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Only a small proportion of the world's bananas are preserved for storage, most of the fruit being consumed raw, in the case of dessert bananas, or cooked for immediate consumption in the case of cooking bananas and plantains (Simmonds, 1966). No extensive post-harvest technology for these foods exists in most traditional societies dependent on them.
Nearly all edible bananas and plantains are derived from two wild diploid species Musa acuminate Colla. (AA) and M. balbisiana Colla (BB) of the Eumusa series of the genus Musa (Musaceae) and most are triploids believed to have been formed as a result of hybridization within or between these two species. Simmonds (1966) has developed a classification of bananas according to the contribution to the genetic make-up of the hybrid and using this technique the bananas used as staple foods can be considered as falling within three triploid groups (AAA, AAB and ARE). The first (AAA) comprises the sweet cultivars having a low starch content and high sugar content when ripe and which includes the Cavendish sub-group which dominates the international trade in bananas. These are only used for cooking when green and are used as staple foods mainly as by-products of export orientated industries. The AAB group consists predominantly of fruit of the plantain sub-group which are starchy even when ripe and hence eaten only after cooking and the ABB group consists of the starchy cooking bananas known as "bluggoes" in the Caribbean. The importance of the different cultivars varies in different areas of the tropics. As a cooked vegetable, bananas and plantains form an important source of carbohydrate throughout the tropical world, except possibly India and Southeast Asia where, while dessert bananas are consumed in large quantities, the use of cooked bananas and plantains is not so widespread. In many parts of tropical Africa, most notably Ghana and Uganda, they are important staple food crops. In contrast, the preserved products do not generally contribute very greatly to diets, although they are important in some localized areas, especially in times of food scarcity.
Once ripe, the shelf-life of bananas and plantains is only a few days but traditionally plantains are harvested as an entire bunch while still green and hung in the house or other building. The fruits within the bunch ripen progressively from the proximal end of the bunch to the distal end and in this way the fruit is available for use over a longer period of time. Also the fruits may be cooked when green, half ripe or when fully ripe and so if not used while green, are still available for use at a later stage of ripeness (Coursey, 1981a). Thus, within traditional societies, there is seldom a high degree of wastage, although there may be in modern urban markets.
The methods used to cook bananas and plantains for immediate consumption do not generally entail elaborate processes, the fruit normally being prepared by one of three main techniques: boiling or steaming, baking or roasting and frying. However, in some areas, particularly West Africa, the fruit is also pounded, like other perishable staple food crops in these regions into a fatu-type product (see cassava, yam, aroids).
The preferred technique varies from region to region. In Uganda, where bananas are an especially important part of the diet, steaming is the normal method. In a typical dish, green bananas are peeled, wrapped in banana leaves, placed in a pan on a base of other leaves and steamed for 1 to 2 hours. When ready, the bananas are removed from the pan and mashed while still in the leaves to obtain a solid mass of pulp which is either eaten as such or resteamed for a while (Goode, 1974; Mukasa and Thomas, 1970). Other preparations in Uganda involve boiling green bananas or plantains, often with beans and peas or groundnuts, with ghee, onions and condiments added for flavour (Goode, 1974).
In West Africa, plantains boiled in their skins and then peeled are eaten alone or with a sauce usually based on palm oil and containing meat and/or fish, vegetables and seasonings (Dalziel, 1937; Johnston, 1958; Tezenas du Montcel, 1979; Walker, 1931) . Often the plantains are pounded in a mortar after boiling to form a paste or dough known variously as fufu, foofoo, foufou or foutou which is eaten with soup or a sauce of meat and vegetables (Johnston, 1958; Lassoudière, 1973). Fufu is also prepared from a mixture of plantains and cassava (Hartog, 1972; Lassoudière, 1973), and from cassava alone or yams or cocoyams. Frying ripe or unripe slices of bananas and plantains in oil, usually palm or groundnut oil, is also popular in this region of Africa (Boscom, 1951; Dalziel, 1937, Johnston, 1958; Tezenas du Montcel, 1979; Walker, 1931). In Ghana, a type of pancake is prepared from a mixture of pounded ripe plantains and fermented wholemeal maize dough (Del-Tutu, 1975). This is known as fatale and is prepared by steeping the maize in water for two days, then draining off the water and washing the grain which is ground into a dough with water and left to ferment for three days. The pounded plantain pulp is mixed with the fermented maize dough into a paste which is seasoned with ginger, pepper, onion and salt and then fried in palm oil. The pancake may be served with beans as a main meal or used on its own as a snack or dessert. A similar product known as krakro is made by mixing pounded plantains with corn dough, ginger, onion and salt. This mixture is left to rise for half an hour and then formed into balls and fried (Eshun, 1977) .
