Caballero B. (ed.) Encyclopaedia of Food Science, Food Technology and Nutrition. Ten-Volume Set

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techniques like cold chain, refrigeration, and con-

trolled-atmosphere storage, and with the develop-

ment of rapid transport by land, sea, and air, trade

in such highly perishable commodities is growing

steadily. (See Controlled-atmosphere Storage: Effects

on Fruit and Vegetables.)

0008 The USA imports tropical vegetables from Mexico

and other Latin American countries, the European

countries import these vegetables from the Middle

East and some countries of North Africa, and the

Persian Gulf countries import vegetables mostly

from the Indian subcontinent and other South Asian

countries. Apart from fresh vegetables, processed

products enjoy a good international trade. Taiwan is

the major country exporting processed vegetables to

several countries.

0009 Information on international trade in some of the

vegetables dealt with is meager, but from the point of

view of their nutritive value, these vegetables deserve

attention for future exploitation in the world market.

Importance of Specific Tropical

Vegetables

0010The importance of individual vegetables in nutrition,

diet, commerce, and world trade is discussed under

separate groups.

Beans

0011The major crops are the cluster bean (Cyamopsis

tetragonoloba), cowpea (Vigna unguiculata), French

bean or kidney bean (Phaseolus vulgaris), hyacinth

bean (Lablab purpureus), lima bean (Phaseolus luna-

tus), and winged bean (Psophocarpus tetragonolo-

bus). Beans (also called legumes) are second only to

cereals as a source of human food. Nutritionally, they

are rich in proteins, soluble carbohydrates, and vita-

mins. The essential amino acid composition of trop-

ical beans is given in Table 4. Most beans are deficient

in sulfur-containing amino acids, and a few are

deficient in tryptophan. Sprouted seeds contain

more vitamin, particularly vitamin C. Consumption

of food legumes has been reported to decrease the

concentration of cholesterol. (See Beans; Legumes:

Legumes in the Diet.)

0012Legumes offer a variety of edible products. Mature

seeds, known as pulses, serve as the major item of diet

in the Indian subcontinent and China. Immature pods

along with seeds of all the beans listed, except lima

bean, are used as a cooked vegetable before the fibers

lignify and harden. Lima bean seeds (green or dried)

are boiled or baked and used as a side-dish. Only

lima beans and French beans are canned or frozen.

Canned beans in tomato sauce are an important item

of commerce.

Cucurbits

0013Cucurbits constitute the largest group of tropical

vegetables, consisting of the bitter gourd (Momordica

charantia), bottle gourd (Lagenaria siceraria), cho

cho or chayote (Sechium edule), cucumber (Cucumis

sativus), Indian squash (Praecitrullus fistulosus), ivy

tbl0002 Table 2 Important trace elements of some tropical vegetables

(mg per 100 g)

Cu Mn Zn

Amaranth 0.08 0.36 0.18

Bitter gourd 0.10 0.08 0.46

Bottle gourd 0.03 0.06 0.22

Brinjal 0.12 0.13 0.22

Cluster bean 0.08 0.10 0.36

Cucumber 0.09 0.14 0.23

Drumstick 0.01 0.05 0.16

Drumstick leaves 0.07 0.37 0.16

Fenugreek leaves 0.01 0.23 0.36

French bean 0.06 0.12 0.42

Okra 0.11 0.15 0.42

Ridge gourd 0.08 0.07 0.38

Snake gourd 0.27 0.14 0.31

Sweet potato 0.02 0.22 0.11

Yam 0.12 0.12 0.45

Source: Gopalan C, Sastri BVR, Balasubramanian SC et al. (1999) Nutritive

Value of Indian Foods. Hyderabad: National Institute of Nutrition.

tbl0003 Table 3 Essential amino acid content (g) of vegetable leaves per 100 g of protein

Amino acids Amaranth Colocasia Drumstick Fenugreek Pumpkin

Arginine 3.8 4.0 6.1 5.6 6.9

Histidine 2.1 2.1 2.2 1.8 1.6

Isoleucine 4.6 5.0 4.5 5.3 5.0

Leucine 5.9 5.8 7.4 6.2 10.1

Lycine 4.0 4.2 5.1 4.8 5.4

Methionine 1.1 1.0 1.8 1.4 1.8

Phenylalanine 2.9 2.9 4.6 4.8 5.4

Threonine 2.2 2.4 4.0 3.2 5.0

Tryptophan 1.1 0.6 1.6 1.3 1.3

Valine 4.5 4.5 5.6 5.1 5.8

Source: Gopalan C, Sastri BVR, Balasubramanian SC et al. (1999) Nutritive Value of Indian Foods. Hyderabad: National Institute of Nutrition.

5958 VEGETABLES OF TROPICAL CLIMATES/Commercial and Dietary Importance

gourd (Coccinia indica), kakrol (Momordica dioica

and M. cochinchinensis), muskmelon or cantaloupe

(Cucumis melo), pumpkin (Cucurbita moschata),

summer squash (Cucurbita pepo), winter squash

(Cucurbita maxima), ridge gourd (Luffa acutangula),

sponge gourd (Luffa cylindrica), snake gourd

(Trichosanthes cucumerina), pointed gourd (Tricho-

santhes dioica), watermelon (Citrullus lanatus), and

wax or ash gourd (Benincasa hispida). (See Melons,

Squashes, and Gourds.)

0014 Cucurbits, in general, are not rich in calories, min-

erals, or vitamins. There are a few exceptions like

the bitter gourd, which is rich in vitamin C, the

squash, pointed gourd, and muskmelon, which con-

tain large amounts of carotene (provitamin A), the

kakrol, which is high in protein, and the pointed

gourd, which is rich in calcium. Some of the species

of Cucumis, Luffa, Coccinia, and Momordica exhibit

varying degrees of bitterness in the fruits, leaves, and

twigs, caused by terpenes called momordicins. Owing

to its bitter principle, the bitter gourd is used in the

Ayurvedic system of medicine in India. Scientists have

isolated a hypoglycemic phytoceutical, cheratin, in

the fruit, which causes a lowering of blood sugars.

