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Morton, J. 1987. Soursop. p. 75–80. In: Fruits of warm climates. Julia F. Morton, Miami, FL.


Soursop

Annona muricata




Of the 60 or more species of the genus Annona, family Annonaceae, the soursop, A. muricata L., is the most tropical, the largest-fruited, and the only one lending itself well to preserving and processing.

It is generally known in most Spanish-speaking countries as guanabana; in E1 Salvador, as guanaba; in Guatemala, as huanaba; in Mexico, often as zopote de viejas, or cabeza de negro; in Venezuela, as catoche or catuche; in Argentina, as anona de puntitas or anona de broquel; in Bolivia, sinini; in Brazil, araticum do grande, graviola, or jaca do Para; in the Netherlands Antilles, sorsaka or zunrzak, the latter name also used in Surinam andJava; in French-speaking areas of the West Indies, West Africa, and Southeast Asia, especially North Vietnam, it is known as corossol, grand corossol, corossol epineux, or cachiman epineux. In Malaya it may be called durian belanda, durian maki; or seri kaya belanda; in Thailand, thu-rian-khack.

In 1951, Prof. Clery Salazar, who was encouraging the development of soursop products at the College of Agriculture at Mayaguez, Puerto Rico, told me that they would like to adopt an English name more appealing than the word "soursop", and not as likely as guanabana to be mispronounced. To date, no altematives have been chosen.

Soursop
Plate 10: SOURSOP, Annona muricata
Exceptionally large and well-formed soursops
Fig. 20: Exceptionally large and well-formed soursops (Annona muricata) in a Saigon market, 1968.

Description

The soursop tree is low-branching and bushy but slender because of its upturned limbs, and reaches a height of 25 or 30 ft (7.5-9 m). Young branchlets are rusty-hairy. The malodorous leaves, normally evergreen, are alternate, smooth, glossy, dark green on the upper surface, lighter beneath; oblong, elliptic or narrowobovate, pointed at both ends, 2 1/2 to 8 in (6.25-20 cm) long and 1 to 2 1/2 in (2.5-6.25 cm) wide. The flowers, which are borne singly, may emerge anywhere on the trunk, branches or twigs. They are short stalked, 1 1/2 to 2 in (4 5 cm) long, plump, and triangular-conical, the 3 fleshy, slightly spreading, outer petals yellow-green, the 3 close-set inner petals pale-yellow.

The fruit is more or less oval or heart-shaped, some times irregular, lopsided or curved, due to improper carper development or insect injury. The size ranges from 4 to 12 in (10-30 cm) long and up to 6 in (15 cm) in width, and the weight may be up to 10 or 15 lbs (4.5-6.8 kg). The fruit is compound and covered with a reticulated, leathery-appearing but tender, inedible, bitter skin from which protrude few or many stubby, or more elongated and curved, soft, pliable "spines". The tips break off easily when the fruit is fully ripe. The skin is dark-green in the immature fruit, becoming slightly yellowish-green before the mature fruit is soft to the touch. Its inner surface is cream-colored and granular and separates easily from the mass of snow-white, fibrous, juicy segments—much like flakes of raw fish—surrounding the central, soft-pithy core. In aroma, the pulp is somewhat pineapple-like, but its musky, subacid to acid flavor is unique. Most of the closely-packed segments are seedless. In each fertile segment there is a single oval, smooth, hard, black seed, l/2 to 3/4 in (1.25-2 cm) long; and a large fruit may contain from a few dozen to 200 or more seeds.

Origin and Distribution

Oviedo, in 1526, described the soursop as abundant in the West Indies and in northern South America. It is today found in Bermuda and the Bahamas, and both wild and cultivated, from sea-level to an altitude of 3,500 ft (1,150 m) throughout the West Indies and from southern Mexico to Peru and Argentina. It was one of the first fruit trees carried from America to the Old World Tropics where it has become widely distributed from southeastern China to Australia and the warm lowlands of eastern and western Africa. It is common in the markets of Malaya and southeast Asia. Very large, symmetrical fruits have been seen on sale in South Vietnam. It became well established at an early date in the Pacific Islands. The tree has been raised successfully but has never fruited in Israel.

In Florida, the soursop has been grown to a limited extent for possibly 110 years. Sturtevant noted that it was not included by Atwood among Florida fruits in 1867 but was listed by the American Pomological Society in 1879. A tree fruited at the home of John Fogarty of Manatee before the freeze of 1886. In the southeastern part of the state and especially on the Florida Keys, it is often planted in home gardens.