Roasted or baked bananas and plantains are also prepared in both East and West Africa by placing peeled or unpeeled fruit either in the ashes of a fire or in an oven (Boscom, 1951; Dalziel, 1937; Goode, 1974; Tezenas du Montcel, 1979; Walker, 1931; Whitby, 1972).
A product similar to fufu is also prepared in the Caribbean area from semi-ripe bananas which are boiled and pounded and eaten with soup, although more often the bananas are simply boiled and eaten with salted fish or meat. Over-ripe fruit is normally sliced and fried (Kervégant, 1935). In the South Pacific, unpeeled, ripe bananas are traditionally cooked in hot stone ovens or in the embers of a fire, while unripe bananas are peeled, grated, sometimes mixed with coconut cream, wrapped in leaves and cooked in an oven. In Samoa, pounded bananas are mixed with coconut cream, scented with citrus leaves forming a liquid mash called poi which is generally reserved for the chiefs (Massal and Barrau, 1956) .
Bananas and plantains are traditionally preserved by drying or fermenting the dried products and, in particular, flour being the most important nutritionally, although beer is also a major product in Uganda and Rwanda where the utilization of green bananas is particularly high.
Drying as a means of preservation is a widely used method for both unripe and ripe bananas and plantains, the end product from unripe fruit generally being chips which are pounded into flour while the ripe fruit is used to make sweet meats known as banana figs which are very popular in many areas but do not contribute very largely to a total diet. Traditionally, the fruit is sun-dried or sometimes dried in ovens or over fires; usually as slices, although banana figs are sometimes prepared from whole fruits (Fawcett, 1921; Goode, 1974; Hayes, 1941; Kervégant, 1935; Mukasa and Thomas, 1970; Simmonds, 1966; Walker, 1931).
Typically, slices of unripe banana are spread out to dry on bamboo frameworks, on mats, on cemented areas, on roadsides or simply on the ground (Kervégant, 1935). In Uganda, dried slices known as mutere are prepared chiefly as a famine reserve, the slices being stored and used only in times of need when they are cooked directly or first ground into a flour (Goode, 1974; Mukasa and Thomas, 1970). After sun-drying for one to two weeks the slices are packed into oval shaped bundles made of banana fibre and hung either in the house, or if large amounts are to be stored, in millet granaries (Hayes, 1941).
A method for preparing banana figs from a local variety known as rajeli (a French plantain type) used in the Bombay area of India has been described in some detail by Kulkarni ( 1911) . The fruit are harvested green and ripened by placing them in layers, covered with plantain leaves inside a storehouse and left for about three days, during which time a patch of bare earth is prepared as a drying area. A mat is spread out on this area and the peeled bananas arranged in rows to be dried for three days, each night being gathered in and covered and then spread out again the next day. The dried fruit is then wrapped in leaves for sale at the local market. The bananas prepared in this way are said to keep for six months.
In Polynesia ripe fruit are normally oven dried and then wrapped in leaves and bound tightly to store until needed (Massal and Barrau, 1956), while in East Africa peeled fruit is said sometimes to be dried over a fire for 24 hours before sun-drying in order to hasten the drying process (Kervégant, 1935).
The dried product keeps well in the form of slices, although liable to insect attack, whereas flour is hydroscopic and deteriorates rapidly under tropical conditions, tending to lose its flavour (Kervégant, 1935; Tezenas du Montcel, 1979). The dried slices of banana known as mutere in Uganda can be cooked as they are by soaking, boiling and then mashing to be served with a fish sauce (Goode, 1974) but more normally the slices are ground to a flour. In East and West Africa flour is used to make a thick paste known as fufu (or one of its variants) (Goode, 1974; Tezenas du Montcel, 1979) .
