MAJOR EDIBLE NUTS 2


There are twelve major edible nuts that are marketed commercially (Woodroof, 1979; Rosengarten, 1984). They are:
 
cashew nuts Anacardium occidentale, Anacardiaceae  
  pistachios Pistacia vera, Anacardiaceae  
  sunflower seeds Helianthus annuus, Compositae  
  filberts Corylus avellana, Corylaceae  
  chestnuts Castanea dentata, Fagaceae  
  pecans Carya illinoinensis, Juglandaceae  
  Persian walnuts Juglans regia, Juglandaceae  
  Brazil nuts Bertholletia excelsa, Lecythidaceae  
  peanuts or groundnuts Arachis hypogea, Leguminosae  
  macadamia nuts Macadamia integrifolia, Proteaceae  
  almonds Prunus dulcis, Rosaceae  
  coconuts Cocos nucifera, Palmae  

Sunflower seeds and peanuts are here regarded as agricultural crops and are consequently not dealt with in detail. However, their marketing prospects are discussed because they do have an impact on the prospects of other nut crops. Coconut, although being an agricultural crop, is included here since it is a major component of agroforestry systems in many tropical countries.
 

Cashew or monkey nut:Anacardium occidentale, Anacardiaceae

 

Distribution and ecology


Native of tropical America, probably originating in equatorial northeastern Brazil. Widely cultivated in the tropics with commercial production concentrated in India, Brazil and East Africa. High potential for development in West Africa, where plantations have been quickly developing recently. It occurs in warm and humid climates with 1 000-2 000 plus mm annual rainfall, from sea level to 1 000 m altitude (FAO, 1982; ITC, 1993).
 

Description


Evergreen shrub or tree to 15 m tall; leaves simple, oblong-ovate, 6-20 cm x 4-15 cm, leathery. Inflorescence polygamous, with ca. 60 hermaphrodite and ca. 10 male flowers. Pedicel and receptacle swollen and fleshy in fruit (cashew apple), thin-skinned, bright yellow, red or scarlet, eventually larger than fruit, 10-20 cm x 4-4 cm. Fruit obliquely kidney-shaped, 2-3 cm x 1.5-2.5 cm, compressed, greyish-brown; mesocarp oleaginous; seeds kidney-shaped with thick cotyledons (Purseglove, 1987; Kokwaro, 1986).

Cultivation


Fast growing, drought-resistant and easy to grow under cultivation by direct seeding of germinated seeds - seedlings do not transplant readily. Well-drained friable soils at low altitudes recommended, frost-free with an annual rainfall of 1 000-3 000 mm, preferably with a pronounced dry season of 3-4 months. Cashews can also be grown satisfactorily in semi-arid areas but can show erratic production as a result of relative small variations in rainfall. Trees with a productive life span of 30-40 years, normally bearing in fruit in third or fourth year and, under favourable conditions, attaining maximum production in ca. 7 years. The effectiveness of insect pollination variable, for example, satisfactory in Tanzania, artificial pollination required in India. Fruits mature in 2-3 months (Menninger, 1977; FAO, 1982; Rosengarten, 1984; Purseglove, 1987; ITC, 1993).


Fig 1. Anacardium occidentale 1: fruiting branch, 2: bixesual flower, 3: male flower, 4: fruit, 5: leaves.

Harvesting


Fruits harvested when fully ripe. In Tanzania the nuts are collected after falling to the ground. In dry weather they can be left on the ground until the apple dries but should be collected daily in wet weather. The nuts are then removed from the apples and dried (Rosengarten, 1987).
 

Post-harvest treatments


After drying and roasting the kernels are separated from the shells and graded. Care must be taken when shelling to avoid the caustic juice that squirts out on roasting. Shelling is usually done manually, using cheap labour in India, elsewhere mechanical processing has been introduced. Stored in vacuum packed, hermetically sealed tins where cashews remain stable at room temperatures; under refrigeration a shelf life of one year (Menninger, 1977; Matz, 1984; Rosengarten, 1984; ITC, 1993).
 

Production and consumption/utilization


Approximately 60% of cashew kernels are marketed as salted nuts; they are also used in confectionery and bakery products. Un-shelled, un-roasted cashew nuts should not be eaten (Rosengarten, 1984).
 

Nutritional value


Cashew nuts contain approximately 12.8% protein, 46.7% digestible fat or oil and 18% carbohydrates (Melville, 1946); vitamin content high (Menninger, 1977).
 

By-products and other uses


Seeds yield an edible oil but, due to the high value of the kernels, this is not usually extracted. The shells or pericarp yield cashew nut shell liquid (CNSL), which contains toxic cardol and anacardic acid and acts as a vesicant. CNSL has high polymerizing and friction-reducing properties and is used as a waterproofing agent and preservative. Distilled and polymerized, the oil is also used in insulating varnishes and in the manufacture of typewriter rolls, oil- and acid-proof cements and tiles, friction-modifying material for brake linings, as a component of space-rocket lubricants, inks, etc. It is also used in tropical medicine for treating scurvy, leprous sores, warts, ringworms, etc. (Menninger, 1977; Rosengarten, 1984; Purseglove, 1987).

The cashew apple (swollen pedicel) is juicy, astringent and edible; the juice may be drunk fresh or fermented for wine; the pulp may be made into preserves, jellies, syrups, etc., or, in Brazil, fermented into wine resembling Madeira. With the emphasis on nut production about 95% of the world cashew apple crop is allowed to rot, about 1.25 million tonnes in India are wasted each year. The sap from the bark provides an indelible ink. Timber is used for construction and general carpentry but subject to termite attack; also used for firewood and charcoal. Grown as a shade tree, hedges and for dune stabilization. Flowers attractive to honey bees (FAO, 1982; Rosengarten, 1984; Purseglove, 1987; Anthony et al., 1993).
 

Marketing


World production has risen from 446 000 tonnes in 1979-81 to 726 000 tonnes in 1992, falling dramatically to 479 000 tonnes in 1993, largely due to an unexplained fall in production in India from 35 000 tonnes to 15 000 tonnes (FAO, 1994).

India is the largest exporter with ca. 50% of the market (also with a large internal consumption), Brazil is second with ca. 25% of the world market, followed by Indonesia, Mozambique and Viet Nam, the two latter plus Tanzania mainly export raw, unprocessed seed to India for processing. The USA is by far the largest importer (about 59 000 tonnes in 1992) with the UK the largest market in Europe for raw cashew. Most of the international trade is in raw nuts, with less than 25% of the trade in processed nuts, which are salted and/or roasted (Purseglove, 1987; ITC, 1993).
 

Discussion


Cashew is regarded as a good crop for the Andean countries for which North America should be the main target market. Despite ca. 20% decline in import prices during the period 198791 demand has increased and has been met by increased imports (ITC, 1993).

The appalling waste of cashew apple each year is intolerable, however, there is almost certainly limit to the quantity of cashew drinks and jams that can be consumed. The possibility of fermenting the cashew apple for the production of an industrial alcohol should be investigated.
 

Pistachio: Pistacia vera, Anacardiaceae

 

Distribution and ecology


Native of Iran, Afghanistan and central Asia from Turkmenia to Pamir-Alai and Tien Shan. Now cultivated and perhaps naturalized in Spain, France, Italy, Greece, Cyprus, Syria, Lebanon, Israel, Turkey and Iran. Grows in subtropical, warm and Mediterranean climates with a hot dry season with a daily mean temperature of 30° C for 3 months (Townsend and Guest, 1980; Macrae et al., 1993).
 

Description


Winter deciduous, dioecious tree to 10 m tall; leaves pinnate, leathery, leaflets 3-7. Flowers in panicles, appearing before the leaves. Fruit a narrowly ovoid to oblong or subglobose, 1-seeded, drupe, 1-2 cm x 0.6-1.2 cm; mesocarp fleshy, endocarp bony, dehiscent or semi-dehiscent; kernel light green, agreeable flavour (Menninger, 1977; Townsend and Guest, 1980; Matz, 1984; Macrae et al., 1993).

Fig2. Pistacia vera.

Cultivation


Pistachio requires well-drained soils, is tolerant of drought and poor soils, it prefers cool winters with 1 000 hours below 7.5 ° C enough to break bud dormancy (temperatures can fall as low as -10° C). A frost-free period of 200 days is necessary to ensure that the inflorescence develops undamaged and long hot summers (to 45° C or more) to ensure ripening of the fruit. Cold and wind resistant but intolerant of excessive dampness and high humidity (Rosengarten, 1984; Macrae et al., 1993).