(See Hypoglycemia (Hypoglycaemia).)

0015 The cucumber is mostly used as a salad crop. Imma-

ture fruits, also called gherkins, are pickled in various

ways. Muskmelon and watermelon are used fresh as

dessert fruits, alone or in combination with other fruits

in salads. Watermelon rind is pickled. In Russia, beer is

produced from watermelon juice. Pumpkin and squash

fruits are cooked with other vegetables or used in pie-

making. Luffa, bottle gourd, ash gourd, bitter gourd,

pointed gourd, and Indian squash are cooked, and

some are fried for the preparation of various dishes.

Mature ash gourd fruits are used in making sweet

candy in India. Leaves, twigs, and flowers of squash,

pumpkin, and ash gourd are consumed in the tropics.

0016Most cucurbits are used fresh. Some of the cucur-

bits, such as bitter gourd, pointed gourd, coccinia,

squash, and pumpkin, are canned and some frozen.

Squash, pumpkin, melons, and cucumber are shipped

to distant markets. During the winter, cucumbers

from tropical countries are exported to Europe and

North America. A variety of muksmelon called Sarda,

which is grown in Afghanistan, is exported to several

countries.

Leafy vegetables

0017In the tropics, apart from cultivated leafy vegetables,

a large number of leaves from different sources such

as perennial trees, aquatic plants, and annuals other

than vegetable crops are consumed. The most import-

ant of these are amaranth (Amaranthus sp.), Basella

(Basella alba), bitter gourd (Momordica charantia),

bottle gourd (Lagenaria siceraria), cassava (Manihot

esculenta), Chinese cabbage (Brassica chinensis),

cowpea (Vigna unguiculata), drumstick (Moringa

oleifera), fenugreek (Trigonella sp.), jute (Corchorus

olitorius), mustard and rape (Brassica sp.), pumpkin

(Cucurbita moschata), purslane (Portulaca oleracea),

sweet potato (Ipomoea batatas), taro (Colocasia

esculenta), water spinach (Ipomoea aquatica), and

winged bean (Psophocarpus tetragonolobus). Most

leafy vegetables are rich in carotenes, fibre, and min-

erals. Several studies have demonstrated an inverse

relationship between a diet rich in carotenoids and

lung cancer. Dietary fibre may help prevent certain

cancers, such as cancer of the colon and rectum. (See

Amaranth; Mustard and Condiment Products.)

0018Some of the leafy vegetables contain toxic ingredi-

ents. Cassava leaves contain glucosides that may lib-

erate hydrocyanic acid by the action of enzymes. It is

highly volatile, and therefore, any preparation that

involves heating will render the leaves harmless.

Amaranth, Portulaca, Celosia, and Basella contain

tbl0004 Table 4 Essential amino acid content (g) of bean seed per 100 g of protein

Amino acids Cowpea

(Vigna unguiculata)

Cluster bean

(Cyamopsis

tetragonoloba)

French bean

(Phaseolus

vulgaris)

Hyacinth bean

(Lablab

purpureus)

Lima bean

(Phaseolus

lunatus)

Winged bean

(Psophocarpus

tetragonolobus)

Arginine 7.3 12.5 5.1 6.6 6.3 4.7

Histidine 3.2 2.5 2.6 3.2 3.2 3.2

Isoleucine 4.0 3.2 4.2 4.4 5.3 4.4

Leucine 7.2 5.9 8.1 8.5 8.9 7.0

Lysine 6.4 4.0 6.7 6.8 7.5 7.7

Methionine 1.2 1.4 0.9 0.9 1.2 1.3

Phenylalanine 6.0 3.7 5.3 4.9 6.4 5.0

Threonine 3.6 2.8 4.2 4.2 5.1 4.8

Tryptophan 1.9 1.5 3.5

Valine 4.7 4.2 5.1 5.2 5.8 6.1

Source: Duke JA (1981) Handbook of Legumes of World Economic Importance. New York: Plenum Press; Summerfield RJ and Roberts EM (eds) (1985) Grain

Legume Crops. London: Collins.

VEGETABLES OF TROPICAL CLIMATES/Commercial and Dietary Importance 5959

appreciable quantities of oxalic acid and oxalates.

Oxalic acid converts calcium from food consumed to

insoluble calcium oxalate, rendering it unavailable for

absorption. In amaranth, under certain conditions,

the nitrate content of leaves exceeds tolerable limits.

Both of these problems can be eliminated by boiling

and discarding the cooking water. Calcium oxalate,

present in the form of fine crystals in the leaves of

taro, causes itching of the fingers and a pricking

sensation on the tongue and throat. This can be re-

moved by adding a little tamarind or citric acid to the

cooking water and then discarding the water. (See

Cassava: The Nature of the Tuber; Plant Antinutri-

tional Factors: Detoxification.)

0019 Leafy vegetables are mostly used fresh as they

are highly perishable. They are fried or boiled singly

or in combination. Some of the leafy vegetables are

dried for use out of season and for export to a limit-

ed extent to meet the requirements of the ethnic

population. Examples are fenugreek and curry leaves

in India, jute leaves in Egypt, and baobab leaves in

West Africa. Mustard leaves are considered an item of

delicacy in the Indian subcontinent and are exported,

after canning, for the ethnic population abroad. Some

of the dried and powdered leafy vegetables, which are

rich in carotene and minerals, can be blended with

cereal flours to improve the nutritional status of

people of the developing world who often suffer

from nutritional deficiency diseases.

