Carob

The carob is a flowering evergreen tree or shrub in the Caesalpinioideae subfamily of the legume family, Fabaceae. The carob tree is native to the Mediterranean region and the Middle East. It is widely cultivated for its edible fruit, which takes the form of seed pods, and as an ornamental tree in gardens and landscapes. Spain is its largest producer, followed by Italy and Morocco.
Carob pods have a number of culinary applications, including a powder or chips that can be used as a chocolate alternative. The seeds are used to produce locust bean gum or carob gum, a common thickening agent used in food processing.

Description

The carob tree grows up to tall. The crown is broad and semispherical, supported by a thick trunk with rough brown bark and sturdy branches. Its leaves are long, alternate, pinnate, and may or may not have a terminal leaflet. It is frost-tolerant to roughly.
Most carob trees are dioecious, so strictly male trees do not produce fruit, but some are hermaphroditic. When 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 ; they are pollinated by both wind and insects. The male flowers smell like human semen, an odor that is caused in part by amines.
The fruit is a legume, that is elongated, compressed, straight, or curved, and thickened at the sutures. The pods take a full year to develop and ripen. When the sweet, ripe pods eventually fall to the ground, they are eaten by various mammals, such as swine, thereby dispersing the hard inner seed in the excrement.
The seeds of the carob tree contain leucodelphinidin, a colourless flavanol precursor related to leucoanthocyanidins.

Etymology

The word "carob" comes from Middle French carobe, which borrowed it from Arabic wikt:خروب and Persian khirnub, which ultimately borrowed it perhaps from Akkadian language harūb- or Aramaic חרובא ḥarrūḇā. '
Ceratonia siliqua, the scientific name of the carob tree, derives from the Greek κερατωνία keratōnía, "carob-tree", and Latin siliqua "pod, carob".
In English, it is also known as "St. John's bread" and "locust tree". The latter designation also applies to several other trees from the same family.
In Yiddish, it is called באקסער bokser, derived from the Middle High German bokshornboum "ram's horn tree".
The carat, a unit of mass for gemstones, and a measurement of purity for gold, takes its name via the Arabic qīrāṭ from the Greek name for the carob seed wikt:κεράτιον.

Distribution and habitat

The carob tree is native to the Mediterranean region and the Middle East. Although cultivated extensively, carob can still be found growing wild in eastern Mediterranean regions, and has become naturalized in the western Mediterranean.
The tree is typical in the southern Portuguese region of the Algarve, where the tree is called alfarrobeira, and the fruit alfarroba. It is also seen in southern and eastern Spain, mainly in the regions of Andalusia, Murcia, Valencia, the Balearic Islands and Catalonia ; Malta, on the Italian islands of Sicily and Sardinia, in Southern Croatia, such as on the island of Šipan, in eastern Bulgaria, and in Southern Greece, Cyprus, as well as on many Greek islands such as Crete and Samos.
In Israel, the Hebrew name is . The common Greek name is χαρουπιά, or ξυλοκερατιά. In Turkey, it is known as "goat's horn".File:Arcosu07.jpg|thumb|upright=1.35|A large carob tree in Sardinia, Italy|alt=Carob tree
The various trees known as algarrobo in Latin America belong to a different subfamily of the Fabaceae: Mimosoideae. Early Spanish settlers named them algarrobo after the carob tree because they also produce pods with sweet pulp.

Ecology

The carob genus, Ceratonia, belongs to the legume family, Fabaceae, 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 xerophyte, carob is well adapted to the conditions of the Mediterranean region with just of rainfall per year.
Carob trees can survive long periods of drought, but to grow fruit, they need of rainfall per year. They prefer well-drained, sandy loams and are intolerant of waterlogging, but the deep root systems can adapt to a wide variety of soil conditions and are fairly salt-tolerant. After being irrigated with saline water in the summer, carob trees could possibly recover during winter rainfalls. In some experiments, young carob trees were capable of basic physiological functions under high-salt conditions.
Not all legume species can develop a symbiotic relationship with rhizobia to make use of atmospheric nitrogen. It remains unclear if carob trees have this ability: Some findings suggest that it is not able to form root nodules with rhizobia, while in another more recent study, trees have been identified with nodules containing bacteria believed to be from the genus Rhizobium. However, a study measuring the ¹⁵N-signal in the tissue of the carob tree did not support the theory that carob trees naturally use atmospheric nitrogen.

