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

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quinoa suitable for the agroecological and food

requirements of the producer and national consumer.

Classification

0011 Quinoa belongs to the Chenopodiceae family, genus

Chenopodium. Its botanical name is Chenopodium

quinoa, Willd. Common names used in the Andean

region are: quinua, kiuna, parca (Ecuador, Peru,

Bolivia); supha, jopa, jupha, jiura, aara, ccallapi,

vocali (Bolivia); quinhua (Chile); and suba, pasca

(Colombia).

0012 The classification of quinoa was first made from

the color of the plant and fruits. Subsequently it was

based on the morphological types of the plant. Des-

pite the wide variation observed, quinoa is considered

to be one single species. For practical reasons, quinoa,

like maize, was classified as a race.

0013 The most extensive collection of different races of

quinoa belongs to Peru and Bolivia; each has over

2000 ecotype samples. However, other collections

do exist in Argentina, Colombia, Chile, Ecuador,

England, the USA, and the Former Soviet Union.

0014 Quinoa collected in Ecuador, Peru and Bolivia has

been classified into 17 races; however, more races

may exist. Two types of inflorescence are described:

0015 Glomerulates – small groups of flowers (glom-

eruli) originate from tertiary axes

0016 Amaranthiformes have glomeruli originating

mainly from secondary axes

According to this, the races of quinoa are classified

as follows: first, glomerulate inflorescence: Caja-

marca, Copacabana, Cuzco, Challapata, Cocha-

bamba, Sicuani, Junı

n, Ancash, Glorieta, and Dulce;

second, amaranthiforme inflorescence: Achacachi,

Puno, Real, Potosi, Puca, Sucre, and Pichincha.

0017Quinoa grows from sea level to the Andean high-

lands. Thus, one of the most useful classifications is

that describing five ecotypes: sea-level, valley, sub-

tropical, salar, and altiplanic (Table 1).

Cultivation Practices

0018The cultivation of quinoa is related to the crop rota-

tion seen in potatoes. This is the usual practice that

improves quinoa yield and preserves soil fertility.

Moreover, the biological cycle of several pathogenic

microorganisms is broken down. Together with resi-

dues of fertilizer previously applied to the crop, nitro-

gen is sometimes applied. Cultivation of the quinoa

plant requires loose soil that can retain an adequate

amount of moisture.

0019Quinoa tolerates a wide range of acidic conditions

of the soil, from pH 6.0 to 8.5. The plant is not

affected from around 1



C. However, it tolerates

high temperatures not above 35



C. Quinoa is frost-

resistant when the frost occurs before flowering; after

that significant damage may occur. Quinoa flowers

are sensitive to frost. Quinoa is drought-resistant. It is

able to develop even in regions where annual rainfall

is in the range 200–400 mm.

0020The planting season varies from August, in the

Andean highlands, extending through December,

and in some areas from January to March. Seeds

may be spread, but weed control and mechanized

practices become difficult. Quinoa is planted in

rows (row spacing range 40–80 cm) when mechan-

ized agriculture practices are used. In dry areas, seeds

can be deposited at the bottom of the furrows; once

tbl0001 Table 1 General categories of quinoa

Ecotypes Location Growth altitude (m) Varieties Characteristics

Sea-level South of Chile < 500 Chilean varieties Unbranched, long day plants,

yellow, bitter seeds

Valley Andean valley 2000–4000 Blanca de Junı

n, Rosada de

Junı

, Amarilla de

Matangani, Dulce de

Quitopamba, Dulce de Lazo

Big plants, branched, short

growth period

Subtropical Subtropical area of Bolivia

(Yungas)

2500–3000 Plants with intense green color

that turns orange as they

mature; small seeds, white or

orange

Salar Bolivian Salares 3700–3800 Real Plants adapted to salty and

alkalinic soils; bitter seeds;

high saponin content

Altiplanic Area around Lake Titicaca 3500–4000 Cheweca, Kancolla,

Blanca de Julı

Short plants with straight stems;

short growth period; resistant to

frost

4896 QUINOA

planted, the seeds are covered with soil. When rain is

more abundant, seeds are deposited on the top of the

ridge.

0021 Sowing density may vary according to the region. It

has been reported from 0.4 to 0.6 g m

2

in Bolivian

Altiplano, from 0.5 to 2.3 g m

2

in Puno, and from

0.8 to 1.4 g/m

2

in Ecuador. A density of 1.2 g m

2

has been recommended in Puno for mechanical

drilling. However, sowing density could be related

to the climatic conditions of the region where it is

cultivated.

0022 At physiological maturity quinoa is harvested. The

grains become dry and hard, making it difficult to

break them with a finger nail. Physiological maturity

may be reached within 70–90 days after flowering.

