Amaranth

Amaranth is a group of more than 60 different species of grains that have been cultivated for about 8,000 years.

These grains were once considered a staple food in the Inca, Maya and Aztec civilizations.

When the Spanish colonized the Americas, they banned crops like amaranth. They were considered part of Aztec religious ceremonies, which unfortunately included human sacrifice. In 1521, Hernán Cortés ordered the burning of all amaranth fields in the Valley of Mexico, a command that would be repeated by conquistadors throughout Latin America. For many years following, amaranth was a lost seed for generations until it finally made a comeback.

Amaranth is classified as a pseudocereal-- similar to quinoa, in the family Amaranthaceae-- meaning that it's not technically a cereal grain like wheat or oats, but it shares a comparable set of nutrients and is used in similar ways. Its earthy, nutty flavor works well in a variety of dishes.

It is rich in fiber and protein, as well as many important micronutrients.

Grain amaranths are predominately self-pollinated diploids, though outcrossing rates may range from 3.5% to 34% (Brenner et al., 2000). Most are monecious (male and female flowers on the same plant). The haploid chromosome number (n) for most amaranths is 16 or 17.

Description

Amaranth is made up of annual or short-lived perennial, herbaceous plants or shrubs collectively known as amaranths. Some names include prostrate pigweed and love lies bleeding. Some amaranth species are cultivated as leaf vegetables, pseudocereals, and even ornamental plants.

Catkin-like cymes of densely-packed flowers grow in summer or fall. Amaranth varies in flower, leaf, and stem color with a range of striking pigments from the spectrum of maroon to crimson and can grow longitudinally from 1 to 2.5 metres (3 to 8 feet) tall with a cylindrical, succulent, fibrous stem that is hollow with grooves and bracteoles when mature. There are approximately 75 species in the genus, 10 of which are dioecious and native to North America, and the remaining 65 are monoecious species that are endemic to every continent (except Antarctica) from tropical lowlands to the Himalayas. Members of this genus share many characteristics and uses with members of the closely related genus Celosia. Amaranth grain is collected from the genus.

An evolutionary lineage of around 90 species within the genus has acquired the C4 carbon fixation pathway, which increases their photosynthetic efficiency. This probably occurred in the Miocene.

Storage

The main challenge with storing amaranth is preventing rancidity, so always store it in an airtight container in a cool place, away from bright light. Whole uncooked amaranth can be kept in the pantry for up to four months and for twice that long in the freezer. Amaranth flour will stay fresh in the pantry for 2 to 3 months and in the freezer for up to 6 months.

Uses

Nutrition

Uncooked amaranth grain by weight is 12% water, 65% carbohydrates (including 7% dietary fiber), 14% protein, and 7% fat (table). A 100-gram (3+1⁄2-ounce) reference serving of uncooked amaranth grain provides 1,550 kilojoules (371 kilocalories) of food energy, and is a rich source (20% or more of the Daily Value, DV) of protein, dietary fiber, pantothenic acid, vitamin B6, folate, and several dietary minerals (table). Uncooked amaranth is particularly rich in manganese (159% DV), phosphorus (80% DV), magnesium (70% DV), iron (59% DV), and selenium (34% DV). Amaranth has a high oxalate content. Cooking leads to an apparent substantial decrease in nutritional value, though this is mainly due to an increase in water content to 75% by weight.

Cooked amaranth leaves are a rich source of vitamin A, vitamin C, calcium, and manganese, with moderate levels of folate, iron, magnesium, and potassium.

Amaranth does not contain gluten.

Amaranth vs. Quinoa

Because these seeds are from the same family, they share several qualities. Although amaranth and quinoa are referred to as ancient grains, they are both seeds; the two pseudocereals are also naturally gluten-free. Compared to other grains, amaranth and quinoa have short cooking times, although it does take slightly longer for amaranth to reach the desired doneness.

A visual difference is size: amaranth is a much smaller grain than quinoa. Another obvious differentiation is found in the aroma and flavor. Amaranth is much more distinctive compared to quinoa, with a grassy smell and nutty, strong herbal taste that can be overwhelming for some. While quinoa's mildness allows it to take on the flavors of the other ingredients in the dish, amaranth takes center stage.

