Original:Amaranth Modern Prospects for an Ancient Crop 7

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[edit] Amaranth: Modern Prospects for an Ancient Crop (BOSTID, 1984, 74 p.)

[edit] Grain Amaranths

As already mentioned, amaranth is one of the few nongrasses with potential for becoming a cereal-like grain crop. The main species for this are Amaranthus caudatus, Amaranthus cruentus, and Amaranthus hypochondriacus.


AMARANTHUS CAUDATUS

This species is a crop in the Andean highlands of Argentina, Peru, and Bolivia. It has pendulous, blazing-red inflorescences and is commonly sold in Europe and North America as an ornamental under names such as "love-lies-bleeding" or "red-hot cattail," a name shared with unrelated plants. Other forms of the species give much better grain yields. One good variety that has club-shaped inflorescences is Amaranthus caudatus cv edulis (sometimes classified as Amaranthus edulis or Amaranthus mantegazzianus).

Amaranthus caudatus originated in the same region in the Andean highlands as the common potato. The Spanish conquerors called it Inca wheat, but it is much more ancient than the Incas. Some of its pale seeds, placed in tombs as food for the dead, are more than 2,000 years old.

The plant is still widely grown in the Andean region, mostly by the Indians who maintain traditional customs. It is usually planted in small patches close to houses, not in large fields as a staple crop. The grain is toasted and popped, ground into flour, or boiled for gruel. It is considered especially good for children and invalids.

The crop contains a great deal of genetic diversity in South America, and, although only a small sampling has been introduced to other continents, much genetic diversity has been observed in the germplasm collections from northern India.

Amaranth P28A.GIF
Amaranthus caudatus (Line drawings on pages 28, 30, 42, and 44 are reprinted with permission of the Department of Plant Taxonomy and Plant Geography, Wageningen Agricultural University, Wageningen, The Netherlands. For complete taxonomic details of numbered items, see Grubben and van Sloten, 1981.) ]


AMARANTHUS CRUENTUS

This Mexican and Guatemalan species is useful both as a grain or a leafy vegetable (see next chapter). The grain types have white seeds; the vegetable types (as well as those used to extract red dye) usually are dark seeded. It is probably the most adaptable of all amaranth species, and it flowers, for example, under a wider range of daylengths than the others. Amaranthus cruentus is an ancient food, and in the famous Tehuacan caves in central

Mexico, archaeologists have dug up remains-both the pale grain and the bundles of plants brought in for threshing-at a dozen levels, dating back 5,500 years. The species is still grown in the region, and popped amaranth seedcakes are sold on the streets of the towns.

Amaranthus cruentus has also survived as a grain crop in a few Indian villages of southern Mexico and Guatemala and as a crop used to extract a red dye for coloring corn-based foods in the Indian pueblos of the arid southwestern United States, where it probably became established in prehistoric times.


AMARANTHUS HYPOCHONDRIACUS

The most robust, highest yielding of the grain types, Amaranthus hypochondriacus was probably domesticated in central Mexico, farther north and at a later time than Amaranthus cruentus. It first appeared in the Tehuacan caves about 1,500 years ago as a pale-seeded, fully domesticated type. It, too, reached the United States in prehistoric time but later became extinct there. Its maximum cultivation today is in India, particularly in the Sutlej Valley in the state of Himachal Pradesh and in the Garhwal and Kumaon regions of Uttar Pradesh.

Some types of Amaranthus hypochondriacus are bushy; others are tall and unbranched. The species is particularly useful for tropical areas, high altitudes, and dry conditions. It has excellent seed quality and shows the greatest potential for use as a food ingredient. It pops and mills well and has a pleasing taste and smell.

