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

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extract. However, there are no strict standards of

identity, which results in a great diversity and vari-

ability between and within products.

0008 Direct extract or essence of meat is manufactured

by extracting minced beef muscle with water for a

sufficiently long time to produce a gel upon cooling.

Gel or jelly formation is due to extraction of collagen

by heat so that it solidifies upon cooling. Approxi-

mately 13–14 kg of lean meat is required to yield

about 1 kg of extract, or essence of meat that contains

around 34% moisture.

0009 No. 1 extract, sometimes simply called meat ex-

tract, is produced as a byproduct of corned beef. Its

production involves immersion of chipped beef into

boiling water for a short period of time. Little gelatin

is extracted by this procedure. About 50 kg of meat is

needed to produce 1 kg of extract containing approxi-

mately 17% moisture. The US Department of Agri-

culture Code of Federal Regulations of 1986 states

that meat extract should contain not more than 25%

moisture. Thus, it is considered to be a preserved

product because it contains only 20% moisture or

less and a minimum of 5% sodium chloride and 7%

creatinine. The fat content should not exceed 0.6%

and the nitrogen content should be at least 8%. The

nitrogenous components should consist of at least

40% meat bases and 10% creatine plus creatinine.

0010 Fluid extract of meat is made by cooking fresh meat

to produce a stock containing 3–4% of solids. The

stock is concentrated and evaporated under vacuum

to yield a product with 60% solids. Salt is then added

to the water fraction at 25.5% (w/w). This results in

an extract containing 9.3% of added salt (10.2 kg of

added salt per 100 kg of concentrated extract).

0011 Broth (beef or pork) or stock are terms used

interchangeably to describe the product obtained

by simmering meat and/or bones (crushed) in water

along with seasoning ingredients. The product(s)

must have a moisture-to-protein ratio of 135:1. A

concentrate of broth or stock can be made by

reducing the moisture-to-protein ratio to 67:1.

0012 Liver extract is produced by extracting raw ground

livers with slightly acidified hot water at pH 5. The

stock is then concentrated to a paste under vacuum at

low temperature to a moisture content of 35%. Thus,

liver extract contains more moisture than meat

extract (35 versus 25%). Its high moisture content

makes liver extract highly perishable so more salt

needs to be added or it must be refrigerated or heat-

sterilized. In contrast to meat extract, which is pri-

marily used as a flavor base for soups, sauces, and

other foods, liver extract is used by the pharmaceut-

ical industry as a nutritional supplement.

0013 Although individual companies producing meat

extract may have their own grading sytems, there is

no standard grading. Some companies divide their

products into no. 1 and no. 2 grades on the basis of

their creatinine content, with the former contain-

ing 7% and over and the latter grade containing less

than 7% creatinine. Some other processors produce

three grades of meat extract, with International

Packers Limited calling their products Supreme,

Premium, and Select. Supreme contains 16.75–

17.25% moisture, a minimum of 44% soluble or-

ganic material and 7% creatinine, and a maximum

of 1.5%water-insoluble material, 25% ash, and 4%

salt. Premium contains 19–20% moisture, a min-

imum of 44% soluble organic material and 7%

creatinine and a maximum of 1.5% hot-water-insol-

uble material, 25% ash, and 4% salt. Select contains

23–24% moisture, a minimum of 40.5% soluble

organic material and 6.4% creatinine and a max-

imum of 1.4% hot-water-insoluble material, 23%

ash, and 3.75% salt.

Composition of Meat Extract

0014The chemical compositions of beef extract, mutton

extract and liver extract are shown in Table 1. The

data provided give the moisture, salt, creatinine,

and ash contents as well as the percentages of solu-

ble organic material for beef and mutton extracts.

For liver extract, however, the compositional data

are presented in terms of moisture content,

solids, and ash. Although data are given for a number

of B-vitamins for all three extracts, the list of vita-

mins is more complete for liver extract, reflecting its

greater nutritional contribution. Particularly notice-

able are the higher values for vitamin B

(15.4 times

greater), riboflavin (3.5-fold greater), and panto-

thenic acid (20-fold higher) in liver extract. (See

Beef and refer to individual nutrients.

0015Table 2 provides information on the non-

volatile constituents present in meat extract. Parti-

cularly note worthy is the presence and relatively

large amounts of creatine and creatinine, which are

important quality parameters. Although yeast extract

is frequently used as a substitute for meat extract, it

does not contain either creatine or creatinine. These

two guanidine compounds combined should not

comprise less than 10% of the total nitrogen on a

dry basis in high-quality meat extracts.

0016Another interesting characteristic of meat extract is

the considerable amount of inosine and inosinic acid,

which have been shown to be meat flavor enhancers.

Thus, inosine and inosinic acid probably make a

major contribution to the desirable flavor and/or

aroma of meat extract. The relatively high con-

centration of amino acids may also contribute to

the Maillard reaction during heating of the extract

3814 MEAT/Extracts

for concentration and play a role in the flavor

of meat extracts. (See Browning: Nonenzymatic;

Flavor (Flavour) Compounds: Structures and Charac-

teristics.)

Microbiology of Meat Extract

0017 Although commercial meat extract usually contains

bacteria and mold spores, pathogenic organisms are

seldom present. Boiling of the stock to concentrate it

results in a product that is nearly sterile, but subse-

quent handling and use of contaminated equipment

result in recontamination. As meat extract provides

an excellent medium for the growth of bacteria and

temperatures used during concentration by vacuum

are favorable for growth of microorganisms, the

finished meat extract contains viable bacteria and

molds. The best procedures for controlling the

growth of microorganisms are to decrease the mois-

ture content and increase the salt content. Neither

procedure, however, can be relied upon to control

the growth of microbes alone, although together

they provide some degree of safety from spoilage.

