From Progress in
New Crops, Proceedings of the Third National Symposium NEW CROPS: New
Opportunities, New Technologies
by Joan Tous and Louise Ferguson
Carob
The carob (Ceratonia siliqua,
Fagaceae) is a perennial leguminous tree native to the Mediterranean
basin and southwestern Asia (Smith 1976). Its cultivation began before
written history. This species is also known as "St. John's Bread,"
"algarrobo" in Spain, "carrubo" in Italy, and "caroubier" in France.
The beans and kernels are useful for a variety of purposes including
food, fodder, and as a source of industrial products such as gums,
sugar, and alcohol. The tree is also used for shade and erosion control
(NAS 1979). World production of carob pods was estimated about at
330,000 t (Tous and Batlle 1990), mainly in Spain (45%), Italy (16%),
Portugal (9%), Morocco (7.5%), Cyprus (6%), Greece (5%), and Turkey
(4.5%). Lesser quantities are produced in Algeria, Tunisia, and Israel.
Spain is also the world's largest exporter of carob beans. The only
significant recent plantings outside the Mediterranean region are in
Australia (Esbenshade and Wilson 1986; Tous 1995).
The tree
grows best in a Mediterranean-type climate with cool, not cold,
winters, mild to warm springs, and warm to hot summers with little
rain. A frost of -4°C or below may kill the young trees, or shoots and
flowers in mature trees. Although drought-resistant, carob trees do not
bear commercial crops unless they get enough rainfall, a minimum
average rainfall of about 500-550 mm is needed to ensure a profitable
crop (NAS 1979). The tree survives in a wide variety of soils, like
pistachio, but must have good drainage. Although it is a legume, it is
unable to fix nitrogen (Martins-Loucao 1985).
The carob is a
large (7 to 10 m) trioecious tree with staminate, pistillate and
hermaphrodite inflorescences in different trees. Pollination is by
insects (bees, flies, etc.) and the wind (Tous and Batlle 1990). In new
commercial orchards the ratio of staminate or hermaphrodite trees to
pistillate trees should be 1:8. In traditional orchards male branches
are grafted on female trees to provide pollen in situ. The carob, like
the pistachio, matures slowly and most budded cultivars begin to bear
in the 5-6th year after planting. It is also a strongly
alternate-bearing species, particularly when growing conditions are
poor. Today, commercial cultivars differ in pulp quantity or yield of
seeds. The most important cultivars are: 'Negra', 'Rojal',
'Matalafera', and 'Duraio' in Spain; 'Gibiliana' and 'Amele' in Italy;
'Mulata' and 'Galhosa' in Portugal; 'Tylliria' in Cyprus; 'Hemere' in
Greece; 'Sfax' in Tunisia; and 'Santa Fe' in California (Tous and
Batlle 1990).
The tree requires little pruning, and minimal
cultural care. Carobs respond to N fertilization by increasing pod
yield (Lloveras and Tous 1992). They are propagated mainly by budding
or grafting onto seedling rootstocks. The flowers, which are borne in
small lateral racemes or clusters, bloom during Sept.-Nov. on older
wood. The carob bean is a dark-brown, fleshy edible pod, 10-30 cm long,
containing 5-15 hard seeds, and ripening in late summer, during bloom.
Carob seeds comprise about 10% to 20% of the weight of the pod. Fruits
can be harvested by hand, by knocking down with a long pole, or by
shaking. No serious problems of carob have been reported in the
Mediterranean area. The major pests are the stem borer (Zeuzera pyrina) and carob moth (Myelois ceratoniae), and only one fungus, Oidium ceratoniae, is occasionally a problem in the leaves and young pods.
The
carob pod is very rich in sugar (up to 45%) and low in protein. Mixed
with other feeds higher in protein, it is good source of stock feed
(horses, calves, goats, milk cow). Finely-ground pods make a sweet
nutritious human food, and are used in a similar manner to cocoa in
cakes, drinks, puddings, breakfast cereals, and candy. The carob powder
has more vitamins, minerals, and fewer fats, carbohydrates, and
calories than chocolate made with cocoa. Additionally carob powder
contains no caffeine and theobromine (Whitheside 1981). The carob gum
or locust bean gum (LBG) surrounding the endosperm is an important
commercial stabilizer and thickener in many food industries (bakery
goods, ice creams, baby foods, sauces, jams, cheese, jellies, and
canned meats), as well as in pet foods, cosmetics, and pharmaceuticals
(NAS 1979; Morton 1987; Di Lorenzo 1990; Tous and Batlle 1990).
The
overall production trend is stationary. Several countries, such as
Spain, Portugal, and Australia, are expected to have new plantings of
this crop. In the world market, there is an increasing demand for carob
seed and a stable demand for carob pulp. In the last 5 to 10 years,
because of the rising prices of the carob seed derivatives (LBG), the
carob has been the object of renewed interest (Tous and Batlle 1990).
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