Okra

0020 Okra (Abelmoschus esculentus) fruits are not a rich

source of nutrients, but they do supply some minerals

and vitamins. A considerable amount of okra is

processed by drying, freezing, canning, and pickling.

Okra pods have a mucilaginous substance that inter-

feres with processing and remains in the canned prod-

uct also. To overcome this, slices can be canned in

tomato sauce.

0021 A considerable quantity of okra is air-freighted from

India to distant markets in the Persian Gulf countries.

Solanaceous Vegetables

0022 Major crops are tomato (Lycopersicon esculentum),

brinjal or egg plant (Solanum melongena), sweet

pepper or Capsicum and hot pepper or chilli (Cap-

sicum annum). (See Potatoes and Related Crops:

Fruits of the Solanaceae; Tomatoes.)

0023 In most countries, the tomato ranks second after

the potato in production and consumption. It is a

low-calorie vegetable and is a good source of vitamins

A and C. The content of these vitamins is less in fruits

ripened off the vine than in those ripened on the

plants. The red color of tomato is due to a carotenoid

pigment, lycopene. Egg plants contain substantial

amounts of some vitamins and minerals. Several

chemicals that help lower cholesterol have been

detected in brinjal in a recent study. Brinjal is also

rich in bioflavonoids, which can provide protection

from stomach cancer. Peppers are rich in vitamins A

and C, and the pungency of hot peppers is due to

capsaicin.

0024Tomatoes serve as the major ingredient of salads.

Tomatoes are commercially the most important vege-

table used for processing to make sauce, ketchup,

pure

e, etc. and are also preserved by canning. In the

present fast-food era, the tomato is an indispens-

able ingredient of hamburgers, pizzas, and pastas.

Sweet peppers are boiled, stuffed, and baked to pro-

duce various dishes. Hot peppers are dried and used

as spices, mostly in the tropics. They are also pickled

in oil. The mild, nonpungent varieties of chilli,

commonly known as paprika, are valued chiefly for

their brilliant red color and mild flavor and are used

for coloring dishes. Chilli extracts are used in the

preparation of ginger beer and are also used in

the preparation of chilli sauces. The eggplant is an

important vegetable of Asia, and the fruits are fried,

roasted, baked, or cooked to prepare various dishes.

Boiled and hollowed eggplants are stuffed with

potato, fish, or meat and are also canned.

0025The tomato occupies a prominent position in world

trade, mostly in the form of processed finished prod-

ucts or as an intermediate, tomato paste. Some quan-

tities of fresh fruits are also air-freighted. According

to an FAO estimate, the total world export of tomato

and all types of pepper (Capsicum, chilli, paprika,

etc.) during 1997 was 2.80 million tonnes and 0.21

million tonnes, respectively. The European countries

rank first in tomato export, exporting 1.99 million

tonnes with a market share of 71.07% and for pepper,

Asian countries are the largest exporters, with a

61.90% market share, exporting 0.13 million tonnes.

India is the largest exporter of dry chillies and oleo-

resin. There is considerable demand for paprika

powder in the Western countries.

Starchy Roots, Tubers, and Corms

0026The major root crops are sweet potato (Ipomoea

batatas) and cassava or manioc (Manihot esculenta),

a tuberous crop is yam (Dioscorea sp.), and the corm

crops are arum or taro (Colocasia esculenta), tannia

(Xanthosoma sp.), and elephant-foot yam (Amorpho-

phallus campanulatus). These crops are important

sources of energy in many tropical countries. These

vegetables are high in starch. The yellow-fleshed

sweet potato is rich in carotene (provitamin A).

Cassava and sweet potato contain considerable

amounts of vitamin C. Cassava roots contain a toxic

5960 VEGETABLES OF TROPICAL CLIMATES/Commercial and Dietary Importance

hydrocyanic glucoside, which, on enzymatic action,

liberates HCN; the harmful effect can be destroyed by

peeling, washing, and boiling. Some species of Dios-

corea contain a toxic alkaloid, dioscorine, which can

be destroyed by roasting or boiling. (See Alkaloids:

Toxicology.)

0027 Sweet potatoes are baked, boiled, fried, or pre-

pared mixed with other vegetables. They are used

for the production of alcohol. Taro, tannia, cassava,

and yam are fried, roasted, baked, or boiled for the

preparation of various dishes. Taro is recommended

for gastric patients, and its flour is a good baby food.

In Hawaii, a fermented product prepared from taro is

very popular. In Africa, a paste prepared from taro,

after boiling, is consumed. The leaves and young

shoots are used as greens. Cassava roots are processed

to produce starch and tapioca granules. Yam is used

for the preparation of chips, flakes, and flours. A

sapogenin compound called diosgenin, present in

some species of yam, is used for the production of

cortisone and contraceptive drugs.

0028 Cassava is an important staple food of Africa.

Being perishable in nature, it is mostly consum-

ed locally where it is grown. Some fresh cassava

roots are air-freighted to the USA from Venezuela.

Yams are also a staple food in some African countries

and South-east Asia. Mostly, they are consumed lo-

cally where they are produced, but some quantities

are shipped to distant markets. Taro and tannia can be

shipped to distant markets because of their good

keeping qualities. Taro is more popular in Asia and

tannia in Africa.

Other Vegetables

0029 There are several other vegetables, like plantain

(Musa paradisiaca), bread fruit (Artocarpus altilis),

jack fruit (A. heterophyllus), papaya (Carica papaya),

drumstick (Moringa oleifera), and lotus (Nelumbo

nucifera), which are popular in the tropics. The plan-

tain is high in carbohydrate and provitamin A. The

fruits, pseudostem, and inflorescence are cooked, as

they contain a considerable amount of tannin, which

renders them unpalatable even when ripe because of

astringency. The fruits are boiled or cooked to pre-

pare various dishes and are also used for making

alcohol. The inner sheaths of the pseudostem of

banana are cooked in India, and the immature, male

flower buds, after removal of the boat-like fibrous

bracts, are cooked in many South Asian countries.