Introduced from Iran to California in 1930, California is now the second largest producer worldwide. Commercial crop after 7-10 years with peak production at ca. 20 years; trees with a life span of ca. 700 years. Yields alternating with a heavy crop followed by a lighter crop in the next year (Rosengarten, 1984; Paramount Farms Pistachios, 1991).
 

Harvesting


The correct stage of maturity is critical when harvesting. The outer skin or hull turns from translucent to opaque rosy when ripe, the husk splitting naturally to expose the kernel when ready to harvest. The mature nuts hang on the tree and may be left until nearly all are ripe. However, if the harvest is unduly delayed the husk may dry onto the nut and cause staining. Primitive methods of harvesting involves either picking by hand or knocking the nuts from the tree with long poles onto sacking spread on the ground. The enveloping husk is manually removed by squeezing and empty shells are removed by flotation with the full nuts sinking to the bottom of the tank. The nuts are then sun-dried.

In USA a machine is used to shake the pistachios from their grape-like clusters while another, equipped with a catching frame encircling the tree, collects the falling nuts before they touch the ground (Menninger, 1977; Paramount Farms Pistachios, 1991; Macrae et al., 1993).
 

Post-harvest treatments


To prevent the tannic acid in the rosy hull from staining the nuts, the pistachios are either hand or mechanically peeled within hours of harvesting, after which they are washed and rapidly dried before storing. Humid or showery weather, especially favours staining as well as aflatoxin.

Any blank shells can be removed by flotation. Freshly harvested nuts can contain up to 45% moisture, which small producers may reduce by sundrying and any stained nuts removed by hand. In large commercial plantations the pistachios are artificially dried in silos at 65-72° C, which can reduce the moisture content to 5% in 10 hours. Mechanical pin prickers are used to separate naturally split pistachios from the closed shell product. The in-shell pistachios are then passed through an electronic colour sorter to remove any stained nuts. They are then graded for size and quality where they are shelled and stored (Ryall et al., 1974; Rosengarten, 1984; Paramount Farms Pistachios, 1991; Macrae et al., 1993).
 

Production and consumption/utilization


Marketed locally in Middle East either in-shell or as roasted and salted kernels. Because of the antiquated harvesting techniques in the Middle East which yielded stained shells, the early imports to the North American market were dyed red in order to cover the blemishes and make them more appealing. Roasted nuts are hygroscopic and require moisture resistant packaging, which gives a shelf life in excess of 24 months (Menninger, 1977; Paramount Farms Pistachios, 1991; Macrae et al., 1993).
 

Nutritional value


High in carbohydrates, especially sucrose (16%), oil consisting largely of unsaturated fats (55%) and essential amino acids (25%) (Macrae et al., 1993). See also Table 6 for comparison with macadamia nuts.
 

By-products and other uses


Wood much prized in Iran and Afghanistan for agricultural implements, spoons, etc. Resin yielded from tapped stems and larger branches similar to mastic from P. lentiscus and used in local medicine, high quality paints and nitro-lacquers. Galls and fruit pericarp employed in India to dye silk, the fruit husks used as a mordant and tan. Fruit yields ca. 60% of a greenish fatty oil, sweet flavoured and aromatic, which is sometimes extracted for medicinal use, however, because of the high price obtainable for the nuts the oil is not extracted commercially (Townsend and Guest, 1980; Rosengarten, 1984).
 

Marketing


World production has soared from 109 000 tonnes in 1979-81 to 345 000 tonnes in 1993 and, in North America particularly, production has increased during those years from 8 800 tonnes to 69 000 tonnes (FAO, 1994).

About 1 500 tonnes of pistachios are consumed annually in USA and is expected to reach 23 000 tonnes in the next decade. Pistachios are exported from California to Japan, Hong Kong, China, Singapore, Germany and UK. Other major exporting countries are Iran and Turkey, and to a lesser extent, Syria, Afghanistan, Italy, India, Greece, Pakistan and Tunisia. Premium nuts made up 25% of the UK snack market in 1990 and is expected to reach 30% by 1995 (Rosengarten, 1984; Paramount Farms Pistachios, 1991).
 

Discussion


There are 11 species of Pistacia but only P. vera has a dehiscent shell. Pistachios, like the macadamia nut, are expensive. Although future expansion may reduce prices, greater emphasis is still needed on market development and promotion in order to compete with other nut products. Unlike lesser-known nuts, pistachios should develop beyond present regional boundaries (Macrae et al., 1993). Prospects for an expansion in production would appear to be good.
 

Sunflower seeds: Helianthus annuus, Compositae

 

Discussion


Sunflower seed is currently catering for a small and specialized market, especially in the health-food, confectionery and snack trade in USA (ca. 3 500 tonnes in 1977). It is relatively little known elsewhere but, with its high nutritional rating and low price compared to other nuts, there are good prospects for production to increase, especially since it has been recommended as a major ingredient in concentrated food for human consumption in the developing countries (Rosengarten, 1984).
 

Filbert, cob or hazel: Corylus species, Corylaceae


Historically "filbert" refers to a nut where the enveloping husk is longer than the nut, "cob" where the husk is as long as the nut and "hazel" where the husk is much shorter than the nut (Menninger, 1977).
 

Distribution and ecology


European hazel: Corylus avellana, throughout Europe and eastward through West Asia to Syria and Iran; cultivated in North America for its nuts.

Turkish filbert: Corylus maxima, Balkan peninsula; cultivated elsewhere for its nuts.
 

Description


Deciduous trees or shrubs; leaves alternate, simple, stipules soon falling. Inflorescence monoecious, male flowers in pendent catkins, female flowers in small, bud-like inflorescences. Fruit a large nut surrounded by more or less tubular involucre (Tutin et al., 1964).
 

Cultivation


The European hazel is chiefly cultivated, the Turkish filbert to a lesser extent. Hybridization between the two species and others, both naturally and by breeders, has made identification difficult. Commercial production limited to regions with mild winters, rather warm spring, late frosts rare and summers cool. Approximately 70% of world production is from Turkey along the southern coast of the Black Sea. The coastal regions of Italy and the Mediterranean coast of Spain supply a further 20% and 7% respectively. The remaining 3% is from the coastal valleys of Oregon and Washington in USA.

Turkish production is based on rather haphazard clumps of four or five multi-stemmed bushes arranged in 1.5 m circles on the rocky hillsides. Stems grow to 3-4.5 m and are removed after 30 years to allow younger stems to come into production. Livestock are frequently allowed to graze among the bushes to control the weeds.

Bushes are more regularly spaced and planted either along the contour or in rectangles in Italy although, like Turkey, the multi-stemmed clump habit is usually maintained. Yields are higher due to the warmer climate, better use of fertilizers and more fertile soils.

In Tarragona, Spain, single bushes are planted out in regular rows, although elsewhere clump planting is still practised. Irrigation is standard practice in Tarragona as well as in other areas where the soils are poor and rocky.

In USA the filberts are planted in regular rows and trained to form a single-stemmed tree in order to permit mechanical cultivation. To facilitate wind pollination every sixth tree in every third row is a pollinator. Average yield of dry in-shell nuts from good orchards is 2 250 kg/ha (Rosengarten, 1984).

Fig 3. Corylus avellana !: branch with fruits. 2: branch with catkins. 3: Shoot with male catkins. 4: Elementary male inflorescence. 5: Female flower with bract. 6: Fruit and section of the fruit.

Harvesting


Nuts tend to drop uniformly when ripe, hence easy harvesting from the ground, although frequent pick-up still necessary to avoid fungal infections. In Turkey the nuts are picked by hand before the crop drops while in Italy the bushes are beaten and the fallen nuts picked from the ground. In USA the nuts are also allowed to fall naturally and then swept into windrows and picked up by a mechanical harvester which also provides a preliminary cleaning (Ryall and Pentzer, 1974; Rosengarten, 1984).
 

Post-harvest treatments


Drying is required to reduce moisture content of in-shell nuts to 7-8% and 3.5-4.5% for shelled nuts.

In Turkey the filberts are mainly sun-dried, drying with the use of artificial heat is less common. The husks are usually removed by husking machines, less commonly by hand-beating with sticks. The nuts are then cracked between revolving millstones and blowers used to remove the shells. The kernels are finally screened, graded according to size, sorted and bagged for export.

The harvested nuts in USA are washed, further cleaned and then dried to 8-10% moisture content for marketing or processing.
 

Production and consumption/utilization


Nuts are sold to consumers either in-shell or shelled as kernels for salted kernels or use in the food trade, especially in confectionery for nut chocolate; kernels may be ground to a flour and baked as filbert bread, which is reputed to be delicious (Menninger, 1977; Rosengarten, 1984).
 