Traditionally, banana beer is made in both Uganda and Rwanda by the following method: Bananas are harvested green and ripened artificially by placing them in a pit, surrounded and covered with banana leaves and soil. In Rwanda the ripening process is aided by lighting a fire near or around the hole containing the fruit or by placing the bananas on the hot ashes of a fire previously lit in the hole. The fruit are left to ripen for 5 - 6 days and then removed, peeled and placed in a wooden trough made from a hollowed-out tree trunk. In Uganda the task of mashing the fruit to release the juice is carried out by the men who trample on the bananas which have been mixed with grass (Imperata species) whereas in Rwanda it is the women's task to knead the fruit by hand with the aid of handfuls of hard grasses such as Agrostis species. The juice is filtered into jars and the troughs washed with water to transfer the last traces of juice into the jars. Roasted sorghum flour is added to the banana juice and the mixture left to ferment for 1 to 2 days after which time the beer, known locally in Rwanda as urgwawa is ready for drinking (Adriaens and Lozet, 1951; Champion, 1970; Masefield, 1938). A similar method is used in Benin, but fermentation is initiated using some beer previously prepared or fermented banana flour (Kervégant, 1935). The juice before fermentation is sometimes consumed as a nonalcoholic drink while a very potent beverage is obtained by mixing honey with the banana pulp before fermenting; irrespective of their alcohol content, most banana beers have a high solids content and contribute substantially to the carbohydrate intake. Banana wines and distilled spirits are made in other areas of the world such as the West Indies and South Pacific but are of only minor importance (Fawcett, 1921; Kervégant, 1935). However, bananas and plantains do not appear to be used for this purpose in India or Southeast Asia (Simmonds, 1966).
Finally, in Western Samoa unripe bananas are preserved by fermentation using a technique normally applied to breadfruit in the Pacific Islands (Cox, 1980a). The product is a fermented paste which is baked to form a bread-like substance called mast. Both the paste and the bread can be stored or buried in leaf-lined pits for over a year until needed and exceptionally bread recovered after generations has been found still to be edible. To prepare, the unripe bananas are peeled, washed and placed inside pits lined with and covered by leaves of Heliconia paka A.C. Smith, and banana, forming a relatively air-tight pocket which is finally covered by soil and rocks. The fruit are left for 34 days and then uncovered to reveal a homogeneous paste which is formed into loaves, wrapped in leaves and baked.
Breadfruit (Artocarpus altilis (Park.) Fosberg), is native to Southeast Asia, but is now found throughout the tropics and is an important staple in the South Pacific and parts of the Caribbean. The fruit is only suitable for use over a very limited period, that is when mature or nearly mature, but before it ripens, as during ripening rapid flavour and texture changes occur which render it unpalatable. It cannot, therefore, be stored in the fresh state for more than a few days, although in parts of Jamaica the storage life is extended a little longer by keeping the fruits under water in large tanks (Thompson et al., 1974).
For long term storage breadfruit is normally either dried or subjected to a period of fermentation. Most simply the fruit is cut into slices and dried in the sun as is done, for example, in the West Indies where the dried fruit is subsequently prepared for consumption by pounding and sifting for use as a breakfast food or in puddings (Brotbaum, 1933). However, a number of more complex techniques have evolved in the various islands of the South Pacific. For example, a method observed on Kapingamarangi in the East Caroline Islands is used to prepare dried sheets of breadfruit known as tipak. The skin, seeds and core are removed from nearly mature fruits which are then cut into small pieces and packed in coconut leaf baskets. The baskets are placed in an oven of hot coral stones covered with mats and sand and left for one day. After this time the fruit is removed and mashed in a wooden bowl and the resulting brown, sweet smelling paste is then spread out on coconut leaf mats to dry in the sun. The paste dries in sheets, usually about 1.5 m by 50 cm, which are then rolled up, wrapped in Pandanus leaves and tied with strings of coconut fibre. The Islanders claim that in this form the breadfruit can be preserved in good condition for at least three years (Coenen and Barrau, 1961).
A method used in the Reef Islands (Solomon Islands) involves firstly cooking ripe breadfruit in the ashes of a fire for about an hour. The fruit is then left for a day after which time it is peeled, quartered and the seeds removed and then cut up further into smaller pieces. The pieces of fruit are then placed to a depth of 10 - 12 cm on a net which is suspended over a hole 60 - 90 cm in diameter and 30 cm deep containing the coals of a smokeless fire and hot stones. The net is lowered as the fire and stones cool and the pieces turned continuously for about 6 hours until dry. The fruit is then placed in coconut baskets lined with breadfruit leaves covered with more leaves and the baskets sown up with bark fibre. The breadfruit biscuits or nambo are stored on racks above the kitchen fire and are said to keep for a year or more (Tedder, 1956).