Depending on the variety, it takes between 5 and 8

months for a plant to mature.

0023 Traditional harvesting is done manually. The plants

are either pulled or cut with a sickle, then placed in

windrows to dry completely. Threshing is performed

by rubbing the panicles by hand against a stone or

using threshing on the floor with sticks, animals,

or vehicles followed by winnowing. Mechanical

threshers have been applied using stationary threshers,

some of which are adapted from those used for

cereals. The yield of quinoa can be in the range of

45–500 g m

2

depending on the variety and growing

conditions.

0024 The most important fungus disease is downy

mildew (Peronospora farinosa), which requires high

humidity and temperature as ideal conditions to

grow. However, it succeeds in low humidity and low

temperature (6–10



C) found in the north Altiplano.

The main symptom is chlorotic lesions on the upper

surfaces of the leaves, with a white or purple myce-

lium on the lower surfaces.

0025 The disease brown stalk rot is produced by Phoma

exigua var. fovaeta. Low temperature, high humidity,

and wounds in the plant, such as those produced by

hail, favor the growth of pathogen. Dark brown

lesions with a vitreous edge (5–15 cm) on the stem

and inflorescence are the main symptoms. The stem

is often shrunken, the plant may become chlorotic,

and progressive defoliation toward the apex may

occur.

0026 Kcona kcona (Scrobipalpula sp.) is probably the

most serious pest of quinoa. When drought periods

and high temperatures are present, insects attack in-

tensely. Larvae destroy first leaves and inflorescence.

Later on, when the plant is mature, larvae destroy

the panicle and grains. Sometimes, a white powder

around the base of the plant is seen as a result of grain

destruction. Treatment is performed just before

harvest to prevent contamination of seeds and

consequently postharvest losses.

Morphology of the Plant

0027Quinoa is not a true cereal grain: it is a pseudocereal,

which is dicotyledonous. In contrast, cereals are

monocotyledonous. In spite of that, the composition

of cereals and quinoa is similar as regards the main

components.

0028Quinoa, as a plant, grows 1–3 m high (Figure 1).

The seeds can germinate very fast, in a few hours after

being exposed to moisture. Roots can reach depths of

up to 30 cm. The stem is cylindrical (3–5 cm diam-

eter); it can be either straight or with branches, and its

color is variable. Depending on the variety it changes

from white, yellow, or light brown to red. Leaves are

shaped like a goose’s foot. They are formed by peti-

oles and lamina; petioles are long-channeled on their

upper side. Lamina is polymorphous in the same

plant; rhomboidal or triangular in the lower lamina

of leaves, triangular or lanceolate in upper leaves.

0029The flowers are incomplete; they do not have

petals. Quinoa has both hermaphrodite flowers, lo-

cated at the distal end of a group, and female flowers

located at the proximal end. Quinoa inflorescence is

full of bunches (racemose), which emerge on the

upper part and do not have branches. The arrange-

ment of flowers in raceme is considered to be the

panicle; the length of the panicle varies from 15 to

70 cm high. Flowers can be clustered in different

forms – either amaranthiforme or glomerulate.

fig0001Figure 1 (see color plate 124) Quinoa plant. Courtesy of Ing.

Carlos Nieto C. Pronaleg-Iniap.

QUINOA 4897

0030 Quinoa is a fruit of the Chenopodium family. The

fruit of quinoa is an achene. It produces small, circu-

lar-shaped seeds, about 2 mm diameter (250–500

seeds per gram: Figure 2). It is covered by perigonium,

which is the same color as the plant: white, yellow,

gray, light brown, pink, black, or red. It is easily

removed when it is dried. Another two layers enclose

the seed. Pericarp adheres to the seed; it contains

saponins which confer the bitter taste characteristic

of quinoa. Episperm encloses the cylindrical seed as a

thin layer. The embryo can be up to 60% of the seed

weight. It forms a ring around the perisperm. The

high protein content in quinoa, unlike cereals, is

explained by the high proportion of embryo.

Chemical Composition and Nutritional

Value

0031The diet of ancient inhabitants of the Inca empire has

generated interest due to its extremely nutritious

quality. Quinoa seeds contain carbohydrates, protein,

fat, minerals, and vitamins. The chemical compos-

ition of quinoa depends on the variety and the envir-

onment of its cultivation.

Quinoa seeds

0032Protein The protein content of quinoa seeds varies

from 8 to 22%, which on average is higher than

common cereals such as rice, wheat, and barley

(Table 2). However, it presents less than 50% of the

protein found in most legumes. In quinoa, most of the

protein is located in the embryo.