Nutritional value


On a moisture-free basis hazel nuts contain approximately 16.3% protein, 61.2% fat and 11.5% carbohydrates (Melville, 1947).
 

By-products and other uses


Broken but edible nuts are utilized for the extraction of edible filbert oil, rancid and inferior nuts are used for industrial filbert oil. The combustible trash from bushes, husks and shells are used for fuel (Rosengarten, 1984).

Wood formerly a principal source of charcoal for gunpowder. Coppice growth formerly used for hurdles, wattle and daub, legume poles, firewood (Mabberley, 1987).
 

Marketing


Up to 65% of Turkish filberts are sold through the government financed FKB (Fiskobirlik) cooperative, which stabilizes the market and prices paid to the farmers. The government also has a strict system of inspection and certification before export. The plantations in Oregon and Washington yield larger nuts than found in the Mediterranean countries and are becoming increasingly popular (Menninger, 1977; Rosengarten, 1984).
 

Discussion


As USA imports ca. 45% of the filberts it consumes annually, there is a promising future for expansion in Oregon and Washington, especially since they are able to produce the desired larger nut (Rosengarten, 1984). The European nut producing countries will have to increase quality and productivity if they are to compete with America. The fact that the filbert was introduced to America suggests the larger nut may be due to management rather than breeding.
 

Chestnut: Castanea species, Fagaceae

 

Ecology and distribution


American chestnut: Castanea dentata, native to USA, east of the Mississippi River.

European chestnut: Castanea sativa, native to southern Europe from Italy to Iran and extending northwards to Hungary, also in North Africa; extensively planted and naturalized elsewhere in Europe. Usually a calcifuge, in woods on well-drained soils.

Chinese chestnut: Castanea mollissima, from northern China, introduced into USA.

Japanese chestnut: Castanea crenata, native to Japan; grown for timber in southern Europe

(Rosengarten, 1984).
 

Description


Deciduous trees or shrubs; leaves simple. Catkins erect, flowers monoecious with male in upper and female in lower portion of the same catkin. Fruit 1-3 nuts, brown, coriaceous, in a swollen, spiny cupule which dehisces irregularly by 2-3 valves (Tutin et al., 1964).

Fig 4. astanea sativa. 1: shoot with leaves 2: male flower 3: anther 4: section of female catkins 5. female flower 6: mature fruit 7: open cupule.

Cultivation


Populations of American chestnut were devastated by the mid-20th century by chestnut blight, Cryphonectria parasitica, syn. Endothia parasitica; Chinese chestnut and Japanese chestnut are relatively immune. Devastation was such that American chestnuts are no longer commercially viable. The European chestnut is also susceptible and has been attacked by blight since 1938 and production is consequently decreasing. Attempts are being made to develop benign strains of the fungus to inoculate trees against chestnut blight as well as hybridizing American chestnut with blight resistant introductions. Japanese chestnut is less hardy and more susceptible to blight than the Chinese chestnut (Payne et and Pentzer, 1983; Rosengarten, 1984).

The average yields of the European chestnut grown in California are 2 220 kg/ha. However, recent plantations with high-yielding, large nut, grafted cultivars are expected to yield 3 360-4 480 kg/ha. The Chinese chestnut, which are adaptable to a range of edaphic and climatic conditions apart from frost pockets, bear in 5 to 6 years and are expected to yield 3 000 kg/ha, with yields of experimental plantings as high as 4 400 kg. At least two cultivars should be grown to ensure cross-pollination otherwise the kernels will not develop (Menninger, 1977; Payne et al., 1983).
 

Harvesting


Traditionally mature nuts are allowed to fall from the tree and may remain on the ground for several days or longer before gathering by hand. To reduce hand harvesting costs, attempts are being made to develop strains where the burrs drop to the ground before the nuts fall out. Since at dehiscence the undamaged nut contains an array of weakly parasitic organisms which can cause serious damage under unfavourable storage conditions, daily gathering is strongly recommended. Tree shakers and catchers, which can be used after 4-9% of the ripe nuts have fallen naturally, are being developed, as well as the necessary means of removing the burr (Ryall and Pentzer, 1974; Menninger, 1977; Payne et al., 1993).
 

Post-harvest treatments


Commercially nuts may be held in refrigerated storage at 0° C to -1° C for several months in ventilated polyethylene liners. Weevil damage may occur during storage and later; unfortunately it is not possible to remove infested nuts by flotation before storage. The risk of incipient fungal infection is increased by the absence of visible moulds on many infected kernels although no mycotoxins have yet been observed on the marketed product. Unless properly handled, fresh nuts quickly dry out and harden and cannot be roasted or boiled satisfactorily unless regenerated by soaking (Ryall and Pentzer, 1974; Payne et al., 1983).
 

Production and consumption/utilization


Chestnuts are starchy and a brief curing period (3-4 days) is required to permit some starch to convert to sugar, especially after refrigeration. Eating quality is best at harvest time. In-shell nuts are roasted and sold as "hot chestnuts"; shelled nuts can be ground to a flour and eaten as chestnut bread or porridge, roasted or boiled they can be eaten as a vegetable or used for stuffing poultry. In France chestnuts are preserved in syrup as marrons glacés and other sweetmeats (Ryall and Pentzer, 1974; Rosengarten, 1984).
 

Nutritional value


The nutrient value of chestnuts varies according to species. Respectively, raw American, European and Chinese chestnuts contain approximately 43.7%, 54.9% and 44% water; 4.8%, 2% and 4.2% protein; 1.3%, 1.6% and 1.1% fat; and 48.6%, 40.3% and 49.1% carbohydrates (McCarthy and Meredith, 1988). High in carbohydrates they are readily digestible when roasted or boiled. They also have the lowest fat content of all the major edible nuts as well as being very low in calories with ca. 1 700 calories per kg (Rosengarten, 1984).
 

By-products and other uses


Timber is durable and rot-resistant, used for fencing, furniture, ship masts, telegraph poles, mine props, railway sleepers. Bark and wood extracts used for tanning leather (Rosengarten, 1984).
 

Marketing


European chestnuts, which are larger but less sweet than the American chestnut, are marketed in-shell for roasting. Chinese chestnuts are smaller and less sweet than the American chestnut but sweeter than the European chestnut. Japanese chestnuts are a variable product with some trees producing huge nuts up to 5 cm in diameter and weighing 30 g or more while others bear smaller nuts; their nuts are also less sweet than those from the Chinese chestnut. Despite the strong demand for chestnuts and chestnut products, the problems outlined above regarding harvesting and storage and the difficulties in obtaining a good, clean nut make chestnut production a difficult venture (Payne et al., 1983; Rosengarten, 1984).
 

Pecan: Carya illinoinensis, Juglandaceae

 

Distribution and ecology


Native of the rich bottom lands of the Mississippi Valley from Indiana and Illinois west to Kansas and Texas and at higher altitudes south into central Mexico, with local outliers to the north and east. Cultivated in USA, Mexico, Brazil, Australia, South Africa and Israel (Menninger, 1977; Townsend and Guest, 1980; Rosengarten, 1984; Prescott-Allen and Prescott-Allen, 1986).
 

Description


Large deciduous tree to 50 m or more tall with ascending and outwardly arching branches. Flowers monoecious with slender male catkins and small erect clusters of female flowers. Fruit borne in clusters of 4-12, a globose to oblong drupe, angled and narrowly 4-winged at the sutures, 2.5-7 cm x 1.25-2.5 cm, exocarp more or less separating by 4-valves; nut ovoid to ellipsoid, cylindrical or faintly 4-angled; seed solitary, deeply divided longitudinally, somewhat grooved and convoluted, not closely adherent to the shell (Menninger, 1977; Townsend and Guest, 1980; Rosengarten, 1984).

Fig 5. Carya illinoinensis.

Cultivation


Orchards largely planted out with grafted and budded trees in the southeast USA, and with seedling trees in the southwest, although there is now a trend towards selected cultivars. Over 300 cultivars have been recognized. Varietal differences range from nuts less than 0.6 cm in diameter to more than 2.5 cm and weighing from over 90 to 18 nuts per kg. Production begins at 6-10 years and can continue profitably for up to 200 years - some native trees are known to be over 1 000 years old. Yields from 9-27 kg per tree at 8-10 years rising to 45-68 kg at 16 years or more with exceptional individuals attaining 360 kg under unusually favourable conditions (Ryall and Pentzer, 1974; Rosengarten, 1984).

Trees prefer a deep, well-drained soil, adequate rainfall or supplementary irrigation and a frost-free growing season of 140-210 days. A cool period is also essential in order to break dormancy; the climatic requirements vary with the variety (Rosengarten, 1987).
 