The practice of preserving breadfruit by fermentation was traditionally used in the islands of the South Pacific and similar techniques are found on many different islands, the fermented paste being called by names such as masi in Samoa, ma in the Marquesas, mahi in Tahiti, maratan in Ponape and namandi in Vanuatu (Cox, 1980b; Massal and Barrau, 1954). A detailed description of the technique used in Samoa for both breadfruit and banana has been given by Cox (1980a), and has already been referred to in the section on banana in this report. Briefly, the fruit is peeled and washed, placed in a hole lined with Heliconia leaves which are folded over the fruit forming a fairly air-tight pocket. The whole pit is then covered with more leaves and layers of soil and rocks. After 34 days the fermented product, now a dough-like fermented paste, is removed and kneaded, made into loaves, wrapped in leaves and baked. The fermented paste can be left in the pits for over a year without deteriorating, although successful preservation is said to be dependent on the type of leaves used in construction of the pit, the care taken in building the pit and local conditions. A similar technique has been described from Anuta (Yen, 1973b). In Namu atoll a different technique is used. Fallen breadfruit is collected in June, peeled and placed in sacks which are then immersed in salt water for a day. The fruit is then laid on palm fronds for 2 - 3 days during which time it ferments and the fruit, which is by now soft, is kneaded. The pulp is placed in pits lined with breadfruit leaves and covered with sacks and stones where it is left until required: generally it is all used between the months of July and September when fresh breadfruit is unavailable. The fermented paste is most often prepared for consumption by rubbing on a board to produce a dry crumbly substance called drikwal which is wrapped in the breadfruit leaves and baked for about an hour (Pollock, 1974).
There are numerous ways of preparing fresh breadfruit for consumption but generally the fruits are either baked or boiled. Traditionally, on many of the South Pacific Islands breadfruit is baked or roasted simply by placing fruits on heated stones, coral or charcoal (Anonymous, 1951; Coenen and Barrau, 1961; Pollock, 1974). In Hawaii an underground oven or imu is used (Miller et al., 1937). In the East Caroline Island of Kapingamarangi a dish known as ti-kul palpon is very popular. The breadfruit is picked when nearly mature and stored until ripe. The rind, core and seeds are then removed and the hole left by removal of the core filled with coconut cream. The hole is plugged using a section of the core and the fruit wrapped in green breadfruit leaves tied firmly and baked for 1 hour (Coenen and Barrau, 1961).
A Tahitian dish known as poe uru is prepared by first cooking the entire breadfruit in an oven, peeling the fruit and reducing it to a paste to which is added a mixture of cassava starch and water. The paste which has gelatinous consistency is sweetened and seasoned with lemon juice and then divided into portions, wrapped in banana leaves and cooked again in an oven. Poe uru is served with sweetened coconut cream (Massal and Barrau, 1954).
Roasted breadfruit is also an important part of the West Indian diet, ripe fruit being piled over glowing embers and allowed to cook slowly for about 1 hour after which time the charred skin and fruit core are removed before eating (Brotbaum, 1933). Steamed breadfruit mixed with grated coconut is also popular, and pounded, steamed or boiled fruit is used to prepare a mashed product, cou-cou, which can also be prepared from other starchy ingredients (C.I.A.T./I.A.D.B., 1979). In parts of Indonesia the seedless form of breadfruit is cut into slices and fried in oil either as a main meal or for consumption as a delicacy (Ochse, 1931). In some areas the fruits of seeded varieties are considered not fit to be eaten although the ripe seeds are sometimes prepared as a delicacy (Ochse, 1931).
There are about 600 species of Pandanus, the most widespread being P. odoratissimus L.f. (P. tectorius Soland ex Park.), which is commonly found on sea coasts and islands from southeastern Asia eastwards to the islands of the South Pacific (Purseglove, 1972). Other edible species include P. brosimus Merr. and Perry, P. jiulianetii Mart., P. leram Jones, P. utilis Bory. The Pandanus fruit is an important food on many of the Pacific atolls, especially in Micronesia, although it is little used elsewhere. It is eaten raw or cooked and is preserved in the form of flour or paste (Stone, 1963).
The fruit is allowed to ripen naturally on the tree although ripening is sometimes hastened by twisting the fruit to separate the fruit stem (Hiyane, 1971). When eaten raw the fleshy base of the fruit is chewed to extract the soft pulp and sweet juice (Hiyane, 1971). The boiled fruit is often mixed with either coconut milk or grated coconut, or with other starchy foods and eaten hot or cold (Catala, 1957; Stone, 1963). For storage purposes a flour or paste is prepared, the former being more common in Kiribati while the latter is used more in the Marshall Islands of the Trust Territories of the Pacific Islands (Stone, 1903).
