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

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Salsify:

Tragopogon porrifolius

0049 Salsify is a biennial plant, belonging to the family

Asteraceae and native to Europe, North Africa, and

Asia. From the appearance of its foliage, the plant

acquired the name of ‘goat’s beard’ and from the taste

of the root ‘vegetable oyster.’ It is grown for its long,

tapering roots, frequently branched, which are used

for flavoring. The long, grass-like narrow leaves form

a rosette and the plant can reach 1.2 m (4 ft) in height,

with purple daisy-like flowers. Salsify is very hardy

and the root may be harvested well into the winter

with no damage. Little salsify is grown commercially

in the USA. Roots are ready for use in mid-fall to late

spring, and are lifted and stored for winter in boxes

of sand.

0050 Salsify contains the highest amount of protein

(2.9%), carbohydrates (18.0%), phosphorus (66 mg

100 g

1

), and potassium (380 mg 100 g

1

) among

root salad crops (beet, carrot, radish, turnip, ruta-

baga, and parsnips).

0051 Roots, leafy shoots (known as chards), buds, and

open flowers can be used as raw salad. Salsify is

cooked with its peel on and after cooking the peel is

removed and the vegetable is served hot or cold with

dressing. Flowers as used raw or cooked.

Squawroot:

Perideridia gairdneri

Mathias

0052 Other names: yampah, epos root.

0053 The squawroot is perennial, and belongs to the

Apiaceae family. It is grown wild in the western

USA (southern Oregon, northern California) and

British Columbia. Enlarged storage roots are col-

lected in the summer and fall by local people and

are eaten raw or cooked. They are also dried for

use during summer. Epos was served as food for

natives and early settlers in these regions. The

starchy dark-skinned roots resemble nuts with a

white flesh.

Turnip and Rutabaga:

Brassica rapa

L. ssp. Rapa

= 20);

B. napus

L. ssp. Napobrassica (2

= 38)

0054 These are biennial herbs, belonging to the family

Cruciferae, and are cultivated as annual root crops

for both animal and human consumption. Rutabaga

is evolved as a cross of cabbage (18 chromosomes)

with turnip (20 chromosomes), followed by spontan-

eous chromosome doubling. Turnip and rutabaga

have been grown for nearly 4000 years and were

known by the Greeks and Romans at the beginning

of the Christian era. Their original home is considered

to be temperate Europe. They reached Mexico in

1586, Virginia in 1610, and New England in 1628.

The early European settlers introduced them to North

America in the seventeenth century.

0055Although both are similar in flavor, most common

cultivars can be distinguished by their foliage appear-

ance and root shape, size, and color. The enlarged

fleshy storage organ in turnip and rutabaga varies in

form, and these may be round, cylindrical, or flat-

tened globes. The exterior may be white, green

bronze, or purple color and the interior is white or

light yellow. Their nutritional values also differ.

Turnip generally has hairy leaves and a small white

flesh root, whereas rutabaga has smooth, large leaves

with a large, yellow-fleshed root. Turnip is a short-

season crop; rutabaga requires a full season.

0056Purple-Top White Glove and Seven Top are the

important cultivars of turnip whereas American

Purple-Top and Laurentian are the important culti-

vars of rutabaga.

0057A cup of turnip greens provides 165% of the RDA

of vitamin C, 182% of vitamin A, one-sixth of iron

and thiamin RDA and one-fifth of riboflavin.

0058Turnips are used in roasts, stews, soups, and cas-

seroles and as a boiled vegetable or sliced in salads.

They may be eaten wholes or halved or mashed and

served with a variety of sauces. When young and

tender, turnip greens are cooked and eaten.

0059The flavor of rutabaga makes it suitable not only as

a cooked vegetable but also in soups, salads, and

baked goods. Rutabaga may be boiled or roasted

with meat and eaten in pieces or boiled and mashed.

Fresh uncooked rutabaga can be shredded into salads.

0060Rutabagas have much more vitamin A than

turnips, considerably more ascorbic acid and more

of the other vitamins, but less iron. This comparison

refers only to the roots.

0061Turnip and rutabaga are of best-quality roots (mild

and tender) when they are medium-sized, are com-

monly packed in transparent film bags, and require

storage temperatures of 0–2



C (32–35



F) and rela-

tive humidity of 90–95%.

Yacon:

Polymnia sonchifolia

Poepp. and Endl.

0062Other names: jiquama, jacon, apple of the earth.

0063The yacon is perennial, belonging to the Asteraceae

family, and is cold-tolerant; overground portions are

damaged by frost and reestablish from the under-

ground portion. The crop is grown as an annual for

its foliage and as a perennial for the underground

tuberous roots. Wild forms of yacon are found in

the Andean regions of Colombia, Ecuador, and

Peru. Plant height is approximately 1.5 m. Stems are

hairy and green with purple markings. Lower auxil-

iary stems bear yellow or orange flowers. After

flowering, the tops become senescent and die. Usually

four or more developing tuberous roots form clusters

that can be separated. Shapes vary from spindle to

round. The thin skins are tan or purplish brown color.

SALAD CROPS/Root, Bulb, and Tuber Crops 5067

The flesh can be white, pale yellow, or orange and is

of varying sweetness.

0064 Moisture and protein ranges are 70–85% and 6–

7%, respectively, in roots. Stems and leaves are often

fed to animals and can be used as cooked vegetables

or eaten raw. Roots are high in potassium. Carbohy-

drate is stored as inulin, a polymer of fructose, and

65% dry weight is sugar.

0065 Before use, skin must be removed because it is

resinous. The crisp-textured tuberous roots are juicy

and frequently eaten raw in snacks and salads, and

also boiled or baked. The tubers are a rich source of

fructose.