Combined with a low storage temperature, a low

moisture and high salt content are synergistic and

help to control microbial growth. (See Spoilage: Bac-

terial Spoilage; Molds in Spoilage.)

0018At a moisture content of 16%, meat extract stored

at 20



C has been shown to be relatively stable during

48 days of storage. At 20% moisture, however, meat

extract needs to be protected from microbial spoilage

by addition of salt. Since extracts made from liver and

bones are hard to dehydrate below 25% moisture,

they are more susceptible to bacterial and mold

growth so must be either held at low tempera-

tures (> 10



C) or have a greater amount of added

salt or both.

0019Table 3 presents some average microbial counts for

meat extract. The data demonstrate that there is con-

siderable variation in both the kinds and numbers of

organisms present. The great amount of variability is

no doubt associated with sanitation, processing, and

tbl0001 Table 1 Chemical composition of beef, mutton, and liver extract

Minimum (%) Maximum (%) Average (%)

Beef extract

Moisture 18.80 19.95 19.41

Salt 4.00 4.97 4.76

Creatinine 7.00 7.10 7.02

Soluble organics 43.00 44.50 43.70

Insoluble in water 1.50 2.00 1.70

Ash 23.00 25.00 24.00

Thiamin 10 mgg

1

Riboflavin 35 mgg

1

Niacin 1200 mgg

1

Pyridoxine 5 mgg

1

Pantothenic acid 25 mgg

1

Vitamin B

0.52 mgg

1

Mutton extract

Moisture 17.90%

Salt 3.97%

Creatinine 5.90%

Organics soluble in alcohol (80



C) 46.55%

Insoluble in water 1.90%

Ash 23.35%

Protein 57.83%

Liver extract

Moisture 35+1%

Solids 65+1%

Ash 11+1%

Vitamin B

Not less than 8 mgg

1

Thiamin Not less than 10 mgg

1

Riboflavin Not less than 200 mgg

1

Folic acid Not less than 15 mgg

1

Nicotinic acid Not less than 1000 mgg

1

Pantothenic acid Not less than 500 mgg

1

Choline Not less than 15 000 mgg

1

Insoluble: the product gives a clear solution in water

Reproduced from Ockerman HW and Pellegrino JM (1988) Meat extractives. Advances in Meat Research 5: 303–339, with permission.

MEAT/Extracts 3815

storage conditions, as well as the final contents of

moisture and salt. Although any great increase in

the number of thermophilic bacteria would not be

expected to occur in a meat extract containing 16%

moisture, a potential danger may exist upon adding

it to other foods having a higher moisture content.

Good sanitation and clean-up and avoiding cont-

aminated tanks, pipes, and evaporators can help

to reduce recontamination of meat extracts. Low-

temperature storage is also an important step in

controlling bacteria and molds.

Uses for Meat Extract

0020Meat extract is a common flavoring additive for

soups, stews, sauces, casseroles, canned meat items,

pot pies, bouillon and bouillon cubes, gravies, and

other items where meat flavoring improves the prod-

ucts. The flavor of meat extract makes it a desirable

additive to a variety of products. The percentage of

meat extract needed for flavoring varies widely,

depending upon the food to which it is being added,

but generally falls in the range 5–25%. Its desirable

flavor and aroma may enhance the flavor of some

products at even lower concentrations. Although

yeast extract is used as a substitute, chefs and food

connoisseurs prefer the characteristic flavor and

aroma that meat extract imparts to other foods.

tbl0002 Table 2 Chemical analysis showing nonvolatile components in

meat extract

(a) Composition of no. 1 meat extract (17–28% moisture and

13.21% protein)

Component Dry weight

Amount

(% of total)

(% of total wt)

Amino acids

3-Methylhistidine Tr

a-Alanine

1.32

Serine 0.10

Methionine

0.01

Isoleucine

0.08

Leucine

0.08

Histidine

0.03

Taurine

0.32

Citrulline

0.26

Total

2.20 0.22

Peptides

Carnosine

3.70 0.92

Anserine

0.75 0.16

Iminazole peptide

1.88 0.47

Guanidines

Creatine

4.80 1.54

Creatinine

5.51 2.04

Methylguanidine

(*0.1)

Guanidine

(*0.1)

Purines, etc.

Hypoxanthine

1.90 0.78

Inosine

0.70 0.15

Inosinic acid Tr

Protein (14.9% N, 0.1% ash)

10.92 1.65

Organic acids

Lactic acid

14.60

Glycollic acid

0.98

Succinic acid

1.26

b-Hydroxybutyric acid

(>1)

Carnitine

3.3 0.29

Choline Tr

Urea

0.11

Ammonia

0.42

Inorganic matter

(8.95% K; 7.3% P

)

Coloring matters

18.30 4.23

Total

100.73 12.85

(b) Composition of volatile components of beef extract

Component Peak size

Hydrogen sulfide Large

Methyl mercaptan Large

Ethyl mercaptan Small

Dimethyl sulfide Small

Acetaldehyde Large

Propionaldehyde Small

Isobutyraldehyde Small

Acetone Medium

Isovaleraldehyde Small

Methyl ethyl ketone Small

Methanol Small and only in some samples

Ethanol Small and only in some samples

Tr, trace.