In regions where sweet fruits are preferred, as in South India and Guam, the soursop has not enjoyed great popularity. It is grown only to a limited extent in Madras. However, in the East Indies it has been acclaimed one of the best local fruits. In Honolulu, the fruit is occasionally sold but the demand exceeds the supply. The soursop is one of the most abundant fruits in the Dominican Republic and one of the most popular in Cuba, Puerto Rico, the Bahamas, Colombia and northeastern Brazil.

In 1887, Cuban soursops were selling in Key West, Florida, at 10 to 50 cents apiece. In 1920, Wilson Popenoe wrote that: "In the large cities of tropical America, there is a good demand for the fruits at all times of the year, a demand which is not adequately met at present." The island of Grenada produces particularly large and perfect soursops and regularly delivers them by boat to the market of Port-of Spain because of the shortage in Trinidad. In Colombia, where the soursop is generally large, well-formed and of high quality, this is one of the 14 tropical fruits recommended by the Instituto Latinoamericano de Mercadeo Agricola for large-scale planting and marketing. Soursops produced in small plots, none over 5 acres (2.27 ha), throughout Venezuela supply the processing plants where the frozen concentrate is packed in 6 oz (170 g) cans. In 1968, 2,266 tons (936 MT) of juice were processed in Venezuela. The strained pulp is also preserved commercially in Costa Rica. There are a few commercial soursop plantations near the south coast of Puerto Rico and several processing factories. In 1977, the Puerto Rican crop totaled 219,538 lbs (99,790 kg).

At the First International Congress of Agricultural and Food Industries of the Tropical and Subtropical Zones, held in 1964, scientists from the Research Laboratories of Nestle Products in Vevey, Switzerland, presented an evaluation of lesser-known tropical fruits and cited the soursop, the guava and passionfruit as the 3 most promising for the European market, because of their distinctive aromatic qualities and their suitability for processing in the form of preserved pulp, nectar and jelly.

Varieties

In Puerto Rico, the wide range of forms and types of seedling soursops are roughly divided into 3 general classifications: sweet, subacid, and acid; then subdivided as round, heart-shaped, oblong or angular; and finally classed according to flesh consistency which varies from soft and juicy to firm and comparatively dry. The University of Puerto Rico's Agricultural Experiment Station at one time cataloged 14 different types of soursops in an area between Aibonito and Coamo. In El Salvador, 2 types of soursops are distinguished: guanaba azucaron (sweet) eaten raw and used for drinks; and guanaba acida (very sour), used only for drinks. In the Dominican Republic, the guanabana dulce (sweet soursop) is most sought after. The term "sweet" is used in a relative sense to indicate low acidity. A medium-sized, yellow-green soursop called guanabana sin fibre (fiberless) has been vegetatively propagated at the Agricultural Experiment Station at Santiago de las Vegas, Cuba. The foliage of this superior clone is distinctly bluish-green. In 1920, Dr. Wilson Popenoe sent to the United States Department of Agriculture, from Costa Rica, budwood of a soursop he named 'Bennett' in honor of G.S. Bennett, Agricultural Superintendent of the Costa Rican Division of the United Fruit Company. He described the fruit as large and handsome (as shown in the photograph accompanying the introduction record No. 51050) and he declared the tree to be the most productive he had seen.

The soursop tree may bear fruits anywhere on its trunk.
Fig. 21: The soursop tree may bear fruits anywhere on its trunk or branches. Multiple-stems of this tree are the result of its having been frozen to the ground more than once.

Climate

The soursop is truly tropical. Young trees in exposed places in southem Florida are killed by only a few degrees of frost. The trees that survive to fruiting age on the mainland are in protected situations, close to the south side of a house and sometimes near a source of heat. Even so, there will be temporary defoliation and interruption of fruiting when the temperature drops to near freezing. In Key West, where the tropical breadfruit thrives, the soursop is perfectly at home. In Puerto Rico, the tree is said to prefer an altitude between 800 and 1,000 ft (244300 m), with moderate humidity, plenty of sun and shelter from strong winds.

Soil

Best growth is achieved in deep, rich, well-drained, semi-drysoil, but the soursop tree can be and is commonly grown in acid and sandy soil, and in the porous, oolitic limestone of South Florida and the Bahama Islands.