0066 Yacon production is more than 20 t ha

1

and is

stored well at 5



C and in the dark for a few weeks.

Yam beans/jicama:

Pachyrhizus erosus

L. Urban

0067 Other names: sincamas or sinkamas (Philippines),

fanko and sargott (China), dolique bulbeus (France),

jimaca (Spanish), xicamatl (Nahuatl Indian).

0068 Yam bean is a perennial, belonging to the Fabaceae

(leguminoseae) family. It is a native of tropical Amer-

ica, from Mexico to northern South America. It is

widely grown for its tuberous roots in these regions,

and in the Philippines, and South China and is a

domestic crop in Bolivia, northern Argentina, and

the Amazon river headwaters.

0069 Jicama (yam bean) is a herbaceous climbing vine.

Leaves are entire or lobed rhomboidal shape. The

tuberous root shape can be a flattened sphere, much

like a turnip, elongated, spindle-like, and lobed. The

skin is colored tan to light brown and flesh is white,

has a watery crisp texture and sweet taste. In Mexico,

two major types are grown:

0070 Jicama de leche: this type has a dark skin, slender

spindle-shaped root, and a milky taste.

0071 Jicama de aqua: this type has a light skin, turnip-

shaped root, is very succulent, and has a sweet

watery taste.

0072 The young brown-skinned and white-fleshed roots

are sweet and watery and often eaten raw as a snack

food and appreciated for their mild flavor and succu-

lent crispy texture. Roots are harvested by hand-

digging, yielding 15 – 45 t ha

1

and can be stored at

13–15



C for more than a month.

Bulbs

0073 It is monocotyledonous, assigned to Amaryllideceae

(Liliaceae), a distinct family of Alliaceae and has bulb

or corms, belonging to the Allium genus. Scaly leaves

are the underground edible portion and are valued for

their pungency.

0074The genus Allium contains about 500 widely

distributed species. The most important cultivated

species are onion (A. cepa L.), leek (A. ampeloprasum

L.), Japanese bunching of onion (A. fistulosum L.),

rakkyo (A. chinesensis G. Don), Chinese chive (A.

tuberosum Rott. Ex. Spr), chives (A. schoenoprasum

L.), and shallots (A. cepa L.).

0075These crops are native to the temperate regions of

South Africa and the Mediterranean. The alliums

have been cultivated for food, medicine, or religious

purposes and spices. The best-known feature of the

alliums is their characteristic smell and taste.

0076The remarkable sulfur-containing compounds they

contain characterize alliums, giving them their dis-

tinctive smell and pungency. In alliums most of the

sulfur is in the form of various nonprotein amino

acids, including the precursors (S-methyl, S-propyl,

S-(1-propenyl) and S-allyl) of the volatile flavor

compounds. These precursors are odorless, nonvola-

tile amino acids of the general name 5-alk (en) yl

cysteine sulfoxides. When fresh tissue is damaged,

flavor precursors react under the control of the

enzyme allinase (S-alk (en) yl-l-cysteine sulfoxide

lyase) to release the highly reactive sulfenic acids

plus ammonia and pyruvate. Allium crops are almost

totally lacking in starch but store carbohydrates as

fractans (polymers of fructose), including sucrose,

glucose, and fructose.

Garlic:

Allium sativum

L. (2

= 16)

0077Garlic is a cool-season, bulbous perennial plant of the

Alliaceae family. The name comes from the Welsh

word garleg, transformed into the English word

‘garlic.’ Carl Linnaeus gave the name Allium sativum

to garlic in 1754. The Romans disliked the strong

flavor of garlic but they fed it to their laborers and

soldiers for strength and courage. In the world of the

occult, garlic is believed to be a protection against

known and unknown evil. Garlic wreaths hung on an

outside door are said to ward off witches.

0078Garlic is native to middle Asia and the Mediterra-

nean region. Central Asia, in particular the high

mountain plateaus of Pamir and Tian Shan, is the

original home of garlic. Garlic culture appeared con-

siderably later in Europe and the rest of Asia, and was

introduced to North and South America by the Span-

ish and Portuguese at the beginning of the fifteenth

century. Anglo-Saxon settlers cultivated garlic in Aus-

tralia, neighboring islands, and in Central and South-

ern Africa at the beginning of the nineteenth century.

Garlic was used in Egypt before 2000 bc and in China

and India for more than 1000 years. With the in-

creased consumption of garlic in almost all countries,

both home and international trade have developed

rapidly. China is the highest producer of garlic,

5068 SALAD CROPS/Root, Bulb, and Tuber Crops

followed by South Korea, Spain, and India. World

production of garlic in 1990 was estimated to be

3 012 000 metric tons. Asia leads the world in garlic

production, with more than 82% of total world

supply, with China producing 63% of world supply.

0079 The biggest exporters of garlic are Spain, Italy,

France, and the USA. Fresh garlic and tinned foods

are the target of much interest. Garlic for the fresh

market was $261.5 million in 1997. Per capita con-

sumption of garlic was 94 g (2.1 lb) per person in

1996. Most of the 37 000 acre of garlic grown in the

USA is in California. The Republic of Korea con-

sumes the most garlic.

0080 The garlic bulb is composed of a disk-like stem,

thin dry scales, which are the bases of foliage leaves,

and smaller bulblets or cloves (usually 10 or more).

The edible part of garlic is termed the clove; this is a

small bulb that, together with other cloves, forms an

aggregate or cluster covered with the outermost leaf,

a white or purplish papery sheath. Cloves are formed

from auxiliary buds of younger foliage leaves and

enclosed by dry outer scales. Each clove consists of a

protective cylindrical sheet, a single thickened storage

leaf sheath and a small control bud. Garlic leaves

have solid, thin blades.