Harvesting


Fallen nuts formerly harvested by hand. Hand harvesting now largely replaced by mechanization, including tree or limb shakers, shake and catch harvesters, windrowers, sweepers, vacuum harvesters, conveyers and trash separators (Ryall and Pentzer, 1974; Rosengarten, 1984).
 

Post-harvest treatments


Pecans harvested mechanically have a higher moisture content than nuts that have fallen naturally. Artificial drying is essential in order to reduce moisture to 4.5% as soon as possible in order to prevent mould and discoloration. Matz (1984) recommends dry storage for 3 weeks at room temperature to cure and reduce moisture in entire nuts to 8.5-9% and to 4.5% for kernels. During curing the free fatty acids and peroxide value of lipids increase and seed coat tannin oxidize to pale or medium brown, the general effect of which is to give the pecan its characteristic appearance, aroma, flavour and texture. Pecans are then stored until required for shelling at temperatures below 2°C and less than 70% relative humidity in order to prevent the development of rancidity and/or insect infestation. Long-term storage should be at ca. -8° C in order to maximize freshness and shelf life. Any traces of ammonia during refrigeration, not detectable by odour, can rapidly and permanently blacken the seed coat but not affect the flavour. Storage facilities not using ammonia as a refrigerant are essential. Nuts are shelled using a rotary cracker which delivers a shock wave to the pecan and explodes the shell without damaging the kernel. Shell fragments are removed using a double flotation system in addition to air separation systems and infrared colour sorting equipment (Ryall and Pentzer, 1974; Rosengarten, 1984; Young Pecan Company, undated).
 

Production and consumption/utilization


Approximately 85-90% of the crop is shelled prior to marketing, the balance being sold in-shell. Shelled pecans are sold to bakeries (36%) and confectioners (20%), the remainder to retailers, grocery-wholesalers and dairies for ice cream production, etc. Trade in in-shell is declining, sales being mainly to Europe (Ryall and Pentzer, 1974; Rosengarten, 1984; Prescott-Allen and Prescott-Allen, 1986).
 

Nutritional value


Nutritional analyses of pecans are given in Table 3.
 

By-products and other uses


Pecan shells are used for gravelling paths, as a fuel and as a garden mulch, stock and poultry litter; ground to a flour for degreasing aero engines, as an ingredient of carpet cleaners and as a filler in feeds, insecticides and fertilizers, soft abrasives in hand soap, non-skid paints and metal polishes, as fillers in plastic wood, adhesives and dynamite, also for veneer and polyesters. An excellent hardwood, the wood and veneer is in high demand for decorative panelling, fine furniture and flooring. The tree is also grown as an ornamental and for shade (Menninger, 1977; Rosengarten, 1984).

Table 3: Nutritional Analyses per 100 g Sample of Raw Pecans and

Pecans Roasted in Cotton Seed Oil with Butter and Salt

  Raw Roasted
Calories
710.0
740.0
Calories from fat (kJ)
630.0
673.0
Protein (g)
10.0
9.3
Total fat (g)
70.0
74.7
Saturated fat (g)
6.7
9.3
Cholesterol (mg)
0.0
0.0
Carbohydrates (g)
13.3
13.7
Sugars (g)
3.3
3.0
Dietary fibre (g)
6.7
5.7
Ca (mg)
73.0
73.0
P (mg)
603.0
603.0
Fe (mg)
2.4
2.4
K (mg)
603.0
603.0
Na (mg)
0.0
128.0
Mg (mg)
142.0
142.0
Vitamin A (IU)
130.0
120.0
Vitamin C (mg)
2.0
0.0
Thiamin (mg)
0.9
0.9
Riboflavin (mg)
0.1
0.1
Niacin (mg)
0.9
0.9

 

Source: Young Pecan Company, undated.
 

Marketing


Undoubtedly North America's most important native nut tree with an annual average production of over 90 million kg, of which 18% is still obtained from wild sources (Prescott-Allen and Prescott-Allen, 1986; Rosengarten, 1987).
 

Discussion


The pecan is relatively little known outside America and there is certainly a possibility for developing a wider market.
 

English, Persian, European, royal, Italian, madeira, French, Chile, Manchurian, Caucasian or circassian walnut:Juglans regia, Juglandaceae

 

Distribution and ecology


Balkan peninsula, Turkey to the Himalayas at altitudes up to 3 000 m; widely cultivated and often naturalized (Menninger, 1977).
 

Description


Monoecious, deciduous, aromatic tree to 30 m tall; leaves alternate, pinnate, leaflets 7-9. Male catkins on twigs of previous year's growth, female flowers few, on twigs of current year's growth. Fruit a large, subglobose, indehiscent drupe 4-5 cm in diameter; stone ovoid, acute, wrinkled, easily splitting (Tutin et al., 1964; Townsend and Guest, 1980).
 

Cultivation


Grown in orchards in California and southern Europe, propagated by budding and grafting of cultivars on rootstock of various species of Juglans (Menninger, 1977).

Fig 6. Juglans regia. 1: blanchlet with leaves with female flower, 2: male catkin, 3: male flower. 4: stamen, 5: female flower, 6: fruit showing, 7: seed covered by one valve of endocarp, 8: section of fruit.

Harvesting


Walnuts mature when hull easily separable from the shell; the hull normally opening while fruit still attached to the tree. Harvesting by hand or by machine. Older plantings tend to be of large trees and harvesting is by mechanical shaking of the branches using slings attached to a cable and tractor-driven eccentric. Approximately 80% of the nuts can thus be removed from the tree; with care, tree shakers may also be used. For smaller trees the shake and catch method may be used. Nuts may be caught in sheets or mechanically windrowed and collected by a machine with which the leaves and trash are separated, the harvested crop consisting of a mixture of hulled and unhulled walnuts. Prior land preparation to remove weeds and obstacles will speed up the harvest operations. Average yield for California range from about 2.2 tonnes per ha to 6.7 tonnes; in Italy the average yield from specialist orchards is also about 2.2 tonnes per ha while yields from other producing countries are undoubtedly lower (Ryall and Pentzer, 1974; Rosengarten, 1984).
 

Post-harvest treatments


Walnuts contain as high as 35% moisture when harvested. They should be hulled, washed and dried as quickly as possible to 8% moisture or less and graded. Shelled walnuts quickly darken and develop rancidity under unfavourable conditions; maximum stability is achieved at ca. 3% moisture. Contamination by ammonia during storage can cause severe damage (Ryall and Pentzer, 1974; Matz, 1984; Rosengarten, 1984).
 

Production and consumption/utilization


Immature walnuts are pickled and the ripe walnuts eaten as a dessert nut; they are also widely used in baking and confectionery. In the Himalayan region walnuts are an important item in the diet. The kernels yield ca. 50% of a clear sweet oil, the first pressing, known as virgin oil, is largely used for culinary purposes. Expression is carried out 2 to 3 months after harvesting, earlier the kernel contains a sort of emulsive milk, if expressed later the oil is less sweet and possibly rancid. Pounded walnuts and walnut oil is the basis of the delicious Circassian dish "charkasîya" (Menninger, 1977; Townsend and Guest, 1980; Rosengarten, 1984).
 

Nutritional value


On a dry weight basis walnuts contain approximately 17% protein, 65% fat and 16.5% carbohydrates. Although the vitamin C content of mature walnut kernels is low, that of immature green fruit is exceptionally high, as for walnuts used for pickling. However, the vitamin is destroyed where the method of pickling turns the nuts black. They should remain green, or white if the centres only are used (Melville, 1947).
 

By-products


The second pressing of seed oil, known as fire drawn, is used as a salad oil or as a drying oil for use in paints, printing ink, manufacture of soap. Residual cake used for feeding livestock. The husk is the source of a dark brown dye used for darken hair. The sap is the source of sugar in the Caucasus. Large shells are made into trinket boxes. Shells are also used as a filler for external plywood glue, plastics, hard rubber products, asphalt roofing material, fire bricks, tiles, and stuffing in toys. Shells reduced to dust are used as insecticides and as an abrasive for cleaning jet aircraft engines. The timber is highly valued for cabinet work and gunstocks. Various parts are used medicinally as an alternative laxative and detergent (Menninger, 1977; Townsend and Guest, 1980; Rosengarten, 1984).
 

Marketing


The USA is the largest producer with approximately 90% of the exports as in-shell. However increasing competition may be expected from India and China as their walnut industries expand. Walnut oil for salads and cooking is produced by France while pickled walnuts are exported from the United Kingdom (Rosengarten, 1984).
 