0033In pseudocereals, such as quinoa, albumins and

globulins are the major protein fraction (44–77% of

total protein), which is greater than prolamins (0.5–

7.0%). Using a modified Osborne’s method, a protein

fraction of quinoa was reported – 75.1% of albumins

þglobulins and 19.4% of glutelins (insoluble); no

prolamins were found. Thus, quinoa is considered to

be a gluten-free grain because it contains very little or

no prolamin. Quinoa provides a nutritional, econom-

ical, easy-to-prepare, flavorful food source which is

of particular relevance for people with gluten intoler-

ance, such as those with celiac disease.

0034Quinoa has a good balance of the amino acids that

make up the protein. It is exceptionally high in lysine

(Table 3), an amino acid which is not overly abundant

in the vegetable kingdom. It is also a good comple-

ment for legumes, which are often low in methionine

and cystine.

0035The nutritional evaluation of quinoa protein

has been reported in several studies. The protein

fig0002 Figure 2 (see color plate 125) Quinoa seeds. Courtesy of Silvia

Valencia Ch.

tbl0002 Table 2 Chemical composition of quinoa and some cereals and legumes (g 100 g

1

dry wt)

Quinoa Barley Maize Rice Wheat Oat

Rye

Bean Lupine Soya

Protein 16.5 10.8 10.22 7.6 14.3 11.6 13.4 28.0 39.1 36.1

Fat 6.3 1.9 4.7 2.2 2.3 5.2 1.8 1.1 7.0 18.9

Fiber 3.8 4.4 2.3 6.4 2.8 10.4 2.6 5.0 14.6 5.6

Ash 3.8 2.2 11.7 3.4 2.2 2.9 2.1 4.7 4.0 5.3

Carbohydrates 69.0 80.7 81.1 80.4 78.4 69.8 80.1 61.2 35.3 34.1

kcal 100 g

1a

399 383 408 372 392 372 390 367 361 451

kcal 100 g

1

:4 (%protein þ carbohydrates) þ 9  (%fat)

Source:

Kent N (1983) Chemical composition of cereals. In:TechnologyofCereals, 3rd edn. pp. 27–48. Oxford: Pergamon Press; Koziol MJ (1992) Chemical

composition and nutritional evaluation of quinoa (Chenoodium quinoa Willd). Journalof Food Composition Analysis 5: 35–68.

4898 QUINOA

efficiency ratio (PER) in raw debittered quinoa was

78–93% that of casein. These figures increased when

quinoa was cooked, and became 102–105% those of

casein. Similar results were found when quinoa from

the San Luis Valley of Colorado was used. Thus,

the quality of protein in quinoa matched that of the

milk protein casein. (See Amino Acids: Metabolism;

Protein: Quality.)

0036 Carbohydrates The major component in quinoa is

carbohydrates, which varies from 67 to 74% of the

dry matter. Starch is about 52–60%. The starch com-

pound is located in the perisperm of the seed; starch

can be present as simple units or as spherical aggre-

gates. The amylose content is about 11%, which is

lower than in cereals, for example, rice (17%), wheat

(22%), and barley (26%).

003 7 The diameter of quinoa starch granules is in the

range of 0.4–2.0 mm. Starch granules in quinoa are

smaller than those reported for maize (range 1–

23 mm) and for wheat (2–40 mm). Small-granule

starches exhibit a higher gelatinization temperature;

for quinoa the gelatinization temperature range is

57–64



C. Other carbohydrates are found in small

amounts, such as monosaccharides (2%) and disac-

charides (2.3%), crude fiber 2.5–3.9%, and pento-

sans 2.9–3.6%. (See Carbohydrates: Classification

and Properties.)

0038 Fat, vitamins, and minerals Quinoa contains from

2 to 10% fat. Quinoa and soya oils exhibit similar

fatty acid composition; thus, quinoa is a rich source

of essential fatty acids such as linolenic (18:2n-6:

52%) and linolenic (18:3n-6: 4%). Quinoa is a good

source of minerals. It contains more calcium, magne-

sium, iron, and zinc than common cereals, and the

iron content is particularly high (Table 4). Polishing

and washing quinoa seeds reduce the mineral content

to some extent 12–15% in the concentration of

iron, zinc, and potassium, 27% loss of copper and

3% loss of magnesium. Quinoa contains more ribo-

flavin (B

) and a-tocopherol than rice, barley, or

wheat (Table 4). Quinoa seeds can be a source of

vitamin E.

0039Nutritional disadvantages Saponins and phytic acid

are the main disadvantageous factors in quinoa. Other

inhibitors, trypsin inhibitor, and tannins are present

in low levels.

0040Trypsin inhibitor in eight varieties of quinoa (range

1.36–5.04 TIU mg

1

) was lower than for soybean

(24.5 TIU mg

1

). Trypsin inhibitor is a thermolabile

compound which is inactivated by heat treatments.

