Amaranth Part 2—Sustainability, Processing, and Applications of Amaranth

Chapter 16

Amaranth Part 2 Sustainability, Processing, and Applications of Amaranth D.K. Santra1 and R. Schoenlechner2 1

University of Nebraska-Lincoln, Scottsbluff, NE, United States, 2University of Natural Resources and Life Sciences, Vienna, Austria

16.1 SUSTAINABILITY OF AMARANTH PRODUCTION 16.1.1 Origin and Distribution Amaranths are broad-leaved plants, one of the few nongrasses that produce significant amounts of edible small-seeded grain, also often called pseudocereals. It was reported to have originated both in Central and Latin America (Sauer, 1967, 1993; Stallknecht & Schulz-Schaeffer, 1993; Sumar, 1983). Among the three grain-type species of amaranth, Amaranthus cruentus was reported to be cultivated 6000 years ago in Central America, Amaranthus hypochondriacus was cultivated in Mexico at least approximately 1500 years, and the third grain type Amaranthus caudatus was reported to be grown in Andean mountain valleys of south America (Sauer, 1993). Presently, A. cruentus production is limited to Andean mountains because of its adaptability to higher elevation. Amaranthus hypochondriacus is the most common grain amaranth since it is more adapted to lower elevation, which is represented by the worlds’ major production regions (Myers, 1996). Grain amaranth was a major food in Aztecs, Mayan, and Incan diets and cultures until the 1500s when the Spanish conquered (Graham, 2010; NRC, 1989; Sooby et al., 1998). By the 1700s it was spread from Latin America and grown in Eastern Europe and Russia as a herb and ornamental (NRC, 1984). Grain amaranth was presumably introduced from these points of origin to the northern Indian subcontinent, the mountain valleys of Nepal, and part of Africa in the late 1800s (Joshi and Rana, 1991; Sauer, 1967, 1993). During the 20th century, its production was reported in Asia, Africa, Europe, and North and South America (Sooby et al., 1998). It was largely ignored in the United States until the 1970s, when amaranth grain protein was reported as high quality and could be used as a food ingredient in the American diet (Breene, 1991; Senft, 1980).

16.1.2 Production and Yield Although traditionally cultivated within 30 latitude of the equator, amaranth can be grown in higher latitudes using varieties requiring longer day length than that of the tropics (NRC, 1989; Weber, 1987). Most grain amaranth cultivation was concentrated in highland valleys, such as those in the Sierra Madre, Andes, and Himalayas. By the middle of the 20th century, cultivation of grain amaranth had declined to the point where it was grown only in small plots in Mexico, the Andean highlands, and in the Himalayan foothills of India and Nepal (Kauffman & Weber, 1990; Myers, 1996; Weber, 1987). Cultivation of grain amaranth is now in the process of expanding in a number of countries (Mexico, Guatemala, Peru, Venezuela, Kenya, Uganda, Nigeria, India, China, Thailand, United States, and Canada) (Graham, 2010). As of the mid-1990s, South Asia was the world’s only region where grain amaranth production was increasing (Brenner et al., 2000). Amaranth production was slowly started and increased in the United States during the 1980s and 1990s, primarily because of an initiative by the Rodale Research Center, Pennsylvania (Weber, 1987). The United States has been the leading commercial producer of grain amaranth during this period, although production has been less than 2000 ha annually (Myers, 1996; Weber, 1987). Most of the United States production has been in the upper Midwest and Great Plains (Nebraska, South Dakota, North Dakota, Missouri, Minnesota, Kansas, and Iowa) and with widely scattered Sustainable Protein Sources. DOI: http://dx.doi.org/10.1016/B978-0-12-802778-3.00016-0 © 2017 Elsevier Inc. All rights reserved.