Discussion


A popular dessert nut whose production has increased significantly since 1979-81 to 1993 from 79 000 tonnes to 1 million tonnes. The gourmet trade in salad oil and pickled walnuts currently monopolized by France and the United Kingdom could be developed in other producing countries.
 

Brazil nut: Bertholletia excelsa, Lecythidaceae

 

Distribution and ecology


Probably originated in southeastern Amazonia. Present in natural stands (castanhais) of 50-100 trees at densities of 5-20 trees per ha, each stand separated from one another by up to 1 kilometre as emergent trees in rainforest on non-flooded ground in the Guianas, Amazonian Brazil, southeastern Colombia, southern Venezuela, eastern Peru and northern Bolivia. Climatic limits for its natural distribution are a mean annual rainfall of 1 400-2 800 mm, a mean annual temperature of 24-27° C and a mean annual relative humidity of 79-86%. In eastern Amazonia, in the lower limits of its climatic range there can be 2-7 months where the monthly rainfall is less than 100 mm.

Cultivated in South America outside its natural range. Nuts from trees growing on barium-rich soils can accumulate up to 0.29% barium and should be avoided due to danger of barium toxicity (Prance and Mori, 1979; Mori and Prance, 1990; Clay and Clement, 1993). It has been introduced to Malaysia, Sri Lanka, Java, Hawaii and the Caribbean (FAO, 1982; Rosengarten, 1984).
 

Description


Large, deciduous tree to 50 m tall; leaves simple, leathery. Fruit (pyxidium) a globose, circumscissile, woody capsule 10-12.5(-16) cm x 10-12.5(-14) cm, lined with hard fibres; seeds acutely trigonoid, 10-25, ca. 3.5-5 cm x 2 cm, packed in 2 concentric rings around a core; seed coat woody (Menninger, 1977; Prance and Mori, 1979; Mori and Prance, 1990).

Fig 7. Bertolletia excelsa, 1: leaves, 2: fruit, 3: open fruit.

Cultivation


There exist problems with pollination because the natural bee pollinators require natural forest for their survival. Strip plantations within the rainforest may be the solution (Mori and Prance, 1990). Nuts mainly harvested from the forest where they are managed under a traditional system of swidden agroforestry. Nuts may take 1-3 years to germinate, 1-6 months if shelled. Seedlings are transplanted into new swiddens and then managed during the succeeding swidden fallow, thereby creating the "castanhais". The seedlings quickly develop a vigorous taproot and need to be planted out when 40-60 cm tall. Attempts are now being made by the Agricultural Research Centre of the Humid Tropics (CPATU-EMBRAPA) in Brazil to identify elite trees, create a clonal germplasm collection and provide grafted clones for commercial plantations (Clay and Clement, 1993; Clement and Villachica, 1994).

Forest trees are 12-16 years old before fruiting, with maximum production from 25-30 years; cultivated compact, grafted trees may start production after 8 years. The trees grow best on deep, well-drained, alluvial soils on high ground not subject to flooding (Prance and Mori, 1979; Rosengarten, 1984; ITC, 1993).
 

Harvesting


High yielding mature trees may produce 200-400 fruits yielding 100-120 kg unshelled seeds (commercial nuts), however production variable with a good yield often followed by a poor yield in the following year. Within the area of distribution mature fruits fall between November and August. The seeds (Brazil nuts) are retained within the capsule because they are larger than the opening. Nuts are harvested regularly to avoid damage by agoutis, insects and fungi. Harvesting is a hazardous operation and usually starts after most of the fruits have fallen because of the danger of being hit by the 0.5-0.75 kg fruit falling from a height of up to 50 m (Menninger, 1977; Prance and Mori, 1979; Clay and Clement, 1993).

In Brazil the gatherers are paid in advance in cash or kind and are contracted to deliver the nuts to the shipper's agent (the trading agent is known as the shipper). In Bolivia the major shippers own large estates and largely make use of bonded labour, exchanging Brazil nuts and rubber for over-priced goods from the estate shops. The nuts are then brought by truck or barge to Belém for onward shipment (Holt, 1991).
 

Post-harvest treatments


After sufficient fruits have been harvested they are split open, washed and dried before on-site storage under rather primitive conditions; the nuts then have a moisture content of ca. 35%. By the time the nuts have reached the collecting point moisture content would have fallen to ca. 27%. The nuts are then cleaned and dried to ca. 16% moisture content or 12% if they are to be sold in-shell. In Brazil giant rotary driers are used while in Bolivia and Peru nuts are dried on slatted floors in the warehouses.

In Brazil and Bolivia the "autoclave" process is used for removing the shell, using a brief burst of stem to expand the shell and loosen the inner skin (testa), thereby producing a whiter kernel. The process produces a dry nut with little attached testa. Those from Brazil have a 4.5-5% moisture content, those from Bolivia have slightly more skin and 5-5.5% moisture. In Peru the nuts are first soaked for 24 hours to expand the shell; here the testa remains fixed to the kernel, giving a darker kernel. The individual nuts are then manually cracked in small vices and roughly graded.

Grading is by machine in Brazil and by hand in Bolivia and Peru. The nuts are then oven dried, or, in Peru, sun-dried, resulting in a skin-covered nut with 6.5-8% moisture, often with pieces of shell still attached. The high moisture makes mould and aflatoxin more common (Holt, 1991). Properly dried and aerated intact seeds can be stored for 1-1.5 years, with seed coat removed they can be kept for 2-3 years (Prance and Mori, 1979).

Attempts at freeze cracking has been tried in a few factories in Bolivia where the frozen nut is centrifugally thrown against a steel screen. Unfortunately the process is difficult to control in order to prevent broken kernels or excessive fragmenting of the shell, resulting in an almost unmarketable product (Holt, 1991).

After drying in-shell nuts are graded as follows: Extra Large, 40-45 nuts per pound; Large 46-50; Weak Large 51-56; Medium "Tocs", 57-62; and Small, 63-110 nuts per pound (ITC, 1993).
 

Production and consumption/utilization


Deforestation in the Amazonian rainforest has brought about a reduction in the harvest of Brazil nuts from about 104 000 tonnes in 1970 to only about 50 000 tonnes in 1980 (Mori and Prance, 1990). In-shell Brazil nuts are traditionally for the Christmas market in UK, Germany and USA as "mixed nut in-shell pack". Kernels are used in USA for roasting and salting for inclusion in mixed salted kernel packs. Approximately 60% of the UK market is in kernels for coating with chocolate (enrobing), the remaining 40% are marketed as raw packed kernels. The kernels are used for repacking in Continental Europe (Holt, 1991).
 

Nutritional value


Brazil nuts are highly nutritious, containing approximately 14% protein, 67% digestible fat or oil and 11% carbohydrates in addition to calcium, phosphorus, potassium, vitamin B and the rare vitamin excelsine (ITC, 1993). The oil is rich in unsaturated fatty acids (Table 4); the nut is also rich in the sulphur amino acids methionine and cysteine, which are deficient in seeds of Phaseolus vulgaris (common bean), a major source of protein in developing countries (Clay and Clement, 1993).

Table 4: Percentage Fatty Acid Composition of Pressure Extracted

Brazil Nuts Kernel Fat

C14:0 
C16:0
C16:1
C18:0
C18:1
C18:2
C18:3
%IS
0.05
13.85
0.45
10.25
30.50
44.90
-
75.85
0.48
13.74
-
5.45
42.79
26.54
-
69.33

C14:0 = myristic;

C16:0 = palmitic acid;

C16:1 = palmitoleic;

C18:0 = stearic;

C18:1 = oleic;

C18:2 = linoleic;

C18:3 = linolenic;

%IS = insaturation = C16:1 + C18:1 + C18:2 + C18:3

Source: Adams, 1975 cited by Clay and Clement, 1993.
 

By-products and other uses


Seed oil is bright yellow, nearly odourless and with a pleasant nutty flavour. The first extraction yields an excellent cooking oil, the second extraction is suitable for soap-making and as an illuminant. The seed cake may be used for feeding livestock (Prance and Mori, 1979).

The capsule (pyxidium) may be used for fuel, and is a preferred source of smoke for coagulating rubber latex. Variously used for local craft work for ashtrays, trinket cases, candle holders and ornaments; also used by the native tribes for containers or mortars. Timber is excellent but little used because of the high value of the nuts as well as felling being prohibited by law in Brazil (Mori and Prance, 1990; Clay and Clement, 1993).
 

Marketing


The world supply of Brazil nuts has varied from as high as 60 000 tons to ca. 30 000 tons and over the past 22 years has decreased at the modest rate of ca. 820 tons a year (Table 5). This decrease can be attributed to the destruction of the rainforest (LaFleur, 1992).