(See Papayas.)

0030 Immature bread fruits and jack fruits are used as

vegetables in many countries of Asia; the fruits, when

tender, contain a high level of starch. After removing

the skin and outer layer of the fruit, the flesh is sliced

or cubed and then boiled, cooked, or fried. In India,

seeds of mature jack fruit are cooked, and drum stick

is a popular vegetable. Lotus rhizomes, commonly

called roots, are cooked in many Asian countries.

0031Maize (also called sweetcorn) is popular in Western

countries and is rich in starch. The tender cobs are

consumed raw, boiled, or roasted and can be canned

or frozen.

0032These vegetables have local demand and are mostly

consumed where they are produced.

See also: Alkaloids: Toxicology; Amaranth; Beans;

Cassava: The Nature of the Tuber; Controlled-

atmosphere Storage: Effects on Fruit and Vegetables;

Hypoglycemia (Hypoglycaemia); Legumes: Legumes

in the Diet; Melons, Squashes, and Gourds; Mustard

and Condiment Products; Papayas; Plant

Antinutritional Factors: Detoxification; Potatoes and

Related Crops: Fruits of the Solanaceae; Tomatoes;

Vegetables of Temperate Climates: Commercial and

Dietary Importance

Further Reading

Bose TK, Som MG and Kabir J (eds) (1993) Vegetable

Crops. Calcutta: Naya Prokash.

Choudhury B (1990) Vegetables, 8th edn. New Delhi:

National Book Trust.

Decoteau DR (2000) Vegetable Crops. Englewood Cliffs,

NJ: Prentice Hall.

Duke JA (1981) Handbook of Legumes of World Economic

Importance. New York: Plenum Press.

FAO (1968) Food Composition Table for Use in Africa.

Bethesda, MD: FAO and US Department of Education

and Welfare.

FAO (1972) Food Composition Table for Use in East Asia.

Rome: FAO.

Gopalan C, Sastri BVR, Balasubramanian SC et al. (1999)

Nutritive Value of Indian Foods. Hyderabad: National

Institute of Nutrition.

Jeana G (1991) Pigments in Vegetables. New York: Van

Nostrand Reinhold.

Oomen HAPC and Grubben GJH (1977) Tropical Leaf

Vegetables in Human Nutrition. Communication 69.

Amsterdam: Department of Agricultural Research,

Royal Tropical Institute.

Sharon M (1999) Nutrients A to Z. London: Prion Books.

Summerfield RJ and Roberts EH (eds) (1985) Grain

Legume Crops. London: Collins.

Tindall HD (1983) Vegetables in the Tropics. London:

Macmillan.

Vaclavik VA (1998) Essentials of Food Science. New York:

Chapman & Hall.

Watt BK and Merrill AL (1963) Composition of Foods –

Raw, Processed, Prepared. Agricultural Handbook No.

8. Washington, DC: USDA.

Yamaguchi M (1983) World Vegetables. New York: Van

Nostrand Reinhold.

VEGETABLES OF TROPICAL CLIMATES/Commercial and Dietary Importance 5961

Root Crops of Uplands

SKO’Hair, University of Florida, IFAS, Tropical

Research and Education Center, Homestead, FL, USA

D N Maynard, University of Florida, IFAS, Gulf Coast

Research and Education Center, Bradenton, FL, USA

Introduction

0001 Highland and midaltitude tropical root crops include

several little-known crops that are regionally valued as

stable foods in the South American Andes. Nearly all

are ancient foods, domesticated possibly by pre-Incan

people. All are either solely or mainly propagated

through vegetative cuttings. It has been speculated

that somatic mutations are a likely source of many of

the varieties, since flowering and seed set are rare in

many. Several are considered to be underexploited and

deserving of considerably more scientific and commer-

cial attention. Since these crops are mostly propagated

vegetatively, appropriate methods to control the

spread of diseases should be observed.

Ahipa

0002 Ahipa (Pachyrhizus ahipa (Weddell) Parode, Family

Fabaceae), also known as ajipa or Andean yam

bean, is one of the few leguminous plants cultivated

for its edible roots. When Rhizobium is present,

the plant can fix nitrogen. Its crisp, white roots are

very similar to those of its close relative, jicama

(P. erosus).

0003 Production is mainly limited to Peru and Bolivia at

elevations of 1500–3000 m. Although there is little

commercial importance for this crop, the potential

exists for it to be grown as a vegetable in temperate

regions for use as a fresh or salad vegetable. There are

no recorded varieties of this crop. However, landraces

are known to exist.

0004 Each plant produces one enlarged root weigh-

ing 0.5–0.8 kg. A relatively thin, pale yellow skin

covers the white flesh. Root production is signifi-

cantly increased by manual removal of entire inflores-

cences.

0005 Most plant parts are toxic, except for the enlarged

edible storage root. Roots can be eaten raw or cooked.

Specific nutritional data are not known. However,

they are likely to be similar to its close relative,

jicama.

0006 Little is known about either handling or storage

after harvest. Roots are normally harvested as needed

since they lose moisture quickly after harvest.

0007 There are no current industrial uses for the crop.

Arracacha

0008The arracacha or Peruvian carrot (Arracacia xanthor-

rhiza Bancroft, Family Apraceae) is grown for its

edible roots, which have been described by the noted

naturalist, David Fairchild, as one of the tastiest of all

vegetables.

0009Of the crops covered in this article, arracacha pro-

duction has spread to other food production areas the

most. Current production areas include much of

South America, Puerto Rico, Mexico, and parts of

Africa. In the Andean region, production is found

between 1800 and 2600 m. At higher latitudes, pro-

duction is found at lower elevations. Commercial

trade is limited to local markets. Plants are normally

propagated vegetatively as clones of three general

types: white, yellow, and purplish. Viable seeds are

produced on older plants, resulting in possibilities for

numerous varieties.