0081 Cultivars There are two different types of garlic:

those that send up a seed stalk (hard-neck cultivars)

and those that do not (soft-neck cultivars).

0082 Rocabole type (hard neck):

0083 Spanish roja produces 6–13 cloves per bulb and

cloves are brown to reddish purple and are easy

to peel.

0084 Carpathian produces 6–10 cloves per bulb. The

bulbs are large and uniform with bulb wrap-

pers that have purple blotches. Carpathian has

a hot and spicy flavor.

0085 German Red produces 10–15 cloves per bulb. It

is very vigorous and has a deep green large

bulb. The cloves are light brown with some

purple at the base.

0086 Artichoke type (soft neck):

0087 Inchellium Red produces 4–5 clove layers with

8–22 cloves. The bulbs can be over 7 cm in

diameter and have a mild, lingering flavor.

0088 California Early produces four clove layers

with 10–22 cloves. The cloves can have a tan

to off-white color with pinkish blush. The

flavor is mild and slightly sweet.

0089 Silver Skin types (soft neck):

0090 Mild French produces four clove layers with

13–16 cloves. The color of the cloves is reddish

pink blush on a yellow-white background and

it is better adapted to hot climate. It has a sharp

taste when raw but has a smooth, nutty taste

when cooked.

0091Silver Skin produces 15–20 cloves, usually in

five layers. The clove color is off-white to tan

with pink blush. It is a good producer of large

bulbs that taste mild and sweet.

0092Two distinct cultivars, Fawari and Royalle Gaddi,

are reported from India. Odeskii-13 and Imeruli-23

are grown in CIS. The principal varieties grown in

the USA for drying are California Late (Pink and

Italian) and California Early (White or Mexican and

Creole).

0093Garlic is largely used fresh and stored as a condi-

ment and a flavoring agent in soups, stews, tomato

combinations, spaghetti, sausages, pickles, and

salads. Spray-dried garlic products are also available.

Garlic is used to enhance the smell and flavor of

salted meat and fish. Dried garlic in powdered or

granulated form is sometimes used in place of fresh

bulbs. A number of garlic products, including cap-

sules, extracts, garlic oil, and tablets, are now

marketed and are odor-free. Garlic salt has much

wider culinary potential than garlic powder. One

tablespoon is equivalent to a clove of fresh garlic.

Garlic butter has many uses in home and restaurant

cooking and many restaurants offer garlic bread with

meals.

0094Garlic has been used medicinally and there is some

belief in its mythical properties. Garlic is a gastric

stimulant, and helps in the digestion and absorption

of food. Allicin has a hypocholesterolemic action and

blood sugar-lowering effect. Garlic possesses antibac-

terial, insecticidal, and insect repellent properties, as

well as nematicidal and larvicidal properties. Ancient

folk medicine says that a cold can be cured if a person

rubs the soles of the feet with cut garlic cloves or if a

tonic of honey and garlic is drunk. Garlic prepar-

ations are given in whooping cough, lung disease,

stomach complaints (such as to heal intenstinal

ulcers) and disorders resulting from childbirth and

specifically to treat for sore eyes and earache.

0095Garlic is harvested when the foliage collapses and

starts to senesce. In a warm, dry climate, the bulbs

may be left to dry and cure indoors or in windows in

the field for about 1–3 weeks, using the foliage to

protect the bulbs from sun injury. After drying, plants

are tied in small bundles and then stored hanging on

bamboo sticks or ropes. Trimmed bulbs can be stored

in 2-m-deep bins or stacks provided with forced ven-

tilation, as well as in shallow containers or sacks.

Cold air (down to 0



C) of low relative humidity

is best for ventilating the stacks. Garlic cloves are

stored best at 1



C. Garlic cloves sprout most rapidly

at 4–18



SALAD CROPS/Root, Bulb, and Tuber Crops 5069

Leek:

Allium ampeloprasum

(Porrum group),

= 4x = 32)

0096 The leek is herbaceous, biennial, and belongs to the

family Alliaceae. Leak probably originated in the

eastern Mediterranean area and spread to Europe by

the Middle Ages; it was introduced to North Ameri-

can by European settlers. Leek are popular year-

round as a salad vegetable in northern and western

Europe and China. France is the largest producer of

leeks in the world. Leeks are especially important in

northern European countries such as Belgium, Den-

mark, and The Netherlands. Wild forms extend into

western and southern Russia.

0097 Leek is a tall, hardy robust herbaceous biennial

with white, narrowly ovoid bulb and broad flat

leaves. It resembles a green onion but is larger and,

unlike onion and garlic, it does not form bulbs or

cloves. Leeks are made up of sheaths of basal leaves

that can be 15–25 cm long and 5 cm in diameter. The

leaf base of leek stores some reserve, and has a milder

and more delicate flavor than onion. When tender, it

is eaten raw; is also cooked with other vegetables or

used as a flavoring in soups and stews.

0098 Cultivars Leek varieties have been classified into a

number of major types that differ in pseudostem

length and slenderness, leaf color, winter hardiness,

and the tendency for bulbiness. Types are:

0099 Bulgaarse Reuzen cv. Longa: very long, high-

yielding leeks with pale green leaves and little

frost resistance.

0100 Danish cv. King Richard: long, high-yielding types

with pale to mid-green leaves, suitable for late

summer production and frost-susceptible.

0101 Franse Zomer Selections cv. Pancho: long leek

with mid-green leaves, limited frost resistance,

and a tendency to form bulb.

0102 Swiss Giant Selections cv. Tilina: medium to long

leaves, with pale to mid-green, rather spreading

leaves, frost-resistant.

0103 Blauwgroene Herfst cv. Verina: medium shank

length, dark leaf varieties, tendency to form bulb.