Reproduced from Bender AE and Ballance PE (1961) as modified by

Ockerman HW and Pellegrino JM (1988) Meat extractives. Advances in

Meat Research 5: 303–339, with permission.

tbl0003Table 3 Average microbiological count for meat extract with

values for products from Argentina and the USA

Argentine product

Soup in evaporator before

going to evaporator

32 g

1

TPC

Soup going to evaporator 1300 g

1

TPC

Concentrated soup out of evaporator 2000–30 000 g

1

TPC

Thermophiles 500 g

1

Anaerobes 100 g

1

Coliforms 0

Clostridium perfringens Negative in 0.1 g

Meat extract out of can (30



C) 100 000 g

1

TPC

Meat extract out of can (55



C) 237 500 g

1

TPC

Putrefactive anaerobes 927 g

1

Indole producers 0 (sometimes present)

S producers 0 (sometimes present)

Staphylococcus group 0

Salmonella^Shigella group 0

US product

Total plate count (TPC) <1000 g

1

Coliforms <10 g

1

Escherichia coli Negative g

1

Staphylococcus aureus <10 g

1

Salmonella spp. Negative per 25 g

Flat sour spores (FSS) <50 per 10 g

Total thermophilic spores (TAS) <125 per 10 g

Reproduced from Ockerman HW and Pellegrino JM (1988) Meat

extractives. Advances in Meat Research 5: 303–339, with permission.

3816 MEAT/Extracts

See also: Beef; Browning: Nonenzymatic; Flavor

(Flavour) Compounds: Structures and Characteristics;

Spoilage: Bacterial Spoilage; Molds in Spoilage

Further Reading

Bender AE and Ballance PE (1961) A preliminary examin-

ation of the flavor of meat extract. Journal of the Science

of Food and Agriculture 12: 683–687.

Dvorak Z (1981) Creatine as an indicator of net muscle

proteins. Journal of the Science of Food and Agriculture

32: 1033–1036.

Liebig J (1847) Ueber die Bestaudtbeile der Fliisigbeetin

des Fleisches. Aundleu der Chemie und Pharmacia 62:

257–298.

LJ Minor Corporation (1984) Quality Food Bases – An

Essential Culinary Tool. Cleveland, OH: LJ Minor.

Ockerman HW and Pellegrino JM (1988) Meat extractives.

Advances in Meat Research 5: 303–339.

Wood T and Bender AE (1957) Analysis of tissue constitu-

ents. Commercial ox muscle extract. Biochemical

Journal 67: 366–373.

Megaloblastic Anemia See Anemia (Anaemia): Iron-deficiency Anemia; Megaloblastic Anemias;

Other Nutritional Causes

MELONS, SQUASHES, AND GOURDS

A A Schaffer, Agricultural Research Organization,

Bet Dagan, Israel

H S Paris, Agricultural Research Organization, Ramat

Yishay, Israel

Background

0001 The Cucurbitaceae family encompasses over 800

species of plants known collectively as gourds or

cucurbits. These include cucumbers, melons, water-

melons, pumpkins, squash, and many others. Perhaps

more than 20 genera are used for culinary purposes,

which usually includes consumption of the mature

fruit flesh, whole immature fruits, and/or seeds.

Three genera, Cucumis (cucumbers, melons), Cucur-

bita (pumpkins, squash), and Citrullus (watermelons),

rank among the top 10 in economic importance

among the vegetable crops of the world, and several

others have regional importance. Cucurbits are also

grown for use as ornaments and containers, and some

are used for medicinal applications and other pur-

poses. Some wild cucurbits have potential economic

value. This article reviews the botany, horticulture,

and food value of cucurbits, with emphasis on the

three leading genera.

Botany

0002 Most cucurbits are herbaceous, tendril-bearing vines

that are adapted to warm climates and are sensitive to

frost. The natural distribution of most species is in the

tropics, but some genera (Bryonia, Cucurbita, Ecbal-

lium, Echinocystis) contain species that are distrib-

uted in temperate regions. In cultivation, cucurbits are

distributed in almost all arable regions worldwide.

Those cucurbits that are not adapted to cool tempera-

tures and that are grown for their mature fruits and

seeds are usually not successful in regions with short,

cool summers. Others, most notably cucumber

(Cucumis sativus) and summer squash (Cucurbita

pepo), are grown for their immature fruits and are

more tolerant of cool temperatures than most cucur-

bits, and therefore have an especially wide distribu-

tion in cultivation.

0003Most cucurbit species are mesophytes and have

large palmate leaves, fibrous roots, and prominent

fruits. Under favorable conditions, the plants grow

and spread quickly, as stems can elongate 30 cm or

more within 24 h. The foliage can be glabrous, softly

or stiffly hairy, or spiculate. The plants usually are

monoecious, that is, have separate staminate (male)

and pistillate (female) flowers on the same plant.

Most often, the flowers are nectar-producing and

foraged by bees, with green calices consisting of five

sepals fused at the base and yellow corollas consisting

of five petals fused at the base. Staminate flowers

differentiate at lower nodes and are produced in

greater numbers than pistillate flowers. However,

once differentiated, the pistillate flowers can develop

at a faster rate than the staminate flowers. The stam-

inate flowers have thinner, longer pedicels than the

MELONS, SQUASHES, AND GOURDS 3817

pistillate flowers. The pistillate flowers have inferior

ovaries that usually are round or oval in shape. In

cross-section, the triloculate ovary can be seen to

contain 10 subepidermal main veins, five of which

connect the pedicel with the central vein of each

sepal and five of which connect the pedicel with the

central vein of each petal. In addition to the main

vasculature system of the cucurbit ovary, there is

also a highly anastomosing vasculature system in the

fruit, which contributes to some of the genetic vari-

ability of fruit structure in the family. For example,

the fibrous flesh of the spaghetti squash (Cucurbita

pepo) and the fibrous net of the dried sponge gourd

(Luffa cylindrica) are products of this anastomosing

vasculature.