0041Polyphenols (tannins) are present in small amounts

(0.53 g 100 g

1

in whole quinoa seeds), which are

reduced after scrubbing and washing with water

(0.23 g 100 g

1

0042Saponins A bitter taste compound called saponin

is located in the outer layers of quinoa seeds. This

protects them from birds and insects.

0043Saponins are glycoside compounds which occur in

two groups. According to the nature of the sapogenin

moiety they are conjugated with hexoses, pentoses, or

uronic acids. The sapogenins are steroids (C27) or

triterpenoids (C30). Using a gas chromatography

method, the sapogenins oleanolic acid, hederagenin,

30-o-methylspergulagenate, and phytolaccagenic

acid are identifiable in sweet and bitter genotypes of

quinoa.

tbl0004Table 4 Mineralcomposition(mgkg

1

drywt)andvitamin

concentration(mg100g

1

drywt)ofquinoaandsomecereals

Minerals(mgkg

1

)QuinoaWheatRiceBarley

Ca 1487 503 69 430

Mg 2496 1694 735 1291

K 9267 5783 1183 5028

P 3837 4677 1378 3873

Fe 132 38 7 32

Cu 51 7 2 3

Zn 44 47 6 35

Vitamins (mg 100 g

1

)

Thiamin (B

) 0.38 0.55 0.47 0.49

Riboflavin (B

) 0.39 0.16 0.10 0.20

Niacin (B

) 1.06 5.88 5.98 5.44

Ascorbic acid (C) 4.00 0 0 0

a-Tocopherol 5.37 1.15 0.18 0.35

b-Carotene 0.39 0.02 NR 0.01

NR, not reported.

Source: Koziol MJ (1992) Chemical composition and nutritional evaluation

of quinoa (Chenoodium quinoa Willd). Journal of Food CompositionAnalysis

5: 35–68.

tbl0003 Table 3 Essential amino acids in quinoa and other foods

(g 100 g

1

protein)

QuinoaMaizeRiceWheatBeanMilkFAO

Hiistidine 3.2 2.6 2.1 2.0 3.1 2.7 2.6

Isoleucine 4.9 4.0 4.1 4.2 4.5 10.0 4.6

Leucine 6.6 12.5 8.2 6.8 8.1 6.5 9.3

Lysine 6.0 2.9 3.8 2.6 7.0 7.9 6.6

Methionine

5.3 4.0 3.6 3.7 1.2 2.5 4.2

Phenylalanine

6.9 8.6 10.5 8.2 5.4 1.4 7.2

Threonine 3.7 3.8 3.8 2.8 3.9 4.7 4.3

Tryptophan 0.9 0.7 1.1 1.2 1.1 1.4 1.7

Valline 4.5 5.0 6.1 4.4 5.0 7.0 5.5

As reported by Koziol (1992): see below.

Methionine þ cystine.

Phenylalanine þ tyrosine.

FAO, Food and Agriculture Organization.

Source: Koziol MJ (1992) Chemical composition and nutritional evaluation

of quinoa (Chenoodium quinoa Willd). JournalofFood CompositionAnalysis

5: 35–68.

QUINOA 4899

0044 Quinoa saponins are soluble in methanol or water.

They have strong detergent properties which form

very stable foam in water solutions, and reduce the

superficial tension of aqueous solutions. They also

show hemolytic activity and are in general toxic to

cold-blooded animals which obtain oxygen directly

from water. Saponins are also present in common

foodstuffs such as peanuts, asparagus, garlic, onion,

and spinach.

0045 The amount of saponins present depends on the

variety of quinoa. It is higher in bitter-flavor varieties

than in sweet, or low-saponin, varieties. Quinoa com-

prises saponins from 0.1 to 5%.

0046 The saponins of quinoa seeds are reduced to low

levels after dry polishing and washing with water.

These levels are apparently nontoxic to humans.

0047 The reduction of plasma cholesterol and bile salt

concentration has been attributed to the presence of

certain saponins in the diet. However, some saponins

can form insoluble complexes with minerals, such as

zinc and iron, which make the minerals unavailable

for absorption in the gut.

0048 Phytic acid Phytic acid (myoinositol 1,2,3,4,5,6-

hexakis dihydrogen phosphate) is found in most

cereals and legumes at concentrations of 1–3% dry

matter. It is also found in some fruits and vegetables.

0049 In cereals, phytic acid is located in the germ. In

quinoa seeds, phytic acid is located in the external

layers as well as in the endosperm. It has been

reported that mean (value) phytic acid concentration,

in five varieties of quinoa, was 1.18 g 100 g

1

0050 Studies in vivo and in vitro have shown that phytic

acid interferes with mineral absorption in the gut of

humans, because of its ability to form insoluble com-

plexes with divalent minerals such as iron, zinc, and

calcium. Even small amounts (0.5 mmol g

1

) of inosi-

tol hexaphosphate or pentaphosphate may reduce the

solubility of iron.