0104 Autumn Mammoth selection cv. Goliath: medium

shank length, mid-green, spreading leaves, little

bulbing, very frost-hardy, high-yielding.

0105 Giant winter cv. Winterreuzen: variable in appear-

ance between varieties; all have good frost resist-

ance.

0106 Blauwgroene Winter cv. Bleu Star: short leeks with

dark leaves and a high degree of bulbiness, very

hardy, low-yielding.

0107 The cultivars listed by American seedmen include

London Flag, American Flag, Elephant or Monstrous,

Carentan, Giant Nussenburgh, and Lyon. Acadia,

Derrick, and Electra are suitable for fall cultivation

in Belgium, while Alberts, Brizzard, and Carina are

better for winter. Longa, Odin, Kilima, Goliath,

Cyberia, and Artico are promising cultivars in Canada.

Highest yield of leeks was obtained from King

Richard, Verina, Tivi, Kazan, Kilima, and Albana.

0108Commercially important leek cultivars include the

following:

0109Carina has heavy thick, long white shanks and is

good for overwintering.

0110Titan is an extra long, early type that has vigorous

growth. The leaves are dark green with white

stems.

0111Alaska has dark blue-green foliage and is tolerant

to subfreezing temperatures.

0112Pancho is considered an early leek, has thick white

shanks, and resists bulbing.

0113American Flag is very hardy and cold-resistant, and

has large, thick shanks; it blanches to clear white

with blue-green leaves.

0114Slender minileeks, which are very tender, may be

eaten raw or cooked. The sharp flavor of leeks disap-

pears upon boiling. They are used extensively in

soups and stews because of their mild flavor and

mucilaginous character.

0115Compared to onion, leek contains more protein

and minerals. The energy value of 100 g of edible

portion of leek is also higher than that of onion.

0116Leeks are harvested when their stalks reach a size of

2.5 cm or more in diameter and are tenderer. Hydro-

cooling, icing, or vacuum cooling to preserve the

freshness of harvested leeks has been adopted. Leeks

can be stored at near 0



C (32



F) and about 90%

relative humidity for 2–3 months.

Onion:

Allium cepa

= 2x = 16)

0117The onion is a biennial herbaceous, belonging to the

Alliaceae family, and is typically grown for bulbs as

annuals. Onions are native to southern Asia and the

Ural mountains and have long been valued in China

and India for their pungent flavor. The onion is an

essential ingredient of the cuisine of many regions; it

was the staple food of workers at the pyramids in

Egypt; it has been worshipped since before the Chris-

tian era; and it has also been used in ancient Druid

rites. The onion is the oldest salad crop known to

humans.

0118Onions have been grown in England for centuries.

The onion was introduced into the West Indies by the

Spanish and spread to all parts of America, including

California, Oregon, Colorado, Texas, and Georgia.

China, India, CIS, Turkey, Japan, Pakistan, Mexico,

5070 SALAD CROPS/Root, Bulb, and Tuber Crops

Egypt and Chile and Spain are the major producers

and exporters of onion, whereas Malaysia, United

Arab Republic, Canada, Japan, Lebanon and Kuwait

are the major importers.

0119 India, Indonesia, the former Soviet Union and the

USA are the leading producers of onion. Onion is a

major commodity of international trade. Imports in

1987 by Germany, France, the UK, and the USA were

valued at US$265 m. Annually, the US onion crop is the

third most valuable commercial vegetable ($426 m in

1988). Onion production for fresh market and pro-

cessing increased from $581.5 m to $648.4 m in 1997.

0120 The size, shape, and color of skin and flesh, single

centers, skin retention, firmness, dormancy, pungency,

and concentration of soluble solids are important

quality traits for bulb production. Onions are becom-

ing the mainstay of our diets. The bulbs may be white,

red, brown, or yellow; round, piriform, or flat, soft,

or firm. Dormancy is important because onions are

often stored and marketed when prices are higher.

Higher soluble solids are important to the dehydrat-

ing industry, producing onion chips or powder, which

is used as seasoning.

0121Consumers in the USA prefer a less pungent onion,

whereas many tropical onions are prized for their

strongly pungent flesh.

0122The edible part of the onion is the bulbs, which are

composed of concentric, fleshy, enlarged leaf bases or

scales. The outer leaf bases lose moisture and became

scaly. The inner leaves generally thicken as the bulb

develops.

0123Table 8 lists important onion cultivars, and Table 9

gives a classification.

0124Starlite, Sunlite, BRI, Buffalo, Utalian Red Tor-

pedo, California, Early Red, and Sweet Sandwich

are important onion cultivars. Kyoto market

tbl0008 Table 8 Important onion cultivars

Country Cultivars

India Pusa Red, Pusa Ratnar, Nasik Red, Patna Red, N404, N207-1, white Patna, N-53, N2-4-1, Bellary Red,

Bellary Big Onion, B-780, Udaipur 101, Udaipur 103, Hisar-2, Hisar-II, Kalyanpur Red Round, Arka Pragati,

Arka Niketan, Arka Kalyan, Bangalore Rose and Punjab 48, Udaipur 102, Pusa White Round, Pusa White Flat,

Phule Safed, Phule Suwama, Basawant 780

Pakistan Phulkara, Faisalabad, Early and Desi Red, Local White (Kasmir)

Bangladesh Faridpuri Vati, Taherpuri

Egypt Giza6, Beherl

Israel Haemek, Moab

Spain Babosa, Valenciana, Temprana

South Africa De Wildt, Pyramid, Bon Accord, Hojein

Mexico Cojumatlah

Brazil Baia Performe, Grano 502, Texas Early Grand

USA Brigham Yellow Globe, Yellow Globe Danvers, Early Yellow Globe, Mountains Danvers, Ebenzer,

