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Page 277 Pacay (Ice-Cream Beans) All legumes have their seeds encased in pods, and a few of these pods are widely eaten as vegetables—green beans and snow peas, for example. A few lesser known legumes produce pods containing a sweet, mealy pulp and are eaten as fruits. Carob, tamarind, and honey locust are the best known. 1 However, trees of the genus Inga also produce sweet pods. They deserve much greater recognition and could become widely known and enjoyed. For people in Central and South America, inga pods have long been favorite snacks. The pods are mostly narrow, straight, and in some species as long as a person's forearm. They are easily cracked open to expose the white, sugar-rich pulp—reminiscent of cotton candy—surrounding the seeds. In English they have been called “ice-cream beans” because this white pulp has a sweet flavor and smooth texture. Most Inga species occur in the lowland tropics of the Americas, but several occur in the upland Andes. The main Andean one is Inga feuillei (pronounced “few-i-lee”). It is widely grown in highland valleys as well as in coastal lowlands of Peru and Ecuador where it is often employed as a shade tree or street tree. Its pods, prized as snacks, are found in markets and on street vendors' carts and are often consumed by children. Most commonly called “pacay” and “guama,” 2 this particular inga has long been popular. Its pods are depicted in ancient ceramics. The Incas had pacay pods carried to their mountain capital of Cuzco. Pedro Pizarro reports that the Inca emperor Atahualpa sent to Francisco Pizarro a basketful of guamas as a gift. It is surprising that this plant (as well as other Inga species 3 ) is not 1 See National Research Council, 1979. 2 Pacay (pacae) is a Quechua word used in Spanish specifically for the upland Andes species. “Guama” or “guaba” are names widely used for any Inga species whose pods have sweet pulp. 3 Most Inga species are tropical lowland species unknown in the Andes. Inga edulis is considered the best species for shade in coffee plantations in Colombia; I. vera is common in Central America. (I. vera and related species are covered in the companion report, Firewood Crops Volume I. National Research Council. 1980. National Academy Press, Washington, D.C.)
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Page 278 more widely known. Inga species are dependable, they produce in abundance, and they provide sustenance in bad times. They are a source of snacks for their owners and cash for the enterprising. 4 They grow rapidly, are tolerant of diverse soils, and are resistant to diseases and fire. They are easy to establish, spread their shade quickly, and provide fruit for years. Inga trees produce abundant root nodules, which fix nitrogen, and benefit the land by raising fertility levels. They can produce food without occupying the farmland used for food crops, because they can grow on sites neglected by agriculture. Pacay is cultivated specifically for its fruits; the fruits of other Inga species in the Andes are only a by-product of trees whose main purpose is to shade plantations of coffee and cacao. Other common species in the Andes are I. edulis, I. vera, I. adenophylla, and I. densiflora. The fruits of I. densiflora are sold in markets and fruit stalls, especially in Colombia. So far, however, the others are more often used for shade, not food. Pacay and other inga trees have important futures. They are multipurpose trees and are potentially valuable additions to gardens, orchards, fields, hedgerows, or wayside wastelands throughout most warm parts of the world. They also have outstanding prospects as urban trees for much of the tropics. 5 PROSPECTS The Andes. Although pacay pods are already widely consumed in rural areas of the Andes, there are still many possibilities for developing inga fruits as cash crops. One potential for expanding markets exists in cities, particularly among newly urbanized campesinos. As with other fruit crops, pacay lends itself to new entrepreneurial ventures, small-business enterprise, and economic development among the poorest levels of society. Other Developing Areas. This delectable snack that comes in its own natural wrapper should become much better known in coming decades. Inga trees can promote self-reliance, and they have potential not just in Latin America but throughout the tropics. Some species are already grown in the West Indies, Hawaii, and East Africa, but 4 In Mexico, coffee-plantation workers can double their annual salary by selling the pods from the inga trees used to shade the coffee plants. In Central America, the seeds are cooked and eaten as a vegetable. In Mexico, at least, the seeds are roasted and sold outside theaters to moviegoers. Information from J. Roskoski. 5 If the pods are not eaten, however, during years of bumper crops of pods, the sidewalk stroller may have to wade through pods half-a-foot deep. This may make this species less than “outstanding.” Information from J. Roskoski.