0051 Inositol hexaphosphate (IP

) was mainly found in

varieties from Ecuador: sweet INIAP-Tunkahuan

(11.3 mmol g

1

) and bitter INIAP-Ingapirca

(8.6 mmol g

1

). These figures were almost completely

reduced to 0.3 mmol g

1

after fermentation of the

germinated quinoa flour. At the same time a five- to

eightfold increase in the amount of soluble iron was

found.

Quinoa Leaves

0052 The leaves of quinoa are compared to spinach as

regards flavor. Quinoa leaves are cooked as a green

vegetable or used raw in salad. Leaves contain (on a

dry basis) carbohydrates 4.8 g 100 g

1

; protein 3.3 g

100 g

1

; fat 1.8 g 100 g

1

; ash 3.3 g 100 g

1

, fiber

1.9 g 100 g

1

. The protein concentration of quinoa

leaves is similar to spinach; however, it contains

slightly more isoleucine (5.8 g 100 g

1

protein) and

valine (7.5 g 100 g

1

protein). The amount of fatty

acids such as palmitic (16:0; 16.7%) and stearic

(18:0; 1.3%) is higher than in the grains. Quinoa

leaves are a rich source of vitamin A: they

contain 2085 mg RE (retinol equivalents) 100 g

1

(fresh wt), and vitamin E 2.9 mg a-TE (alpha-

tocopherol) 100 g

1

. Fresh quinoa leaves contain

more magnesium (83 mg 100 g

1

fresh wt) and

sodium (289 mg 100 g

1

fresh wt) than spinach

leaves. Using a gas chromatography method, sapo-

genins were detected in the leaves of four sweet and

bitter genotypes of quinoa. Sapogenins increased

as the plant matured. After 120 days of sowing,

the sapogenin content on the leaves of sweet geno-

types varied between 0.013 and 0.017 g 100 g

1

(dry matter) and in bitter varieties varied between

0.02 and 0.16 g 100 g

1

(dry matter). Hederagenin

was the major sapogenin present in the leaves.

(See Phytic Acid: Properties and Determination;

Nutritional Impact.)

Uses

0053Quinoa has a natural seed coating containing sap-

onins, which encases the seed and confers the bitter

taste which is characteristic of quinoa. Saponins must

be removed before consuming. External coatings are

removed using either a wet or dry process. The trad-

itional wet process used in rural areas is hand scrub-

bing in alkaline water. This process is used on a

commercial scale; it involves abrasive dehulling to

remove the external coverings, followed by a thor-

ough washing. However, this method has economical

and ecological restrictions: the water demand is high

and waste water is contaminated with saponins,

which are toxic to cold-blooded animals. Moreover,

wet seeds must be dried immediately, or they may

germinate after a few hours in wet conditions.

0054A dry method is also used. The seeds are scrubbed

and polished in order to remove, as fine powder,

external coatings. The equipment used to polish

other grains has been adapted for use with quinoa

seeds, with excellent results. This method presents

several advantages; no water is needed, no heat treat-

ment to dry the seeds is required, and no environ-

mental contamination is produced. This method is

best suited to sweet varieties (low saponin content)

of quinoa.

0055A combination of dry and wet processes is applied

to bitter varieties (high saponin content) of quinoa.

Saponin is first removed by polishing, when most of

the saponin is removed. Then, saponins that remained

in the seeds are washed with water, followed by a dry

4900 QUINOA

process. Any of the processes described above makes

the quinoa ready for use by the consumer or further

processing such as grinding.

0056 After removing the saponins, quinoa seeds can be

boiled in water (15–20 min) and served as a grain.

Cooked seeds swell to about two or three times their

original size. Seeds become transparent, with tiny

white bands circling across the midsection.

0057 In Chile, Ecuador, Peru, and Bolivia, the whole

seeds are used in soups, salads, casseroles, chilli and

stew, as well as roasted and ground in several kinds of

desserts.

0058 Quinoa can be eaten as a rice replacement, as a hot

breakfast cereal, or boiled in water to make an infant

cereal. The seeds can even be popped like popcorn.

Seeds can be ground and used as a flour, or sprouted.

The sprouts need to turn green before they can be

added to salads.

0059 Quinoa flour can be mixed with maize or wheat

flour. Several levels of substitution of quinoa flour

have been reported, for instance, in bread (10–13%

quinoa flour), noodles, and pasta (30–40% quinoa

flour) and sweet biscuits (60% quinoa flour). All yield

products of excellent quality. Quinoa flour can also

be drum-dried and extruded, providing products with

good physical, sensorial, and nutritional qualities.

