AMARANTH: GRAIN & VEGETABLE TYPES
INTRODUCTION
 Amaranth
[Amaranthus hypochondriacus, A. cruentus (Grain) & A. tricolor (Vegetable)]
is a plant
with an upright growth habit, cultivated for both its seeds which are
used as a grain and its leaves which are used as a vegetable. Both the
leaves and seeds contain protein of an unusually high quality. The grain
is milled for flour or popped like popcorn. The leaves of both the grain
and vegetable types may be eaten raw or cooked. The amaranths that are
grown principally for vegetable use have better tasting leaves then the
grain types.
Amaranth has been
cultivated for more than 8,000 years, dating back at least to the Mayan
civilization of South and Central America. It was a staple of the Aztecs
and was incorporated into their religious ceremonies. In 1516 the conquistadors
prohibited the growing of amaranth. In that area today only a limited
amount of grain is grown, most of which is popped and mixed with honey
to make "alegria" candy. However, much of the genetic base has been maintained
because amaranth has continued growing in the area as a weed.
Amaranth is considered
native to South and Central America, but over 400 varieties are found
throughout the world in both temperate and tropical climates. Vegetable
amaranth has been used in China for 400 years, and is commonly found in
the Caribbean and Africa.
Amaranths are moderately
branched from a main stem. Grain types form large loose panicles at the
tips of the stems. Vegetable types form flowers and seeds along the stems.
They are indeterminate in growth habit, but may set seed at a smaller
size during short days. Grain amaranth grown in winter at ECHO (southern
Florida) began flowering at less than half of the height of amaranth growing
in May. Grain types may grow 1 to 2 meters tall and produce yields comparable
to rice or maize. Amaranth has the "C-4" photosynthetic pathway (along
with such plants as corn and sorghum), which enables it to be uniquely
efficient in utilizing sunlight and nutrients at high temperatures. It
is more drought-resistant than corn.
NUTRITIONAL VALUE
As can
be seen in Table I, amaranth is quite nutritious. Amounts of vitamin C,
iron, carotene, calcium,
folic acid and protein are especially high. There are reports that the
incidence of blindness in children
due to poor nutrition has been reduced with the use of 50 to 100 g of
amaranth leaves per day. On a dry
weight basis, the content of protein in leaves is approximately 30%.
TABLE I. The proximate composition of
grain and raw leaves of amaranth (100 g portions). 
Component
Vegetable
Grain
Moisture
86.9 g
9.0 g
Protein
3.5 g
15.0 g
Fat
0.5 g
7.0 g
Total carbohydrates
6.5 g
63.0 g
Fiber
1.3 g
2.9 g
Calories
36
391
Phosphorus
67 mg
477 mg
Iron
3.9 mg
--
Potassium
411 mg
--
Vitamin A
6100 i.u.
0
Riboflavin
0.16 mg
0.32 mg
Niacin
1.4 mg
1.0 mg
Ascorbic acid (C)
80 mg
3.0 mg
Thiamin (B1)
0.08 mg 0.14
mg
Ash
2.6 g
2.6 g
Calcium
267 mg
490 mg
Compiled from J.N. Cole, Amaranth: from the Past, for the Future, Rodale
Press, Emmaus, PA
(1979)
The presence
of rather high amounts of oxalic acid and nitrates places some limitation
on the quantity of
amaranth leaves that can be consumed daily. The amount of oxalic acid
is roughly the same as that found
in spinach and chard. Excessive amounts (over 100 g per day?) may result
in a level of oxalic acid that
begins to reduce the availability of calcium in humans. This is especially
a concern if calcium intake
levels are low to begin with. Nitrate in vegetable portions of amaranth
is a concern because it is
hypothesized that nitrates may be chemically changed in our digestive
tracts into poisonous
nitrosamines. Evidence for this is lacking at the present time. Nevertheless,
over 100 g per day may be
an unsafe amount to eat, according to scientists. Boiling the leaves like
spinach, then discarding the
water reduces the levels of both oxalic acid and nitrates.
Amaranth
grain has more protein than corn, for example, and the protein is of an
unusually high quality.
The protein is high in the amino acid lysine, which is the limiting amino
acid in cereals like maize, wheat
and rice. The protein is also relatively rich in the sulfur-containing
amino acids, which are normally
limiting in the pulse crops (e.g. beans). The "protein complement" of
amaranth grain is very near to the
levels recommended by FAO/WHO. It has a protein score of 67 to 87. Protein
scores are determined by
taking the ratio of the essential amino acids to the level for those amino
acids recommended by
FAO/WHO, and multiplying by 100. By comparison, wheat (14% protein) scores
47, soybeans (37%)
score 68-89, rice (7%) scores 69, maize (9%) scores 35. Although amaranth
is theoretically close to the
ideal, combining it with another grain increases the quality to very close
to the FAO/WHO standards.
Weight gain studies
with rats point out, however, that the actual nutritional value is considerably
less
than would be expected from the above considerations. This is apparently
due to certain anti-nutritional
factors in raw amaranth. Performance is improved somewhat by cooking.