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fields in other parts of the country (Montana, California, Maryland, and Kentucky) (Myers, 1996; Sooby et al., 1998; Weber, 1987). Production in none of these states is on a large scale, which possibly will not change in the near future based on the limited market. In 1988, approximately 1200 ha of grain amaranth were planted in the Great Plains of the United States. According to the 2002 US Census of Agriculture, 10 farms grew amaranth on 939 acres. Although the United States has been the leading producer of grain amaranth for retail food products, the largest production area in the last decade is believed to have been in China (Sooby et al., 1998). The main Chinese use of amaranth is reportedly to feed the forage to hogs, rather than harvesting the grain (Myers, 1996). In North America (United States and Canada), optimal planting time is between mid-May to mid-June when soil temperature is at or above 65 70 F (Myers, 1996; Weber, 1987). Yield was decreased substantially when planting time was delayed to July. Grain amaranth was usually harvested either after natural senescence (such as Missouri, Texas) or after first frost (northern Great Plains and upper mid-west) in September October (Myers, 1996; Weber, 1987). Yields of grain amaranth, like any new crop, are highly variable. One of the most important factors of grain loss is seed loss due to shattering before harvest from wind or during harvest (Myers, 1996; Weber, 1987). Seed yield of grain amaranths is very comparable to the yields of most other cereals when yield loss due to shattering was minimal. Handharvested yield has been as high as 4000 kg/ha in Montana (Cramer, 1988) and 6000 kg/ha in Peru (Sumar, 1983). When harvested mechanically, 1000 kg/ha is considered to be a good yield, which has often been achieved in research plots in a number of states throughout the United States (Myers, 1994). However, potential yields could be several-fold more than this base level depending on location and condition of the trials. In Pennsylvania, test plots yielded 1800 kg/ ha, whereas in California the yield was B3000 kg/ha (Myers, 1994). In the sub-Himalayan region in India (Himachal Pradesh and Uttar Pradesh) selected landraces yielded 3000 kg/ha in a research plot (Joshi, 1985, 1986). Grain yield of up to 5000 kg/ha has been reported in Uganda (Stallknecht & Schulz-Schaeffer, 1993). Grain amaranth breeding programs in Latin America have achieved yields of 7200 kg/ha and 4600 kg/ha for certain varieties in Peru and Mexico, respectively (Brenner et al., 2000).

16.1.3 Land, Water, and Energy Uses Conventional cereals (eg, corn, wheat, rice) require high levels of water and nitrogen fertilizer, which is chemically produced through energy-intensive chemical processes. Therefore, such modern food grain crops are very energy-intensive for production of protein-rich human diet. In contrast, pseudocereal crops like grain amaranth are low energy-requiring crops because of the low requirement for water and fertilizer. The grain amaranths exhibit C4 photosynthesis, grow rapidly, tolerate a variety of unfavorable abiotic conditions, including high salinity, acidity, or alkalinity, making them highly suited for production under subsistence agricultural practices that are inhospitable to conventional cereal crops (Myers, 1996; Sooby et al., 1998; Weber, 1987). Therefore, by implication, the grain amaranth has the potential for a significant impact on malnutrition (Emokaro & Ekunwe, 2007). Historically, people have cultivated amaranths in environments ranging from the true tropics to semiarid lands and from sea level to some of the highest farms in the world. Amaranth has evolved so that it can produce grain under moisture stress. Grain amaranth has the ability to produce good seed yield even under severe drought conditions when most modern grain crops fail. The grain amaranth field in western Nebraska during 2012, an historic drought year in the United States, is a perfect example (Fig. 16.1). Little is known about actual water requirements of grain amaranth. Amaranths require well-moistened soil for germination and root establishment but once seedlings are established, it does well with limited water, making it especially valuable in areas with limited water resources such as Sub-Sahara Africa and the west-central Great Plains of the United States (Chaudhari, Patel, & Desai, 2009; Johnson & Henderson, 2002; Joshi & Rana, 1991; Mng’omba, Kwapata, & Bokosi, 2003; Piha, 1995; Sooby et al., 1998). In fact, they grow best under dry, warm conditions. Grain amaranths have been grown in dry-land agriculture in areas receiving as little as 200 mm of annual precipitation (Putnam, 1990). Observations in many test plots and farmers’ fields suggest that grain amaranth is drought-tolerant at later stages of growth. Amaranth has the ability to grow back to full vigor if rain occurs within a few days of wilting. Researchers in China have reported that the water requirement for growing grain amaranth is 42 47% that of wheat, 51 62% that of maize, and 79% that of cotton (Kauffman & Weber, 1990). Kenyan farmers in regions with marginal rainfall plant amaranth rather than maize because they believe there is less risk of a crop failure with amaranth (Gupta & Thimba, 1992). Observations indicate that amaranth in the coastal desert of Peru requires half the irrigation required by corn (Sumar, 1983). In the United States, total water use by grain amaranth ranged from 27 32 cm on an average year in eastern North Dakota (Henderson, Schneiter, & Johnson, 1993). A farmer in western Nebraska uses 30 cm water for irrigated grain amaranth production, which is about 50% of irrigated corn production (Sooby et al., 1998).