Health Benefits

Amaranth has many micronutrients and anti-inflammatory properties. It may help lower cholesterol, aid weight loss, and is gluten-free. It's easy to make and great in any dish.

Amaranth grain contains phytochemicals that are not defined as nutrients and may be antinutrient factors, such as polyphenols, saponins, tannins, and oxalates. These compounds are reduced in content and antinutrient effect by cooking.

Amaranth as a Weed

Amaranth weed species have an extended period of germination, rapid growth, and high rates of seed production, and have been causing problems for farmers since the mid-1990s. This is partially due to the reduction in tillage, reduction in herbicidal use and the evolution of herbicidal resistance in several species where herbicides have been applied more often. The following 9 species of Amaranthus are considered invasive and noxious weeds in the U.S. and Canada: A. albus, A. blitoides, A. hybridus, A. palmeri, A. powellii, A. retroflexus, A. spinosus, A. tuberculatus, and A. viridis.

A new herbicide-resistant strain of A. palmeri has appeared; it is glyphosate-resistant and so cannot be killed by herbicides using the chemical. Also, this plant can survive in tough conditions. The species Amaranthus palmeri (Palmer amaranth) causes the greatest reduction in soybean yields and has the potential to reduce yields by 17-68% in field experiments. Palmer amaranth is among the "top five most troublesome weeds" in the southeast of the United States and has already evolved resistances to dinitroaniline herbicides and acetolactate synthase inhibitors. This makes the proper identification of Amaranthus species at the seedling stage essential for agriculturalists. Proper weed control needs to be applied before the species successfully colonizes in the crop field and causes significant yield reductions.

How to Grow Amaranth

Although the full potential of grain amaranth in the food supply has not yet been achieved, its production is increasing due to its nutritious gluten-free grain and resilience to abiotic stresses.

Amaranth has been proposed as an inexpensive native crop that could be cultivated by indigenous people in rural areas for several reasons:

Three species of amaranth have been domesticated for use as a grain crop: Amaranthus cruentus in Central America, A. hypochondriacus in Mexico, and A. caudatus in the Andean region of South America (Santra et al., 2024).

Genomic analysis confirms that A. hybridus is the progenitor of all three species (Clouse et al., 2016).

Although similar for culinary applications, the three species have different adaptations. A. cruentus is relatively daylength neutral and is the most widely adapted across different latitudes and soil types (Santra et al., 2024). The other two species are daylength sensitive and flower during short days; they are best adapted to higher elevations in lower latitudes (Santra et al., 2024).

Domesticated amaranths have white seeds, whereas their wild relatives are dark-seeded.

Amaranth is a versatile and resilient crop that is tolerant to a wide range of weather conditions (Aderibigbe et al., 2022). Amaranth requires less water and fertilizer than conventional cereals like corn, wheat, and rice, and is therefore considered an energy-conserving crop (Santra et al., 2024). Having the C4 photosynthetic pathway, amaranths have a fast growth rate and are well adapted to hot, dry conditions. In addition to being grown for grain, amaranths are used for forage, as a leafy vegetable, and as an ornamental plant, due to the richly pigmented leaves and inflorescences of some variants (Brenner et al., 2000).

Red Amaranth (Amaranthus cruentus)

Amaranthus cruentus is an annual herbaceous plant originating from Central America and cultivated since ancient times for its grain. Introduced to many countries, it is now widespread and naturalized in many parts of the world.

A. cruentus is listed as invasive in China, Israel and Italy, with evidence of impact. Although also reported as invasive in New Caledonia, New Zealand, Papua New Guinea and the Philippines, no further information is provided on its impact in these countries. This species is also described as a casual alien, an escape from cultivation and agricultural weed; it is listed in the Global Compendium of Weeds.

Other scientific names:

  • Amaranthus hybridus subsp. cruentus (L.) Thell.
  • Amaranthus hybridus var. cruentus (L.) Moq.
  • Amaranthus hybridus var. patulus (Bertol.) Thell.
  • Amaranthus paniculatus L.
  • Amaranthus sanguineus L.