0010Storage organs arise as enlargements of a main

cylindrical rootstock with enlarged edible lateral,

parsnip-like roots near the base of the plant. The

young blanched stems can also be eaten.

0011Peeled roots have nutritional qualities similar to

other root and tuber crops (Table 1). Refer to individ-

ual nutrients.

0012Harvested roots have a short shelf-life of 1 week or

less. Thus, roots are harvested as needed. However, as

the roots age, they become fibrous and, eventually,

unpalatable. Little research has been carried out

regarding postharvest handling of the roots. Refriger-

ated storage at 3



C extends the storage period. They

can be frozen, like cassava, for shipment to foreign

markets. (See Cassava: The Nature of the Tuber.)

tbl0001Table 1 Average composition (per 100 g of raw product) of

tropical root crops

Constituent Arracacha Yacon Canna Oca Mashua Ulluco

Moisture (g) 72 79 75 82 85 86

Carbohydrate (g) 25 24 16 11 11

Starch (g) 15 20

Sugars (g) 12

Protein (g) 1 1.5 1 1 1.6 1.8

Fat (g) 0.1 0.1 0.1 0.1 0.1

Fiber (g) 0.7 1 0.6 0.8 1.2 0.6

Ash (g) 1.6 1 1.4 0.5 0.5 0.7

Calcium (mg) 24

Phosphorus (mg) 65

Iron (mg) 0.7

Vitamin A (IU) 40

Ascorbic acid (mg) 21.5

Data from Kay DE (1973) Root Crops. London: Tropical Products Institute;

King SR (1987) Four endemic Andean tuber crops: promising food

resources for agricultural diversification. Mountain Research and

Development 7: 43–52; National Research Council (1989) Lost Crops of the

Incas. Washington, DC: National Academy Press, with permission.

5962 VEGETABLES OF TROPICAL CLIMATES/Root Crops of Uplands

0013 There is no commercial processing of arracacha.

However, it is a popular source of carbohydrate

among children. Starch can be extracted from both

the main rootstock and lateral roots.

Edible Canna

0014 Achira (Canna edulis Ker-Gawler Family Canna-

ceae), sagu, or Queensland arrowroot, is similar in

appearance to its close relative, the ornamental

canna. A related species grown in South-east Asia is

C. discolor Lindl.

0015 Production is found throughout the low- to mid-

altitude tropics, with most concentrated in South

America, especially in Peru, where it is a valued

crop. Its commercial importance is limited to starch

production in a few regions and production as a

staple food in parts of Peru, Ecuador and South-east

Asia. Starch extracted from rhizomes is used to pro-

duce noodles in Asia. Two main types are described,

one with white corms and green foliage, and a second

with violet-skinned corms. There are many variations

in plant characteristics.

0016 The storage organ forms at the lower part of the

stem, at or below the soil surface, forming a corm.

Occasionally, plants form a rhizome, which may be a

factor of clonal variation or environmental conditions.

0017 Nutritional composition is similar to most of the

root and tuber crops (Table 1). The rhizomes are high

in food value, containing 70% carbohydrate, 12%

protein, and 22% fiber on a dry-weight basis. Edible

canna is one of the few root and tuber crops that can

be eaten raw. Thus, nutritional value is maximized if

the corms are eaten uncooked. The starch granules

are among the largest known and considered to be

easily digested by infants and invalids.

0018 Little is known about the handling and storage of

this crop. Usually, the plant is harvested as needed.

However, as the corms age beyond 8–10 months, the

fiber content increases.

0019 Mechanization exists for most stages of produc-

tion, and the crop is widely adaptable. Thus, there is

potential for greater exploitation of this crop as a

source of speciality starch.

Maca

0020 The turniplike maca (Lepidium meyenni Walp.,

Family Brassicaceae) is among the least-known of

the Andean root and tuber crops. There are at least

29 cultivated varieties in the Andes.

0021 Nearly all of the production is between 3500 and

4000 m in the Peruvian and Bolivian Andes. Because

of their altitude constraints, the potential for com-

mercialization is limited. Elite plants are selected and

cultured with added care to procure botanical seed

for the next crop. Yellow-fleshed types are preferred.

0022Storage organs arise as enlargements of the root

region of the plant.

0023Roots have high concentrations of sugars and

starch. Low quantities of alkaloids, fatty acids,

tannins and saponins in the roots have been reported.

(See Alkaloids: Properties and Determination; Sap-

onins; Tannins and Polyphenols.)

0024Roots are aromatic and occasionally used as a

flavoring agent. They are dried and stored for 1 or

more years in protected, cool locations. However, the

flavor deteriorates over time. In Peru maca is pro-

cessed and marketed for its medicinal and therapeutic

properties.

Mashua

0025Mashua or an

u(Tropaeolum tuberosum Ruiz and

Pav., Family Tropaeolaceae) is little known outside

of its native production areas in the high Andes of

South America. However, it resembles its close

relative, the ornamental nasturtium.

0026Most of the production is limited to altitudes above

3000 m in Bolivia and Peru, with little commercial-

ization. The area of production in Peru is estimated to

be 4000 ha. Plants are vegetatively propagated as

clones, with over 100 being recognized by their vari-

ation in tuber coloration.

0027Edible tubers are conical or ellipsoidal, 5–15 cm in

length and 3–6 cm in width. Skin colors can be very

attractive, ranging from white or yellow to red or

purple. The flowers are also edible.

0028In comparison with other root and tuber crops,

some mashua tubers have a relatively low moisture

content of 55%. Most are comparable with the other

root and tuber crops (Table 1), yet genetic variation in

protein content and quality has been documented.