Table 5: World Production of Brazil Nuts by Country, 1970-1991

Year
Brazil
Bolivia
Peru
Total
Approximate price FOB 
 
('000 tons)
£/ton or US$/lb
1970
50
   
50
£378/ton
1971
30
   
30
£487/ton
1972
65
   
65
£466/ton
1973
65
   
65
US$ 0.63/lb
1974
33
   
33
US$ 0.77/lb
1975
50
   
50
US$ 0.59/lb
1976
32
   
32
US$ 0.76/lb
1977
38
   
38
US$ 1.28/lb
1978
32
8
2
42
US$ 1.33/lb
1979
50
7
3
60
US$ 1.04/lb
1980
60
   
60
US$ 0.98/lb
1981
40
   
40
US$ 1.07/lb
1982
28
   
28
US$ 1.63/lb
1983
35
   
35
US$ 1.41/lb
1984
35
10
6
51
US$ 0.81/lb
1985
40
6
4
50
US$ 0.82/lb
1986
35
8
5
48
US$ 0.90/lb
1987
33
10
7
50
US$ 1.09/lb
1988
29
7
5
41
US$ 1.18/lb
1989
25
9
6.5
40.5
US$ 1.70/lb
1990
42
9
3
54
US$ 1.48/lb
1991
24
5.5
2.5
32
US$ 1.36/lb
Average
36.3
8.0
4.4
45.2
US$ 1.20/lb

 

Source: LaFleur, 1992.

It was formerly second only to rubber as an export crop from Amazonian Brazil and still is a major crop in the overall economy of the region. Nuts are mainly exported to USA, United Kingdom and Germany (Prance and Mori, 1979).

Export is mainly concentrated in northwestern Amazonia, Acre State and the Pando/Beni regions of Bolivia. The in-shell nuts are from the generally larger and round nuts from central and lower Amazonia and Pará and the kernels from Acre and Pando/Beni regions. However, over the past decade the demand for in-shell has been decreasing worldwide as traditions have changed and the Food Authorities have become more demanding; the demand for kernels, however, has remained relatively constant. Over 80% of the commercial supply is from Acre where the differences between the Cruzeiro "official" and the Cruzeiro "parallelo" generally favours a contraband traffic between Bolivia, Peru and Brazil (Holt, 1991).

The three influencing factors between production and final usage are the out-turn quality at the shipper's factory, the quality received by the importer at the port of destination and the quality delivered to the consumer, resulting in a rather precarious market. The situation is further complicated by three of the major processing/exporting facilities in Brazil being owned by members of the same family and controlling over 50% of the market.

The importer buys a Fair Average Quality (FAQ) of the crop, which is determined by Combined Edible Nut Trade Association (CENTA) or by the Association of Food Industries, New York (AFI) from time to time during the year. This theoretically allows the market to trade different qualities as determined by the state of the crop at the point or origin. Sale by the importer to the final customer will invariably include guarantees and conditions not covered by the original purchase. Manufacturers have to conform to increasingly tighter legal specifications, particularly with regard to aflatoxin and coli bacteria, especially in Europe where raw or enrobed nuts are eaten. Since much of USA import is rendered sterile by roasting or blanching and detoxification processes, their import regulations tend to be less strict (Holt, 1991; LaFleur, 1992).

Blanched grades have been shown to be 99% less contaminated than naturals (shelled but not processed) and are marketed as blanched whole, sliced, diced, slivered, balls, ovals, broken and paste; natural grades are marketed as natural wholes, sliced and powder.
 

Discussion


The feudal contract system by which the disenfranchised gatherers are bonded to harvest the nuts means that any benefits of high prices are not passed onto the gatherers. The destruction of the rainforest has resulted in a steady decrease in both production and share of the edible nut trade, promising a bleak future for the Brazil nut trade (LaFleur, 1992).

However, long-term prospects are considered reasonably promising. Producers from the Andean region can expect little or no competition from other parts of the world. However, their main concern should not be production and exports but quality control (ITC, 1993).

Brazil nut trees can continue be managed under the present "castanhais" system, thereby helping to conserve the tropical forest and Amerindian cultures. A second possibility is one of agroforestry/forest management to restore degraded forest sites with the Brazil nut as a multipurpose species, yielding nuts after 15-20 years and timber after 50-100 years, which could lead to the provision of long-term capitalization for the Amazonian farmer. The third option is that of investment in a monoculture plantation crop but with the inherent risks of pests and diseases. Clay and Clement (1993) prefer the second option. However, there is also a case for the Amerindians to be allowed to continue their traditional way of life in their own territories and the second option to be used in degraded areas.
 

Peanut or groundnut: Arachis hypogaea, Leguminosae subfamily Papilionoideae


See Smartt (1994) for agronomic details, etc.
 

Discussion


Peanuts are the second largest source, after soya beans, of vegetable oil; the crops from all the major producing countries with the exception of USA is predominantly for oil extraction (Purseglove, 1987).

As a dessert nut, peanuts were first introduced in USA as roasted, in-shell in 1870; packaged, salted and roasted, shelled peanuts were introduced around 1906 (Matz, 1984).

It is a valuable, high protein, legume crop widely grown throughout the tropics, especially in the lower rainfall areas. Where other sources of food protein are not readily available the emphasis should be on peanuts for local consumption rather than commercial oil extraction.
 

Macadamia or Queensland nut: Macadamia integrifolia, Proteaceae

 

Distribution and ecology


Native of Queensland and northern New South Wales of Australia; occurs along fringes of subtropical lowland rainforests. Introduced to Hawaii in 1880s for growing as windbreaks. The commercial potential as a dessert nut was developed by the University of Hawaii in the 1930s although a plantation had been established in Australia as early as 1888; recent plantations in California, Florida, Jamaica, Mexico, Guatemala, El Salvador, Costa Rica, Colombia, Venezuela, Brazil, Peru, Ethiopia, Kenya, Tanzania, Malawi, Zimbabwe, South Africa, Thailand, China, Indonesia, Tahiti, Samoa, Fiji, New Caledonia, New Zealand and Israel. Optimum temperature is 25° C; mature trees are frost tolerant for short periods down to -6° C, longer periods or lower temperatures are fatal. The developing inflorescence is susceptible to frost while the critical temperature above which flowering is suppressed is 20° C (Rosengarten, 1984; ITC, 1993; Macrae et al., 1993).
 

Description


A spreading, evergreen tree up to 10 m tall; leaves in whorls of 3, simple, entire 10-28 cm long, new leaves pale green (in whorls of 4 and margins serrate with ca. 40 per margin, new leaves pink to red in the closely related M. tetraphylla). Inflorescence 10-15 cm long with up to 200 creamy white flowers (racemes up to 30 cm long and bearing more than 500 reddish pink flowers in M. tetraphylla). Follicles 1-sutured, only 1 out of 2 ovules develops (rarely both, then whole kernel difficult to extract). Fruit borne in hanging clusters of 12 or more, globose, 2-3 cm in diameter, exocarp fleshy, dehiscing on the tree; endocarp very hard, kernels globose (Menninger, 1977; Rosengarten, 1984; Macrae et al., 1993).

Fig 8. Macadamia integrifolia. 1: leaf, 2: branchlet, 3: nut showing dehiscence of husk, 4: cross-section, 5: longitudinal section.

Cultivation


Macadamia prefers well-drained soils, sheltered from strong winds and a mild, frost-free, subtropical climate with a well distributed annual rainfall of at least 1 200 mm. Plantations from seed start profitable bearing after 7 years, with productivity peaking after 15 years; the economic life of the tree being 50 years. At full production the yield is from 23 to 70 kg in-shell nuts per tree. Desirable clones may be developed by grafting. The species is cross pollinated, therefore desirable that at least two cultivars are grown in orchards, preferably in alternate rows. The presence of bees should be encouraged (Rosengarten, 1984; Macrae et al., 1993).
 

Harvesting


Mature trees bear continuously and ripe fruits are difficult to distinguish from immature ones on the tree as the mature fruits usually abscise when the fibrous husk is still green. As the husk dries it splits along the suture to release the nut with its thick, rough, strong, light tan shell enclosing the kernel. Consequently the ripe nuts are usually harvested from the ground. A blower is used to move leaves and nuts away from the base of the tree where they can be swept into windrows and picked up by a mechanized harvester, although some hand labour is always necessary. Harvesting should be carried out every 6-8 weeks to avoid any deterioration (Menninger, 1977; Rosengarten, 1984; Macrae et al., 1993).
 