International common names:

  • English: African spinach, Mexican grain amaranth
  • Spanish: amaranto, cola de zorro
  • French: amarante, amarante étalée, brède de Malabar
  • Chinese: lao ya gu
  • Portuguese: bredo caruru-branco

Physiology and Phenology

(The following information is provided by Grubben (2004))

In cool or dark conditions the seed remains dormant; light and high temperatures break the dormancy. In moist soil above 15°C emergence takes place 3-5 days after sowing. Vegetative development is fast. The genus Amaranthus is characterized by the C4 cycle photosynthetic pathway, giving it a high rate of photosynthesis and excellent water use efficiency at high temperatures and radiation intensity. Water consumption is high due to its rapid growth; a crop with a closed leaf canopy uses about 6 mm/day. Depending on cultivar, day length and cultural practices, flowering may start 4-8 weeks after sowing, making the plant less suitable for consumption. There are at least four times as many female flowers as male flowers. Pollination is affected by wind, but the abundant pollen production causes a high rate of self-pollination. Some pollination is also affected by insects (bees, flies) and up to 40% outcrossing may occur. Seeds mature after 3-5 months and then the plant dies.

Environmental Requirements

(The following information is provided by Grubben (2004))

Vegetable amaranths grow well at day temperatures above 25°C and night temperatures not lower than 15°C. In Indonesia, A. cruentus is grown up to elevations of 2000 m. Shade is disadvantageous except in cases of drought stress. Amaranth is a quantitative short-day plant, which is an advantage in the subtropics where the generative stage is retarded during summer. Amaranths like fertile, well-drained soils with a loose structure. The mineral uptake is very high. Although A. cruentus is fairly tolerant of adverse climate and soil conditions, escapes growing as a weed tend to disappear because they cannot compete with true weeds like A. spinosus or A. hybridus.

After seedling emergence, many amaranth cultivars are tolerant to drought and highly wet conditions, but sensitive to complete flooding. Amaranth is photoperiod-sensitive and most species will flower when day lengths are shorter than 12 h. Amaranth grows best in a fertile loam or silty-loam soil with good water-holding capacity, but depending on the species, also adapts to poor soil conditions and low soil moisture levels. The mineral uptake from the soil is high (Ebert et al., 2011).

Evidence indicates that [quite a few] amaranths adapt to many environments and tolerate adversity because they use an especially efficient type of photosynthesis[--C4 --] to convert the raw materials of soil, sunlight and water into plant tissues (National Research Council, 1984).

Notes on Natural Enemies

According to Grubben (2004), wet rot or stem rot caused by the fungus Choanephora cucurbitarum is the main disease in amaranths. Damping-off caused by Pythium aphanidermatum and Rhizoctonia is often serious in seedbeds. Pythium also attacks older plants. No viral diseases have been reported.

A review of the main fungal diseases affecting A. cruentus worldwide and more specifically in Poland is given by Pusz (2007); the most common are leaf spots caused by Alternaria alternata, Phoma levellei [P. leveillei], Phoma medicaginis and a range of other fungi, and stem rot caused by Phomopsis amaranthicola. Leaf and stem blight caused by Phomopsis amaranthophila has been reported in Brazil while Alternaria leaf spot occurs on A. cruentus in Tanzania (Ebert et al., 2011). In Taiwan and other countries, white rust (Albugo bliti [Wilsoniana bliti]) and amaranth anthracnose (Colletotrichum erumpens var. amaranti) may turn into serious diseases (Ebert et al., 2011).

