|Illustration of the carob tree's vegetative components (Ceratonia siliqua).|
Ceratonia siliqua, commonly known as the carob tree and St John's-bread, is a species of flowering evergreen shrub or tree in the pea family, Fabaceae. It is widely cultivated for its edible legumes, and as an ornamental tree in gardens. The seed pod may be crushed and used as ersatz chocolate.
It is native to the Mediterranean region including Southern Europe, Northern Africa, the larger Mediterranean islands; to the Levant and Middle-East of Western Asia into Iran; and to the Canary Islands and Macaronesia.
The vernacular names in other cultures and languages for Ceratonia siliqua include: Arabic: خروب kharrūb; German: Johannisbrotbaum; Greek: χαρουπιά kharoupia or ξυλοκερατιά ksylokeratia; Spanish: algarrobo, caroba; French: caroubier, caroube; Hebrew: חרוב ḥaruv; Portuguese: alfarrobeira; Catalan: garrofa; Sicilian: carrubba; Turkish: harnup, keçiboynuzu; Croatian: rogač. The word Carat, a unit of purity for gold alloys, was derived from the word carob.
The Ceratonia siliqua tree grows up to 15 metres (49 ft) tall. The crown is broad and semi-spherical, supported by a thick trunk with brown rough bark and sturdy branches. Leaves are 10 to 20 centimetres (3.9 to 7.9 in) long, alternate, pinnate, and may or may not have a terminal leaflet. It is frost-tolerant.
Most carob trees are dioecious. The trees blossom in autumn. The flowers are small and numerous, spirally arranged along the inflorescence axis in catkin-like racemes borne on spurs from old wood and even on the trunk (cauliflory); they are pollinated by both wind and insects. Male flowers produce a characteristic odour, resembling semen.
The fruit is a pod that can be elongated, compressed, straight or curved, and thickened at the sutures. The pods take a full year to develop and ripen. The ripe pods eventually fall to the ground and are eaten by various mammals, thereby dispersing the seed.
Habitat and ecology 
The carob genus, Ceratonia, belongs to the Fabaceae (legume) family, and is believed to be an archaic remnant of a part of this family now generally considered extinct. It grows well in warm temperate and subtropical areas, and tolerates hot and humid coastal areas. As a xerophytic (drought-resistant) species, carob is well adapted to the ecological conditions of the Mediterranean region. Trees prefer well drained loam and are intolerant of waterlogging, but the deep root systems can adapt to a wide variety of soil conditions and are fairly salt-tolerant.
While previously not believed to form nitrogen fixation nodules typical of the legume family, trees have been identified more recently with nodules containing bacteria believed to be from the Rhizobium genus.
Although used extensively for agriculture, carob can still be found growing wild in eastern Mediterranean regions, and has become naturalized in the west. The carob tree is typical in the southern Portuguese region of the Algarve, where it has the name alfarrobeira (for the tree), and alfarroba (for the fruit), as well as in southern Spain (Spanish: algarrobo, algarroba), Catalonia and Valencia (Catalan: garrofer, garrofa), Malta (Maltese: Ħarruba), on the Italian islands of Sicily and Sardinia (Italian: carrubo, carruba), and in Southern Greece, Cyprus as well as many Greek islands such as Crete and Samos. The common Greek name is (Greek: χαρουπιά, charoupia), or (Greek: ξυλοκερατιά, ksilokeratia), meaning "wooden horn". In Turkey, it is known as "keçiboynuzu", meaning "goat's horn". In Israel it's called "Haroov" (חרוב),known as "life saving tree - kav kharoovin". The various trees known as algarrobo in Latin America (Albizia saman in Cuba and four species of Prosopis in Argentina and Paraguay) belong to a different subfamily, Mimosoideae.
According to FAO, the top 5 carob producing countries are (in metric tonnes (2010):
Ceratonia siliqua, the scientific name of the carob tree, derives from the Greek kerátiοn (κεράτιον), "fruit of the carob" (from keras [κέρας] "horn"), and Latin siliqua "pod, carob." The term "carat", the unit by which gem weight is measured, is also derived from the Greek word kerátiοn (κεράτιον), alluding to an ancient practice of weighing gold and gemstones against the seeds of the carob tree by people in the Middle East. The system was eventually standardized, and one carat was fixed at 0.2 grams.
In late Roman times, the pure gold coin known as the solidus weighed 24 carat seeds (about 4.5 grams). As a result, the carat also became a measure of purity for gold. Thus 24-carat gold means 100% pure, 12-carat gold means the alloy contains 50% gold, etc.
Subsistence on carob pods is mentioned in the Talmud: Berakhot reports that Rabbi Haninah subsisted on carob pods. It is probably also mentioned in the New Testament, in which Matthew 3:4 reports that John the Baptist subsisted on "locusts and wild honey"; the Greek word translated "locusts" may refer to carob pods, rather than to grasshoppers. Again, in Luke 15:16, when the Prodigal Son is in the field in spiritual and social poverty, he desires to eat the pods that he is feeding to the swine because he is suffering from starvation. The use of the carob during a famine is likely a result of the carob tree's resilience to the harsh climate and drought. During a famine, the swine were given carob pods so that they would not be a burden on the farmer's limited resources.
Carob consumed by humans is the dried (and sometimes roasted) pod, and not the 'nuts' or seeds. Carob is mildly sweet and is used in powdered, chip, or syrup form as an ingredient in cakes and cookies, and as a substitute for chocolate.