Solid-state fermentation of quinoa with Rhizopus

oligosporus Saito was performed, giving a good-

quality tempeh.

0060 In Bolivia, in 1975, the government adopted a

resolution mandating that 5% of quinoa flour must

be added to all pastas, crackers, and breads.

0061 Leaves, like the seed, can also be cooked, made into

a spinach-like dish, or may be served raw in a salad.

Tonics, puddings, and syrups can also be prepared

from the leaves. The foaming qualities of saponin

are sometimes used to produce a frothier chicha.

0062 In industry, saponins from quinoa have multiple

purposes. They are used as soap for washing hair or

clothes, in a compound for a fire extinguisher, or in

photo processing. Dried stalks of the plant are used as

fuel, or may be used in preparing bleach or dyes.

Future Perspectives

0063 The nutritional excellence of quinoa has been known

since ancient times in the Inca empire. Nowadays,

quinoa has been recognized for its nutritional benefits

all over the world, and for its protein, mineral, and

vitamin content.

0064 The importance that quinoa could play in nutri-

tional behavior is being emphasized, not only in de-

veloping countries but also in the developed world. In

the Andean countries, quinoa crops could play an

important role in the future of their economies, giving

a new export market, as well as in national subsist-

ence. Moreover, quinoa could be a strategic crop used

to complement the diet in rural/marginal regions

where energy-protein malnutrition affects most of

the population of the developing countries. Quinoa,

as the ‘mother grain,’ represents an exotic and healthy

rediscovery in the developed world.

0065Germplasm collection should continue in countries

of the Andean region. Agronomic research, including

plant density, potential cultivation, phenology,

morphology, physiological maturity, yield, and weed

control, should be performed. Further research is

needed in order to study the adaptability of different

cultivars to ‘new homes of quinoa’ in the USA and

Europe. Using mechanized agriculture may facilitate

mechanical harvesting of the grain, reducing post-

harvest losses.

0066Improving methods for removing saponins without

significant modification of nutritive value are encour-

aged. The selection of sweet genotypes with a very

low saponin content in the seeds, large grain, and

high yield are the main breeding goal. Sweet geno-

types could be selected early in plant development in

order to speed up the selection process. Further re-

search is needed to find markers for indirect selection

for sweet genotypes.

0067The need for intensive cultivation of quinoa should

be emphasized; this could meet quality and quantity

needs by the food industry. Besides, aggressive pro-

moting campaigns should be carried out to encourage

greater consumption of the grain. Finally, quinoa is

been promoted as an extremely healthy food – a

supergrain – of the future (gluten free). It is a food

of the twenty-first century.

See also: Amino Acids: Properties and Occurrence;

Metabolism; Phytic Acid: Properties and Determination;

Nutritional Impact; Protein: Food Sources; Requirements;

Quality; Saponins; Starch: Sources and Processing;

Functional Properties; Vitamins: Overview

Further Reading

Berti DM, Serri GH, Wilckens ER, Urbina PM and Figueroa

CI (1997) Determination of physiological maturity and

the optimum maturity for harvesting quinoa (Chenopo-

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4902 QUINOA

Radiation See Drying: Theory of Air-drying; Drying Using Natural Radiation; Fluidized-bed Drying; Spray

Drying; Dielectric and Osmotic Drying; Physical and Structural Changes; Chemical Changes; Hygiene; Equipment

Used in Drying Foods

RADIOACTIVITY IN FOOD

J F Diehl, Karlsruhe, Germany

Principles

0001 Radioactivity is the process of spontaneous disinte-

gration of unstable atomic nuclei, a process associ-

ated with emission of ionizing radiation. Radioactive

substances, of natural origin or man-made, are pre-

sent in all foodstuffs. This article describes the

radionuclides of interest and considers the internal

radiation exposure of man resulting from incorpor-

ated radionuclides. The relative contribution of nat-

ural and man-made radionuclides to the resulting

effective dose is discussed.

Naturally Occurring Radionuclides

0002 Radioactive species of certain elements are continu-

ously formed in the upper atmosphere by interaction

of cosmic radiation with elements present in the

atmosphere (‘cosmogenic radionuclides’). Thus,

carbon-14 (

C) and tritium (

H) are produced by

interaction of cosmic-ray neutrons with nitrogen.

They disintegrate,

C with a half-life of 5730 years,

H with a half-life of 12.3 years, emitting electrons or

b-radiation. (The half-life, also called the physical

half-life or radioactive half-life, is the time required

for the disintegration of half of the atoms of a given

radioactive substance.) The unit of radioactivity is the

becquerel (Bq); 1 Bq corresponds to one nuclear dis-

integration per second. Formerly, the Curie unit (Ci)

was used; 1 Ci equals 3.7 10

Bq.