0004 After fertilization, the ovary develops into a fleshy

fruit possessing exocarp, mesocarp, and endocarp.

Generally, the fruits of wild cucurbits are small,

round, and green, and the flesh often extremely bitter

due to alkaloid compounds known as cucurbitacins.

A fruit can contain as many as several hundred seeds,

which, at maturity, contain two cotyledons each but

no endosperm. The seeds are not bitter and usually

are flat, but there is a greater than 10-fold range in

seed length among cucurbit genera, from several

millimeters to a few centimeters.

0005 Domestication of some of the Cucurbitaceae is

ancient, predating that for some major grain crops.

There is evidence that Cucurbita pepo (pumpkin,

squash) was first domesticated at least 10 000 years

ago. Several other cucurbits have also been domesti-

cated for thousands of years. In the Bible (Numbers

11:5), the Israelites longed for the avattihim (water-

melons) and qishu’im (melons, var. chate) of Egypt

during their wanderings in the Sinai Desert.

0006 Following the thousands of years of domestication

by man, the cultivated cucurbits differ from their

wild counterparts, most obviously in their larger

and fewer vegetative and reproductive parts. Culti-

vated forms have larger leaves, thicker stems, fewer

branches, and larger and fewer fruits and seeds. In

some cultivated forms, fruit shape is not round

but distinctly elongate. Also, different fruit colors

and color patterns occur among cultivated forms.

Cultivated forms also differ sharply from their wild

cousins by having fruits that are more palatable,

being nonbitter and less coarsely fibrous, but higher

in starch, sugar, and carotenoid contents. A wealth of

variability for fruit size, shape, and color occurs in the

Cucurbitaceae family.

0007 Quality traits desired in mature cucurbit fruits in

some cases are the same as those desired in immature

cucurbit fruits but differ in other cases. Some charac-

teristics, such as sweetness and flesh color, are fully

expressed in mature fruits but hardly at all in young

fruits. Other characteristics, such as size of the seed

cavity, can be important in determining the palatabil-

ity of immature fruits but are less important in mature

fruits. Many of the cultivated cucurbit species have

been grown for the culinary use of their immature

fruits, and some for their mature fruits. A few, most

notably pumpkins and squash (Cucurbita spp.) and

melons (Cucumis melo) have been grown for the dual

usage of their immature fruits as well as their mature

fruits, or for the use of immature fruits in some regions

but for the use of mature fruits in other regions, and

as a consequence possess a great deal of intraspecific

variation in fruit characteristics.

0008Among the cucurbits are some of the largest and

fastest growing fruits in the plant kingdom. For this

reason, some of the larger cucurbits have served as

experimental material to study growth rates, carbo-

hydrate import, and translocation physiology in de-

veloping fruit. Large pumpkins may show dry weight

gains of 1.71g h

1

, whereas the smaller fruited cu-

cumbers and melons may increase in dry weight by

100–500 mg h

1

. The large differences in fruit size

and shape in the cucurbits are already determined at

the early stages of ovary development, prior to and

immediately after anthesis. These traits are under

strict genetic control, although nongenetic factors

such as environmental conditions and intraplant

competition for photoassimilates play strong roles in

determining fruit size. Assimilate supply in the form

of photosynthetic products can often be a limiting

factor of fruit growth and final fruit size.

Melons

0009Melons (Cucumis melo L.) are prostrate, highly

branched, softly hairy vines possessing rounded,

heart-shaped leaves and unbranched tendrils. They

are most commonly andromonoecious, producing a

hermaphroditic flower at the first one or two nodes

of the branches and one or more male flowers at

all other nodes. Less commonly, they are mono-

ecious, with pistillate flowers being produced instead

of hermaphroditic flowers. Rare, recessive mutants

produce perfect flowers or pistillate flowers at every

node. The flowers are bright yellow but small,

approximately 3 cm in diameter. C. melo is diploid,

with 12 pairs of chromosomes (2n ¼24), but some

members of the genus Cucumis are polyploids.

0010Melons originated from tropical Africa north of the

equator, and their cultivation spread northward and

eastward thousands of years ago. Much diversity of

melons is found in Iran, Turkey, Spain, India, China,

and the central Asian republics of the former Soviet

Union. Apparently, the first culinary use of melons by

man was of the immature fruits, much in the manner

3818 MELONS, SQUASHES, AND GOURDS

of cucumbers. Immature melons are not sweet but

instead bland, similar to cucumbers. Sweet melons

are a relatively recent development, perhaps dating

back only to the Middle Ages.