Evidently, the Spanish took seeds back to Europe at an early date (possibly inadvertently), and, as shown by sixteenth- and seventeenth century herbals, the plant soon spread through European gardens as an ornamental. Around 1700 it was grown as a minor grain crop in Central Europe and Russia and eaten as mush and groats. By the early nineteenth century it had been taken to Africa and Asia, where it is now planted as a grain crop in such widely scattered regions as the mountains of Ethiopia, the hills of South India, the Nepal Himalaya, and the plains of Mongolia.

Amaranth P30A.GIF
FIGURE

PHYSICAL COMPOSITION

Amaranth seeds are very small; 1,000-3,000 seeds per gram are common. Although selections have been made over the years for pale seeds (the wild species all have black seeds), large inflorescences, and more seeds per plant, there has apparently been little selection for larger seed size.

Amaranth germ and bran constitute 26 percent of the seed; the flour 74 percent-about the same as in a grain of wheat. When the whole grain is milled, its protein, vitamins, fat, and minerals are concentrated significantly in the bran/germ fraction. Amaranth germ, for example, can contain as much as 30 percent protein. It also contains about 20 percent oil. This shows promise as an edible oil, but no attempts at extracting it have yet been made. The bran is high in fiber, protein, vitamins, and minerals.

The starch that makes up the bulk of amaranth flour has extremely small granules (average diameter I micron*), a unique dodecahedral structure, and high water-absorption capacity. It is likely to prove useful for applications in the food, plastics, cosmetics, and other industries.


CHEMICAL COMPOSITION

Average chemical composition of amaranth grain is shown in Table 1, amino acid content in Table 2. Amaranth has a protein content as high as 16 percent, which is somewhat higher than that found among commercial varieties of common cereals. However, the 'white" flour that is milled out of it has only 7 percent protein, not a substantially different quantity from the protein content of wheat flour used in making white bread.

The charts on page 7 show the composition of amaranth in comparison with the more common grains. The protein in amaranth seeds is unusual because its balance of amino acids is closer to the optimum balance required in the human diet than that of most plant proteins. As noted already, the lysine content is especially high compared with that found among the most common cereals. Thus, amaranth's importance is that its essential amino acids complement those of corn, rice, and wheat. For example, corn protein is low in both tryptophan and lysine, whereas amaranth has high levels of both.


TABLE I Proximate Composition of Amaranthus Seeds(a)







Nc

Protein(b)

Fat

Fiber

Ash

Species

(%)

(%)

(%)

(%)

(%)

A. cruentus(c,d)

3.05

17.8

7.9

4.4

3.3

A. cruentus x hypochondri- acus(d)

2.97

17.4

8.0

4.3

3.0

A. edulisd (A. caudatus)

2.70

15.8

8.1

3.2

3.2

A. hypochondriacus(e,f)

2.67

15.6

6.1

5.0

3.3

a Dry basis (original moisture contents, 6-11%)
b N x 5.85
c Average of two A. cruentus samples
d Becker et al., 1981
e Cheeke and Bronson, 1980
f Average of four A. hypochondriacus samples

Source: Saunders and Becker, 1983


Amaranth protein, itself, is low in the amino acid leucine, which is not a serious limitation because leucine is found in excess in most common grains.

The nutritional value of amaranth protein is very good. Protein efficiency ratios (PER) have ranged from 1.5 to 2.0 (corrected to casein 2.5) for cooked grain, and its total digestibility is about 90 percent. Amaranth protein, at a biological value of 75, comes closer than any other grain protein to the perfect balance of essential amino acids, which theoretically would score 100 on the nutritionists' scale of protein quality based on amino acid composition. By contrast, corn scores about 44, wheat 60, soybean 68, and cow's milk 72. When amaranth flour is mixed with corn flour, the combination almost reaches the perfect 100 score, because the amino acids that are deficient in one are abundant in the other.

The fatty acids of amaranth oil comprise about 70 percent oleic and linoleic acids, about 20 percent stearic acid, and about 1 percent linolenic acid. The oil also contains uncommonly high levels of squalene.

