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Tropical Plant "Carob"
Ceratonia siliqua
Non-fleshy and bean-like, the carob would not be generally regarded
as a fruit, in the food-use sense, except for its sweetness.
To many people it is familiar only by name as "St. John's Bread"
(Ceratonia siliqua), in allusion to the "locusts" which,
according to the Bible, sustained St. John the Baptist in the
desert, and the "husks" which tempted the hungry Prodigal Son,
though "no man gave unto him." The word "locust" was originally
applied to the carob tree; later to migratory and other grasshoppers;
and the name is attached to a number of other leguminous trees
with pinnate leaves and oblong pods (Gleditsia, Hymenaea,
Parkia, Robinia). The carob tree is called carrubo in
Sicily, carrubio in Italy, algarrobo in Guatemala,
alfarrobeira in Brazil.
Carob Description
The
tree reaches 50 to 55 ft (15-17 m) in height and at an age
of 18 years may have a trunk 33 in (85 cm) in circumference.
The evergreen leaves are pinnate with 6 to 10 opposite leaflets,
oval, rounded at the apex, dark-green, leathery, 1 to 2 1/2
in (2.5-6.25 cm) long. The tiny red flowers are in short,
slender racernes borne in clusters along the branches-male,
female or hermaphrodite on separate trees.
The pod is light- to dark-brown, oblong, flattened, straight
or slightly curved, with a thickened margin; 4 to 12 in (10-30
cm) long, 3/4 to 1 in (1-2.5 cm) wide, glossy, tough and fibrous.
It is filled with soft, semi-translucent, pale-brown pulp,
scant or plentiful, and 10 to 13 flattened, very hard seeds
which are loose in their cells and rattle when the pod is
fully ripe and dry. The unripe pod is green, moist and very
astringent; the ripe pod sweet when chewed (avoiding the seeds)
but the odor of the broken pod is faintly like Limburger cheese
because of its 1.3% isobutyric acid content.
Carob Origin
and Distribution
Alphonse
de Candolle said that the carob "grew wild in the Levant,
probably on the southern coast of Anatolia and in Syria, perhaps
also in Cyrenaica. Its cultivation began within historic time.
The Greeks diffused it in Greece and Italy, but it was afterwards
more highly esteemed by the Arabs, who propagated it as far
as Morocco and Spain. In all these countries the tree has
become naturalized here and there in a less productive form
. . . ".
In
Spain and Portugal it survives only on their Atlantic coasts.
Throughout the Mediterranean region, it is grown only in the
warmest areas near the coast, and the neighboring islands-Cyprus,
Crete, Sicily, Sardinia and Majorca.
Producers in the Bari region of Italy on the Adriatic coast
have long exported the pods to Russia and central Europe.
Prince Belmonte in the Province of Salerno, Italy, was a leading
influence in the 19th century in the use of the carob as an
ornamental and avenue tree and in the planting of thousands
for reforestation of the slopes of the Appenines.
Spanish
missionaries introduced the carob into Mexico and southern
California. In 1856, 8,000 seedlings, from seed brought in
from Spain by the United States Patent Office, were distributed
in the southern states. More seeds came from Israel in 1859.
Many carobs were planted in Texas, Arizona, California and
a few in Florida as ornamental and street trees. Seeds privately
imported from Dalmatia were planted in California in 1873.
In
the Mediterranean region, peasants have virtually lived on
the pods in times of famine, but the tree is valued mostly
as providing great amounts of pods as feed for livestock,
as it is also in the State of Campinas, Brazil. Imported pods
used to be regularly sold by street vendors in the Italian
section of lower New York City for chewing.
In the early 1920's, there was much promotion of carob culture
in California, especially allied with the development of arid
lands, and there was a flurry of activity in producing "health
food" products from imported pods. Some of these products
are still sold today, especially as substitutes for chocolate.
Dr. J. Eliot Coit, of Vista, California, led in the study
of the carob and wrote extensively on its potential improvement
as a crop and its utilization.
In
1949, Dr. Walter Rittenhouse provided funds for the establishment
of a 30-year test plot in northern San Diego County, where
400 local nursery seedlings and many trees grafted with Mediterranean
budwood were planted and evaluated. Fruits from several thousand
ornamental carob trees in California and Arizona were collected
in an effort to identify superior types for human food use.
Budwood of the most promising clones was supplied to horticulturists
in Tunisia, Israel, Australia, South Africa, Hawaii, Mexico,
Brazil and Chile.
Carob Varieties
From
more than 80 clones, 7 selections made by Coit were set out
at the Citrus Research Center of the University of California
for preservation. The 7 are, briefly:
'Amele'-an
old commercial variety from Italy; S.P.I. #19437. Female.
Pods light-brown, straight or slightly curved, 5 1/2 to 6
1/4 in (14-16 cm) long, 3/4 to 1 in (2-2.5 cm) wide; 53.8%
sugar content under irrigation near Indio. Flavor good. Season:
September at Indio; October at Vista.
'Casuda'-a
very old cultivar from Spain. Female. Pod brown, mostly straight;
4 3/4 in (12 cm) long; 3/5 in (1.5 cm) wide; 51.7 % sugar
at Vista; 56.7 % under irrigation at Indio. Flavor fair. Season:
September at Indio; October at Vista.