0011 Botanically, melons are considered to consist of

two subspecies, C. melo ssp. melo and C. melo ssp.

agrestis Jeffrey. Melons contain a wide diversity of

fruit sizes, shapes, and colors (see Figure 1). This

diversity has been the subject of many attempts at

classification. Probably the most comprehensive and

comprehensible classification is that of Pitrat et al.,

who have recognized 16 cultivar-groups. Their classi-

fication is summarized in Table 1. The inodorus

group includes the winter or casaba melons, as well

as the honeydew, Jaune Canary and Piel de Sapo

melons. The major netted muskmelons, especially

those grown in the USA as ‘cantaloupes’ are in the

reticulatus group. These include the heavily netted

varieties such as PMR45, Hale’s Best Jumbo, Top

Mark and also the lightly netted, nonribbed varieties

such as the Galia and Persian melons. The French

Charentais-type melon, which is ribbed but generally

smooth skinned, is classified in the cantalupensis

group. However, the distinction between groups may

become blurred with increasing breeding efforts, since

all the groups of Cucumis melo are easily hybridized

with one another. For example, while, in the past, the

smooth cream-skinned honeydew melons were green-

fleshed, there are now varieties of honeydew melons

with the orange flesh of the reticulatus group. In the

USA, melons are often classified as either canta-

loupes, honeydews or ‘specialty melons,’ which

include all the other types.

0012According to FAO statistics, approximately 19

million tonnes of melons were produced in 2000,

fig0001 Figure 1 (see color plate 104) Melons.

tbl0001 Table 1 Classification of melons, Cucumis melo, to subspecies and cultivar-groups

Subspecies Group Maturityat consumption Description

agrestis (ovary with short hairs)

conomon Immature, similar to cucumber, in Eastern Asia Elongate

makuwa Mature in Eastern Asia White flesh, little aroma, flat/round/pyriform

chinensis Mature in Eastern Asia Colored flesh, little aroma, pyriform

momordica Immature in India Skin bursting when ripe

acidulus Cooked in India, firm with crisp flesh, no sweetness

or aroma

melo (ovary with long hairs)

cantalupensis Mature in Europe Sweet flesh, aromatic, smooth or warted,

climacteric

reticulatus Mature in North America, Japan, Western Asia,

and Europe

Sweet flesh, aromatic, netted, climacteric

adana Mature in Turkey Thin flesh, low in sugar, climacteric

chandalak Mature in Central Asia Sweet, climacteric, slightly wrinkled, low aroma

ameri Mature in Central Asia Sweet, climacteric, low aroma, netted

inodorous Mature in Central Asia, Europe, and North

America

Sweet, no aroma, usually wrinkled, not climacteric,

long-keeping

flexuosus Immature in North Africa Very long fruit, climacteric

chate Immature in North Africa Elongate

tibish Immature in Sudan Small, oval, no sugar, no aroma

dudaim Mature Used as an ornamental or aromatic, small, round,

no taste, highly aromatic, climacteric

chito Very small, round, smooth yellow fruits

From Pitrat M, Hanelt P and Hammer K (2000) Some comments on infraspecific classification of cultivars of melon. In: Katzir N and Paris HS (eds)

Proceedings of Cucurbitaceae 2000: the 7th Eucarpia Meeting on Cucurbit Genetics and Breeding. Acta Horticulturae 510: 29–36.

MELONS, SQUASHES, AND GOURDS 3819

one-third of that in China. Other important produ-

cing countries are Turkey, USA, Spain, Romania,

Morocco, India, Mexico, and Egypt. The mature

fruits of the orange-fleshed melons rank high in as-

corbic acid and carotenoid content.

Cucumbers

0013 Cucumbers (Cucumis sativus L.) are prostrate,

branched, stiffly hairy vines possessing sharply five-

cornered leaves and unbranched tendrils. They are

placed botanically in the same genus as melons

only because the Swedish botanist Linne

had done

so. They are in fact a distantly related species, with

cucumber having a diploid chromosome number of

14 (2n ¼14). Cucumbers are monoecious, but many

newer cultivars are gynoecious and several old

cultivars are andromonoecious. The flowers are bright

yellow and fairly small, approximately 4 cm in

diameter.

0014 Whilst the melons and their relatives are of African

origin, the cucumber is native to the foothills of the

Himalayas of Nepal, where the wild, bitter-fruited

form, C. sativus var. hardwickii (Royle) Alefeld, can

be found. Cucumbers have been in cultivation several

thousand years and spread from their native habitat

to neighboring eastern and southern Asia, and later to

Europe and Africa. Cucumbers are almost invariably

used when immature, and eaten raw in salads, but in

eastern Asia, they are also cooked. Cucumber con-

tains a large amount of diversity in fruit characteris-

tics when compared with other species, but relatively

little when compared with melons, pumpkins, and

squash. There is some variation in mature fruit

color, immature fruit color, uniformity of color, size,

and number of fruit spines, and color of spines. Much

variation can be found for the length but not width of

mature fruits; thus, fruit size is essentially a function

of fruit length. The fruits can range in length from

approximately 10 cm in some forms to 60 cm or more

in some Chinese cultivars. Mature fruit range in

width from 4 to 8 cm.

0015 Cucumbers can be classified into six main groups

on the basis of variation in fruit characteristics and

geographic origin. The French cornichons are short

fruits with small, numerous spines and are usually

grown for pickling. The European greenhouse cu-

cumbers are long, smooth fruits that are grown for

slicing into salads. The American pickling cucumbers

are short fruits with protruding warts and large spines.

The American slicing cucumbers are medium-long

fruits having a thick skin and protruding warts

that bear large spines. The Middle Eastern cucumbers

are medium-short, spineless, and wartless, and are

used for both slicing and pickling. The Far Eastern

cucumbers are very long with protruding warts and

spines. Interestingly, short-fruited kinds tend to be

used for pickling, and long-fruited kinds are used

fresh or, in the Orient, for cooking. Two additional

groups of cultivars have been reported, one from

southwestern China and the other from Nepal and

high elevations of India. An interesting novelty is the

‘Lemon’ cultivar, which bears a striking resemblance

to its namesake.