Propagation

The soursop is usually grown from seeds. They should be sown in flats or containers and kept moist and shaded. Germination takes from 15 to 30 days. Selected types can be reproduced by cuttings or by shield-budding. Soursop seedlings are generally the best stock for propagation, though grafting onto custard apple (Annona reticulata), the mountain soursop (A. montana), or pond apple (A. glabra), is usually successful. The pond apple has a dwarfing effect. Grafts on sugar apple (A. squamosa) and cherimoya (A. cherimola) do not live for long, despite the fact that the soursop is a satisfactory rootstock for sugar apple in Ceylon and India.

Culture

In ordinary practice, seedlings, when 1 ft (30 cm) or more in height are set out in the field at the beginning of the rainy season and spaced 12 to 15 ft (3.65-4.5 m) apart, though 25 ft (7.5 m) each way has been suggested. A spacing of 20 x 25 ft (6x7.5 m) allows 87 trees per acre (215/ha). Close-spacing, 8 x 8 ft (2.4x2.4 m) is thought aufficient for small gardens in Puerto Rico. The tree grows rapidly and begins to bear in 3 to 5 years. In Queensland, well-watered trees have attained 15 to 18 ft (4.5-5.5 m) in 6 to 7 years. Mulching is recommended to avoid dehydration of the shallow, fibrous root system during dry, hot weather. If in too dry a situation, the tree will cast off all of its old leaves before new ones appear. A fertilizer mixture containing 10% phosphoric acid, 10% potash and 3% nitrogen has been advocated in Cuba and Queensland. But excellent results have been obtained in Hawaii with quarterly applications of 10-10-10 N P K—1\2 lb (.225 kg) per tree the first year, 1 lb (.45 kg)/tree the 2nd year, 3 lbs (1.36 kg)/tree the 3rd year and thereafter.

Season

The soursop tends to flower and fruit more or less continuously, but in every growing area there is a principal season of ripening. In Puerto Rico, this is from March to June or September; in Queensland, it begins in April; in southern India, Mexico and Florida, it extends from June to September; in the Bahamas, it continues through October. In Hawaii, the early crop occurs from January to April; midseason crop, June to August, with peak in July; and there is a late crop in October or November.

Harvesting

The fruit is picked when full grown and still firm but slightly yellow-green. If allowed to soften on the tree, it will fall and crush. It is easily bruised and punctured and must be handled with care. Firm fruits are held a few days at room temperature. When eating ripe, they are soft enough to yield to the slight pressure of one's thumb. Having reached this stage, the fruit can be held 2 or 3 days longer in a refrigerator. The skin will blacken and become unsightly while the flesh is still unspoiled and usable. Studies of the ripening process in Hawaii have determined that the optimum stage for eating is 5 to 6 days after harvest, at the peak of ethylene production. Thereafter, the flavor is less pronounced and a faint offodor develops. In Venezuela, the chief handicap in commercial processing is that the fruits stored on racks in a cool shed must be gone over every day to select those that are ripe and ready for juice extraction.

Yield

The soursop, unfortunately, is a shy-bearer, the usual crop being 12 to 20 or 24 fruits per tree. In Puerto Rico, production of 5,000 to 8,000 lbs per acre (roughly equal kg/ha), is considered a good yield from well-cared-for trees. A study of the first crop of 35 5 year-old trees in Hawaii showed an average of 93.6 lbs (42.5 kg) of fruits per tree. Yield was slightly lower the 2nd year. The 3rd year, the average yield was 172 lbs (78 kg) per tree. At this rate, the annual crop would be 16,000 lbs per acre (roughly equal kg/ha).

Pests & Diseases

Queensland's principal soursop pest is the mealybug which may occur in masses on the fruits. The mealybug is a common pest also in Florida, where the tree is often infessed with scale insects. Sometimes it may be infected by a lace-wing bug.

The fruit is subject to attack by fruit flies—Anastrepha suspensa, A. striata and Ceratitis capitata. Red spiders are a problem in dry climates.

Dominguez Gil (1978 and 1983), presents an extensive list of pests of the soursop in the State of Zulia, Venezuela. The 5 most damaging are: 1) the wasp, Bephratelloides (Bephrata) maculicollis, the larvae of which live in the seeds and emerge from the fully-grown ripe fruit, leaving it perforated and highly perishable; 2) the moth, Cerconota (Stenoma) anonella, which lays its eggs in the very young fruit causing stunting and malformation; 3) Corythucha gossipii; which attacks the leaves; 4) Cratosomus inaequalis, which bores into the fruit, branches and trunk; 5) Laspeyresia sp., which perforates the flowers. The first 3 are among the 7 major pests of the soursop in Colombia, the other 4 being: Toxoptera aurantii; which affects shoots, young leaves, flowers and fruits; present but not important in Venezuela; Aphis spiraecola; Empoasca sp., attacking the leaves; and Aconophora concolor, damaging the flowers and fruits. Important beneficial agents preying on aphids are A phidius testataceipes, Chrysopa sp., and Curinus sp. Lesser enemies of the soursop in South America include: Talponia backeri and T. batesi which damage flowers and fruits; Horiola picta and H. lineolata, feeding on flowers and young branches; Membracis foliata, attacking young branches, flower stalks and fruits; Saissetia nigra; Escama ovalada, on branches, flowers and fruits; Cratosomus bombina, a fruit borer; and Cyclocephala signata, affecting the flowers.