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Page 279 ~ enlarge ~ Pacay is one of the most unusual fruits on earth. Inside these huge pods is a sweet, frothy pulp that is a special favorite of children. (H. Popenoe) outside Latin America the edible pods at present are hardly exploited. The development of markets for the pods could contribute additional income to local farmers. Fruit trees such as ingas are underutilized in reforestation efforts. Give a peasant a pine tree and it's likely to be neglected, but give him a fruit tree and he'll protect it with his life, especially if it is productive. Inga has major potential for acid soils in the lowland humid tropics, especially in Southeast Asia and Africa. As a nitrogen-fixing, multipurpose tree that can be used to produce fruit, fuel, and green manure, it should find ready acceptance by farmers. The wide range of agricultural systems within which it can be integrated include hedgerow intercropping, 6 live fences, shade trees for plantation crops or animals, and fuelwood plantations. Industrialized Regions. Most ingas are frost-sensitive tropical trees with little or no potential for cultivation in Europe, North America, Japan, or most of Australasia. Their pods do not ship well, so the possibility for ice-cream beans to be on dinner tables is slight. 6 This involves growing trees in rows and crops in the alleys formed between the tree rows. The trees are pruned periodically to provide mulch and nutrients for the crops while minimizing competition for nutrients and water. Ingas seem ideally suited for such purposes. Information from P.A. Sánchez.
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Page 280 ~ enlarge ~ The pacay tree is a nitrogen-fixing legume that is promising in forestry, both in plantations and village backyards. It provides the benefits of shade, erosion control, and wood products—all in addition to food. (W.H. Hodge) USES Most ice-cream beans are eaten fresh. They are merely split open and the pulp dipped out with the fingers. However, ice-cream beans can also be handled as a processed product. They are washed and split and the contents removed and strained to separate the pulp from the seeds. As noted, inga trees have many other uses, including those discussed below: Forage. Cows and other livestock eat the foliage. In Mexico, farmers cut and carry the leaves to feed their livestock. Beautification. The trees can be planted along urban streets and in home orchards. Inga trees are also frequently grown as single trees near homes. Their pods add to their value as shade and shelter.
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Page 281 Lumber. The wood is moderately heavy (that of I. vera has a specific gravity of 0.57; the others are probably similar). It can be used for furniture, boxes, crates, light construction, and general carpentry. However, it is highly susceptible to drywood termites and when in contact with the ground decays readily. Fuel. Inga wood makes excellent fuel and is utilized for charcoal throughout the West Indies. Certain species pollard and coppice well. 7 Shade. Inga species grow rapidly and are common shade trees used on coffee and cacao plantations in Central America and the West Indies, where their cultivation and characteristics are well established. Soil Improvement and Intercropping. One of the Andean species, I. edulis, is being used in trials of alley cropping in Chile. Like most legumes, inga trees fix nitrogen and improve the soil around them. The leaves have extrafloral nectaries, which may support beneficial insects, such as parasitoid wasps, that are natural enemies of crop pests. NUTRITION Although pleasing, the pulp is not particularly nutritious. It contains about 1 percent protein and 15 percent carbohydrate—mainly sugars. 8 SILVICULTURE In the forest, ingas grow naturally from seeds. In silviculture, they are usually planted from seedlings grown in nurseries. All species studied so far are self-incompatible—they need at least two genetically different individuals for fruit set. Vegetative propagation would lead to little or no fruit unless cuttings are taken from more than one individual. Ingas usually grow very quickly, with a trunk diameter sometimes increasing more than 2.5 cm a year. A seedling normally begins to provide sufficient canopy to cover plantation crops within three years. Once established, the trees need little attention. 7 The trait is exceptionally valuable. In pollarding, the tree is pruned to 2–3 m (that is, just above the reach of grazing livestock). The tree then puts out a dense flush of new growth. In coppicing, the tree is cut near its base, and its stump regenerates new shoots. Both management systems allow repeated and frequent harvest of wood without the cost and effort of replanting seedlings each time. 8 Pacay seeds are high in protein, but whether they are safe to eat is not certain. In Mexico, boiled inga seeds were once a common vegetable, but their use has declined, probably because of the advent of new vegetables in the markets. Information from J. Roskoski.