'Clifford'-seedling
street tree in Riverside. Hermaphrodite. Pod light-brown,
slightly curved, 5 1/8 in (13 cm) long, 3/4 in (2 cm) wide;
52.9% sugar content. Flavor fair. Season: early October; bears
regularly and heavily.
'Sfax'-from
Menzel bou Zelfa, Tunisia; S.P.I. #187063. Female. Pod red-brown,
straight or slightly curved; 6 in (15 cm) long, 3/4 in (2
cm) wide; 56.6% sugar at Vista, 45.6% at Indio. Excellent
flavor. Season: August at Indio, September at Vista. A regular,
medium-heavy bearer.
'Santa
Fe'-seedling from Santa Fe Springs, California. Hermaphrodite;
self-fertile. Pod light-brown, slightly curved, often twisted;
7 to 7 7/8 in (18-20 cm) long, 3/4 in (2 cm) wide; 47.5% sugar
at Vista. Excellent flavor. Season: October. Bears regular,
good crops. Good for coastal foothills. Not suited to irrigated
culture at Indio.
'Tantillo'-from
Sicily; S.P.I. #233580. Hermaphrodite. Pod dark-brown, mostly
straight; 5 1/8 to 6 in (13-15 cm) long, 3/4 in (2 cm) wide.
Of fair flavor. Season: mid-September to mid-October. Bears
heavily and regularly.
'Tylliria'-from
Cyprus; their chief export variety; S.P.I. # 189008. Female.
Pod dark mahogany-brown, slightly curved, 6 in (15 cm) long,
3/4 to 1 in (2-2.5 cm) wide; 47.4% sugar at Vista; 50.9% at
Indio; 48.8% in Cyprus. Good flavor. Season: mid-August to
mid-September at Indio; October at Vista. Adapted to coastal
foothills. (As reported from Cyprus, seed content is 7.6 to
10.6%; pod contains 51 % sugar and the seeds 49% gum).
These
7 superseded some older cultivars, including 'Bolser', 'Conejo',
'Gabriel', 'Horne', and 'Molino'; all hermaphroditic.
Other
common cultivars in Cyprus are:
'Koundourka'-a
tree with weeping branches; mature pods generally less than
6 1/2 in (17 cm) long; they split readily; have 14.7% seeds
with a high (58%) gum content.
'Koumbota'-a
large-growing tree with "knotty" pods with low seed content.
Pods contain 53% sugar; seeds, 53% gum.
Grafted
types are classed as 'Imera'. The name 'Apostolika' is a general
term for seedlings of fair quality. Wild types as a group
are called 'Agria'.
Carob Pollination
In
a planting of female trees, one male should be included for
every 25 or 30 females. In southern Europe, branches from
male trees are grafted onto some of the females in an orchard
instead of interplanting male trees.
Carob Climate
The
carob is slightly hardier than the sweet orange. Young trees
suffer frost damage. Mature tees can endure a temperature
drop to 20º F (-6.67º C). Frost during the blooming period
will reduce or prevent fruit-set. The tree does best in a
Mediterranean-type climate with cool, not cold, winters, mild
to warm springs, and warm to hot summers with little or no
rain. Temperatures in carob-growing regions of Israel may
reach 104º to 122º F (40º-50º C) in summer. Ideal annual precipitation
is 30 in (75 cm), but widely spaced trees will thrive with
only 6 to 15 in (15-37.5 cm) without irrigation in mild climates.
The pods should not be exposed to rain or heavy dew after
they have turned brown and developed a high sugar content.
Wet pods ferment quickly.
Carob Soil
The
tree flourishes in widely divergent soils, from rocky hillsides
to deep sand or heavy loam, but must have good drainage. In
Nicosia, Cyprus, a large plantation was developed by dynamiting
planting holes in caprock underlaid with limestone (pH 9).
The carob is not tolerant of acid or wet soils; it is extremely
drought-tolerant.
Carob Propagation
Fresh
seeds germinate quickly and may be sown directly in the field.
Dried, hard seeds need to be scarified or chipped and then
soaked in water or dilute sulfuric or hydrochloric acid solutions
until they swell. In Cyprus, seeds are planted in sand and
kept wet for 6 weeks or more, periodically sifting out those
that have swollen to 3 times normal size. Germination rate
may be only 25%.
The swollen seeds are traditionally planted in flats and when
they produce the second set of leaves they are transferred
to small pots. When 12 in (30 cm) tall, they are transplanted
to large containers or nursery rows. A recently developed
technique is to plant the seeds in 2 halves of clay drainpipes
bound together or in plastic tubes packed in deep wooden boxes
to accommodate the long taproot.
In perhaps a year, the tubes are split and the seedlings are
planted in the field in holes made with a post-hole digger.
Budding is done when the stem is at least 3/8 in (1 cm) thick.
The
shield-budding system is employed, or sometimes a blend of
budding and grafting, in February and March in Cyprus, in
April, May and June in California and Mexico. Male trees or
those that bear poorly are top-worked to productive cultivars.