In Trinidad, the damage done to soursop flowers by Thecla ortygnus seriously limits the cultivation of this fruit. The sphinx caterpillar, Cocytius antueus antueus may be found feeding on soursop leaves in Puerto Rico. Bagging of soursops is necessary to protect them from Cerconota anonella. However, one grower in the Magdalena Valley of Colombia claims that bagged fruits are more acid than others and the flowers have to be handpollinated.

It has been observed in Venezuela and El Salvador that soursop trees in very humid areas often grow well but bear only a few fruits, usually of poor quality, which are apt to rot at the tip. Most of their flowers and young fruits fall because of anthracnose caused by Collectotrichum gloeosporioides. It has been said that soursop trees for cultivation near San Juan, Puerto Rico, should be seedlings of trees from similarly humid areas which have greater resistance to anthracnose than seedlings from dry zones. The same fungus causes damping-off of seedlings and die-back of twigs and branches. Occasionally the fungus, Scolecotrichum sp. ruins the leaves in Venezuela. In the East Indies, soursop trees are sometimes subject to the root-fungi, Fomes lamaoensis and Diplodia sp. and by pink disease due to Corticum salmonicolor.

Canned soursop concentrate
Fig. 22: Canned soursop concentrate is produced in Venezuela. On the branch at the right is a soursop flower.

Food Uses

Soursops of least acid flavor and least fibrous consistency are cut in sections and the flesh eaten with a spoon. The seeded pulp may be torn or cut into bits and added to fruit cups or salads, or chilled and served as dessert with sugar and a little milk or cream. For years, seeded soursop has been canned in Mexico and served in Mexican restaurants in New York and other northern cities.

Most widespread throughout the tropics is the making of refreshing soursop drinks (called champola in Brazil; carato in Puerto Rico). For this purpose, the seeded pulp may be pressed in a colander or sieve or squeezed in cheesecloth to extract the rich, creamy juice, which is then beaten with milk or water and sweetened. Or the seeded pulp may be blended with an equal amount of boiling water and then strained and sweetened. If an electric blender is to be used, one must first be careful to remove all the seeds, since they are somewhat toxic and none should be accidentally ground up in the juice.

In Puerto Rican processing factories, the hand-peeled and cored fruits are passed through a mechanical pulper having nylon brushes that press the pulp through a screen, separating it from the seeds and fiber. A soursop soft drink, containing 12 to 15% pulp, is canned in Puerto Rico and keeps well for a year or more. The juice is prepared as a carbonated bottled beverage in Guatemala, and a fermented, cider-like drink is sometimes made in the West Indies. The vacuum-concentrated juice is canned commercially in the Philippines. There soursop drinks are popular but the normal "milk" color is not. The people usually add pink or green food coloring to make the drinks more attractive. The strained pulp is said to be a delicacy mixed with wine or brandy and seasoned with nutmeg. Soursop juice, thickened with a little gelatin, makes an agreeable dessert.

In the Dominican Republic, a soursop custard is enjoyed and a confection is made by cooking soursop pulp in sugar sirup with cinnamon and lemon peel. Soursop ice cream is commonly frozen in refrigerator ice-cube trays in warm countries.

In the Bahamas, it is simply made by mashing the pulp in water, letting it stand, then straining to remove fibrous material and seeds. The liquid is then blended with sweetened condensed milk, poured into the trays and stirred several times while freezing. A richer product is made by the usual method of preparing an ice cream mix and adding strained soursop pulp just before freezing. Some Key West restaurants have always served soursop ice cream and now the influx of residents from the Caribbean and Latin American countries has created a strong demand for it. The canned pulp is imported from Central America and Puerto Rico and used in making ice cream and sherbet commercially. The pulp is used, too, for making tarts and jelly, sirup and nectar. The sirup has been bottled in Puerto Rico for local use and export. The nectar is canned in Colombia and frozen in Puerto Rico and is prepared fresh and sold in paper cartons in the Netherlands Antilles. The strained, frozen pulp is sold in plastic bags in Philippine supermarkets.