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(A)

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FIGURE 16.1 Grain amaranth production field (A) with large and healthy head (B) in Garden Co. in western Nebraska during 2012 when most of the dryland crops in the area failed due to severe drought. Photos were taken by Mr. Gary L. Stone, Extension Educator, Panhandle Research and Extension Center, University of NebraskaLincoln.

Limited information is available on the fertility requirements of amaranth. In general, amaranth’s fertility requirement, especially for nitrogen (N), in not high. Under dry-land production conditions in western Nebraska typically 22 45 kg N/ha is applied and the rate is 45 90 kg/ha under irrigation (Sooby et al., 1998). More N application above this level increases vegetative growth, which induces more lodging (Elbehri, Putnam, & Schmitt, 1993l; Myers, 1998). Typical phosphorus (P) requirement in western Nebraska is 22 kg/ha (Sooby et al., 1998). With respect to energy requirement, grain amaranth is environmentally friendly and a sustainable source of high-quality protein for healthy human diet. Therefore, grain amaranth is an excellent plant protein source for economically poor people living in the area where water resources are limited, farmers are not able to apply chemical fertilizer, and farmland is poor quality, all of which make the area impossible for the production of conventional crops such as corn, rice, wheat, and soybean.

16.1.4 Harvesting When it comes to harvesting grain amaranth, “Amaranth is easy to grow but hard to harvest” is a common phrase among the United States grain amaranth farmers, especially in the region with short growing season. The main problem is grain shattering before harvesting and during combine. Although amaranth is a widely adapted plant and can be grown anywhere in the United States, harvesting is more difficult in warm and moist regions. Harvesting time depends on the regional climate. For short growing-season in the northern High Plains and upper mid-west of the United States, harvesting should be done as soon as possible after frost-mediated drying in October (Putnam, 1990; Sooby et al., 1998). It usually takes 2 weeks after the frost to dry enough for combining since plants are full of moisture at first frost. In regions with a longer growing-season (eg, Missouri, Maryland) natural senescence followed by drying usually occurs in September through mid-October before the first frost. In such areas, harvesting is usually done when amaranth heads turn brown (Myers, 1996; Sooby et al., 1998). Windrowing is not desirable in amaranth since soil particles are usually picked up at the time of threshing and particle size is similar to amaranth seed, which makes it difficult to clean later on. Many a time farmers harvest amaranth at higher moisture to minimize seed loss due to shattering and dry the grains later. A standard small-grain combine is usually used to harvest with special precautions to minimize loss of tinny amaranth grain during combining (Myers, 1996; Putnam, 1990; Weber, 1987). Combine setting is similar to wheat but with reduced cylinder speed as much as possible. A canvas or draper type of header may be used to catch the seed and most of these come with a bat reel with no fingers, but a pick-up reel is better for lifting heads that have fallen over (Sooby et al., 1998).

16.1.5 Postharvest Processing (Cleaning and Storage) Postharvest processing (drying and cleaning) is very important for maintaining high-quality grain. Problems with grain drying will vary from year to year depending on weather conditions. Grain moisture of 10 12% is optimum for storage without further drying. It is important to harvest the grain when the plants are as dry as possible. The longer the plants stay in the field after the first frost, the higher the likelihood that the quality of the grain will be reduced by wet weather. Grain maturity will vary even on a single head because amaranth is an indeterminate type, that is, it is a plant

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that continues to produce new flower and form seed throughout the season. Therefore, harvested seed will be a mixture of optimally matured (solid “opaque” white or tan appearance) and less matured grain with more moisture (glossy or translucent appearance) (Sooby et al., 1998). Translucent-looking seeds will be lighter and poorer quality than matured seeds and, therefore, should be cleaned to maintain high food quality grain (Myers, 1996). Amaranth grain will mold quickly and become unfit for human consumption if stored when it has a moisture content that is too high. The moisture content of grain amaranth is usually monitored before harvest and accordingly arrangements for drying should be made in advance. It is important to remove as much vegetative material as possible from the harvested grain before drying to reduce the potential sources for the introduction of mold and undesirable flavors. Small quantities of grain can be dried by moving ambient air over a pile of grain with occasional stirring of the grain if possible. In the case of a large pile of grain, forced air is run through a perforated pipe under the pile. Due to the small size of amaranth, conventional grain dryers need to be adapted (eg, fine-mesh nylon cloth over the perforated pipe) for drying amaranth. It is necessary to pay close attention to cleaning the grain for high-quality food-grade grain amaranth (free from soil dirt, small stem pieces, black seed, mold, and other contamination). Preliminary cleaning of bulk of trash by scalping always minimizes the cost of cleaning since specialized equipment is needed to adequately clean amaranth (Sooby et al., 1998). Many local grain cleaners can do the final cleaning. Specialized cleaning usually involves auguring through a rotary screen to remove large stems and sticks. Then the grain is passed through screens and run over a gravity table to remove smaller foreign materials and dry but immature amaranth seed with lower bulk density. Optical sorters are usually used to remove black-seeded pigweed seed or discolored amaranth seed. Such sophisticated cleaning process finally produces very high-quality grain amaranth with uniform color and without any foreign material. Dried, cleaned grain should be placed in rodent-proof storage with adequate ventilation to prevent a build-up of condensation. Good storage conditions are needed to maintain grain quality at high level. Often heavy-duty paper bags with poly liners are used to store completely dried grain amaranth (Sooby et al., 1998; Weber, 1987). The producers possibly will adapt different strategies for harvesting and postharvest processing depending on resources. However, it should be remembered that suboptimal processing usually makes for inferior quality grain and potentially would make for a lower price or the grain being rejected in the market.

