for market in early August, while Venezuelan fruits arrive in October and Californian fruits in late November.

Other varieties of navels

Blood oranges

Blood oranges are a natural mutation of C. sinensis, although today the majority of them are hybrids. High concentrations of anthocyanin give the rind, flesh, and juice of the fruit their characteristic dark red color. Blood oranges were first discovered and cultivated in Sicily in the fifteenth century. Since then they have spread worldwide, but are grown especially in Spain and Italy under the names of sanguina and sanguinella, respectively.

The blood orange, with its distinct color and flavor, is generally considered favorably as a juice, and has found a niche as an ingredient variation in traditional Seville marmalade.

Other varieties of blood oranges

Acidless oranges

Acidless oranges are an early-season fruit with very low levels of acid. They also are called "sweet" oranges in the United States, with similar names in other countries: douce in France, sucrena in Spain, dolce or maltese in Italy, meski in North Africa and the Near East (where they are especially popular), şeker portakal ("sugar orange") in Turkey, succari in Egypt, and lima in Brazil.

The lack of acid, which protects orange juice against spoilage in other groups, renders them generally unfit for processing as juice, so they are primarily eaten. They remain profitable in areas of local consumption, but rapid spoilage renders them unsuitable for export to major population centres of Europe, Asia, or the United States.

Nutritional value and phytochemicals

As with other citrus fruits, orange pulp is an excellent source of vitamin C, providing 64% of the Daily Value in a 100 g serving (right table). Numerous other essential nutrients are present in low amounts (right table).

Oranges contain diverse phytochemicals, including carotenoids (beta-carotene, lutein and beta-cryptoxanthin), flavonoids (e.g. naringenin) and numerous volatile organic compounds producing orange aroma, including aldehydes, esters, terpenes, alcohols, and ketones.

Acidity

Being a citrus fruit, the orange is acidic: its pH levels range from 2.9 to 4.0.

Grading

The United States Department of Agriculture (USDA) has established the following grades for Florida oranges, which primarily apply to oranges sold as fresh fruit: US Fancy, US No. 1 Bright, US No. 1, US No. 1 Golden, US No. 1 Bronze, US No. 1 Russet, US No. 2 Bright, US No. 2, US No. 2 Russet, and US No. 3. The general characteristics graded are color (both hue and uniformity), firmness, maturity, varietal characteristics, texture, and shape. Fancy, the highest grade, requires the highest grade of color and an absence of blemishes, while the terms Bright, Golden, Bronze, and Russet concern solely discoloration.

Grade numbers are determined by the amount of unsightly blemishes on the skin and firmness of the fruit that do not affect consumer safety. The USDA separates blemishes into three categories:

1. General blemishes: ammoniation, buckskin, caked melanose, creasing, decay, scab, split navels, sprayburn, undeveloped segments, unhealed segments, and wormy fruit
2. Injuries to fruit: bruises, green spots, oil spots, rough, wide, or protruding navels, scale, scars, skin breakdown, and thorn scratches
3. Damage caused by dirt or other foreign material, disease, dryness, or mushy condition, hail, insects, riciness or woodiness, and sunburn.

The USDA uses a separate grading system for oranges used for juice because appearance and texture are irrelevant in this case. There are only two grades: US Grade AA Juice and US Grade A Juice, which are given to the oranges before processing. Juice grades are determined by three factors:

1. The juiciness of the orange
2. The amount of solids in the juice (at least 10% solids are required for the AA grade)
3. The proportion of anhydric citric acid in fruit solids

History

The orange is unknown in the wild state; it is assumed to have originated in southern China, northeastern India, and perhaps southeastern Asia, and that they were first cultivated in China around 2500 BC.

In Europe, the Moors introduced the orange to Spain which was known as Al-Andalus, modern Andalucia, with large scale cultivation starting in the 10th century as evidenced by complex irrigation techniques specifically adapted to support orange orchards. Citrus fruits—among them the bitter orange were introduced to Sicily in the 9th century during the period of the Emirate of Sicily, but the sweet orange was unknown until the late 15th century or the beginnings of the 16th century, when Italian and Portuguese merchants brought orange trees into the Mediterranean area.[5] Shortly afterward, the sweet orange quickly was adopted as an edible fruit. It also was considered a luxury item and wealthy people grew oranges in private conservatories, called orangeries. By 1646, the sweet orange was well known throughout Europe.[5]

Spanish travelers introduced the sweet orange into the American continent. On his second voyage in 1493, Christopher Columbus may have planted the fruit in Hispaniola. Subsequent expeditions in the mid-1500s brought sweet oranges to South America and Mexico, and to Florida in 1565, when Pedro Menéndez de Avilés founded St Augustine. Spanish missionaries brought orange trees to Arizona between 1707 and 1710, while the Franciscans did the same in San Diego, California, in 1769. An orchard was planted at the San Gabriel Mission around 1804 and a commercial orchard was established in 1841 near present-day Los Angeles. In Louisiana, oranges were probably introduced by French explorers.