0003 Other radioactive species were formed in the nu-

clear processes associated with the earth’s origin

(‘primordial radionuclides’). A representative of this

group is potassium-40 (

K), which disintegrates with

a half-life of over 10

years, emitting electrons and g

radiation, an electromagnetic radiation. The adult

human body (70 kg) contains about 13 kg of carbon

with 3000 Bq of

C, 50 kg of water with 20 Bq of

H, and 140 g of potassium with 4300 of Bq

K. The

major cosmogenic and primordial radionuclides

and some of their properties are listed in Table 1.

The a radiation emitted by some of the radio-

nuclides listed in the table consists of particles con-

taining two protons and two neutrons (i.e., helium

nuclei).

0004With regard to the cosmogenic radionuclides and

K, data concerning activity concentrations in foods

and in the human body are rather uniform in the

whole world, whereas the radionuclides of the

uranium and thorium series may be present at con-

siderably higher levels (compared with Table 1),

depending on local geological conditions. The popu-

lation living along the Kerala coast of India, for in-

stance, has an annual intake of 40 Bq of radium-226

(

226

Ra) and 2000 Bq of radium-228 (

228

Ra), and

similar intakes are found in the population of the

volcanic Minas Gerais area of Brazil. Another case

of elevated intake relates to aboriginals of uranium-

rich areas of Western Australia, where the annual

intake of lead-210 (

210

Pb) from the carcasses and

offal of sheep and kangaroos can be as high as

3000 Bq. Arctic lichen accumulate polonium-210

(

210

Po), and reindeer graze mostly on lichens in the

winter, so that a further accumulation occurs in rein-

deer meat. Laplanders consuming reindeer meat may

have a 10-fold higher intake of

210

Po than popula-

tions of the temperate latitudes. Refer to individual

foods.

0005 The occurrence of certain natural radionuclides in

food plays a role in analytical methods. Fossil fuels do

not contain

C or tritium, because their age is much

greater than those radionuclides’ half-lives. This is of

interest in food control because adulterations of alco-

holic beverages with synthetic ethanol, natural vin-

egar with acetic acid, or plant extract flavoring with

synthetic flavors can be recognized by a lower

and

H content of the synthetic product. (See Adul-

teration of Foods: Detection.)

0006 In contrast to a and b radiation, which cannot

penetrate matter deeply, g radiation has a high pene-

trating power. The

K in a body can thus be deter-

mined by measuring g radiation outside this body.

Whole-body counters for humans and animals are

available that permit measurement of

K and other

g-emitting radionuclides. Since adipose tissue is more

or less free of potassium, lean body mass can be

determined in this way. The principle can also be

used for nondestructive estimation of the fat content

of meat.

0007 Much of the knowledge of metabolism in animals

and plants is based on tracer studies with radio-

actively labeled substances. In radioimmunoassays

(RIA), which permit extremely sensitive analyses of

veterinary drugs, anabolics, pesticides, bacterial

toxins, and many other substances in food, and in

the RAST inhibition (radioallergosorbent test) for

detection of food allergens, radioactive labeling is

utilized, usually with tritium. (See Analysis of Food;

Immunoassays: Radioimmunoassay and Enzyme Im-

munoassay; Protein: Synthesis and Turnover.)

Man-made Radionuclides

Consequences of Atmospheric Explosions of

Nuclear Weapons

0008Since the first nuclear test explosion in the desert of

New Mexico on 16 July 1945, large amounts of

radioactive fission products have been released into

the stratosphere and have eventually settled on the

earth’s surface as ‘nuclear fallout.’ Short-lived radio-

nuclides such as

131

I, a b and g emitter with a half-life

of 8 days, disappeared quickly, whereas long-lived

species remained in the biosphere for many years,

the most important species being

Sr, a b emitter

with a half-life of 29 years, and

137

Cs, a b and g

tbl0001 Table 1 Radionuclides naturally occurring in foods

Radionuclide Radiation

emitted

Half-life Concentrationin foods Annualintake

(Bq per person)

Human body weighing

70 kg contains (Bq)