Red Wethersfield, South Port Red Globe, California, Early Red, South Port White Globe, White Cresole,

White Portugal or Silverstein, Yellow Bermuda, Crystal Wax, Early Grano, Yellow Sweet Spanish,

White Balbosa, White Sweet Spanish, Barletta, Beltsville, Bunching and White Lisbon

tbl0009 Table 9 Classification of onion cultivars

Daylength Scale color Pungency Representative cultivars Characteristics

Short (European type) Brown Sweet Awahia Very mild, soft-fleshed,

and unsuitable for storageRed Sweet Red Granex

Red Pungent Red Creole

White Sweet White Granex, Crystal Wax

Yellow Sweet Grans, Granex

Yellow Pungent Yellow Croele

Intermediate Brown Moderate Cochise Brown Relatively soft-fleshed

and primarily used

for the fresh trade

Red Moderate Stockton Early Red

White Moderate Fresno White

Yellow Moderate Riaeto

Long (American type) Brown Pungent Australian Brown Very pungent, hard, and store well

Red Pungent Carmen, South Port, Red Globe

White Pungent White Lisbon, Ivory

Yellow Sweet Fiesta, Sweet Spanish

Yellow Pungent Autumn Spice, Downing Yellow Globe

SALAD CROPS/Root, Bulb, and Tuber Crops 5071

(multistem), Ishikuro, and White Evergreen are the

best known and Paris Silver Skin, Barletta, Brunswick

(Reddish Brown), and Purplette (Purple) are import-

ant traditional cultivars.

0125 Bulb onions may be sliced and used in sandwiches

and tried as onion rings or blooming onions. They are

used at both immature (spring onion: bulbs are rudi-

mentary) and mature bulb stages as a vegetable and

spice as well as food for cattle and poultry. Onion can

be eaten raw or cooked. Mild-flavored, colorful bulbs

are often chosen for salads. Onions have many uses as

folk remedies and recent reports suggest that onions

play a part in preventing heart disease and other

ailments. In many countries pickled Allium bulbs

are eaten in large amounts. Onion is liked by the

rich and the poor alike as a vegetable and for

flavoring and pickling. Onions for pickling are either

common yellow-brown-skinned varieties or special

white Silver Skin types.

0126 1-propenyl-sulfenic acid is produced on cutting; it

spontaneously rearranges its chemical structure to

form the tear-inducing thiopropanal S-oxide. Onion

bulbs boiled whole, without previously damaging the

tissue, lack flavor, since the enzyme will be destroyed

before it has access to the flavor precursors.

0127 Onions are generally dried and pickled. In some

parts of West Africa, fermented preparations are

made from crushed onion leaves and tops. These

products are used to flavor food at times when

onion is not available. Onion scales may be sun-

dried for this purpose. Commercially prepared

onion products include dried flakes and powder,

usually made from white cultivars, with high dry-

matter contents and high pungency. Onion oil has a

flavor strength 500 times and onion juice 10 times

that of dried products.

0128 Canned and bottled onion is used in industries in

North America. Onion rings are common products in

fast-food industries. Pickled onions are popular in the

UK: onions covered in vinegar and pasteurized are

used. Onions are said to be stimulant, diuretic, and

expectorant. Onion oil is used to treat stomach ulcers,

eye disorders, gastrointestinal disturbances (flatu-

lence), high blood pressure, malarial fevers, scorpion

bites, and intestinal worms. The onion is known to

possess insecticidal, antibacterial, antifungal, anti-

tumor, hypoglycemic, hypolipidemic, and antiathero-

sclerotic properties. This has been attributed to its

sulfur-containing compounds.

0129 Onion bulbs are harvested when the tops fall over

and begin to turn yellow. The ideal diameter of an

onion bulb is 5–10 cm. Onions are dug and allowed to

dry out in the open sun for a few days to toughen the

skin. The dried soil on the bulb is removed by gentle

brushing. The stems are cut, leaving 5–7 cm attached

to the bulb. Onion bulbs are thoroughly covered

before being stored in crates; these crates, filled with

topped bulbs, are usually stacked in the field or in

open curing sheds, and covered with boards, and

roofing paper to protect the onions from injury by

sun and rain. For fresh usage, a temperature of 0



and relative humidity of about 65–75% for storing

are recommended. Onions can also be stored at high

temperatures of 29.2–34.7



C: 3–5% O

plus 10%

is superior to storage in air at 4.4



Shallot:

Allium cepa

(Aggregatum group)

0130A multiplier onion is an onion-like plant, which ori-

ginated in western Asia, and is popular in southern

USA and some European countries – France in par-

ticular. In the tropics, shallots are often grown in

areas where onion culture is difficult because the

climate is humid. The shallot has a very short growing

season of only 2 or 3 months. The term shallot refers

to the vegetatively propagated forms of Allium cepa

var. ascalonicum. Bulbs usually propagate the crop. A

single plant produces a cluster of from two to more

than 15 distinct small bulbs at the base. Shallots ripen

earlier than onion grown from seeds and generally

give a lower yield. Shallots are reasonably hardy;

they have a distinctively flavored onion-like bulb,

and are a good substitute for onion as they are easily

grown and fast-maturing, and most cultivars store for

an exceptionally long time, much longer than onions.

The shallot grows well where temperatures are too

high for bulb onions over 30



C (86



F). They are nor-

mally roundish in shape, but there are some long and

banana-shaped forms. The flesh is reddish or creamy

(yellow). Red is considered to be better-flavored but it

is smaller, slower-growing, and may not store as well.

0131Varieties/cultivars There are number of different

forms of shallots:

0132The Old Shallot: bulbs are small, about the size of

a walnut, 2.5 cm in diameter, 2.75 cm high and

with an irregular pyriform shape. When ripe, the

outer skin is silvery green or brownish, and

the inner scales are tinged with purple or brown.