The seeds, also known as locust beans, are used as animal feed, and are the source of locust bean gum — a food thickening agent. Crushed pods may be used to make a beverage; compote, liqueur, and syrup are made from carob in Turkey, Malta, Portugal, Spain and Sicily. Several studies suggest that carob may aid in treating diarrhea in infants. In Libya, carob syrup (there called rub) is used as a complement to Asida. The so-called carob syrup made in Peru is actually from the fruit of the Prosopis nigra tree.
Carob is rich in sugars - Sucrose = 531g ± 93 g/kg dry weight for cultivated varieties and 437 ± 77 g/kg in wild type varieties. Fructose and glucose levels do not differ between cultivated and wild type carob.
Ceratonia siliqua is widely cultivated in the horticultural nursery industry as an ornamental plant for planting in Mediterranean climate and other temperate regions around the world, as its popularity in California and Hawaii shows. The plant develops a sculpted trunk and ornamental tree form when 'limbed up' as it matures, otherwise it is used as a dense and large screening hedge. When not grown for legume harvests the plant is very drought tolerant and part of 'xeriscape' landscape design for gardens, parks, and public municipal and commercial landscapes.
Cultural significance 
Use of the carob plant dates back to Mesopotamian culture (modern day Iraq). The carob pods were used to create juices, sweets, and were highly prized due to its many uses. The carob tree is mentioned frequently in texts dating back thousands of years, outlining its growth and cultivation in the Middle Eastern and North Africa. The carob tree is mentioned with reverence in "The Epic of Gilgamesh", one of the earliest works of literature in existence.
The Jewish Talmud features a parable of altruism, commonly known as "Honi and the Carob Tree", which mentions that a carob tree takes 70 years to bear fruit; meaning that the planter will not benefit from his work, but works in the interest of future generations.
In reality, the fruiting age of carob trees varies: cuttings taken from fruit-bearing trees may bear fruit in as few as three to four years, and seedlings grown in ideal conditions may bear fruit within six to eight years. Although it is native to moderately dry climates, two or three summers irrigation will greatly aid the development, hasten the fruiting, and increase the yield of a carob tree."
In the Parable of the Prodigal Son, the Prodigal Son, having squandered his inheritance, wishes that he could also partake in eating the pigs' diet of carob pods.
Traditional uses 
Carob was eaten in Ancient Egypt. Carob juice drinks are traditionally drunk during the Islamic month of Ramadan. It was also a common sweetener and was used in the hieroglyph for "sweet" (nedjem). Dried carob fruit is traditionally eaten on the Jewish holiday of Tu Bishvat. Also it is believed to be an aphrodisiac.
In Cyprus, carob syrup is known as Cyprus's black gold, and is widely exported.
In Malta, a syrup (ġulepp tal-ħarrub) is made out of carob pods. This is a traditional medicine for coughs and sore throat. A traditional sweet, eaten during Lent and Good Friday, is also made from carob pods in Malta. However, carob pods were mainly used as animal fodder in the Maltese Islands, apart from times of famine or war when they formed part of the diet of many Maltese.
See also 
- carat (a unit of purity for gold alloys)
- Ratti (a seed from which the Indian measure unit "tola" derived)
- ITIS Report Page: Ceratonia siliqua . accessed 5.11.2011
- NPGS/GRIN - Ceratonia siliqua information . accessed 5.11.2011
- http://www.tropicos.org/Name/13028551 Tropicos.org. Ceratonia siliqua accessed 5.10.2011
- Battle I, Tous J (1997). Carob tree (PDF). Rome, Italy: International Plant Genetic Resources Institute. p. 16. ISBN 978-92-9043-328-6. Retrieved 2012-03-12.
- Battle I, Tous J (1997). Carob tree (PDF). Rome, Italy: International Plant Genetic Resources Institute. ISBN 978-92-9043-328-6. Retrieved 2011-02-19.[page needed]
- M. Missbah El Idrissi, N. Aujjar, A. Belabed, Y. Dessaux, A. Filali-Maltouf (1996). "Characterization of rhizobia isolated from Carob tree (Ceratonia siliqua)". Journal of Applied Microbiology 80 (2): 165–73. doi:10.1111/j.1365-2672.1996.tb03205.x.
- "Turkish Cuisine". Turkish Cuisine. Retrieved 2010-07-26.
- Harper, Douglas. "carat". Online Etymology Dictionary.
- "A Brief on Bokser - Forward.com"
- Burg, Barbara. Good Treats For Dogs Cookbook for Dogs: 50 Home-Cooked Treats for Special Occasions. Quarry Books, 2007, p. 28
- Fortier D, Lebel G, Frechette A (June 1953). "Carob flour in the treatment of diarrhoeal conditions in infants". Canadian Medical Association Journal 68 (6): 557–61. PMC 1822828. PMID 13059705.
- Bailey, Liberty Hyde. The standard cyclopedia of horticulture. The Macmillan Company, 1914. Retrieved 23 November 2011.
- Turnbull LA, Santamaria L, Martorell T, Rallo J, Hector A (September 2006). "Seed size variability: from carob to carats". Biology Letters 2 (3): 397–400. doi:10.1098/rsbl.2006.0476. PMC 1686184. PMID 17148413. Lay summary – New Scientist (May 9, 2006).
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