DESCRIPTION OF CAROB TREE
Dipartimento di Arboricoltura, Botanica e Patologia vegetale, Università Federico II, Napoli. Italy
BOTANICAL SPECIES: Ceratonia siliqua L.
Origin and diffusion: Native of the Arabian Hhorn, as it is tolerant to drought, it was distributed by the Greeks into the arid areas of the Mediterranean.
Current growing countries: South Europe (Spain, Italy, Portugal, Greece, Cyprus); North Africa (Morocco, Algeria, Tunisia); West Asia (Turkey)
Climatic and soil requirements: Warm spring, hot and dry summers, mild winters. The tree is able to stand high atmospheric temperatures (about 50 °C) but it appears extremely sensitive to low temperatures: vegetative growth is reduced when the temperature falls to below 10 °C and there is serious damages at temperature below 4 °C. Well drained soils are needed to ensure survival.
Tree: Xerophytic, perennial (does not shed their leaves during winter) 7-10 m. high, canopy up to 20 m. Trioecious; male, female and hermaphroditic flowers are usually borne on different trees. However, it is common to have male and female flowered trees as well as female and hermaphrodite or just hermaphrodite flowered trees. Indeed, the presence of male trees in the orchard is necessary to ensure pollination.
Leaf: Alternate and pinnate compound, 10 to 25 cm long; a terminal leaflet can be present. Each leaf is usually composed of 8-15 leaflets 3-7 cm. long. They are coriaceous, dark green and characterized by a thick unilayered upper epidermis showing clustered stomata only on the lower face. Phenolic compounds are reported to be stored in the large vacuoles of the leaf cells. Leaf turnover occurs in spring, mostly during April and May.
Flowers are numerously clustered in lateral racemes borne on the old wood. Depending on the cultivars and the climatic conditions, blooming occurs from September to November. Within the inflorescence the basal flowers open before the apical ones. Pollination is assured by insects, but the wind is also reported to be an effective pollinator.
The fruit is a bean, green during the developmental stages, dark brown when ripe. About 11 months elapse from full bloom to ripening: beans start to change their ground colour in August and usually ripen a month later. At harvest it is common to have on the tree simultaneously ripening fruits and flowers at anthesis. Ripened fruits can remain on the tree for a long time. Although the beans can become large (15-40 g., 10-30 cm. long), the economic factors evaluated are (apart from tree pod yield), the seed number (5-15), weight (10-20%) and sugar content in the pulp (up to 45%), all influenced by cultivar, climate and cultivation techniques.
Use: The Mediterranean countries have traditionally grown Carob as a highly profitable species for human and livestock food use. Because carob has a high sugar and low protein content, the bean pulp is usually mixed with other feeds to obtain a complex fodder that, for its aromatic flavour, makes it more desirable and nutritious for horses, cattle and goats. For the human food industry, as the pulp contains more minerals and vitamins and less carbohydrate and fats than cocoa, the flour obtained by grinding the pulp can be used as a cocoa substitute in preparing ‘diet’ pastry and drinks. However, the most important use is the production of gum, extracted from the seeds after shuttering and separation, and used as a thickener in many food processes (e.g. baby foods, bakery goods, jams and sauces) and in the pharmaceutical and cosmetic industry
Production problems: As a Mediterranean crop, able to survive well and produce seeds in marginal areas characterized by climate and soil limitations, a greater diffusion of Carob can be assumed feasible. The most important requirements to improve Carob fruit growing and make it economically viable are the ease of harvesting , which is related to cultivar selection (growth habit, vegetative behaviour and pomological traits) and the availability of mechanical systems suitable and/or adapted for this kind of tree.
The collection and evaluation of Mediterranean germplasm, as well as accurate breeding programs, appear to be the only way to achieve these objectives and facilitate the diffusion of this neglected species.