A paste known as mokan in the Marshall Islands is prepared by either boiling the phalanges of the fruit or baking them in an earth oven for 12 to 48 hours. The pulp is then grated and spread out on leaves for sun-drying to form a dry paste which is then further dried over a hot stove into thick firm cakes. These are then wrapped in Pandanus leaves and tied with coconut cord for storage (Hiyane, 1971; Miller et al., 1956). The pulp is sometimes mixed with arrowroot flour and sugar before drying (Hiyane, 1971). Flour is made in a similar way but the fruit is only cooked for about an hour. After cooking the pulp is pounded, sun-dried and dried further over heated rocks. The cakes thus formed are then pounded to obtain a coarse flour (Miller et al., 1956) . Both the flour and paste can be stored for several years and traditionally formed an important part of the provisions taken on long sea journeys (Hiyane, 1971; Miller et al., 1956; Stone, 1963). A number of other dishes are prepared from Pandanus fruit and have been described by various authors (Catala, 1957; Hiyane, 1971; Miller et al., 1956).
H. Starches derived from stem crops
Some vegetative stem crops have a localized importance as foods, most notably the Ensete bananas, Ensete ventricosa (Welw.) Cheesm. in Ethiopia and the sago palms Metroxylon sagu Rottb. and M. rumphii Mart. in Southeast Asia and Melanesia and other palms used similarly elsewhere. Once felled, these plants are never stored for any substantial period but are processed immediately.
SAGO
The techniques used to extract sago starch and the methods of storage of sago are very similar throughout the tropics and have recently been reviewed in some detail by Puddle et al. ( 1978) and Stanton and Flach ( 1980) . Palms are selected for high starch content, determined according to the stage of maturity of the palm or sometimes by sampling the pith, felled and cut open. Generally, the pith is removed by a combination of pounding and scraping and the starch is then washed out, the pith being kneaded with water by hand in a trough or trampled with the feet. The water in which the starch is suspended is then run off through a filter into a settling vessel. The system of troughs used for these processes is frequently made out of portions of the felled palms, and is usually erected near a stream from which water is collected by means of a simple long-handled dipper of palm spathe or coconut shell. Sago starch can be stored for some time. For example, it can be stored for a few weeks by wrapping in leaves and hanging to dry in the sun or, for longer storage, by burying the leaf-wrapped packets under mud and water in the sago swamps. Heating or toasting the sago extends its storage life further (Ruddle et al., 1978).
In Southeast Asia much of the sago used for subsistence purposes is consumed as pearl sago. This is prepared in Sarawak by taking wet sago which is mixed with rice bran and grated coconut and leaving the misture overnight. This allows time for yeasts and lactobacilli to give the mixture a slightly acidic flavour. The next day the dough is mixed thoroughly on a Pandanus mat during which process it forms into small pellets. The material is then sieved and any unformed dough re-shaken. The moist pellets are then baked on a clay hearth for 20 to 30 minutes with constant stirring during which time the pearls of sago develop a dark brown colour (Ruddle et al., 1978).
Sago starch can be cooked in a variety of ways. For example, it is often mixed with boiling water to produce a thick porridge or combined in water with leafy greens and meat to make a stew. It may be roasted in bamboo tubes or wrapped in leaves or baked as a flat cake on griddles of stone, earthenware or metal (Ruddle et al., 1978).
ENSETE
In the Sidamo area of Ethiopia the population relies on Ensete as a staple food (Taye and Asrat, 1960; Westphal, 1977). The pseudostem pulp is extracted and placed in a circular leaf-lined pit about 1 m in diameter and 1 m deep and when full covered over and weighted with stones and left to ferment. After 3 or 4 weeks the pit is opened and some strongly fermented Ensete from an older silo is added to accelerate the fermentation. After a further 4 weeks the pit is opened again and the contents rearranged and the pit reclosed, the total fermentation time taking from a few weeks to several months and sometimes up to a year. The fermented product is known as kojo and is mixed with spices and used for making bread which is generally baked on iron griddles or clay pans over a fire. However, in one district the spiced dough is wrapped in leaves and put in a pit about 80 cm in diameter and 80 cm deep and covered with layers of soil and Ensete leaves, on top of which the fire is kept burning for at least 12 hours. The bread thus prepared will keep several days (Anonymous, 1958; Smeds, 1955; Taye and Asrat, 1966).
Another product known as boulla is prepared from the scrapings of parenchymatous tissue of the pseudostem from which the juice is pressed out and the residue then dehydrated. This is then packed in Ensete leaves and left in a silo for fermentation after which it is eaten in the form of a porridge (Anonymous, 1958; Smeds, 1955; Taye and Asrat, 1966).