For example, Dr. Peter Cheeke
at the University of Oregon compared the rate of weight gain by 120 gram
rats fed a corn-soybean diet
to rats fed a diet of corn and seed from A. hypochondriacus, either raw
or cooked. The average daily
gain for rats on the corn-soybean diet during the first 20 days was 3.9
grams. Rats fed the
corn-amaranth diet gained only 0.3 grams per day. The average daily gain
for rats fed corn and cooked
amaranth was 1.6 grams. Raw amaranth seed is extremely unpalatable to
rats (i.e. they will not eat it
readily). Cooked seed also does not seem to be very palatable, though
it smelled good to Dr. Cheeke. In
another study, Dr. Cheeke found that after 11 days on a corn-amaranth
diet, rats (which weighed 120 g
initially) "had an unthrifty hunched-up appearance, and exhibited symptoms
typical of
semi-starvation".
We phoned
Dr. Cheeke to get his perspective on the seriousness of these negative
results. He told us
that there are definitely toxins and/or anti-nutritional factors in the
raw grain, and that it is less of a
problem with cooked grain. He said that a scientist in Australia had been
feeding raw amaranth seed to
poultry as the major component of the diet. He found that chickens went
into spasms, convulsions, and
finally died. This unidentified factor causes liver damage. Other problems
are caused by saponins,
including unpalatability. But to keep this in perspective, Dr. Cheeke
pointed out that there are few raw
foodstuffs that do not have problems. Raw soybeans contain 10 kinds of
toxins. Raw kidney beans will
kill rats, but cooking eliminates the problem. The key seems to be to
use the grain in moderate amounts,
and to cook it. We asked whether we could say that there would be no problem
unless people had little
other than amaranth to eat. He thought that this was probably a fair statement.
It is our opinion that
more research needs to be done before we can recommend amaranth grain
as a major ingredient in animal
feed. To our knowledge it has not been shown whether these factors decrease
the value of amaranth in
human nutrition. Until more work is done, however, the feeding trial results
must moderate our
otherwise enthusiastic promotion of grain amaranth.
CULTIVATION
VEGETABLE TYPES
There
appears to be considerable latitude in choice of plant densities. One
approach is to plant dense
stands (5-10 cm spacing), and harvest by uprooting when the plants are
5-7 weeks old. Another
common approach is to sow less densely (15-30 cm spacing), and harvest
by cutting the stem tips and
plucking tender leaves periodically beginning when the plants are about
15 cm tall (4-6 weeks old).
Seeds
may be planted in a nursery for subsequent transplanting or sown directly
where plants are to be
grown. Transplanting is a very efficient use of seeds, and allows the
growing area to be weeded just
before the seedlings are transplanted. The very small size of the seeds,
however, means that a few seeds
go a long way. The number of seeds saved is probably not a sufficient
justification for the extra work
involved in transplanting. On the other hand, gaining a two-week jump
on the weeds can be significant
because amaranth seedlings are not vigorous growers when very young. Planting
in a nursery also
reduces risk of loss due to disease such as damping off.
Direct
seeding involves much less labor, but incurs a greater risk of poor stand
due to diseases and
predators of young seedlings and to poor competition with weeds in the
crucial initial couple of weeks.
If direct seeding is used, sowing should probably be in rows to facilitate
cultivation.
Whether
sown in the nursery or field, seeds need to be planted about 4 mm deep
(or covered with 4 mm
of soil) for good germination. Because of the shallow depth, special care
must be taken to prevent
drying out of the soil until plants are established. Transplanting or
thinning may be done in about two
weeks when plants should be 5-10 cm tall. Delay in transplanting for even
one week can reduce total
yield.
When
harvesting by repeated clippings, a two- or three-week interval is common
through the end of the
season (usually the shortened days of fall). Both the yield and quality
of leaves are higher with more
frequent clippings.
When
the vegetative stage ends and flowering begins, subsequent harvests are
lower in both quality and
quantity. Short days, water stress or other environmental stresses may
promote flowering. The stress
that comes with delayed transplanting also can cause the plants to flower
more quickly. It is reported
that plucking flower heads from the plant may prolong the vegetative phase
of growth.
Amaranth
is generally considered tolerant of nematodes and is even recommended
as a rotation crop to
reduce nematode populations for subsequent crops. However, one article
reports the presence of root
knot nematodes on amaranth roots. Control of nematodes is such a serious
problem that it is important
to know whether or not amaranth can be used to control them and/or whether
it can be planted where
nematodes are a problem. We will include this question in our list of
research projects that could be
done at Christian colleges. It is possible that the discrepancy in reported
results is because varieties
differ in their susceptibility to nematodes.
Amaranth
is susceptible to damping-off disease, root rot, and caterpillars and
stem borers. It thrives in
30-35o C temperatures. It tolerates poor fertility and drought. However,
plant quality is poor under
stressful conditions. There is good response to fertilizer.
