The Bael
Introduction
Common and regional names
The bael (Aegle marmelos
Correa) is known as Wood apple or Bengal Quince in the English
language; as bel, bela, sirphal, Golden apple, Indian quince, Holy
fruit, Stone apple in India; oranger du malbar in French; marmelos in
Portuguese; bilak or maja pahit in Malaysian; madjo in Java; bau nau in
Vietnam; phneou or pnoi in the Cambodian language; malum and mapin in
Thailand.
Other synonyms of Aegle marmelos Correa are Feronia pellucida Roth and Crataeva marmelos L.
Origin and distribution
The
bael is an Indian native plant, which is also found in Burma, Pakistan,
Bangladesh, Sri Lanka, Thailand, and various other parts of
Southeastern Asia. Historic mention of bael fruits has been traced to
Vedic times (2000-800 BC). It has been considered as a sacred plant by
Hindus and commonly grown in temple gardens in India. It has been
stated that this tree indicates the presence of water. It was
introduced into Europe from India in 1759.
Traditional and medicinal uses
The
bael has got nutritive, curative and pesticidal properties. All of its
parts, i.e., stem, bark, leaves, fruits, and roots at any stage of
development, have one or another usage. The unripe as well as ripe
fruits can be used in different ways, mainly making ‘murabba’ (sweet
preserve), jam, candies, toffees, slabs, and soft drinks. Sundried
fruit slices of green fruit are often stored for future use. The fruit
pulp can be used for washing clothes.
The gum from unripe fruit is used as glue as well as a protective coating on paintings.
The
medicinal properties of this plant has been described in ‘Charaka
samhita’ an early Sanskrit medicinal treatise. For medicinal uses,
young tender fruits are horizontally cut, and sun dried. Major
constituents are mucilage and pectin in unripe fruit, while ripe fruit
is a tonic and is used as mild astringent for diseases like diarrhoea
and dysentery.
Many alkaloids, coumarin and steroids have been
isolated from different plant parts. The pulp contains psoralen, which
is employed in treatment of leucoderma; another compound, marmelosin,
is used as a laxative and diuretic. Fruit is claimed to be prescribed
in case of hepatitis and tuberculosis in Cambodia. Aqueous and
alcoholic extracts have cardiotonic effects on amphibian and mammalian
hearts. A decoction of flowers is used as an eye lotion. A bark
decoction is sometime given for curing malaria. A leaf decoction is
effective in relieving asthma, extracts from leaves in combination with
honey are good for catarrh and fever, adding black pepper relieves
jaundice. All plant parts have antibiotic properties. Roots are used as
an anti-inflammatory and antidote to snake venom in India. The leaves
have got pesticidal constituents. Although the wood is not durable, it
is good for carving and making handles of various tools.
Nutritional value
The
bael is a rich source of riboflavin and is a highly nutritious and
flavoured fruit. On a 100- gram pulp basis it contains 61.5% water; 1.8
g protein; 0.39g fat; 1.7 g minerals; 31.8 g carbohydrates; 55 mg
carotene; 0.13 mg thiamine; 1.19 mg riboflavin; 1.1 mg niacin and 8 mg
ascorbic acid. Its seed contains 62% protein; 32% oil (15.6% palmitic
acid, 8.3% stearic acid, 28.7% linoleic acid and 7.6% linolenic acid);
3% carbohydrate and 3% ash content.
Toxicities
Some
wild species contains about 9% tannin in pulp and up to 20% in rind.
High tannin ingestion over extended periods act as an anti-nutrient and
may be carcinogenic. Leaves can cause abortion in women and bark is
used as fish poison.
Botany
Taxonomy and general description
The
bael belongs to family Rutaceae, orange subfamily Aurantiodae, tribe
Clauseneae and subtribe Balsamocitrine. Its generic name Aegle is Greek
while the species name marmelos is of Portuguese origin. It is a medium size (6-8 metres), deciduous woody tree, with trifoliate aromatic leaves.