Tubers provide an adequate balance of amino acids,

with leucine being low (Table 2). Some clones are

reported to have medicinal properties through the

production of a mustard oil, which is used for treat-

ment of kidney and liver diseases. Others reportedly

have low degrees of antiaphrodisiac properties. Nu-

tritional information for the flowers is not available.

(See Protein: Quality.)

0029Little is known about handling and storage, since

there is little commercial trade in this crop. Typically,

one would expect the handling and storage require-

ments to be similar to those of potato. In the high

Andes, tubers are frozen like chun

o, a freeze-dried

whole tuber that can be reconstituted in water.

0030Currently, there is little or no production of

mashua for industrial purposes. Some cultivars have

pesticidal properties.

VEGETABLES OF TROPICAL CLIMATES/Root Crops of Uplands 5963

Oca

0031 Of the Andean root and tuber crops, oca (Oxalis

tuberosa Molina, Family Oxalidaceae) is possibly

the oldest and is second in importance in Andean

regions only to potato. However, it is considered to

have the potential of great consumer appeal, because

of the brilliant color and pleasant flavor of the tubers.

0032 Until recently, production of oca has been limited

to altitudes of 2500–4000 m the Andes and parts of

Mexico. In Peru, there are more than 16 000 ha in

production. It has recently been commercialized in

New Zealand. Reportedly, the potential exists for it

to become a temperate region crop. In the Andes,

there are approximately 50 cultivated clones. Andean

germplasm collections have over 400 accessions.

0033 Storage organs are formed on underground stolons,

resulting in the production of elongated or rhizomic

tubers 3–20 cm long.

0034 Large amounts of variation in nutritional qualities

are present among oca clones. In general, they are

considered to have a food value comparable with

potato (Table 1). The protein is of a high quality,

being low in valine and tryptophan (Table 2). The

carbohydrate component is largely sugar. Some

tubers have levels of oxalic acid that are detectable

when tubers are eaten raw, giving them a slightly acid

taste. Oxalic acid concentrations can be as high as

500 p.p.m., but are generally only 1% of those found

in spinach.

0035 Little information on handling and storage is avail-

able. In the Andes, tubers are placed in the sun for a few

days to increase the sugar content. However, owing to

the high moisture content, handling should include

means to control moisture loss. Alternatively, the

tubers can be dried, producing a high-carbohydrate

food. In the high Andes, tubers are ‘freeze-dried’ and

stored for several years. (See Drying: Drying Using

Natural Radiation; Freeze-drying: The Basic Process.)

0036Currently, there are no industrial uses for the crop.

The starch is considered to be a quality product.

Ulluco

0037Ulluco or ullucu(s) (Ullucus tuberosus Caldas, Family

Basellaceae) is one of the more popular members of

the Andean root and tuber crops, being considered a

delicacy by many.

0038Production is mostly limited to the Andean region.

Unlike most of the other crops discussed in this art-

icle, there is commercial trade of this crop in larger

South American cities. There are more than 15 000 ha

under cultivation in Peru. Plants are propagated

vegetatively as clones, with most being separated

according to their flesh color, which almost covers

the color spectrum. It is estimated that there are at

least 50–70 distinct clones in the Andean region.

0039Tubers, resembling small potatoes, are produced

on underground stolons. Most are elongated or

slightly curved. The tuber skin is thin and soft, with

inconspicuous buds. The flesh is low in fiber content.

0040The nutritional value of ulluco is similar to the

other crops discussed in this article (Table 1). Un-

documented reports suggest a much higher protein

content. The amino acid balance is adequate; valine

and tryptophan content are low (Table 2). Detectable

levels of saponin are present in plant parts.

0041Tubers are usually harvested as needed. If stored,

they must be kept in dark locations. In the light, tuber

skins turn green, like potatoes stored in areas exposed

to light. In the high Andes, tubers are ‘freeze-dried.’

0042Tubers are dried and milled into flour. They can

also be used to make chun

Yacon

0043Yacon or jiquima (Polymnia sonchifolia Poepp &

Endl., Family Asteraceae), a native of North America,

is a perennial herb being somewhat similar to Jerusa-

lem artichoke.

0044Most of the yacon production is in the tropical and

subtropical Andes of Peru, Bolivia, Colombia, Ecua-

dor, and Argentina at altitudes of 900–2800 m. There

is currently little commercialization of the crop.

However, it has been proposed as a potential source

of high-fructose syrup. The crop is propagated vege-

tatively as clones, which are separated according to

shape and chemical composition.

0045Tuberous, fusiform roots 20 cm in length and 3 cm

in diameter are produced at the base of the plant. The

raw flesh is crisp. The main stem of the plant is used

as a cooked vegetable.

0046Tuberous roots contain about 46 % inulin on a dry

weight basis. They are also higher in protein than

tbl0002 Table 2 Average amino acid content in tropical root crops

Amino acid Amino acid content

(mgper gram of protein)

Oca Mashua Ulluco

Lysine 58 38 48

Threonine 46 23 26

Valine 37 36 35

Isoleucine 38 31 41

Leucine 56 39 49

Phenylalanine plus tyrosine 62 26 60

Tryptophan 7 5 9

Methionine plus cystine 30 14 30

Data from King SR (1987) Four endemic Andean tuber crops: promising

food resources for agricultural diversification. Mountain Research and

Development 7: 43–52, with permission.

5964 VEGETABLES OF TROPICAL CLIMATES/Root Crops of Uplands

most other tropical root and tuber crops (Table 1);

and they are a good source of potassium. Dried leaves

contain 11–17% protein and could be used for live-

stock feed.

0047 Undamaged roots have a long shelf-life. Roots can

also be dried for extended storage.

0048 An alternative use for yacon is as a fodder crop.

The inulin has commercial value as a sweetening

agent for diabetics and in the production of fructose.

(See Fructose.)