Antinutritive factors, such as saponins, trypsin inhibitors, and tannins, occur in amaranth grain but at similar levels to those found in legumes and in some other grains

(notably sorghum). Much more information is needed on these components, but as of now they are not thought to present any nutritional hazard.

PROCESSING

As with other grains, foods containing amaranth can be prepared by using simple low-energy techniques. Cleaned, unprocessed whole grain can be made into porridge by simply boiling it briefly in water. If toasted or parched lightly, the whole grain becomes a pleasant tasting food that can be eaten without further preparation. The whole grain can also be sprouted for use as a nutritious vegetable. Moreover, tasty foods can be prepared by popping or puffing the whole grain into small white kernels that taste like popcorn. This preparation is common in Mexico and Central America, where popped amaranth is often used in confections and condiments.


TABLE 2 Protein Amino Acid Composition (g/16 g of N) of Amaranthus Species



Species


Amino Acid

A. caudatus

A. hvpochondrracus(a).

A. cruentus(b)

Lysine

5.3

5.5

5.1

Histidine

2.5

2.5

2.4

Threonine

3.5

3.6

3.4

Cysteine

2.3

2.1

2.1

Methionine

2.4

2.6

1.9

Met + Cys

4.7

4.7

4.0

Valine

4.1

4.5

4.2

Isoleucine

3.6

3.9

3.6

Leucine

5.3

5.7

5.1

Tyrosine

2.8

3.3

2.6

Phenylalanine

3.4

4.0

3.4

Serine

5.9

6.3

5.4

Glycine

6.9

7.4

7.0

Arginine

...

...

7.9

Alanine

...

...

3.4

Aspartic acid

...

...

7.8

Glutamic acid

...

...

14.2

Proline

...

...

3.6

Tryptophan

...

...

...

Nitrogen recovered

89.6

86.8

85

Chemical score(c)

75

81

73

a Carlsson, 1980
b Besetschart et al., 1981
c The chemical score of whole wheat protein is 73, and of soybean protein, 74 (FAO, 1970)

Source: Saunders and Becker, 1983


Grinding or milling amaranth produces a whole-grain meal or white flour. An abrasive mill like that used for milling sorghum or rice seems best, although a roller mill, as used for wheat, can be adapted to handle amaranth. As with other grains, milled products have a much shorter storage life than the whole grain.

USE IN FOODS

Amaranth meal or flour is especially suitable for unleavened (flat) breads where it can be used as the sole or predominant cereal ingredient. The flour is used in Latin America and in the Himalayas to produce a variety of flat breads (for example, tortillas and chapaties).

For making yeast-raised breads or other leavened foods, amaranth meal or flour must be blended with wheat meal or wheat flour because it lacks functional gluten. In such blends, it is likely that the high lysine content of amaranth improves the protein quality of foods that normally would be made from flours of other grains such as corn, rice, or wheat. This is particularly beneficial for infants, children, and pregnant and lactating women.

Amaranth can be used in many other foods, including:

  • Soups (grain and flour)
  • Pilaf (grain)
  • Pancakes (flour, whole grain, and popped grain)
  • Breakfast cereals (whole, popped, or sprouted-grain flour)
  • Porridge (popped grains in milk)
  • Breads, rolls, muffins, and many other forms of baked foods (flour, popped grain, toasted
    grain, whole grain)
  • Crepes (flour, popped grain)
  • Dumplings, tostadas, tortillas, fritos, and corn pones (flour, whole or popped grain)
  • Cookies and crackers (flour, whole or popped grain)
  • Snack bars (popped grain, toasted grain, or sprouted grain)
  • Toppings (popped grain)
  • Breadings (popped grain, flour)
  • Beverages (flour, popped grain)
  • Fillers (whole or popped grain, flour, or starch)
  • Confections (popped grains).


FEED

Unprocessed amaranth grain probably can be used as an animal feed, particularly for poultry. So far, however, it has not been produced in sufficient quantities to be tested extensively in livestock feeding trials.