0016Cucumbers are an important greenhouse crop in

Europe, the Middle East, and the Far East. Green-

house cucumber cultigens differ from those grown in

the field by being parthenocarpic, that is, they have

the genetic ability to set fruit without pollination, and

by being completely gynoecious, that is, they produce

female flowers exclusively.

0017According to FAO statistics, world cucumber pro-

duction exceeds 29 million tonnes, with China pro-

ducing over half of that. Other important producing

countries are Iran, Turkey, USA, Japan, and Russia.

Cucumbers are an important part of the diet in these

and other countries, but they are low in nutritional

value.

Watermelons

0018Watermelons (Citrullus lanatus (Thunberg) Matsu-

mura & Nakai) are prostrate, basally branched, softly

hairy vines possessing deeply and roundly indented,

blue–gray–green leaves and branched tendrils. They

are monoecious, producing one flower per node. At

most nodes, a male flower is produced but a female

flower appears at every seventh or eighth node. The

flowers are small, approximately 3 cm in diameter,

and light yellow. C. lanatus is diploid, with 11 pairs

of chromosomes (2n ¼22).

0019Watermelons originate from tropical Africa south

of the equator and are well adapted to warm, season-

ally dry habitats. Watermelon culture reached Egypt

no later than 3500 years ago. Watermelons require a

long, warm growing season and are usually grown for

the consumption of their fresh, edible fruit flesh.

Unlike melons and pumpkins, the part consumed is

the placental region, or endocarp. In some regions,

consumption of the seeds is important, too.

0020There is a great variation in fruit size in water-

melons, from approximately 2 kg to over 20 kg.

Fruit shape can range from almost spherical to obov-

ate. Fruit color is almost always green, but some rare

forms have yellow fruits or bicolor, yellow and green,

fruits. The watermelon fruit rind can be of a single

green shade, such as black–green, dark green, or light

green, or have two green shades as striping. However,

the width of the dark and light stripes can vary with

respect to one another, that is, the dark stripes can be

3820 MELONS, SQUASHES, AND GOURDS

much broader, broader, about the same as, narrower,

or much narrower than the light stripes. Fruit interior

(placental) color can vary from light green to white

to light yellow, intense yellow, orange, pink, red, or

intense red. Most cultivars have red flesh. ‘Crimson

Sweet,’ a cultivar bred at Kansas State University in

the USA that was commercially released in 1966, is a

leading cultivar possessing medium-size (8–11 kg),

spherical-oval fruits having an attractive rind of

broad, dark stripes and high-quality, very sweet,

fine-grained red flesh with relatively few small

brown seeds. The idea of triploid (3n ¼33) seedless

hybrids was proposed by Japanese and American

geneticists in the mid-twentieth century. Seedless

cultivars related to ‘Crimson Sweet’ have been de-

veloped, and these are becoming increasingly popular.

0021 In some countries, most notably China, consump-

tion of watermelon seeds is popular. Watermelon

seeds can be black, brown, tan, white, red, or green,

or a combination or pattern of these. Seed size

and number per fruit also vary considerably.

Cultivars grown for seed consumption usually have

a distinctive seed-coat color (such as red or green) or

pattern (such as tan ringed with black) and small

fruits that are packed with many medium- to large-

size seeds.

0022 Watermelons have the greatest world production of

any cucurbit, exceeding 63 million tonnes according

to the FAO. Not surprisingly, China is by far

the largest producer of watermelons, with over 38

million tonnes. However, this tonnage would not

indicate relative economic importance, as other cu-

curbits, such as melons, summer squash, and cucum-

bers, have several times the monetary value per

unit weight than do watermelons. Most of the other

important producers are countries that have

regions with hot, dry summers and include Turkey,

Iran, USA, Egypt, Mexico, Kazakhstan, Spain, and

Saudi Arabia. Watermelons are not high in nutritional

content, but their flesh does contain a large amount of

carotenoids.

Squash and Pumpkins

0023 Squash and pumpkins belong to the genus Cucurbita

and encompass four cultivated species. Plants are

large, usually viney and branched, with branched

tendrils. All are monoecious, bearing showy, large,

10–16-cm-diameter, bright yellow to orange flowers.

Usually, one flower is produced per node, with the

first nodes producing male flowers exclusively. The

species of Cucurbita are diploids, all with 20 pairs of

chromosomes (2n ¼40). Fruit size, shape, and color

vary greatly among cultigens. The species differ from

one another in the aspect of the foliage and shape of

the leaves. Edible fruits that are more or less round in

shape are usually referred to as pumpkins, and those

that are not round in shape are usually referred to as

squash. Unpalatable or inedible fruits are referred to

as gourds.

0024The most widely grown species is Cucurbita pepo L.