See also: Alkaloids: Properties and Determination;

Cassava: The Nature of the Tuber; Drying: Drying Using

Natural Radiation; Freeze-drying: The Basic Process;

Fructose; Protein: Quality; Saponins; Tannins and

Polyphenols

Further Reading

Hermann M and Heller J (1997) Andean roots and tubers:

ahipa, arracacha, maca and yacon. Promoting the con-

servation and use of underutilized and neglected crops,

21 pp. Rome: International Plant Genetic Resources

Institute.

Kay DE (1973) Root Crops. London: Tropical Products

Institute.

King SR (1986) Ancient buried treasure of the Andes.

Garden 10: 6–11.

King SR (1987) Four endemic Andean tuber crops: promis-

ing food resources for agricultural diversification.

Mountain Research and Development 7: 43–52.

King SR and Bastien HHC (1991) Oxalis tuberosa (Oxali-

daceae) in Mexico: an Andean tuber crop in Meso-

America. Advances in Economic Botany 8: 77–91.

National Research Council (1989) Lost Crops of the Incas.

Washington, DC: National Academy Press.

Sperling CR and King SR (1990) Andean tuber crops:

worldwide potential. In: Janick J and Simon JE (eds)

Advances in New Crops, pp. 428–435. Portland, OR:

Timber Press.

Root Crops of Lowlands

D N Maynard, University of Florida, Bradenton,

FL, USA

SKO’Hair, University of Florida, Homestead, FL, USA

Crops

0001 Low-land root and tuber crops, which include sweet

potato, yam, and, to a lesser extent, yam bean, pro-

vide a low-cost and readily available carbohydrate

source in the diets of large populations in the tropics.

Their value, both economic and nutritional, is based

on production of starch-filled storage organs. Fur-

thermore, their usefulness is extended somewhat

through in-ground or common storage to provide

high-caloric food during drought or other times of

shortage.

Sweet Potato

0002The sweet potato (Ipomoea batatas (L.) Lam., Family

Convolvulaceae) can be grown throughout the sub-

tropics and tropics for use as a staple food source. Its

growth habit is conducive to interplanting with other

food crops, and vine tips are often used as a green

vegetable in many cultures.

Global Distribution, Commercial Importance, and

Varieties

0003Although widely distributed, sweet potato produc-

tion historically has been concentrated in Asia; in

2001, production there accounted for about 90% of

world production. Africa, the second most important

area, contributed only about 7% of world produc-

tion (Table 1). The area devoted to sweet potato

production has decreased considerably in the last 20

years; however, yield increases of more than 100% in

Asia have more than compensated for the smaller

area. Asian yield increases can be attributed in part

to improved varieties and production technology de-

veloped at the Asian Vegetable Research and Devel-

opment Center, Tainan, Taiwan. In other parts of the

world, sweet potato production area, yields, and total

production have remained about the same or have

declined.

0004There is little international trade in sweet potato

because of its relatively low value as a world crop, the

relatively short postharvest life of uncured roots,

limited use in industrial products, and legal restraints

associated with the introduction of plant diseases and

insects with the roots. In the tropics, sweet potatoes

are usually left in the ground until needed and sold in

local markets within 1–2 weeks of harvest.

0005Distinct sweet potato clones that differ in growth

habit and pigmentation of vines and roots have been

selected by small growers in the tropics. The clones

are named according to the source of planting stock

or according to some characteristic that distinguishes

it from other clones. Thus, a single clone may be

known under several different names.

0006However, cultivars developed by breeding in the

USA, the International Institute for Tropical Agricul-

ture in Nigeria, and the Asian Vegetable Research and

Development Center in Taiwan are known by specific

names and/or number. The principal cultivars grown

in the USA are Beauregard in the southeast and

Garnet and Beauregard in California.

VEGETABLES OF TROPICAL CLIMATES/Root Crops of Lowlands 5965

Morphology and Anatomy of the Root

000 7 An enlarged tuberous root, possessing typical root

structures and the unique capability of initiating

adventitious shoots, is the principal edible portion

of the plant. Shortly after transplanting, some fibrous

roots begin enlarging, probably in response to en-

dogenous growth regulators. The length of the en-

larged root is largely achieved in the first 8 weeks

after planting, whereas increases in diameter continue

as long as photosynthate is produced by the aerial

portions of the plant. Storage parenchyma accounts

for a major portion of the storage root, but cortex,

secondary phloem, and secondary phloem paren-

chyma also account for a significant portion of the

storage root.

0008 Root shape varies from elongated to nearly globu-

lar; the skin color may be white, tan, yellow–orange,

salmon, red, or copper, and the flesh color may be

white, yellow–orange, orange, salmon, purple, or red.

Normally, each plant produces five to 10 roots that

usually vary in weight from 100 to 300 g each.

Nutritional Composition

000 9 In common with other root crops, sweet potato

roots are rich in carbohydrate, which provides high

energy value (Table 2). The yellow and orange-fleshed

sweet potatoes are exceptional sources of pro Vitamin

A, but white-fleshed types do not provide this

advantage. Sweet potatoes also provide a good source

of vitamin C. A 100 g serving may provide 25–40%

of the recommended dietary allowance (RDA)

depending on cultivar, root size, harvest date, and

storage conditions. Sweet potato is not a superior

source of amino acids, but generally exceeds yam

and yam bean in amino acid composition (Table 3).

The sweet potato protein and amino acid pattern is

affected by cultivar, environment, cultural manage-

ment, and growth duration. Nonetheless, it is

generally high in lysine and provides a supple-

mental protein to cereals. Genotypic variability in

provitamin A, ascorbic acid, protein content, and

protein quality offer the possibility of enhanced nu-

tritional quality through plant breeding. The poten-

tial for increased carbohydrate production from

sweet potato can be best achieved by total yield in-

creases derived from improved cultivars and produc-

tion practices. In order to achieve acceptable levels of

digestibility, it is necessary to cook sweet potato roots

by boiling or roasting, because of the presence of a

trypsin inhibitor in raw roots.

