1467

2: Edible fruits and nuts

Aegle marmelos (L.) Correa

Trans. Linn. Soc. London 5: 223 (1800).

RUTACEAE

2n = 18 (36)

Bael or bel fruit (En). Bel Indien (Fr). Indonesia: maja, maja batu. Malaysia: bilak, bila, bel. Philippines: bael. Burma: opesheet, okshit. Cambodia: bnau. Laos: toum. Thailand: matum, tum (Pattani), ma pin (north). Vietnam: trái mam.

Bael grows wild in dry forests in the Indian Peninsula, Sri Lanka, Pakistan and Bangladesh. It is an old cultivated tree in that region, particularly found in temple gardens in India. It has spread to Indo-China, South-East Asia (in particular Thailand, northern Malaysia, eastern Java and northern Luzon) and other parts of the tropics.

Ripe fruit is eaten fresh and is also prepared as a sherbet, syrup, marmalade and fruit nectar. The mucilage around unripe seeds is used as an adhesive and household glue. The extract of leaf and young fruit was used in Java to adulterate opium. In Java the nearly ripe fruit is sliced, dried and applied against chronic dysentery, diarrhoea and constipation. Ripe fruit extract is also used against rectum inflammation. The rind of unripe fruit can be used as a yellow dye and as a tanning agent.
In Indo-China bark and leaves are used against intermittent fever, but in Sulawesi the bark is used to poison fish. Young leaves are used for seasoning in Java, although one source says they may cause abortion and sterility in women; together with betel pepper and lime they are rubbed on itching skin and used as poultice for wounds. In Madura the leaf juice is used against foot-and-mouth disease in cattle. The root is used against heart palpitation, indigestion and bowel inflammation. The wood is suitable for making small articles such as 'keris' (ceremonial dagger) handles.

The pulp is soft, yellow or orange, very fragrant and pleasantly flavoured. The edible portion (pulp) amounts to 56—77% of the fruit and contains per 100 g: water 61.5 g, protein 1.8 g, fat 0.39 g, carbohydrates 31.8 g, ash 1.7 g, carotene 55 mg, thiamine 0.13 mg, riboflavin 1.19 mg, niacin 1.1 mg, and vitamin C 8 mg. The fruit is rich in tannin (up to 20% in the rind). Marmelosine (C₁₃H₁₂O₃), volatile oil, limonene, alkaloids, coumarines and steroids are also present in different parts of the tree.

Small deciduous tree, 10—15 m tall, trunk 25—50 cm in diameter. Older branches spiny; spines single or paired, 1—2 cm long. Leaves alternate, trifoliolate; petiole 2—4 cm long, lateral petiolules up to 3 mm, terminal up to 15 mm long; lateral leaflets ovate to elliptic, up to 7 cm x 4.2 cm, terminal obovate, up to 7.5 cm x 4.8 cm, densely minutely glandular-punctate. Inflorescences axillary racemes, 4—5 cm long, clustered; sepals broadly deltoid, 1.5 mm long; petals oblong-obovate, 14 mm x 8 mm, greenish to white; stamens 35—45, white, filaments 4—7 mm long; ovary 8 mm x 4 mm, style very short. Fruit a subglobose berry, 5—12.5 cm diameter, often with a hard woody shell, of 8—16(—20) segments, with 6—10 seeds in a clear, sticky, edible pulp. Seeds woolly-pubescent, enclosed in a sac of adhesive mucilage which solidifies on drying; testa white.

Bael is a hardy, deciduous tree of the subtropics. It grows under harsh conditions, including extremes of temperature, e.g. from 49°C in summer to —7°C in winter in Punjab, up to 1200 m elevation. In South-East Asia it only flowers and fruits well where there is a prominent dry season and it is not usually found above 500 m. The tree grows on swampy land as well as dry soils and tolerates alkalinity.

Bael is usually propagated by seed; the seedlings are planted out after one year, 6—9 m apart. It can be propagated vegetatively by root suckers, or through budding, also on seedlings of other Aegle species and Swinglea glutinosa (Blanco) Merr. Vegetatively propagated plants bear fruit after 5 years and full bearing can be attained in about 15 years. The fruit ripens in the dry season, when most leaves have been shed in anticipation of bloom for the next crop. No serious pests and diseases have been reported.
Bael fruit is picked individually and should not be allowed to drop. Yield per tree is 200—400 fruit. The fruit is packed in baskets, gunny bags or wooden boxes. Cracked fruit is susceptible to fungal infection.

Seedlings show much variation in fruit characteristics. Cultivated trees generally are spineless and have much larger fruit with better quality pulp. In India cultivars are named after the locality where they became popular. Even for these cultivars, fruit quality differs greatly; 'Kaghzi' and 'Mitzapuri' have been selected for their large fruit, thin rind, few seeds and fine pulp texture and flavour. Evidently the potential of the fruit can only be appreciated after tasting such superior types.

Since the pulp from ripe fruit turns brown and develops off-flavours during extraction and processing, ripe fruit so far could only be consumed fresh, and green fruit had to be used to make preserves. New processing techniques preserve the quality of pulp from ripe fruits. Coupled with the quality of superior cultivars this may enhance the prospects for growing bael as a fruit for processing. Its soluble solid content is 28—36%, nearly twice as high as in most other fruits, making a wide range of products feasible. To assess the prospects for bael in South-East Asia it should first be investigated whether yield and fruit quality are as good as in India.

Atmodiwirjo, A.T.S., 1983. Maja (Aegle marmelos Corr.) kemungkinan pengembangan dan pengolahan buahnya. [Bael fruit (Aegle marmelos Corr.), the scope for development and fruit processing]. Buletin Kebun Raya 6(2): 35—38.
Roy, S.K., 1985. Bael. In: Bose, T.K. (Editor): Fruits of India, tropical and subtropical. Chapter 19. Naya Prokash, Calcutta. pp. 498—504.
Roy, S.K. & Singh, R.N., 1979. Bael fruit (Aegle marmelos) - A potential fruit for processing. Economic Botany 33(2): 203—212.

A.T. Sunarto

Sunarto, A.T., 1991. Aegle marmelos (L.) Correa. In: Verheij, E.W.M. and Coronel, R.E. (Editors): Plant Resources of South-East Asia No 2: Edible fruits and nuts. PROSEA Foundation, Bogor, Indonesia. Database record: prota4u.org/prosea