Cultivation

The vegetative propagation of carob is naturally restricted due to its low adventitious rooting potential. Therefore, grafting and air-layering may prove to be more effective methods of asexual propagation. Seeds are commonly used as the propagation medium. The sowing occurs in pot nurseries in early spring and the cooling- and drying-sensitive seedlings are then transplanted to the field in the next year after the last frost. Carob trees enter slowly into production phase. Where in areas with favorable growing conditions, the cropping starts 3–4 years after budding, with the nonbearing period requiring up to 8 years in regions with marginal soils. Full bearing of the trees occurs mostly at a tree-age of 20–25 years when the yield stabilizes. The orchards are traditionally planted in low densities of 25–45 trees per hectare. Hermaphroditic or male trees, which produce fewer or no pods, respectively, are usually planted in lower densities in the orchards as pollenizers.
Intercropping with other tree species is widely spread. Not much cultivation management is required. Only light pruning and occasional tilling to reduce weeds is necessary. Nitrogen-fertilizing of the plants has been shown to have positive impacts on yield performance. Although it is native to moderately dry climates, two or three summers' irrigation greatly aid the development, hasten the fruiting, and increase the yield of a carob tree.

Harvest and post-harvest treatment

The most labour-intensive part of carob cultivation is harvesting, which is often done by knocking the fruit down with a long stick and gathering them together with the help of laid-out nets. This is a delicate task because the trees are flowering at the same time and care has to be taken not to damage the flowers and the next year's crop. The literature recommends research to get the fruit to ripen more uniformly or also for cultivars which can be mechanically harvested.
Freshly harvested carob pods have a moisture content of 10–20% and should be dried down to a moisture content of 8% so they do not rot. Further processing separates the kernels from the pulp. This process is called kibbling and results in seeds and pieces of carob pods. Processing of the pulp includes grinding for animal feed production or roasting and milling for human food industry. The seeds have to be peeled which happens with acid or through roasting. The endosperm and the embryo are then separated for different uses.

Pests and diseases

Few pests cause severe damage in carob orchards, so they have traditionally not been treated with pesticides. Some generalist pests such as the larvae of the leopard moth, the dried fruit moth, small rodents such as rats and gophers can occasionally cause damage in some regions. Only some cultivars are severely susceptible to mildew disease. One pest directly associated with carob is the larva of the carob moth, which can cause extensive postharvest damage.
Cadra calidella both attack carob crops before harvest and infest products in stores. This moth, prevalent in Cyprus, will often infest the country's carob stores. Research has been conducted to understand the physiology of the moth, in order to gain insight on how to monitor moth reproduction and lower their survival rates, such as through temperature control, pheromone traps, or parasitoid traps.

Production

In 2022, world production of carob was estimated to be 56,423 tonnes, although not all countries known to grow carob reported their results to the UN Food and Agriculture Organization. Production amounts for Turkey and Morocco accounted for nearly all the world total reported in 2022.
Most of the roughly 50 known cultivars are of unknown origin and only regionally distributed. The cultivars show high genetic and therefore morphological and agronomical variation. No conventional breeding by controlled crossing has been reported, but selection from orchards or wild populations has been done. Domesticated carobs can be distinguished from their wild relatives by some fruit-yielding traits such as building of greater beans, more pulp, and higher sugar contents. Also, genetic adaptation of some varieties to the climatic requirements of their growing regions has occurred. Though a partially successful breaking of the dioecy happened, the yield of hermaphrodite trees still cannot compete with that of female plants, as their pod-bearing properties are worse. Future breeding would be focused on processing-quality aspects, as well as on properties for better mechanization of harvest or better-yielding hermaphroditic plants. The use of modern breeding techniques is restricted due to low polymorphism for molecular markers.