The bulbs are produced in clusters of 5–8 or 10.

Leaves are about 30 cm tall and bright green in

color. This is the earliest variety, and it keeps well

and is rarely cultivated.

0133Large Brown: bulbs are about 5 cm in diameter,

6 cm high, the outer skin is reddish brown, and the

inner skin is tinged deep purple and fleshy. Leaves

are 45 cm long, erect, and deep green.

0134Jersey Shallot: bulbs are fairly large, uneven, and

irregular, often divided into side bulb and divided

crowns.

5072 SALAD CROPS/Root, Bulb, and Tuber Crops

4.0135 Yellow or Dutch shallots: bulbs are round or

slightly flattened, scales are greenish before

drying, and straw-colored when ripe.

0136 Ampenan, Cloja, Bima, Bima Kuning, Bauji, Balizo,

Suminep, Bawang Lambung, Betawi Cipenos, and

Hejakuning cultivars are reported from Indonesia.

0137 Traditional cultivars Traditional cultivars include

Long Keeping Yellow; Long Keeping Red, Hative de

Niort, New Yellows. Sarite Atlantic Creation (grown

for seed), New Reds: Pikant and Deli Cato.

0138 Shallots are used in salads and cooking. Used as

bulb onions, they are superb pickled. Shallots may

contain more fat (Suminep) and soluble solids. Shal-

lots are also used in certain sauces. In Ethiopia small

local red shallots are highly valued in a traditional

sauce to accompany injera bread made from wheat

flour.

0139 Shallots are pulled by hand, when 70–80% of the

leaves have turned yellow. The outer skin is peeled off

and the roots are trimmed after washing, and they are

tied into 1.5-kg bunches. Shallot bulbs are dried for

5–14 days in the field and stored in warm conditions

(30



Cor86



F).

See also: Onions and Related Crops; Vegetables of

Temperate Climates: Oriental Brassicas; Carrot,

Parsnip, and Beetroot; Swede, Turnip, and Radish

Further Reading

Bremster JL (1994) Onion and other Vegetable Alliums.

Wallingford, UK: CAB International.

Decoteau DR (2000) Vegetable Crops. New Jersey: Pren-

tice-Hall.

FAO Production Yearbook (1990) Rome: Food and Agri-

culture Organization.

FAO Production Yearbook (statistic series) (1993) Rome:

Food and Agriculture Organization.

Kalloo G and Bergh BO (eds) (1993) Genetic Improvement

of Vegetable Crops. Oxford: Pergamon Press.

Lancaster JE and Boland MJ (1990) Flavour biochemistry.

In: Rabinowitch HD and Brewster JL (eds) Onions and

Allied Crops, vol. 3, pp. 32–72. Boca Raton, Florida:

CRC Press.

Larkcom J (1995) Salads for Small Gardens. London: Ham-

lyn.

Larkcom J (1995) Vegetables for Small Gardens. London:

Hamlyn.

Leshey Tiersa LAC (1992) The Herbs of Life, Health and

Healing Using Western and Chinese Techniques. Indian

Medical Series no. 65. Delhi, India: Sri Satguru Publica-

tions.

Pierce C (1987) Vegetables: Characteristics. Production and

Marketing. New York: John Wiley.

Rubatzky VE and Yamaguchi M (1997) World Vegetables.

Principles, Production and Nutritive Values. New York:

Chapman & Hall.

Salunkhe DK and Desai BB (eds) (1984) Onion and garlic.

In: Post Harvest Biotechnology and Vegetables, Part II,

pp. 23–38. Boca Raton, Florida: CRC Press.

Salunkhe DK and Kadam SS (eds) (1998) Handbook of

Vegetable Science and Technology. New York: Marcel

Dekker.

Wien HC (ed.) (1997) The Physiology of Vegetable Crops.

Wallingford, UK: CAB International.

Yamaguchi M (1984) World Vegetables: Principles, Pro-

duction and Nutritive Values. Westport, Connecticut:

AVI.

Salad Dressings and Oils See Dressings and Mayonnaise: The Products and Their Manufacture;

Chemistry of the Products

Salami See Meat: Sources; Structure; Slaughter; Preservation; Eating Quality; Sausages and Comminuted

Products; Analysis; Nutritional Value; Hygiene; Extracts

Salmon See Fish: Introduction; Catching and Handling; Fish as Food; Demersal Species of Temperate

Climates; Pelagic Species of Temperate Climates; Tuna and Tuna-like Fish of Tropical Climates; Demersal Species

of Tropical Climates; Pelagic Species of Tropical Climates; Important Elasmobranch Species; Processing;

Miscellaneous Fish Products; Spoilage of Seafood; Dietary Importance of Fish and Shellfish; Fish Farming; Fish

Meal

SALAD CROPS/Root, Bulb, and Tuber Crops 5073

SALMONELLA

Contents

Properties and Occurrence

Detection

Salmonellosis

Properties and Occurrence

C Wray, Greendale Veterinary Laboratories Ltd,

Knaphill, Woking, UK

Background

0001 The clinical and postmortem picture of typhoid fever

was first accurately described by French workers in

the early nineteenth century. The most striking con-

tribution on the natural history of typhoid before the

opening of the bacteriological era was the work of

William Budd, who elucidated many of the epidemio-

logical aspects of the disease. Ebert had observed in

1880 the typhoid bacillus in autopsy specimens from

a patient who had died from typhoid and the organ-

ism was isolated in 1884 by Gaffky. Calf paratyphoid

was first recorded as an endemic disease in northern

Europe in the middle of the nineteenth century and in

1885 the organism now known as Salmonella choler-

aesuis was first isolated from pigs by Salmon and

Smith, who considered the organism to be the cause

of swine fever (hog cholera). Salmonella was first

shown to be the cause of food poisoning by Gartner

in Germany, who isolated an organism which he

called S. enteritidis from the meat of a cow that had

diarrhea and was slaughtered, and from the spleen of

a man who had eaten about 800 g of meat from the

cow and died a day later. Subsequently Salmonella

were isolated from other species of animals and the

new strains were initially named after the disease

condition (e.g., S. abortusovis, S. typhimurium)and

each was considered a different species. With the

refinement of serological techniques for identifica-

tion, the serological subdivisions have increased and

the number of new Salmonella serovars continues to

increase annually. Each newly recognized serovar is

now customarily named after its place of isolation.