Post-harvest treatments


Freshly harvested nuts contain up to 30% moisture in the husk and 10-25% in the rest and it has to be removed within 24 hours if possible to prevent mould. The husk is removed by husking machines and initially dried to 10% moisture before delivery to the processor. The in-shell nuts are then reduced in stages to about 1.5% water content in drying ovens for long-term storage, efficient cracking and more complete removal of whole kernels. The dried nuts are then shelled in stainless steel drums and the kernels separated by a combination of sieving and air blasting before grading by air or water flotation. The final product is either lightly roasted and salted or packaged raw in vacuum-filled, foil laminate bags (Ryall and Pentzer, 1974; Rosengarten, 1984; Macrae et al., 1993).
 

Production and consumption/utilization


The optimum requirements for eating and processing are kernels containing at least 72% oil, i.e., specific gravity (SG) <1.0); second grade kernels with SG 1.0-1.025 can be used for low grade production, while third grade kernels with SG >1.025 are commercially unacceptable. The bulk of the macadamia nuts are traditionally roasted in coconut oil and salted although dry roasting is increasing in popularity; also used in confectionery - chocolate coated kernels and nut chocolate, ice cream and baking (Rosengarten, 1984; ITC, 1993; Macrae et al., 1993).
 

Nutritional value


Kernels contain more than 75% of oil, the rest being protein and little sugar but no starch (Menninger, 1977). The nutritional value of roasted and salted nuts compared with shelled pistachio nuts are shown in Table 6.

Table 6: Nutritional Value per 100 g of Roasted in Oil and Salted Macadamia Nuts

and Dried and Shelled Pistachio Nuts

  Macadamia Pistachio
Water (%)
2
4
Food energy (kJ)
3 064
2 465
Protein (g)
7.1
21.4
Fat (g)
78.6
50
Fatty acids, saturated (g)
11.4
6.1
Fatty acids, monounsaturated
61.1
33.2
Fatty acids, polyunsaturated
0.14
7.5
Cholesterol (mg)
0
0
Carbohydrates (g)
14.3
25
Ca (mg)
46.4
135.7
P (mg)
203.6
510.7
Fe (mg)
1.8
6.8
K (mg)
332.1
1 107.1
Na (mg)
264.3
-
Mg (mg)
0.12
-
Zn (mg)
1.4
-
Mn (mg)
0.38
-
Cu (mg)
0.33
-
Vitamin A, iu
trace
250
Vitamin A, RE (mg)
trace
25
Thiamin (mg)
0.21
0.82
Riboflavin (mg)
0.11
0.18
Nicotinic acid (mg)
2.14
1.07
Ascorbic acid (mg)
0
trace

Source: Macrae et al., 1993.
 

By-products and other uses


Macadamia shell may be used as fuel, generating sufficient energy to dry wet, in-shell nuts. Kernel oil suitable for human consumption (Menninger, 1977; Rosengarten, 1984).


Photo 1: Macadamia tree

Photo 2: Macadamia in flower

Marketing


World production for 1991/1992 was approximately 11 000 tonnes of kernels per year of which 50% were consumed in USA. The major exporter is Hawaii, producing about 5 700 tonnes in 1991, with over 50% of the world production and a projected kernel production of about 13 600 tonnes by the year 2000. Australia, the second largest producer in the world has an annual production of ca. 3 000 tonnes, or near 30% of the world production (ITC, 1993). Considered a gourmet delicacy, it is, with pine nuts and pistachios, one of the world's most expensive nuts (Rosengarten, 1984).
 

Discussion


World production is increasing at an alarming rate and is expected to double by the beginning of the next century. There is still only a small demand for this expensive nut and it is a crop that requires considerable initial investment (ITC, 1993). Nevertheless, the market for macadamia could be expanded considerably into Europe and Asia, where it is still relatively little known. The increase in production can be expected to result in a price reduction.

With our present knowledge there are only limited areas in the world where the trees can be grown successfully. To date there have been no successful plantations within ca. 15° N and S of the equator and, unlike coffee, a suitable altitude cannot be substituted for latitude when seeking a favourable environment (Rosengarten, 1984). Obviously there is a need for further exploration for and selection of potential genotypes and a better understanding of the environmental and management factors involved in establishing productive macadamia plantations.
 

Almond: Prunus dulcis, Rosaceae

 

Distribution and ecology


Naturally occurs in the oak forests of Northern Syria, Turkey, Caucasus, Iran and Iraq. Introduced and widely naturalized in North Africa, Cyprus, Crete, southern Europe, Afghanistan, Kashmir, California, etc. (Townsend and Guest, 1966).
 

Description


Spreading tree up to 10 m tall; leaves deciduous, simple. Fruit ovoid-ellipsoid, 3-4 cm x 22.5 cm (larger in cultivated varieties), splitting at maturity, stone 2.5-3 cm x 1.5-2 cm, pitted, seed ovoid, compressed, ca. 1.5-2 cm x 1-1.5 cm (Townsend and Guest, 1966). Two races recognized, sweet almonds grown for their edible nuts and the bitter almonds for oil of bitter almond. Hard and soft shelled forms are recognized in the former (Ryall and Pentzer, 1974; Matz, 1984; Rosengarten, 1984); the latter will not be considered further here.
 

Cultivation


Most almond cultivars are soft shelled; they are also self-incompatible, consequently plantations require the interplanting of two rows of self-incompatible with a row of cross-compatible cultivars; the keeping of honey bees for pollination is considered an essential part of almond production. Trees in California begin to bear after 3-4 years and reach full productivity in ca. 7-8 years. Irrigation is favoured in California (Rosengarten, 1984).
 

Harvesting


Almonds ready for harvesting when the hulls start to split open. Formerly harvested by beating the tree and collecting the falling almonds on canvas sheets. Now harvested using mechanical shakers which can deal with 120 trees per hour; the fallen nuts are then swept into windrows and picked up mechanically for transport to the factory. The use of shake and catch machines lessens the danger of fruits of the more open cultivars coming into contact with the soil, thereby lessening the risk of mould and aflatoxin infestation (Ryall and Pentzer, 1974; Rosengarten, 1984; Paramount Farms Almonds, 1991).

Fig 9. Prunus dulcis. 1: branch with flowers, 2: longitudinal section of flower 3: branch with fruits 4: fruits without pericarp.

Post-harvest treatments


At the factory the brown, outer, leathery coat (hull) is removed by blanching, which involves placing the almonds in contact with water at 82° C for 3 minutes and either skinning by hand or by a special machine. The almonds are then dried to less than 8% moisture content and stored. Air tight containers must be used to prevent moisture pick-up. Although relatively resistant to rancidity the almonds will deteriorate in time. On delivery to the packing company, the almonds are shelled and graded. The grading process uses ultraviolet scanners for high-tech colour sorting to separate damaged and foreign matter before mechanical grading (Matz, 1984; Paramount Farms Almonds, 1991).
 

Production and consumption/ utilization


Approximately 98% of the crop is sold shelled either as natural and retaining the brown skin or blanched, with the skins removed. Almonds can be eaten as a dessert nut either dry roasted or roasted in almond oil and then salted and seasoned. They are also used for baking, confectionery, cereal, dairy or snack formulations; processing may produce blanched whole, slivered, meal, diced, split, sliced or flaked almonds; almond butter is a recent development (Rosengarten, 1984; Paramount Farms Almonds, 1991).
 

Nutritional value


Almonds contain approximately 22% protein, 57.7% digestible fat or oil and 15% carbohydrates (Melville, 1947).
 

By-products and other uses


The gum exudate may be used as a substitute for gum tragacanth and was formerly exported from Iran via Bombay to Europe. Almond yields both an essential oil and fixed fatty acid for use in perfumery but frequently adulterated with other oils. The essential oil from the bitter variety is highly toxic due to presence of HCN but with careful preparation yields an agreeable essence for use in perfumery and confectionery. Both bitter and sweet varieties may be grown as ornamentals (Townsend and Guest, 1966).

The hulls of sweet almonds can be fed to livestock. The shells can be used for roughage in cattle feed or converted into charcoal briquettes (Rosengarten, 1984).
 

Marketing


Regarded as the most important and versatile of all edible tree nuts. Almond producing countries in current order of importance are USA (California), Spain, Italy, Iran, Greece, Morocco, Turkey, Tunisia, Pakistan, Libya, Syria, Portugal, China and Lebanon (FAO, 1994).

World production rose steadily from 1 million tonnes in 1979-81 to 1.3 million tonnes in 1992 and fell to 1.2 million tonnes in 1993. This trend is reflected in North America by 273, 412 and 356 000 tonnes for 1979-81, 1992 and 1993 respectively. Production in Europe, the largest of the continental scale producers has decreased steadily from 482 000 tonnes in 197981 to 436 000 tonnes in 1993. Spain, the major producer in Europe increased production slightly from 243 000 tonnes in 1979-81 to 251 000 tonnes in 1993, while in Italy production has declined markedly, from 174 000 tonnes in 1979-81 to 99 900 tonnes in 1993 (FAO, 1994).
 