0010The nutritional composition of sweet potato leaves

complements that of the roots (Table 2). Leaves are

much lower in carbohydrates and food energy but are

substantially higher in the essential elements calcium,

iron, magnesium, phosphorus, and potassium. Leaves

have a higher thiamin, riboflavin, niacin, and vitamin

content than roots but are inferior to roots in

ascorbic acid and pro Vitamin A content.

Handling and Storage

0011Harvest of sweet potato may be on an as-needed basis

by hand-digging of the roots to be eaten or sold on

local markets; this is the pattern in much of the

tropics. In the USA, and elsewhere where sweet pota-

toes are grown on an extensive commercial basis, they

are harvested when the maximum number of roots is

appropriate to be marketed; depending on cultivar

and environmental conditions, this may vary from

90 to 130 days after transplanting. In this case, the

entire crop is harvested mechanically on a once-over

basis.

0012Sweet potato roots are subject to a number of

postharvest rots that gain entry through wounds in-

flicted during harvest. Accordingly, it is critical to use

harvesting methods that minimize wounds. Fortu-

nately, harvest by hand, as in small-scale tropical

agriculture, results in little root damage, so roots

can be sold within the usual 1- or 2-week marketing

period. With mechanical harvesting and the need for

long-term storage to provide orderly marketing as in

the USA, it is necessary to insure healing of wounded

areas of the roots. This is accomplished by curing, i.e.,

tbl0001 Table 1 World sweet potato production

Region Areaharvested (10

) Yield (kg ha

1

)Production(10

1989^1991 1995^1996 2001 1989^1991 1995^1996 2001 1989^1991 1995^1996 2001

Africa 1 345 1 544 2 165 4 738 4 602 1 714 6 375 7 098 10 203

North and Central America 176 172 150 6 402 6 453 7 742 1 127 1 130 1 158

South America 127 109 101 10 124 12 000 12 320 1 288 1 307 1 250

Asia 7 347 7 197 6 860 15 608 17 999 17 879 114 672 129 562 122 645

Europe 6 5 6 13 091 12 437 10 498 77 60 60

Oceania 115 114 111 4 885 4 867 5 426 564 552 602

World 9 117 9 139 9 392 13 613 15 285 19 472 12 4104 139 708 135 919

DatafromFAO(2002)www.FAO.org.

5966 VEGETABLES OF TROPICAL CLIMATES/Root Crops of Lowlands

holding the roots at 29



C and 90–95% relative hu-

midity (RH) in a well-ventilated storage for 4–7 days.

Subsequent storage at 13–16



C and 85–90% RH will

maintain sweet potatoes in good condition for several

months.

Industrial Uses

0013Although there is potential for numerous industrial

products, only canning of whole, sliced, or pure

sweet potatoes for long-term preservation has

achieved any measure of commercial importance.

Dehydration of fresh or cooked chips by sun-drying

is practiced in some tropical countries for preserva-

tion or later conversion to flour. Commercial starch

production has been tried in several countries, includ-

ing the USA, but has not proved to be economically

feasible. The same has been true of glucose, pectin, and

carotene production on a commercial basis. Recently,

there has been considerable interest in utilizing sweet

potato roots as a raw material for alcohol production.

Where the environment permits continuous sweet

potato production, yields surpass those of cassava,

and ease of mechanization favors sweet potato produc-

tion. However, it is likely that cassava or other crop

products will be more suitable raw materials

under seasonal production conditions. However, cull

sweet potatoes have consistently provided a high-

energy feed for livestock, especially hogs in the USA

and elsewhere.

tbl00 02 Table 2 Composition(per100gofrawproduct)oftropicalrootcrops

ConstituentSweetpotatoYamYambean

RootsLeavesTuberRoot

Water(g)72.8487.9669.6090.07

Foodenergy(kJ)439146118159

Protein(N6.25)(g)1.654.001.530.72

Totallipid(fat)(g)0.300.300.170.09

Totalcarbohydrate(g)24.286.3827.898.82

Fiber(g)3.02.04.14.9

Ash(g)0.951.360.820.30

Calcium(mg)22371712

Iron(mg)0.591.010.540.60

Magnesium(mg)10612112

Phosphorus(mg)28945518

Potassium(mg)204518816150

Sodium(mg)13994

Zinc(mg)0.280.290.240.16

Copper(mg)0.1690.0370.1780.048

Manganese(mg)0.3550.2560.3970.060

Ascorbicacid(mg)22.711.017.120.2

Thiamin(mg)0.0660.1560.1120.020

Riboflavin(mg)0.1470.3450.0320.029

Niacin(mg)0.6741.1300.5520.200

Pantothenicacid(mg)0.5910.2250.3140.135

VitaminB

(mg)0.2570.1900.2930.042

Folacin( mg)14?80?23.012?

VitaminB

( mg)0000

VitaminA(IU)200631028021

DatafromUSDA(2002)http://www.nal.usda.gov/fnic/foodcomp/.

tbl00 03 Table 3 Aminoacidcompositionoftropicalrootcrops

AminoacidAminoacidcontent(mgper100g)

SweetpotatoYamYambean

Tryptophan2012

Threonine825418

Isolucine825216

Leucine1219625

Lysine815926

Methionine41217

Cysteine13196

Phenylalanine997117

Tyrosine684012

Valine1086222

Arginine7712737

Histidine313419

Alanine906320

Asparticacid282155200

Glutamicacid16118143

Glycine745316

Proline725425

Serine858125

DatafromUSDA(2002)http://www.nal.usda.gov/fnic/foodcomp/.

VEGETABLES OF TROPICAL CLIMATES/Root Crops of Lowlands 5967