GRAIN TYPES
Recommendations
for plant spacing vary widely for grain amaranth. One recommendation is
to space 23
cm between plants and 75 cm between rows. This corresponds to a planting
density of 38,000 plants
per hectare (15,400 per acre). Seeding rates up to nine times this density
have been used successfully! It
would seem that if harvesting is to be done by hand the less dense spacings
are advisable. This results in
fewer but larger heads that can be harvested more quickly. Closer plant
spacing may be advisable for
mechanical harvesting.
The decision as to
whether to transplant or direct seed is subject to the same considerations
that were
discussed for vegetable amaranth. Cultivation is essential until plants
have reached a size where the leaf
canopy can shade out weeds. After the plants are about 30 cm tall, it
is helpful to mound soil from the
centers of the rows up around the plants. This helps to reduce lodging
(plants blowing over in the
wind), suffocates weeds around the plant, and uproots weeds between rows.
Grain amaranth is
grown from tropical lowlands to 3500 m in the Himalayas. In the tropics,
altitudes
above 1000 m are considered best. Although it tolerates droughts and low
fertility, it does much better
under conditions that are considered ideal for maize (corn). It may be
intercropped with maize, beans,
peppers or squash. In some pure stands it has yielded as well as the world
average yields for maize or
rice (2000 kg/ha). Loss of the tiny seeds by shattering before or during
harvest can be a problem,
especially with mechanical harvesting. (There are approximately 1100 seeds
per gram of amaranth.)
The seeds are mature
when they can be easily separated from the heads upon rubbing between
the
hands. Seeds can be chewed to test whether they have passed beyond the
"dough stage". Heads should
be cut from the stalk and side branches as soon as possible after they
have reached maturity. Heads
should be dried if necessary, keeping green plant parts to a minimum.
Once dry, the seeds are knocked
from the heads, sifted through an ordinary window screen, and winnowed
to remove chaff. Although three or four farmers are planting small (around
10 acre) plots in the USA, as of this writing (1982), there appear to
remain serious problems with mechanical harvesting. Primary among these
problems are the tendency for plants to lodge, and the loss of grain during
harvesting.
Grain should be dried
to about 9% moisture for safe storage. It is reported that grain remains
viable for up to seven years. We left heads stacked in a building for
5 summer months (high humidity and temperatures in the 90's). Viability
still appears to be high.
HARVEST
Basically,
you must thrash it like mankind has always done until the invention of
the thrashing machine. The three stages include let the heads dry out,
knock the grain from the heads, and winnow the grain. Many of you live
where local folks know far more than I about such techniques. For others,
here is what we do with small quantities of seed (which must be kept separate
from other varieties).
Cut
the heads when the grain appears to be mature, and put them somewhere
to dry. If left too long much of the grain may shatter (fall to the ground).
Grain
easily shatters from the dried heads. Put a few heads in a burlap bag
and beat it against the cement floor a few times to knock it loose, or
strike the bags with a stick. Then place the grain in a 5-gallon bucket
(many other containers would be suitable). You will notice that a lot
of chaff comes along with the grain. This is where winnowing comes in.
Place
an empty 5-gallon bucket in front of a fan and, cautiously at first, pour
some grain and chaff into the empty bucket. A steady wind will accomplish
the same thing as the fan, but a gusty wind will cause problems. The grain
is denser and will fall closer to the fan than the chaff. Quickly one
begins to get a feel for how far the buckets should be from the fan, and
at what height to hold the one bucket in order for the grain to land in
the empty bucket and the chaff to blow far enough to miss it. Pour the
grain back and forth until it appears to be clean.
Final
cleanup can be done by swirling and shaking the grain around gently. Remaining
chaff will "float" to the top like ice in water, and can be removed by
hand.
PREPARATION
Vegetable
amaranth leaves and stems or entire plants may be eaten raw or cooked
as spinach. As discussed earlier, however, cooking and discarding the
water will remove potentially harmful oxalates and nitrates.
The
seeds from grain amaranth can be ground for use as a good quality flour
for breads or pastries. It must be combined with wheat flour for a yeast
dough. The Organic Farming and Research Center (Rodale) has used a 50:50
ratio successfully, but they suggest that the percent of amaranth could
be even greater if desired. They state that "amaranth flour contributes
to the sweetness and moistness of a baked good".
Alternatively,
seeds can be popped like popcorn. The people at Rodale say that popped
amaranth can be used: in confections bound with sorghum, molasses or honey;
in high-energy granola and granola bars; in cheese spreads; to flavor
salad dressings; in breading for chicken and fish; in crackers, pie crusts
and breads; and as toppings for casseroles and desserts.
Several
recipes can be found in the book Amaranth: from the Past, for the Future
by Rodale Press.
OTHER READING MATERIAL
We found
the research results published in Proceedings of the Second Amaranth Conference
to be
especially helpful. It is available from Rodale Press, Emmaus, PA 18049
for $15.00. For those
interested in larger-scale production, Amaranth Grain Production Guide
1982 would be helpful. As far as we know there is no charge. Order it
from Rodale Press. Rodale has other material that would be helpful if
you wish to pursue the subject in depth.
ECHO, 17391 Durrance Rd., North Ft. Myers FL 33917, USA
Phone: (941) 543-3246; Fax: (941) 543-5317
e-mail: echo@echonet.org;
|