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Page 282 In their native habitats, ingas thrive on many soil types, even limestone. Root nodules are formed by slow-growing rhizobia. 9 Pacay, the Andean species, is a tree of moist areas, but others seem to have some drought tolerance. LIMITATIONS As noted, inga trees are restricted to tropical or subtropical climates. Tropical species produce pods nearly continuously, but in the subtropics fruit production is seasonal and heavy. Spoilage is sometimes a problem. Because of the sugars in the pulp, the pods ferment in about 3–5 days. With cool storage, however, they will keep three weeks. Inga trees are generally healthy. If stressed, however, they can be affected by many common fungi, as well as a mosaic virus and “witches broom.” Fruit predators are numerous. (They include porcupines, which love the immature pods.) Also, the pods are sometimes destroyed by larvae of various insects. Seed predators include wasps, beetles, and organisms that ingest and digest soft seeds. The foliage is susceptible to Psylla species—insects that defoliate some other legume trees. There is little likelihood that inga pods could become a major commercial fruit crop in their own right; they are likely to remain as an additional and occasional source of cash to small landowners who have planted the trees for other purposes. As noted, fruit set requires that more than one genetically different tree be in the same vicinity. This is why solitary ornamental trees normally fail to set fruit. One of inga's biggest limitations is seed viability. Seed storage is very poor. The seeds often start germinating inside the pods. If seed were easier to handle, Inga species would possibly be as widely planted as trees such as leucaena and gliricidia. This is a limitation to dispersal or movement of inga germplasm to new areas in Africa or Asia, which modern communications might overcome. RESEARCH NEEDS Topics for future study (both for pacay and for ingas in general) include the following: Pest control, pruning, and maintenance. Agronomic research to increase and standardize fruit production. 9 Measurements of nitrogen fixation by I. inicuil in Mexico showed that the amount of nitrogen fixed was about 50 kg per hectare per year. Information from J. Roskoski.
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Page 283 Provenance selection for adaptability and fast growth, and for uniform fruit quality: large size and good taste, for example. Study of traditional methods to gain insights into production. Methods that prolong viability of inga seeds. The use of the leaves for fodder, and their nutritional qualities. Development of methods to properly and economically harvest, transport, and store the pods. Toxicological analyses of seeds to determine edibility. Use in intercropping. (Although trials have begun, the overall potential isn't well documented yet.) Methods of pollination. Effect on soil fertility (amounts of nitrogen fixed). Food science and processing of the pods. SPECIES INFORMATION Botanical Name As noted, several species occur in the Andes. The main ones, however, are Inga feuillei de Candolle (used since pre-Columbian times) and its widespread relative, I. edulis von Martius. Family Leguminosae (Mimosoideae) Common Names Quechua: pa'qay, paccai (Cuzco) Aymara: pa'qaya Spanish: pacay, pacae, pacay de Perú, guama, guamo English: ice-cream beans, food inga French: pois sucre Portuguese: ingá cipó, rabo de mico Origin. It seems likely that pacay (Inga feuillei) originated on the eastern slope of the Andes, and, like other fruit crops of that area, was introduced to coastal Peru. That must have happened long ago, because the use of these fruits in the mountains and on the coast is ancient. Inga pods are portrayed on pre-Columbian pottery, and their pods and seeds have been found in tombs dating back to about 1000 B.C. Description. Inga species are usually small trees, normally less than 15 m, although some of them can reach up to 40 m. They can be either evergreen or deciduous. The simply pinnate, dark-green leaves have large, oval leaflets in pairs without a terminal one. Many species have a green wing (rachis) between each pair of leaves. There is a nectary (small pit containing nectar) between each pair of leaves. Ants frequent these nectaries and probably play an important role in protecting the trees from insect pests such as aphids.