Taxonomy and Serological Classification

0002 The genus Salmonella belongs to the bacterial family

Enterobacteriaceae, whose definition is: straight rods,

generally motile with peritrichous flagella, grow on

nutrient agar, facultatively anaerobic, ferment glu-

cose often with the production of gas, reduce nitrates

to nitrites, and the oxidase test is negative. Some

serovars have peculiarities, e.g., the avian serovar

S. gallinarum is nonmotile and nonmotile variants

of other serovars are occasionally observed. The clas-

sification of Salmonella has been controversial for

many years, and according to the latest nomenclat-

ure, which reflects advances in Salmonella taxonomy,

the genus consists of only two species: S. enterica and

S. bongori. S. enterica is divided into six subspecies

which are distinguishable by certain biochemical

characteristics. These subspecies are:

0003Subspecies I ¼ subspecies enterica

0004Subspecies II ¼ subspecies salamae

0005Subspecies III ¼ subspecies arizonae

0006Subspecies IV ¼ subspecies diarizonae

0007Subspecies V ¼ subspecies houtenae

0008Subspecies VI ¼ subspecies indica

Thus the full correct nomenclature of an isolate

would be, e.g., Salmonella enterica subspecies enter-

ica serovar Enteritidis, rather than, as in the past,

Salmonella enteritidis. This, however, is cumbersome

and the concept that is currently in use at many

laboratories is to write Salmonella enteritidis.

0009Most isolates of Salmonella from domestic animals

belong to subspecies enterica, whose behavior is, with

few exceptions, regular and may be classified as

typical for the species. The principal biochemical

tests by which Salmonella can be identified are given

in Table 1. It should be pointed out however that

variable test results may occur because, with a few

exceptions, no test is 100% positive or negative.

0010Strains of Salmonella are classified into serovars

by the characterization of their surface antigens, as

described in the Kauffmann–White–Le Minor

scheme. The identity, known as the Salmonella sero-

var, is designated by the identification of two sets of

antigens. The somatic antigens, known as the O anti-

gens, are present on the main body of the organism.

They are polysaccharide antigens, identified by agglu-

tination with specific antisera, usually prepared in

5074

SALMONELLA

/Properties and Occurrence

rabbits, to give the serogroup, e.g., S. typhimurium is

a group B Salmonella due to the presence of the O4

somatic antigen. Most Salmonella possess two phases

of flagellar antigens (termed H), which are present

on the protein flagellar structures that extend from

the surface of the bacterium and such antigens are

described as diphasic. Some serovars possess only one

flagellar antigen and are described as monophasic.

Examples of antigenic formulas are:

0011 Group B (O4) S. agama O 4,12 : H i : 1,6 Diphasic

0012 S. typhimurium O 1, 4, (5), 12 : H i : 1,2 Diphasic

0013 Group C1 (O7) S. bonn O 6,7 : H 1,v : e,n,x Diphasic

0014 Group D1 (O9) S. enteritidis O9,12:Hgm:– Monophasic

Currently c. 2500 different Salmonella serovars have

been identified, although only a limited number are

encountered in practice. Some Salmonella serovars

possess a capsular polysaccharide which is termed

the Vi antigen. It is only of practical importance in

S. typhi and S. paratyphi, when its presence may mask

agglutination with somatic antiserum.

0015 Salmonella also possess fimbriae, which are a

family of polymeric proteinaceous surface organelles,

but until recently little was understood about their

variety and functions. Several different fimbrial types

may be expressed during the organism’s lifetime and

it is believed that some may assist intestinal coloniza-

tion and others assist their survival.

0016 Further subdivision for epidemiological studies of

the more frequent serovars may be obtained by phage

typing, which evaluates the degree of susceptibility

(or resistance) of isolates to a set of selected bacterio-

phages (viruses active against Salmonella). Such

schemes are in routine use in many laboratories for

the subdivision of S. typhi, S. typhimurium, and

S. enteritidis, and other serovars of more local

importance. Other methods used to show the related-

ness of isolates during disease outbreaks include

biotyping, antibiograms, and molecular genetic tech-

niques to examine plasmid and chromosomal DNA.

In recent years, many different molecular genetic

techniques have been used to fingerprint Salmonella

during disease outbreaks, but it should be pointed out

that while one method may work with a particular

serovar, it may not work with a different serovar.

Antibacterial Resistance

0017In general the prevalence of antibacterial resistance in

Salmonella is low and to some extent relates to the

serovar. However over the years different phage-types

of S. typhimurium have become resistant to a range of

antibacterials and caused epidemics in humans and

other animals. Often the resistance genes are carried

on mobile genetic elements, e.g., plasmids, and thus

may be transmissible to other serovars and other

bacterial species. Recently there has been an epidemic

in many different countries of a multiple-resistant

clone of S. typhimurium DT104 in which the resist-

ance genes are incorporated into the chromosome.