Discussion


The world's major edible nut, there is an obvious need for improving Old World production if it is to compete with the highly mechanized production in USA.
 

Coconut: Cocos nucifera, Palmae

 

Distribution and ecology


Origin unknown, possibly western Pacific; cultivated throughout the lowland tropics. Salt tolerant, the coconut requires an equable climate, good drainage, adequate soil aeration and constant supply of ground water (Purseglove, 1987; Dransfield, 1986).
 

Description


Solitary, unarmed, monoecious tree palm ranging from "dwarfs" with trunks up to 2 m at first flowering to tall forms with trunks to 30 m or more. Leaves pinnate, 4-5 m long. Inflorescence up to 1.5 m long, bisexual; male flowers distal. Fruit massive, obovoid, obscurely trigonous, up to 25 cm long and 25 cm or more in diameter, with basal persistent calyx and corolla; usually with only 1 of the 3 carpels developing; mesocarp massive, fibrous; endocarp to 5 mm thick, extremely hard and woody, with 3 basal "eyes", usually only 1 functional; seed filling the large endocarp cavity, 10-15 cm in diameter; endosperm to 2 cm thick, lining the endocarp (Dransfield, 1986).

Fig 10. Cocos nucifera.

Cultivation


A number of rather heterogeneous cultivars are recognized including one where the endosperm hypertrophies to fill the entire cavity with a thick, edible curd. Tall palms tend to be slow maturing, flowering 6-10 years after planting and with a life-span of 80-100 years. Dwarf palms begin bearing in their third year and have a productive life of 30-35(-40) years.

A satisfactory method of vegetative propagation has yet to be found, although some success has been reported with tissue culture. Propagation is, therefore, from seed. The seed has no dormancy and growth may even begin while the fruit is still attached to the tree. Germination is slow and may take ca. 4 months. Transplanting into the field is from 6-9 months and should be accompanied by stringent selection for early germination, vigour and rapid growth. The normal spacing for tall palms is for 120-175 palms per ha with square planting and 140-200 palms per ha with triangular planting. Palms require careful attention during their initial 4-6 years to ensure good development; catch crops may be grown until the palms come into bearing. Manuring is highly beneficial.

An inflorescence is produced every month and the fruit takes a year to mature (Rosengarten, 1984; Purseglove, 1987).
 

Harvesting


Depending on the cultivar, the average weight of fruit from tall palms ranges from 1.2-2 kg with nuts from 0.7-1.2 kg containing 0.35-0.6 kg endosperm and yielding 0.2-0.29 kg of copra. Dwarf palms bear fruits weighing 1.1 kg with nuts weighing 0.6 kg and yielding 0.2 kg of copra.

Harvesting usually begins when tall palms are 6-8 years old and continues throughout the year. Fully ripe fruits are required for copra production and manufacture of desiccated coconut. The fruits may be harvested by skilled climbers or, in Malaysia, Thailand and Sumatra, by trained pig-tailed monkeys; coconuts may also be cut down using a knife fixed to a long pole or the fallen fruit picked up from the ground (Rosengarten, 1984; Purseglove, 1987).
 

Post-harvest treatments


The endosperm is the source of an edible/industrial oil which is either extracted by the producing countries or dried and exported as copra for extraction elsewhere; copra contains 60-68% oil of which ca. 64% is extractable. The copra is extracted by first removing the husk by impaling and twisting the fruit on an erect steel bayonet and then splitting the nut with a cutlass and gouging out the endosperm. The copra is dried either in the sun or in kilns immediately after breaking the nut in order to avoid any deterioration (Howes, 1948; Purseglove, 1987).
 

Production and consumption/utilization


For domestic consumption in the countries of origin the endosperm is grated and macerated, the emulsion is boiled and the resulting scum skimmed off and the oil poured off. Hydraulic presses are used industrially to extract the oil; additional oil is sometimes recovered from the cake residue using hydrocarbon solvents.

The endocarp of green, unripe fruits contain ca. 500 ml of a sweet and refreshing liquid. The fresh endosperm is variously eaten in the East and Pacific. Coconut milk, which is widely used in curries and other cooking, is obtained by squeezing freshly grated endosperm through a sieve.

The dried endosperm (copra) is an important commercial source of oil for margarine and soap production. The low content of unsaturated acids present makes coconut oil resistant to oxidative rancidity, thereby adding to the keeping quality in baked foods and fillings. With a higher melting fraction, coconut stearin is valued as a confectionery fat and as a substitute for cocoa butter.

The shredded and dried fresh endosperm is used in confectionery and bakery products as desiccated coconut and contains 68-72% oil and less than 2% water.

The haustorial organ or coconut apple within a germinating coconut is eaten in some countries (Howes, 1948; Hedrick, 1972; Menninger, 1977; Johnson, 1983; Rosengarten, 1984; Purseglove, 1987; Mabberley, 1987).
 

Nutritive value


The endosperm contains 36.3% water, 4.5% protein, 41.6% fat, 13.0% carbohydrates, 3.6% fibre and 1.0% minerals, while copra contains 6.8% water, 7.6% protein, 63.7% fat, 16.1% carbohydrates 3.8% fibre and 2.0% minerals (Purseglove, 1987).
 

By-products and other uses


The fibrous mesocarp (husk) yields fibre coir for doormats, matting, cordage, while the residual coir-dust is used as a peat substitute in horticulture. The coconut liquid from unripe fruit, which contains plant growth substances, is used in plant physiology experiments; it has also been used in the Pacific theatre during World War II as a substitute for a glucose drip in surgery. In addition to the commercial importance of coconut oil for margarine it is also used in the soap and cosmetic industries and in the manufacture of detergents and resins, it is also used for cooking and as an illuminant, and the coconut stearin used for candles. The copra residue after extraction of oil is used in cattle and poultry foods; the stony endocarp (shell) may be used for fuel, also used for containers and craft work, buttons, combs, bangles, musical instruments, etc. The finely ground shells are used in the plastics industry as fillers, also in the manufacture of gas absorbent charcoal for use in gas masks, etc.; the distilled shells yield wood tar and, although not currently economic, furfural (C5H4O2), which may be used as a solvent for cellulose nitrate and in the manufacture of dyes and plastics.

The apical buds from old trees are used for tinned palm hearts. The trunk is tapped for the sugary sap known as toddy which, when fresh, may be used as a bread yeast. Evaporated, toddy yields jaggery (palm sugar). Toddy may be fermented to produce coconut vinegar. The distillation of fermented toddy yields a strong alcoholic liquor (arrack) containing 30-40% alcohol. The leaves are used for basketry, thatch, etc., and the midribs for brooms, baskets, fish-traps, fences, etc. The trunk is used for building; the closely grained outer wood (porcupine wood) is used for furniture, carving and veneers. The roots are used for tooth sticks. Almost all parts are used in local medicines and various ceremonial customs. Dwarf cultivars serve as the mother palm in creating productive hybrids, they may also be grown as ornamentals (Howes, 1948; Hedrick, 1972; Menninger, 1977; Johnson, 1983; Rosengarten, 1984; Purseglove, 1987; Mabberley, 1987).
 

Marketing


Coconut has been the major source of vegetable oil in the twentieth century, now surpassed by the soya bean and oil palm. World production of coconuts is currently 43.4 million tonnes (and of copra 4.6 million tonnes), of which Indonesia is the largest producer with 14.2 million tonnes, followed by the Philippines with 9.3 million tonnes; the Philippines is also the largest producer of copra with 1.8 million tonnes followed by Indonesia with 1.1 million tonnes. Mozambique is the largest producer in Africa with 0.4 and 0.07 million tonnes of coconuts and copra respectively with Mexico the largest producer in America with 1.0 and 0.2 million tonnes of coconuts and copra respectively (Purseglove, 1987; FAO, 1994).
 

Discussion


Due to its multiplicity of uses the coconut is known as the "tree of life", the tree of heaven's and mankind's greatest provider in the tropics. New World production from tall palms has been seriously threatened by palm lethal yellowing, a disease of an unknown etiology but probably caused by a mycoplasma-like organism (MLO) (Holliday, 1989). Should the disease spread to the Old World there would have to be a massive replanting with immune, high yielding cultivars for plantations to remain productive. Unfortunately 95% of the coconut producers are small holders and may be unable to bear the cost of replanting.