Carob Culture
The
carob grows slowly during the first year. Stem-elongation
in young plants has been expedited by application of gibberellin
(50 mg/liter monthly, or 25 mg/liter semi-monthly) for 5 months.
It is necessary to cut back the taproot 6 months before transferring
to the field if the plant is not grown by the tube/post-hole
method. Large trees cannot be successfully transplanted.
A
good spacing is 30 ft (9 in) apart each way. Most carob growers
consider fertilizing unnecessary but the government of Cyprus
subsidizes fertilization-so much per tree. Irrigation must
be provided in very dry seasons if the tree is grown for its
fruits. Budded trees begin to bear in the 6th year from planting.
A carob tree may remain productive for 80 to 100 years.
Carob Harvesting
The
pods must be harvested before winter rains. They are shaken
down by means of a long pole with a terminal hook to grasp
the branches. Those that don't fall readily are knocked off
with the pole. The pods are caught on canvas sheets laid on
the ground. Then they are sun-dried for 1 or 2 days until
the moisture content is reduced to 8% or below and then go
through a kibbling process-crushing and grading into 4 categories:
cubed, medium-kibbled, meal, and seed kernels.
Carob Yield
At
6 years of age, a budded tree in California should yield about
5 lbs (2.25 kg). At 12 years, the crop should be 100 lbs (45
kg). Productivity increases steadily up to 25 or 30 years
when the yield may average 200 lbs (90 kg). In Israel individual
trees have produced 450 to 550 lbs (204-227 kg) 18 years after
grafting. Some ancient trees in the Mediterranean area are
reported to have borne 3,000 lbs (1,360 kg) in a season.
Carob Pests
and Diseases
In
the Mediterranean area, the major pest is the carob moth,
Myelois ceratoniae. It lays eggs on the flowers or
newly-formed pods and the larvae bore into the pods and ruin
them. The larvae of a midge, Asphondylia gennadii, cause
stunting of the pods. Some of the best cultivars are resistant
to these pests.
In
Cyprus, the tree is subject to several scale insects: Aspidiotus
ceratoniae, Lecanium sp., Lepidosaphes sp. and the red
scale, Aonidiella aurantii. A beetle, Cerambyx velutinus,
may bore holes in the trunk. Rats climb the trees, hide
among the branches, gnaw the bark until the branches die.
Such branches are pruned out twice a year. The only pests
reported as attacking carob trees in California are scale
insects, including the red scale. Ground squirrels feed on
plants under 2 years of age. Pocket gophers are very fond
of carob roots, and rabbits and deer graze on the young trees.
Diseases
are few. In Cyprus, deformation of young pods may be caused
by the fungus Oidium ceratoniae. Cercospora ceratoniae
occasionally induces leaf-spotting.
Carob Food
Uses
Apart
from being chewed as a sweetmeat, carob pods are processed
to a cocoa -like flour which is added to cold or heated milk
for drinking. It has been combined with wheat flour in making
bread or pancakes. A flour made by beating the seeded pods
is high in fiber and has been utilized in breakfast foods.
The finer flour is also made into confections, especially
candy bars. The pods, coarsely ground and boiled in water
yield a thick, honey-like sirup, or molasses.
The
seeds constitute 10 to 20% of the pod. They yield a tragacanth-like
gum (manogalactan), called in the trade "Tragasol", which
is an important commercial stabilizer and thickener in bakery
goods, ice cream, salad dressings, sauces, cheese, salami,
bologna, canned meats and fish, jelly, mustard, and other
food products. The seed residue after gum extraction can be
made into a starch- and sugar-free flour of 60% protein content
for diabetics.
In
Germany, the roasted seeds have served as a substitute for
coffee. In Spain, they have been mixed with coffee.
It
has been demonstrated that the extracted sugars of the pod
(sucrose, glucose, fructose and maltose in the ratio 5:1:1:0:7)
can be utilized to produce fungal protein. Infusions of the
pulp are fermented into alcoholic beverages.
Carob Other
Uses
Pods:
The pods are relished by horses, cattle, pigs, goats and rabbits.
Whole pods are broken up in a hammermill in order to crush
the seeds as well. Because of the tannin content, carob pods
should constitute no more than 10% of total feed, other-wise
they will depress growth rate. They cannot be fed to chickens.
The flour is often utilized in dog biscuits. Great quantities
of pods have been imported into the United States for flavoring
uncured tobacco.
Seeds:
The seed gum is much employed in the manufacture of cosmetics,
pharmaceutical products, detergents, paint, ink, shoe polish,
adhesives, sizing for textiles, photographic paper, insecticides
and match heads. It is also utilized in tanning. Where rubber
latex is produced, the gum is added to cause the solids to
rise to the surface. It is also used for bonding paper pulp
and thickening silkscreen pastes, and some derivatives are
added to drilling mud. It has many other actual or potential
applications. A flour made from the seeds serves as cattle
feed.
Wood:
The heartwood is hard and close-grained. It is prized
for turnery and cabinetwork. As a fuel it burns slowly and
makes excellent charcoal. It yields algarrobin, which gives
textiles a light-brown hue.
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