This species is native to warm-temperate to temperate

regions of North America and was one of the first

American plants to have been described and depicted

by Europeans. The plants of this species can be viney

or bushy, and leaf shape, while generally pentagonal,

can vary from not incised to deeply incised. The foli-

age is spiculate, a characteristic serving to distinguish

C. pepo from other species of the genus. C. pepo is well

adapted to all temperate regions and is grown mostly

for the use of its immature fruits, also known as

summer squash. In cool regions, this species is also

grown extensively for the culinary use of the flesh of its

mature fruits, for consumption of the seeds or seed oil,

and for ornaments. C. pepo is perhaps the most di-

verse species for fruit characteristics in the entire plant

kingdom. Fruits range in size from less than 100 g to

over 20 kg, ranging in shape from round to extremely

long to flat, can be with or without ribs, grooves,

furrows, wrinkles or warts, and can be green, yellow,

or orange ranging in intensity and shading from

almost black to almost white and possess patterns of

striping, which is longitudinal, or bicolor, which is

latitudinal (see Figure 2). This species is considered

to consist of three subspecies and 10 cultivar-groups,

as summarized in Table 2. The familiar Halloween

and pie pumpkins, the oil-seed pumpkins, the

zucchini, cocozelle, vegetable marrow, scallop, crook-

neck, straightneck, and acorn squash, the unique

fig0002Figure 2 (see color plate 105) Squash and pumpkins.

MELONS, SQUASHES, AND GOURDS 3821

‘Delicata’ and ‘Rolet,’ as well as the small, fancy

ornamental gourds are all members of C. pepo.

0025 Another widely grown species is Cucurbita

maxima Duchesne. Like C. pepo, this species is well

adapted to warm-temperate and temperate regions.

C. maxima is native to warm-temperate regions of

South America, and the plants are usually viney,

infrequently bushy, and with round stems. The leaf

blades are more or less pentagonal but are also

rounded. The foliage is stiffly hairy. In South Amer-

ica, C. maxima is grown for its immature and mature

fruits, but elsewhere, it is grown almost exclusively

for the consumption of the mature fruit flesh and, in

parts of Europe, for consumption of the seeds. There

is also a great deal of variation in fruit characteristics.

C. maxima is well named, as its fruits are the largest

of the plant kingdom, and new records for size are

established every several years. C. maxima pumpkins

exceeding 450 kg have been grown. Many of the

small-fruited kinds are rated high in quality. Among

the familiar named cultigens of C. maxima are ‘At-

lantic Giant,’‘Buttercup,’‘Delica,’‘Delicious,’‘Gold

Nugget,’‘Hubbard,’‘King of the Mammoths,’

‘Lumina,’‘Queensland Blue,’‘Rouge Vif d’Etampes,’

and ‘Turk’s Turban.’

0026 Yet another widely grown species is Cucurbita

moschata Duchesne. Unlike C. pepo and C. maxima,

C. moschata is best adapted to tropical climates. The

nativity for this species has not yet been confirmed,

but apparently, it is in tropical regions of northern

South America. The plants of C. moschata are large,

spreading vines, with angular stems. The leaf blades

are pentagonal and cornered, but not incised. The

foliage is softly hairy. C. moschata is usually grown

for consumption of its mature fruits. This species

is an important source of nutrition, especially of

provitamin A, to peoples of the tropics, particularly

in northern South America, Central America, and the

Caribbean Islands. A great deal of variation in fruit

characteristics can be found in northern South Amer-

ica. Although the fruits of C. moschata are generally

referred to as tropical pumpkins, this species does

include the ‘Cheese’ pumpkin and ‘Butternut’ squash,

which are grown in temperate climates.

0027The fourth species of squash and pumpkins is

Cucurbita argyrosperma Huber, a species that is

native to warm lowland regions of Mexico. Closely

related to C. moschata, this species also has large,

spreading vines, angular stems and cornered leaf

blades but tends to be less hairy. C. argyrosperma is

not as widely cultivated as C. moschata, but it is

important in its native country, more for consump-

tion of its seeds than for its fruit flesh. One

cultigen, ‘Green Striped Cushaw,’ has been grown

for centuries in the USA for consumption of its

mature fruit flesh.

0028A fifth cultivated species of the genus is Cucurbita

ficifolia Bouche

. This species is commonly known as

the fig-leaf gourd rather than as a squash or pumpkin

and has less variation in fruit characteristics than the

other cultivated species of the genus. Its fruits usually

weigh several kilograms, are round to oval or nearly

so, and are mottled green and white. The white,

fibrous fruit flesh is most often used for making

sweets or preserves. C. ficifolia also has large, spread-

ing vines with leaves that usually are similar in shape

to those of fig leaves and is grown in the cool,

highland regions in low latitudes of the Americas.

Although adapted to cooler temperatures, it is day-

length-sensitive and does not flower in the long days

of summer of the mid-latitude regions.

0029FAO statistics list pumpkins, squash, and gourds

together. As gourds can include members of Cucurbita

as well as other genera, most notably the bottle gourd

(Lagenaria), it is difficult to give an accurate estimate

of production of Cucurbita. The production figures

from some large producers of pumpkins and squash,

notably the USA, Austria, and Guatemala, are not

included in the FAO statistics. According to the FAO,

world production of pumpkins, squash, and gourds

was over 15 million tonnes in 2000. The leading

producers, with approximately one-fifth of the total

for each, are China and India, followed by Ukraine,

Egypt, Iran, Italy, Mexico, Argentina, Turkey, South

Africa, and Spain. Pumpkins and winter squash pro-

vide an important source of sustenance in some of

the poorer regions of the world. Of the cucurbits,

and indeed of vegetable crops generally, pumpkins

and squash rank high overall in nutritional value,

most familiarly in the carotenoid content of the fruit

flesh.

tbl0002 Table 2 Classification of Cucurbita pepo (squash, pumpkin,

gourd) to subspecies and cultivar-groups

Subspecies Group Description

pepo (cultivated forms, wild forms unknown)

Pumpkin Spherical, globose, oblate, oval,

obovate

Vegetable marrow Short, tapered cylindrical

Cocozelle Long, bulbous cylindrical

Zucchini Uniformly cylindrical

Pepo gourd Round, smooth or warted

texana (Scheele) Filov (wild and cultivated forms)

Acorn Top-shaped, furrowed

Scallop Flat with scalloped edge

Crookneck Long, narrow neck

Straightneck Short, thick neck

Ovifera gourd Oviform or pyriform, smooth

fraterna (Bailey) Andres (wild forms only)

From Paris HS (2000) History of the cultivar-groups of Cucurbita pepo.

