1517

2: Edible fruits and nuts

Malpighia glabra L.

Sp. Pl.: 425 (1753).

MALPIGHIACEAE

2n = 40

Malpighia punicifolia L. (1762).

Acerola, West Indian cherry, Barbados cherry (En). Cerise-antillaise (Fr). Thailand: choeri (Bangkok), Vietnam: so'ri.

The acerola is native to the Lesser Antilles and from northern South America to southern Texas in the United States. It has been introduced into other parts of the tropics and subtropics. In South-East Asia it is only sporadically grown.

The sour fruits are eaten fresh, but more often preserved with sugar, e.g. in the form of jam. Juice is used commercially to enrich other fruit juices low in vitamin C. The bark has been used for tanning. The wood, which is hard and heavy, can be used for small utensils. The fruits are considered beneficial against liver problems, diarrhoea, dysentery, coughs and colds.

Although acerola was promoted commercially in the 1950s as a rich natural source of vitamin C, it is now only important in Puerto Rico. Canned juice and frozen fruit are exported to the United States, where they are used to enrich fruit preserves and are marketed as baby foods.

The edible pulp represents about half of the fruit weight and contains per 100 g: water 82—91 g, protein 0.7—1.8 g, fat 0.1—0.2 g, carbohydrates 7—14 g, fibre 0.6—1.2 g, ash 0.8 g. The energy value is 247 kJ per 100 g. The fruit — particularly when immature — is one of the richest sources of vitamin C, containing up to 4.7 g per 100 g edible portion.

Shrub or small evergreen tree, 2—3(—6) m tall, with spreading, more or less drooping branches on a short trunk. Leaves opposite, ovate to elliptic-lanceolate, 2—8 cm x 1—4 cm, entire or undulating, dark green and glossy above, petiole short. Inflorescences sessile or short-peduncled axillary cymes with 3—5 flowers; flowers bisexual, 1—2 cm in diameter, pinkish to reddish; calyx with 6—10 large sessile glands; petals 5, fringed, slender-clawed; stamens 10, filaments united below. Fruit a bright-red, juicy drupe, depressed-ovoid, 1—3 cm in diameter and weighing 3—5 g, usually in pairs or threes, obscurely 3-lobed; skin thin, flesh soft, orange, acid to subacid. Seeds 3, triangular, ridged.
The germination rate of the seed is low (5—50%). Trees start to produce well 3—4 years after planting and continue for 15 years. In Puerto Rico flowering appeared to be independent of the daylength and several cropping periods are possible per year, especially with alternating dry and rainy periods. The flowers are pollinated by insects; honey bees substantially improve fruit set. Self- and cross-incompatibility have been reported. Fruits ripen completely 3—4 weeks after flowering. In Puerto Rico the large-fruited (up to 20 g/fruit) selection B-15 is most important. In Florida, 'Florida Sweet' is a high-yielding cultivar.
A distinction is sometimes made in nomenclature between wild and cultivated (improved) plants, the latter being called Malpighia punicifolia L. It is now, however, generally accepted that both taxa belong to Malpighia glabra. Malpighia coccigera L. and Malpighia urens L. are incidentally cultivated in South-East Asia for the same purposes as Malpighia glabra.

Acerola can be grown almost anywhere in the tropics and warm subtropics. Young plants are killed by frost, but mature trees survive brief exposure to —2°C. The plants tolerate long periods of drought and do not stand waterlogging. The soil should preferably be rich, deep and well drained, with a pH above 5.5. On calcareous soils the plants require additional micronutrients, on acid soils addition of lime is required.

Fully developed seeds should be used for planting. Acerola may also be propagated vegetatively by cuttings, budding or grafting. The recommended spacing is 3—4 m on the square, or in double rows, e.g. (4 + 2) m x 3 m. NPK fertilization twice a year and application of organic material are recommended for Puerto Rico. Bearing will be enhanced if mature plants are judiciously pruned after the main crop, followed by a top dressing. Acerola is very susceptible to the root-knot nematode Meloidogyne incognita var. acrita. It can be controlled by soil fumigation, mulching and regular irrigation.
Fruits for home consumption are picked when fully ripe. For processing fruits are harvested when they turn from yellow to red. Picking is carried out every 1—3 days as there is continuous fruiting over long periods. Individual trees may produce 15—30 kg of fruits per year, whereas yields per hectare per year may vary considerably: (10—)15—25(—65) t. Mature fruits bruise easily and are very perishable. Storage up to 3 days at 7°C is possible. Half-ripe acerolas can be kept for a few more days, but if longer storage is necessary the fruit must be frozen and kept at —12°C.

Germplasm collections are available at the Subtropical Horticultural Research Unit USDA, Miami, Florida, United States and the Department of Horticulture, College of Agricultural Sciences, University of Puerto Rico, Mayaguez.

The acerola is a suitable fruit for home gardens. The plants have ornamental value and are very suitable for backyards and places where children play (to eat the fruits and to climb the trees) and for hedges.

Ostendorf, F.W., 1963. The West Indian cherry. Tropical Abstracts 18(3): 145—150.
Moscoso, C.G., 1956. West Indian cherry — richest known source of natural vitamin C. Economic Botany 10: 280—294.
Ledin, R.B., 1958. The Barbados or West Indian cherry. Florida Agricultural Experimental Station Bulletin 594: 1—28.
Yamane, G.M. & Nakasone, H.Y., 1961. Pollination and fruit set studies of acerola (Malpighia glabra L.) in Hawaii. Proceedings American Society for Horticultural Science 78: 141—148.

Sri Setyati Harjadi

Sri Setyati Harjadi, 1991. Malpighia glabra L.. 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