Morphology and biology
The
plant has unusual branches bearing straight spines. The bark is
shallowly furrowed and corky. The leaves have three leaflets, terminal
usually being the largest. The flowers are bisexual, nearly 2 cm wide,
white, fragrant, borne in clusters of 4-7. Its shallow calyx has 5
short, broad teeth, pubescent outside. The flower has usually 5 petals
(rarely 4) of a pale greenish white colour, dotted with oil glands, and
50 or more greenish yellow stamens, sometime coherent in bundles. The
ovary is oblong, ovoid slightly tapering, with 8 -20 cells - numerous
cells in each ovary. Fruits are globose, round, pyriform, oval or
oblong, 5-20 cm in diameter, with greyish yellow pericarp (3 mm thick)
and sweet pulp, yellow to orange in colour. Seeds are numerous,
compressed, closely packed and arranged in the cells surrounded by
transparent mucilage, which on drying becomes hard. The white testa has
woolly hairs and the embryo has large cotyledons.
Culture
Soil and Climate
The
bael is a sub-tropical plant with high adaptability of agro-ecological
conditions up to an altitude of 1200 m. It grows from arid to swampy
conditions and in areas with pH range of 5-10 and temperature of
6-49°C. It will not bear fruit if there is no prolonged dry season, as
in Southern Malaya.
Cultivars
Previously
most of the bael cultivars in India were named after the locality in
which they occur. ‘Mirzapuri’ was the best choice. Other were
‘Darogaji’, ‘Ojha’, ‘Rampuri’, ‘Azamti’ and ‘Kamaria’ in the ranking
order. Another good variety ‘Kaghji Gonda’ had fruit of 1412.82 grams
with very thin rind (0.15 cm).
In a survey of Uttar Pradesh
province in India, data on 7 varieties gave a TSS (total soluble
sugars) range from 28 to 36%, reducing sugars from 2.7 to 5.2%,
non-reducing sugars from 8.3 to 12.4%, total sugars from 11.7 to 16.9%,
acidity from 0.256 to 0.368% and vitamin C from 13.4 to 22.7 mg/100 g.
It
has been suggested that the organoleptic quality of bael fruits mainly
depends upon three factors, i.e. sugars, mucilage, and total phenolics.
The cultivars with higher sugar content, especially the non-reducing
sugars, and low level of phenolics, are good in taste. Size of fruits
is also very important as the larger size fruits have high pulp,
comparatively thin peel, and lower seed, mucilage and phenolic.
Potential
bael cultivars with regard to fruit productivity and quality have been
selected and current popular selections are as below.
NB 5.
Fruits are medium sized, round with smooth surface at maturity. Other
characteristics include low mucilage contents, moderately fibrous, soft
fleshed with excellent taste.
NB 6. Fruits are medium sized. round having smooth surface, thin rind, few seeds, low mucilage and mild acidic.
Pant
shivani. This is a mid-season cultivar with heavy fruits (2 kg) ovoid
oblong shape. Mucilage and fibre contents are low. Fruit rind has
medium thickness; pulp colour is light yellow with sweet taste and good
flavour.
Pant Aparna. A late maturing cultivar with small fruit
size (0.6- 0.8 kg), medium thick rind, globose in shape having less
number of seeds. Mucilage, fibre contents and acidity is low. It has
yellow flesh which is sweet, tasty and of good flavour.
Propagation
Bael
is propagated through seeds, which are recalcitrant and cannot be
stored for a long period in normal storage. Plants produced from seeds
are rarely true to type. Budding (patch or shield) during June-July
gives good success. Budwood should be taken from one-month-old shoots.
Air layering in the tropics and use of root cuttings is also
successful. In-vitro propagation has also been standardized, though
commercially not applicable.
Seedlings start bearing at 6-7
years of age, vegetatively propagated plants bear in 4-5 years, and
full bearing potential can be attained in 15 years. The bael has graft
compatibility with related plants, eg Aegle fraeqlegabonesis, A. chevalier, A. paniculata and Swinglea glutinosa. Grafting of oranges on seedling of bael fruits has also proved successful.
Top
working can successfully rejuvenate old plants. During experiments in
India, 11, 8 and 5-year old plants were cut back to 4 feet from the
ground in March and only 10, 9, and 8 new shoots were retained
respectively. These were shield budded with improved scions in the
following June. The percentage success was 90, 100 and 87.5 %
respectively, and trees started bearing fruits in 5 years.
Planting distance
There
is no recommendation regarding planting distance or method of planting
of bael fruit. However, methods adopted in citrus cultivation can also
be adopted for bael. For planting as an orchard, plants should be
spaced 10 metres apart for getting good plant growth and fruit yield.
Pruning and training
Trees
can be trained in the modified central leader system. Pruning should be
done twice in a year, aiming at removing dead and diseased branches
during May, while in August healthy leaves should be pruned off for
sale purpose.