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Page 284 The fragrant flowers are arranged in crowded heads, spikes, or panicles at the stem tips or axils. Because they are rich in nectar, they attract bees, hummingbirds, and a variety of beetles. Fruit begins to mature a few months after pollination, and production may be nearly continuous (twice a year in I. feuillei in the Andes). The pods may be flat, twisted, or cylindrical. They are often flattened or four-sided, the margins frequently overhanging. They grow up to 70 cm long and 1–3 cm in diameter, usually with the seeds buried in the white, sweet pulp. Horticultural Varieties. In pacay, vegetative selections (apparently made in ancient times) exist, 10 but no true horticultural varieties are known. As noted, a single selection is of little use in fruit production because of self-incompatibility. Because cuttings establish roots poorly, vegetative propagation has not yet been developed. Environmental Requirements Daylength. Pacay is apparently daylength neutral, at least within the subtropics, which in any case are its outer limits. Rainfall. Pacay requires a subtropical climate with plenty of moisture. At Yurimaguas (Peruvian Amazon), both I. feuillei and I. edulis are very productive (wood, leaf, and fruit) at 1,500–2,700 mm annual rainfall. 11 Altitude. Up to 1,500–1,800 m in Peru's inter-Andean valleys. Low Temperature. Most species are damaged by low temperatures and killed by extended freezing weather. 12 High Temperature. Pacay thrives at 25°C; and, with sufficient moisture, seems capable of withstanding short periods above 33°C. Soil Type. These trees are apparently widely adaptable. They withstand soils from pH 4.0 to 8.0. They tolerate high aluminum saturation (70–90 percent) in acid soils. I. edulis and I. feuillei nodulate profusely even at pH 4.5 and are also heavily mycorrhizal (vesicular arbuscular mycorrhizae). These mycorrhizae play an important role in enabling ingas to take up phosphorus even though phosphorus is in very short supply in acid soils. Some are reported to exhibit tolerance to waterlogging and are 10 For example, the I. feuillei from Lima is different from I. feuillei from Cuzco, which seems to be the Andean variety. Information from J. León. 11 Information from P.A. Sánchez. 12 However, at least one (I. affinis) has a hardiness rating to −4°C.
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Page 285 common in riverine thickets and in wooded swamps, sometimes even below the high-water mark. They exhibit better growth rates on clayey or loamy soils. Related Species. Inga is a large, widespread genus of about 350–400 species, and its taxonomic distinctions are uncertain at present. Most are shrubs and trees of tropical and subtropical America. The majority are similar to I. feuillei, differing mainly in the fruit form and other botanical details. Most have the characteristic sweet pulp. A few examples are mentioned below. Inga vera This is the best known of all Inga species. It is commonly used as a plantation shade tree throughout Central America, and its pods are widely eaten. Inga edulis As noted, research at Yurimaguas, Peru, indicates that this is a highly promising species for alley cropping on acid soils in the lowland humid tropics. Inga paterno One of the best fruits of Costa Rica, it is planted widely for shade and fruit. Inga spectabilis The huge pods (about 70 cm long) are sold in the markets of Costa Rica. Inga marginata An attractive Costa Rican ornamental, this species has large spikes of fragrant flowers that bloom more than once a year. For this reason, it is much appreciated by beekeepers. Inga brenesii, Inga punctata, Inga densiflora, Inga oerstediana All are used as shade trees in coffee and cacao plantations, and all have edible fruit. Inga mortoniana This is a good ornamental with attractive reddish new leaves and tasty fruit. The most popular inga fruits in Mexico (especially in Veracruz, where there are many coffee plantations) are I. jinicuil (or inicuil), the most well known, followed by I. sapendoides and I. paterno. There are numerous species in the Amazon that are edible.
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