Archibald Menzies, the botanist and naturalist on the Vancouver Expedition, collected orange seeds in South Africa, raised the seedlings onboard and gave them to several Hawaiian chiefs in 1792. Eventually, the sweet orange was grown in wide areas of the Hawaiian Islands, but its cultivation stopped after the arrival of the Mediterranean fruit fly in the early 1900s.

As oranges are rich in vitamin C and do not spoil easily, during the Age of Discovery, Portuguese, Spanish, and Dutch sailors planted citrus trees along trade routes to prevent scurvy.

Florida farmers obtained seeds from New Orleans around 1872, after which orange groves were established by grafting the sweet orange on to sour orange rootstocks.

Climate

Like most citrus plants, oranges do well under moderate temperatures—between 15.5 and 29 °C (59.9 and 84.2 °F)—and require considerable amounts of sunshine and water. It has been suggested the use of water resources by the citrus industry in the Middle East is a contributing factor to the desiccation of the region. Another significant element in the full development of the fruit is the temperature variation between summer and winter and, between day and night. In cooler climates, oranges can be grown indoors.

As oranges are sensitive to frost, there are different methods to prevent frost damage to crops and trees when subfreezing temperatures are expected. A common process is to spray the trees with water so as to cover them with a thin layer of ice that will stay just at the freezing point, insulating them even if air temperatures drop far lower. This is because water continues to lose heat as long as the environment is colder than it is, and so the water turning to ice in the environment cannot damage the trees. This practice, however, offers protection only for a very short time. Another procedure is burning fuel oil in smudge pots put between the trees. These devices burn with a great deal of particulate emission, so condensation of water vapour on the particulate soot prevents condensation on plants and raises the air temperature very slightly. Smudge pots were developed for the first time after a disastrous freeze in Southern California in January 1913 destroyed a whole crop.

Propagation

It is possible to grow orange trees directly from seeds, but they may be infertile or produce fruit that may be different from its parent. For the seed of a commercial orange to grow, it must be kept moist at all times. One approach is placing the seeds between two sheets of damp paper towel until they germinate and then planting them, although many cultivators just set the seeds straight into the soil.

Commercially grown orange trees are propagated asexually by grafting a mature cultivar onto a suitable seedling rootstock to ensure the same yield, identical fruit characteristics, and resistance to diseases throughout the years. Propagation involves two stages: first, a rootstock is grown from seed. Then, when it is approximately one year old, the leafy top is cut off and a bud taken from a specific scion variety, is grafted into its bark. The scion is what determines the variety of orange, while the rootstock makes the tree resistant to pests and diseases and adaptable to specific soil and climatic conditions. Thus, rootstocks influence the rate of growth and have an effect on fruit yield and quality.

Rootstocks must be compatible with the variety inserted into them because otherwise, the tree may decline, be less productive, or die.

Among the several advantages to grafting are that trees mature uniformly and begin to bear fruit earlier than those reproduced by seeds (3 to 4 years in contrast with 6 to 7 years), and that it makes it possible to combine the best attributes of a scion with those of a rootstock.

Harvest

Canopy-shaking mechanical harvesters are being used increasingly in Florida to harvest oranges. Current canopy shaker machines use a series of six-to-seven-foot long tines to shake the tree canopy at a relatively constant stroke and frequency.

Normally, oranges are picked once they are pale orange.

Degreening

Oranges must be mature when harvested. In the United States, laws forbid harvesting immature fruit for human consumption in Texas, Arizona, California and Florida. Ripe oranges, however, often have some green or yellow-green color in the skin. Ethylene gas is used to turn green skin to orange. This process is known as "degreening", also called "gassing", "sweating", or "curing". Oranges are non-climacteric fruits and cannot post-harvest ripen internally in response to ethylene gas, though they will de-green externally.

Storage

Commercially, oranges can be stored by refrigeration in controlled-atmosphere chambers for up to 12 weeks after harvest. Storage life ultimately depends on cultivar, maturity, pre-harvest conditions, and handling. In stores and markets, however, oranges should be displayed on non-refrigerated shelves.

At home, oranges have a shelf life of about one month. In either case, optimally, they are stored loosely in an open or perforated plastic bag.

Cottony cushion scale

The first major pest that attacked orange trees in the United States was the cottony cushion scale (Icerya purchasi), imported from Australia to California in 1868. Within 20 years, it wiped out the citrus orchards around Los Angeles, and limited orange growth throughout California. In 1888, the USDA sent Alfred Koebele to Australia to study this scale insect in its native habitat. He brought back with him specimens of Novius cardinalis, an Australian ladybird beetle, and within a decade the pest was controlled.