Horticultural Reviews 25: 71–170.

3822 MELONS, SQUASHES, AND GOURDS

Other Cucurbits

0030 Bottle gourd, Lagenaria siceraria (Molina) Standley,

has large vines bearing large (approximately 10 cm

wide), white flowers that open at night. Their leaves

are softly hairy, and large and rounded. This species

contains a tremendous variety of fruit shapes and

sizes, the result of human selection in different cul-

tures of various regions for a variety of purposes.

Young fruits are hairy and usually light green but

become glabrous and beige or brown at maturity.

The moist, white flesh of the immature fruit dries

out as the fruit matures. The young fruits are used

for culinary purposes, much like summer squash, in

Italy (where they are known as cocuzzi), China, and

India. They are also known as calabash gourd. The

mature bottle gourds have a variety of other uses, too,

first and foremost as containers.

0031 Wax gourd, Benincasa hispida (Thunberg) Cog-

niaux, is important in China and other countries of

eastern and southern Asia. It bears some similarities

to Cucurbita by having long, sturdy vines, large

leaves, large yellow flowers, and large fruits. How-

ever, the stamens of its flowers are free rather than

fused, and the mature fruits are covered with a waxy

cuticle. The young fruits are hairy. Fruit color is

green, with shapes ranging from round, pumpkin-

like to cylindrical, and the flesh is white and crisp.

Both the immature and mature fruits are used for

culinary purposes. The young fruits are usually

cooked or pickled but sometimes eaten raw, and are

sometimes referred to as Chinese squash. The mature

fruit is sliced or cut into chunks for cooking in soup

and is also known as Chinese winter melon.

0032 Sponge gourd, Luffa cylindrica (L.) M.J. Roemer is

a fairly large vine bearing large, 8–10 cm wide, bright

yellow flowers. The cylindrical, green fruits are har-

vested when young, approximately 10 cm long, and

usually boiled, but can achieve a length of 40 cm or so

at maturation. They are also called smooth loofah or

dishcloth gourd. The endocarp dries out as the fruit

matures, forming a sponge that has a wide variety of

uses. This fibrous net is the dried remains of the

highly anastomosing vasculature of the fruit meso-

carp. A related species, the angled loofah (Luffa

acutangula) is similarly used and referred to as

Chinese okra.

0033 Bitter melon, Momordica charantia L., also known

as Balsam pear and bitter gourd, is a relatively small,

glabrous or nearly glabrous vine. The elongate fruits

average 15–20 cm in length and several centimeters

in diameter and are eaten prior to maturity, as the

mature fruits are bitter. The seeds are covered with

sweet, red arils, but the seeds themselves are poison-

ous. This species is grown mostly in southern Asia. It

has had considerable medical interest as a treatment

for a variety of ailments, including HIV.

0034Chayote, Sechium edule (Jacquin) Swartz, is a

perennial vine native to Mexico and Guatemala.

Chayote is grown almost entirely in subtropical and

tropical areas and does not flower in the long days of

summer of the middle latitudes. The green fruits are

round to pyriform, averaging 14 cm long, and contain

a single seed. The fruits are harvested when immature

and cooked.

0035Snake gourd, Trichosanthes cucumerina L., is a

hairy vine bearing distinct fringed white flowers that

open at night. The mature fruits are up to 150 cm

long, very slender, and curved. The immature fruit

has distinct broad intense green and narrow pale

stripes. As the mature fruit is fibrous and can be bitter,

usually only the immature fruits are used for culinary

purposes.

Food Value

0036As described in the previous sections, cucurbit fruits

are often consumed when young and immature. Cu-

cumbers, for example, are usually consumed no more

than one week after anthesis. Immature cucurbit

fruits are generally very high in water content;

young cucumbers may contain 96% water and there-

fore are considered to have little nutritional value on

a volume basis (Table 3).

0037The mature fruits of many cultivated cucurbits are

inedible or palatably undesirable for a variety of

reasons, including the accumulation of bitter com-

pounds in the mature fruit flesh. However, the mature

fruits of some cucurbit species are highly appreciated

and have immense worldwide economic value. The

cucurbit fruits that are consumed mature can be

divided into two categories: those that are enjoyed

uncooked for their sweet flesh (melons, watermelons)

and those that are enjoyed after being cooked in some

manner, such as boiling, stewing, roasting, or baking

(pumpkins, winter squash, wax gourd). The water

content of the mature fruit is lower than that of the

immature fruit, and the different cucurbit fruit are

specialized in various types of metabolite accumula-

tion during maturity. For example, melon and water-

melon fruit are characterized by soluble sugar

accumulation during the final stages of fruit develop-

ment. In the case of melon, which has been studied

most extensively, this sugar accumulation is due

almost exclusively to the storage of sucrose, which is

practically absent in the immature fruit and can in-

crease dramatically during the final weeks of fruit

development to 5% on a fresh weight basis, or 60%

on a dry weight basis, of the fruit flesh. This storage

of sucrose is determined by developmental changes in

MELONS, SQUASHES, AND GOURDS 3823