Nutrition
Deficiency
of nitrogen and zinc has been reported from bael plants, and can be
easily corrected by soil or foliar application of required nutrients in
the form of fertilizers.
Pest and diseases
The most common insect pest includes citrus leaf minor (Phylocnistis citrella) while fruit canker, gummosis, and bacterial shot hole are the major diseases. The symptoms of bacterial shot holes caused by Xanthomonas bilvae
on leaves are round, watery spots, 0.5 mm in size, surrounded by a
hole. This spot reaches in size from 0.3 mm to 0.5 mm and will form a
brown lesion. There is a depression in its centre surrounded by an
oily, raised margin. The dead tissue falls, creating shot holes on the
leaf surface. Such lesions occur all over the leaf. Fruit-cracking just
before ripening is a physiological disorder in some genotypes of bael.
Fruit ripening, harvesting and yield
Generally
it takes about 11 months from fruit setting to harvesting in the bael
plant. Under Delhi conditions (India), fruit setting occurs in early
May. Fruit approaches maturity during December, but due to prevailing
low temperatures, ripening is delayed until the following April.
Fruits
are considered to be climacteric in nature, but no climacteric rise in
respiration occurs as long as the fruit is on the tree. During
ripening, the peel turns very hard and brittle. Moisture content,
acidity, and total phenolics decrease while dry matter, pectin, crude
protein, total and reducing sugars are increased. Exogenous application
of ethylene along with high temperatures accelerates the ripening
process. The fruit can be picked up to 2-3 months early and ripened
artificially in 18-24 days by treating with 1000-1500 ppm ethrel
(2-chloroethane phosphonic acid) at 30°C. With artificially ripened
fruits, total sugar contents are lower.
Due to its deciduous
nature the tree has no leaves at ripening time. Fruits are manually
harvested along with their stalk, when colour changes to yellowish
green. Tree shaking is generally discouraged, as the fallen fruits are
likely to develop cracks and later on get infected. Care must be taken
to avoid causing skin cracking during harvesting operations. Yield
depends upon age and cultivars but 200-400 fruits per tree is common at
10-15 years and 400-1000 fruits have been harvested from full-grown
seedling trees (40-50 years old).
Shelf life
Fruits
are generally transported in gunny bags, and wooden crates without any
packing material, but use of any kind of cushioning material is highly
desirable. Fruit can be kept for 2 weeks at 30°C and 4 months at 9°C.
At low temperatures (below 9°c) chilling injuries (brown spots on fruit
surface) occur, while at high temperature (above 13°C) fungus spoils
the fruit. In case of extended storage, mould can develop in cracks of
the rind as well as at the stem end of fruits. It is advisable to use
some kind of cushioning material for packing of fruit to avoid skin
injuries, which results in heavy fungal infection.
Processing
Bael
fruit is very important for the processing industry because it gives
high yields of pulp. The total soluble solids content of bael fruit are
about 40 %, comparable with many other fruits.
Use of mature
green fruit as well as ripened fruit has been widely reported in
preparing preserves, but due to high gummy principles it did not form
jelly, although fruit is rich in pectic substances. For preparing
preserves from mature green fruit, the rind is removed and fruit is cut
into two halves and thinly sliced. After washing with water, slices are
pricked with a fork and kept overnight in cold water, blanched, and put
in sugar syrup. The syrup strength gradually increases to 700 Brix.
Ripe
fruit is not much consumed due to eating difficulty. With conventional
methods of pulp extraction, pulp gets off-flavoured and colour changes
due to enzymatic activities. However pulp can be extracted with an
equal amount of water at pH 4.3 with citric acid (titratable acidity
0.5%) at 80°C for one minute, and afterward passing through a pulping
machine. The pulp extracted by this method has almost the same
consistency as that of mango. The extracted pulp can be improved by
adjusting Brix of pulp to 25% by addition of sugar without altering
acidity. Canning, freezing and addition of S02 can preserve it for
different uses.
References
Morton, J. 1987. Bael Fruits, p 187-190. In: Fruits of warm climates. Julia F. Morton, Miami, Fl.
Singh, R. N. and Susanta, K. roy. 1984. The Bael: Cultivation and processing. IndianCouncil of Research, New Delhi.
Webpage: http://www.hort.purdue.edu/newcrop/CropFactSheets/bael.html
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