Detection of

Salmonella

0018Conventional isolation of Salmonella is accomplished

by using cultural methods, which are often based

on its phenotypic properties. Salmonella and other

members of the Enterobacteriaceae are more resistant

to novobiocin, selenite, tergitol, and bile salts, espe-

cially desoxycholate, than other bacteria. Salmonella

are also more resistant than other Enterobacteriaceae

to some dyes, e.g., brilliant green and malachite

green; however, these properties are not sufficient

for a true selective isolation and no medium is pres-

ently available that would allow the isolation of only

Salmonella and no other bacteria. Because of this

drawback, most differential media often include

tbl0001 Table 1 Biochemical reactions of typical Salmonella enterica subsp. enterica strains

Test Reaction of typical strains Test Reactionof typical strains

Motility þ Fermentation of:

Nitrate reduction þ Glucose þ

Oxidase  Mannitol þ

Oxidation/fermentation Fermentation Maltose þ

Urea hydrolysis  Lactose 

Indole production  Sucrose 

S production þ Salicin 

Citrate utilization þ Adonitol 

Sodium malonate  Dulicitol þ

Growth on potassium cyanide  Lysine decarboxylase þ

Methyl red þ Arginine dihydrolase þ

Voges–Proskauer  Ornithine decarboxylase þ

Gelatin liquefaction  Deamination of phenylalanine 

O-nitrophenyl-b-

D-galactopyranoside 

SALMONELLA

/Properties and Occurrence 5075

lactose, sucrose, and salicin with a pH indicator, since

most Salmonella fail to produce acid from these sub-

strates. (See Salmonella: Detection.)

Rapid Methods for the Detection of

Salmonella

0019 The time span that is necessary to obtain a negative

result can thus take up to 96 h when the whole cul-

tural method has to be applied and presumptive posi-

tive results may take up to 48–96 h. Many alternative

methods have consequently been introduced in recent

years to reduce analytical time and also save staff time

and media requirements. These may include modifi-

cation of conventional methods by including specific

substances to media used either for isolation or

confirmation or the development of tests to detect

specific characteristics of Salmonella. Other rapid

methods do not involve the isolation of the organism

and only provide a presumptive result. This allows

negative samples to be screened out, but positive

samples still have to be investigated further for con-

firmation. Of these methods, techniques based on

electrical conductance and impedance are in use in

many laboratories. When microbial growth and me-

tabolism take place in a culture medium, changes in

conductance of the medium occur but the reliability

of the method largely depends on the performance of

the selective medium used for the assay. Immuno-

logical techniques comprise the largest group of

alternative methods and many test kits are available.

These techniques include immunodiffusion, enzyme-

linked immunosorbent assays (ELISA), and the use of

specific antibodies to ‘capture and concentrate’ the

organism. Nucleic acid-based assays are also avail-

able, including the use of DNA probes to detect the

organism and the polymerase chain reaction (PCR) to

amplify a targeted region of the Salmonella genome.

Rapid methods, however, still require up to 24 h and

for many of the methods no worldwide standardiza-

tion for the validation and approval of the technique

is available.

Epidemiology

0020 Although primarily intestinal parasites of human

beings and other animals, Salmonella are widespread

in the environment and commonly found in human

sewage, farm effluents, and any material subject to

fecal contamination. Salmonellosis has been recog-

nized in all countries of the world, but appears to be

most prevalent in areas of intensive animal produc-

tion, especially in poultry and pigs. Although the

disease may affect all species of domestic animal,

young animals and pregnant animals are the most

susceptible. Many animals may be infected but show

no clinical signs. People are also highly susceptible to

infection, either by direct contact with infected

animals or through their products, as occurs in food-

borne salmonellosis.

Host Range

0021While all Salmonella are considered to be potentially

pathogenic, different serovars differ widely in their

host range and pathogenic syndromes that they pro-

duce. Some serovars show a degree of host adaptation

and primarily infect only one species of animal. Thus

S. typhi and S. paratyphi A, B, and C usually infect

only human beings and typhoid and paratyphoid are

considered as human disease entities. S. choleraesuis,

S. abortusovis, and S. gallinarum/pullorum occur in

pigs, sheep, and poultry respectively, and S. dublin

appears to have a predilection for cattle. In contrast,

S. typhimurium affects all species of animals and is

one of the most common causes of human food

poisoning. Companion animals are a source of Sal-

monella infection; the serovars relate to their feed and

the extent to which they scavenge. Salmonella have

been isolated from wild animals and birds, reptiles,

fishes, and insects.

Animal Infections

0022Most Salmonella infections in farm animals are likely

to be acquired from the same species of animal, espe-

cially the host-adapted serovars. Purchased animals

may acquire infection on their home premises, in

transit, in markets, in collecting centers, or in lorries.

Poultry may be infected vertically by egg-borne trans-

mission of Salmonella when the contents or the shell

may be contaminated or in the hatchery by cross-

contamination. Salmonella typhimurium and other

serovars may be introduced into herds and flocks by

contaminated feedstuff. Many batches of animal

protein, e.g., meat and bone meal, fishmeal, pelleted

feeds, and vegetable proteins have been found to be

contaminated with Salmonella and many new sero-

vars have been introduced into countries in imported

feed ingredients. Recontamination of feedstuffs after

processing is a major problem and heat treatment,

e.g., pelletization, and treatment with organic acids,

e.g., propionic or formic acid, is used to produce a

Salmonella-free product.

0023Infection may also be introduced by other domestic

animals as well as by feral animals and birds. Rats

and mice may acquire Salmonella infection; available

evidence suggests that they do not play a major role in

the spread of disease but that they may prolong the

persistence of infection on a farm.

Environmental Considerations

0024Salmonella may survive for long periods in infected

feces and slurry, where their survival depends on a

5076

SALMONELLA

/Properties and Occurrence