Citrus greening disease

The citrus greening disease, caused by the bacterium Liberobacter asiaticum, has been the most serious threat to orange production since 2010. It is characterized by streaks of different shades on the leaves, and deformed, poorly colored, unsavory fruit. In areas where the disease is endemic, citrus trees live for only five to eight years and never bear fruit suitable for consumption. In the western hemisphere, the disease was discovered in Florida in 1998, where it has attacked nearly all the trees ever since. It was reported in Brazil by Fundecitrus Brasil in 2004. As from 2009, 0.87% of the trees in Brazil's main orange growing areas (São Paulo and Minas Gerais) showed symptoms of greening, an increase of 49% over 2008.

The disease is spread primarily by two species of psyllid insects. One of them is the Asian citrus psyllid (Diaphorina citri Kuwayama), an efficient vector of the Liberobacter asiaticum. Generalist predators such as the ladybird beetles Curinus coeruleus, Olla v-nigrum, Harmonia axyridis, and Cycloneda sanguinea, and the lacewings Ceraeochrysa spp. and Chrysoperla spp. make significant contribution to the mortality of the Asian citrus psyllid, which results in 80–100% reduction in psyllid populations. In contrast, parasitism by Tamarixia radiata, a species-specific parasitoid of the Asian citrus psyllid, is variable and generally low in southwest Florida: in 2006, it amounted to a reduction of less than 12% from May to September and 50% in November.

In 2007, foliar applications of insecticides reduced psyllid populations for a short time, but also suppressed the populations of predatory ladybird beetles. Soil application of aldicarb provided limited control of Asian citrus psyllid, while drenches of imidacloprid to young trees were effective for two months or more.

Management of citrus greening disease is difficult and requires an integrated approach that includes use of clean stock, elimination of inoculum via voluntary and regulatory means, use of pesticides to control psyllid vectors in the citrus crop, and biological control of psyllid vectors in non-crop reservoirs. Citrus greening disease is not under completely successful management.

Greasy spot

Greasy spot, a fungal disease caused by the Mycosphaerella citri, produces leaf spots and premature defoliation, thus reducing the tree's vigour and yield. Ascospores of M. citri are generated in pseudothecia in decomposing fallen leaves. Once mature, ascospores are ejected and subsequently dispersed by air currents.

Production

Brazil is the world's leading orange producer, with an output of 36 million tons (2013), similar in total to the next three countries combined (the United States, China and India). Orange groves are located mainly in the state of São Paulo, in the southeastern region of Brazil, and account for approximately 80% of the national production. As almost 99% of the fruit is processed for export, 53% of total global frozen concentrated orange juice production comes from this area and the western part of the state of Minas Gerais. In Brazil, the four predominant orange varieties used for obtaining juice are Hamlin, Pera Rio, Natal, and Valencia.

With approximately 16 million tons produced in 2013, the United States is the second largest producer. Groves are located especially in Florida, California, Texas, and Arizona. The majority of California's crop is sold as fresh fruit, whereas Florida's oranges are destined to juice products. Mid-south Florida produces about half as many oranges as Brazil, but the bulk of its orange juice is not exported. The Indian River area of Florida is known for the high quality of its juice, which often is sold fresh in the United States and frequently blended with juice produced in other regions because Indian River trees yield very sweet oranges, but in relatively small quantities.

Production of orange juice between the São Paulo and mid-south Florida areas makes up roughly 85% of the world market. Brazil exports 99% of its production, while 90% of Florida's production is consumed in the United States.

Orange juice is traded internationally in the form of frozen, concentrated orange juice to reduce the volume used so that storage and transportation costs are lower.

Other countries with significant production of oranges are China, India, Mexico, Spain and Egypt (table).

Juice and other products

Oranges, whose flavor may vary from sweet to sour, are commonly peeled and eaten fresh or squeezed for juice. The thick bitter rind is usually discarded, but can be processed into animal feed by desiccation, using pressure and heat. It also is used in certain recipes as a food flavoring or garnish. The outermost layer of the rind can be thinly grated with a zester to produce orange zest. Zest is popular in cooking because it contains oils and has a strong flavor similar to that of the orange pulp. The white part of the rind, including the pith, is a source of pectin and has nearly the same amount of vitamin C as the flesh and other nutrients.

Although not as juicy or tasty as the flesh, orange peel is edible and has significant contents of vitamin C, dietary fiber, total polyphenols, carotenoids, limonene and dietary minerals, such as potassium and magnesium.

Products made from oranges

Limonene is considered a natural chemopreventive agent in humans, and there is no evidence for its carcinogenicity or genotoxicity, as once believed. The Carcinogenic Potency Project estimates that D-limonene may affect human cancer on a level roughly equivalent to that for caffeic acid via dietary coffee intake, whereas the International Agency for Research on Cancer (IARC) classifies it under Class 3, which means it is not classifiable as to its carcinogenicity to humans.