In the USA, the lygus bug (Lygus lineolaris) has severely damaged grain amaranth yields by piercing the developing seed and sucking out the juices (Olson and Wilson, 1990; Wilson and Olson, 1992). Leaf miners have also been found on both grain and vegetable amaranth. In Lucknow, India, serious damage to both grain and vegetable types has often been caused by spider mites. The stem weevil (Lixus truncatulus [H. truncatulus]) is a major pest of amaranth; its grubs damage foliage and roots and cause the plants to wilt. Leaf rotters (H. recurvalis [S. recurvalis]) also cause considerable damage during rainy seasons (National Research Council, 1984). Infestations of the weevil, Conotrachelus seniculus, were observed on the roots of A. cruentus in Arizona in 1984 (Terry and Lee, 1990). Significant damage to cultivated A. cruentus in southern Nigeria (Agunloye and Osisanya, 1985) and Brazil (Oliveira et al., 2012) by Herpetogramma bipunctalis has been documented.

Bacterial wilt caused by Ralstonia solanacearum has been reported on A. cruentus in Benin (Sikirou et al., 2019).

Uses

Amaranthus cruentus is useful as a grain or a leafy vegetable. 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, e.g. it flowers under a wider range of daylengths than the others (National Research Council, 1984). is used as an African leafy vegetable (Grubben and van Sloten, 1981) and also widely grown as a dye plant, ornamental and pot herb in Central America, Europe, China, India, southeast Asia, and Africa. The leaves and the softest portions of the shoots are usually boiled in several changes of water and then separated from the cooking liquid (Martin and Telek, 1979) though they traditionally are steamed in Uganda (Stafford et al., 1976). Amaranth leaves are combined with condiments to prepare soup in Nigeria (Okiei and Adamson, 1979; Oke, 1983); used in salad, boiled and mixed with a groundnut (Arachis hypogaea) sauce in Mozambique (Oliveira and de Carvalho, 1975) or pureed into a sauce and served over vegetables in West Africa (Martin and Telek, 1979). In Ethiopia, A. cruentus is used as a tapeworm expellant while in Sudan ash from the stems is used as a wound dressing (Achigan-Dako et al., 2014). In Gabon heated leaves are used on tumours (Grubben, 2004).

Amaranthus cruentus is an important leaf vegetable crop cultivated throughout the tropics (Grubben and van Sloten, 1981). The leaves are rich in vitamin A, calcium and potassium (Early, 1997). The seeds of grain amaranth are valued for their high protein content (up to 15%) (Musa et al., 2014). A. cruentus is used in Mexico to produce typical sweets called alegría, in which the amaranth grains are toasted and mixed with honey or chocolate (Maestri, 2014). The economic value of A. cruentus as a popular market vegetable ranks high. From market surveys, it appears as one of the main African leafy vegetables, possibly the number one in quantity and area. No statistical data are available, since in most cases all leaf vegetables are recorded as one single group. In national or FAO statistics, they are not recorded at all. Correct registration is hampered by the short growing period (3-6 weeks), scattered occurrence of small plots of cultivation and the dispersed sales in small street markets. In the big cities in Benin, the average quantity of fresh leafy vegetables bought daily at the markets was 42 g/head/day, 31% of which was A. cruentus. There is some unregistered export of amaranth from African countries, as well as from Latin America (Caribbean, Suriname) to Western Europe (PROTA, 2016).

The potential of grain and vegetable amaranth as a food resource has been reviewed extensively by Haas and Kauffman (1984), Saunders and Becker (1983), National Research Council (1984) and Sánchez Marroquín (1980). Dye use seems limited to cultures that do not grow amaranth as a grain crop (Sauer, 1950). The red dye from amaranth leaves is used to colour alcoholic beverages in Bolivia and north western Argentina, to colour maize (Zea mays) dough in Mexico and the southwestern United States (Sauer, 1950) and to dye foods and beverages in Ecuador (Jain and Hauptli, 1980).

Amaranth is high in protein, lysine, calcium, iron and fibre, all of which are useful as functional ingredient in cereal products. Amaranth oil is high in squalene, a powerful antioxidant used as a dietary supplement for diabetes and those suffering from hypertension and metabolic disorders (Pal and Khoshoo, 1974; Teutonico and Knorr, 1985). A. cruentus forage meal and extruded grains have been used as feed ingredients for broilers (Tillman and Waldroup, 1988; Fraga et al., 1993; Miazzo et al., 1994).