Cosmogenic

Carbon-14 b 5730 years 230 Bq per kilogram of C 20 000 3 000

Tritium b 12.3 years 0.4 Bq per kilogram of water 500 20

Beryllium-7 g 53 days 2 Bq per kilogram of leafy vegetables, 3 Bq per

kilogram of cereals

1 000

Sodium-22 b/g 2.6 years 50

Primordial

Potassium-40 b/g 1.3  10

years 30.9 Bq per gram of K 33 000 4 300

Rubidium-87 b 4.7  10

years 3 Bq per kilogram of food 300

Uranium series

Uranium-238 a/g 4.5  10

years <2 Bq per kilogram of vegetables, mushrooms 5 1

< 0.05 Bq per kilogram of other foods

Radium-226 a/g 1600 years 50 Bq per kilogram of brazil nuts 19 2

<5 Bq per kilogram of mushrooms

2 Bq per kilogram of cockles

0.5 Bq per kilogram of eggs

0.7 Bq per kilogram of peanuts

< 0.1 Bq per kilogram of other foods

Lead-210 b/g 22.3 years 2 Bq per kilogram of shellfish 32 14

<0.1 Bq per kilogram of other foods

Polonium-210 a/g 138.4 days 2 Bq per kilogram of mussels 55 12

10 Bq per kilogram of reindeer meat

0.7 Bq per kilogram of fish

<0.1 Bq per kilogram of other foods

Thorium series

Radium-228 b 5.8 years 25 Bq per kilogram of brazil nuts 13 1

<0.1 Bq per kilogram of other foods

Thorium-228 a/g 1.9 years 40 Bq per kilogram of brazil nuts 1.3 0.3

<0.1 Bq per kilogram of other foods

Source: UNSCEAR, 1982 and 1993 Reports, updated from other sources.

4904 RADIOACTIVITY IN FOOD

emitter with a half-life of 30 years. The total release

Sr and

137

Cs by atmospheric tests was about 600

and 960 PBq, respectively (P, peta ¼10

). Fallout

radioactivity in food reached a peak in 1964, when

an agreement between the former Soviet Union and

the USA to stop atmospheric nuclear weapons tests

became effective. This is demonstrated in Figure 1 for

Sr in total diet samples collected in New York City.

The majority of nuclear weapons tests were carried

out in the northern hemisphere. The extent of radio-

active contamination was therefore considerably

lower in the southern hemisphere, as shown for

Argentina.

0009 Yearly averages of specific activity of radiocesium

and radiostrontium in total diet samples from Ger-

many are shown in Figures 2 and 3, respectively.

Results obtained during the 1960s and 1970s in

other countries of the north 30–70



latitudes, which

received the highest fallout deposits, were similar.

After the peak of 1964, cesium activity (Figure 2)

decreased faster than strontium activity (Figure 3).

This was a consequence of binding of cesium ions to

clay minerals in the soil, which makes this element

rather unavailable to the roots of plants, whereas the

uptake of cesium ions deposited on the leaves of

plants is quite rapid. In most soils, the availability of

strontium is much higher than that of cesium. Uptake

Sr ions through plant roots continued long after

deposition of fallout had decreased to below a meas-

urable level; indeed, it continues even today, so that

the present food supply still contains traces of the

radiostrontium deposited in the 1950s and 1960s.

The distribution of strontium and cesium in the

human and animal body resembles that of calcium

and potassium, respectively. In vertebrates, radio-

strontium accumulates in the bones, whereas radio-

cesium is rather evenly distributed in muscle tissue.

Consequences of Nuclear Accidents

0010A severe accident occurred on 10 October 1957 at the

Windscale Works, later known as Sellafield, in north-

west England, when a graphite fire broke out in a

uranium reactor primarily designed for production

of plutonium. The accident released 740 TBq of

131

22 TBq of

137

Cs, 0.07 TBq of

Sr and other radio-

nuclides (T, tera ¼10

). Authorities restricted the

consumption of milk in an area of 500 km

for vari-

ous periods of time. Environmental monitoring of

radioactivity was not well developed at that time,

and the extent of contamination remained largely

unknown.

0011The accident at the Three Mile Island reactor in

Pennsylvania, USA, on 28 March 1979 released less

than 1 TBq of

131

I and no

Sr or

137

Cs. Radioiodine

at barely detectable levels was found in some foods

produced in the area.

0012According to information provided by the former

Soviet Government, the catastrophe of the Chernobyl

reactor on 26 April 1986 released 260 PBq of

131

38 PBq of

137

Cs, 18 PBq of

134

Cs, 8 PBq of

Sr, 5 PBq

241

Pu, and large quantities of many other radio-

nuclides during a period of 10 days. Shifting winds

carried the radioactive clouds over various parts

of the former Soviet Union, Scandinavia, Central

Europe, the Balkan countries, and Turkey. The dom-

inant radionuclide during the first 2 weeks was

131

New York City

Argentina

1954 1958 1962 1966 1970 1974 1978

Year

0.7

0.6

0.5

0.4

0.3

0.2

0.1

Concentration (Bq kg

−1

)

fig0001 Figure 1 Strontium-90 in the total diet of Argentina and New York City, 1954–1979 (Bq kg

1

). Source: Ionizing Radiation: Sources and

Biological Effects, United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), 1982 Report to the General

Assembly, New York, United Nations, p. 217.

RADIOACTIVITY IN FOOD 4905