Immature soursops are cooked as vegetables or used in soup in Indonesia. They are roasted or fried in northeastern Brazil. I have boiled the half-grown fruit whole, without peeling. In an hour, the fruit is tender, its flesh off-white and mealy, with the aroma and flavor of roasted ears of green corn (maize).

Food Value Per 100 g of Edible Portion*

Calories 61.3-53.1
Moisture 82.8g
Protein 1.00g
Fat 0.97g
Carbohydrates 14.63g
Fiber 0.79g
Ash 60g
Calcium 10.3 mg
Phosphorus 27.7 mg
Iron 0.64 mg
Vitamin A (B-carotene) 0
Thiamine 0.11 mg
Riboflavin 0.05 mg
Niacin 1.28mg
Ascorbic Acid 29.6 mg
Amino Acids:
Tryptophan 11 mg
Methionine 7 mg
Lysine 60mg
*Analyses made at the Laboratorio FIM de Nutricion, Havana, Cuba.

Toxicity

The presence of the alkaloids anonaine and anoniine has been reported in this species. The alkaloids muricine, C19H21O4N (possibly des-N-methylisocorydine or des-N methylcorydine) and muricinine, C18H19O4 (possibly des-N-methylcorytuberine), are found in the bark. Muricinine is believed to be identical to reticuline. An unnamed alkaloid occurs in the leaves and seeds. The bark is high in hydrocyanic acid. Only small amounts are found in the leaves and roots and a trace in the fruit. The seeds contain 45% of a yellow non-drying oil which is an irritant poison, causing severe eye inflarnmation.

Other Uses

Fruit: In the Virgin Islands, the fruit is placed as a bait in fish traps.

Seeds: When pulverized, the seeds are effective pesticides against head lice, southern army worms and pea aphids and petroleum ether and chloroform extracts are toxic to black carpet beetle larvae. The seed oil kills head lice.

Leaves: The leaf decoction is lethal to head lice and bedbugs.

Bark: The bark of the tree has been used in tanning. The bark fiber is strong but, since fruiting trees are not expendable, is resorted to only in necessity. Bark, as well as seeds and roots, has been used as fish poison.

Wood: The wood is pale, aromatic, soft, light in weight and not durable. It has been used for ox yokes because it does not cause hair loss on the neck.

In Colombia, it is deemed to be suitable for pipestems and barrelstaves. Analyses in Brazil show cellulose content of 65 to 76%, high enough to be a potential source of paper pulp.

Medicinal Uses: The juice of the ripe fruit is said to be diuretic and a remedy for haematuria and urethritis. Taken when fasting, it is believed to relieve liver ailments and leprosy. Pulverized immature fruits, which are very astringent, are decocted as a dysentery remedy. To draw out chiggers and speed healing, the flesh of an acid soursop is applied as a poultice unchanged for 3 days.

In Materia Medica of British Guiana, we are told to break soursop leaves in water, "squeeze a couple of limes therein, get a drunken man and rub his head well with the leaves and water and give him a little of the water to drink and he gets as sober as a judge in no time." This sobering or tranquilizing formula may not have been widely tested, but soursop leaves are regarded throughout the West Indies as having sedative or soporific properties. In the Netherlands Antilles, the leaves are put into one's pillowslip or strewn on the bed to promote a good night's sleep. An infusion of the leaves is commonly taken internally for the same purpose. It is taken as an analgesic and antispasmodic in Esmeraldas Province, Ecuador. In Africa, it is given to children with fever and they are also bathed lightly with it. A decoction of the young shoots or leaves is regarded in the West Indies as a remedy for gall bladder trouble, as well as coughs, catarrh, diarrhea, dysentery and indigestion; is said to "cool the blood," and to be able to stop vomiting and aid delivery in childbirth. The decoction is also employed in wet compresses on inflammations and swollen feet. The chewed leaves, mixed with saliva, are applied to incisions after surgery, causing proudflesh to disappear without leaving a scar. Mashed leaves are used as a poultice to alleviate eczema and other skin afflictions and rheumatism, and the sap of young leaves is put on skin eruptions.

The roots of the tree are employed as a vermifuge and the root bark as an antidote for poisoning. A tincture of the powdered seeds and bay rum is a strong emetic. Soursop flowers are believed to alleviate catarrh.