16.1.6 Production Cost The cost of amaranth is not very high when compared with major crops like corn and soybean. This is due to its ability to grow in marginal land with a low level of input cost associated with fertilizers, water, herbicides (no herbicides are approved for amaranth), and nonsignificant insects and diseases. The only significant insect that may cause yield loss is the Lygus bug. Tarnished leaf bug (Lygus lineolaris P. Beauv.) is considered the greatest pest of amaranth globally, damaging plants through its sucking action on meristematic tissue, developing floral buds, blossoms, and embryos (Brenner et al., 2000; Joshi & Rana, 1991; Myers, 1996). Production costs for amaranth are estimated at $247 per hectare, with additional harvest and marketing costs varying from $50 to $500 per hectare, according to the market channel selected. Total expenses per hectare, including both variable and fixed, would come to approximately $570 1000. Presuming gross returns of $790 1600 per hectare, returns to land, capital, and management could range from $247 to $620 per hectare (Grain Amaranth, University of Kentucky, https://www.uky.edu/Ag/CCD/introsheets/amaranth.pdf; AMRC, 2011).

16.2 PROCESSING OF AMARANTH Processing of amaranth is majorly influenced by the morphology of the seed, particularly as the embryo surrounds the starch-rich perisperm, and by its small seed size, which ranges from 0.8 g to 1.6 g per 1000 seeds (Sooby et al., 1998; Fig. 16.2). Both morphological features pose challenges to many existing food processes that were originally established for cereals, mainly wheat. These existing food processes cannot be simply transferred to amaranth processing. They require several adaptations like choosing the appropriate equipment or modifying the processing parameters. Sometimes rather unconventional and innovative approaches may have to be considered.

16.2.1 Milling and Fractionation Most cereal food products do not utilize whole seed kernels, thus requiring the preparation of (wholemeal) flour or defined flour fractions. Milling and fractionation of starchy seeds is therefore an important step that influences further product development. Milling is a high shear process, which generates heat and thus causes an increase in the

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FIGURE 16.2 Scanning electron microscopy (SEM) picture of a single amaranth grain. Embryo and surrounding starch-rich perisperm are indicated by arrows.

Embryo

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temperature of the flour, which has to be considered, as it may affect the properties of the obtained byproducts. Milling can be performed either by dry or wet milling schemes. The aim of dry milling is mainly to produce wholemeal flour or to separate the grain by physical fractionation techniques (eg, grinding, sifting, sieving) into its anatomical parts, that is, separation of the starch-rich endosperm (perisperm in amaranth) from the outer layers (bran and embryo). Wet milling is applied to separate the kernels into its chemical components, that is, starch, protein (concentrates, isolates), dietary fibers, or oil. The production of wholemeal flour from amaranth is well established and does not have specific problems, so all known processes may be applied. Care has to be taken for the moisture content of the seeds, so tempering (ie, addition of water and resting period) or preconditioning (addition of water and heat treatment) of the seeds is often required to achieve an optimal seed moisture content for easier grinding (Tosi, Re´, Lucero, & Masciarelli, 2000). The production of flour fractions with different chemical composition and physical properties by dry fractionation techniques from amaranth is extremely challenging. Specifically, its small seed size and tightly bound protein and starch cause excess friction on milling equipment designed to handle larger or softer cereal grains. Various milling and fractionation techniques (pilot scale) to produce starch-rich and protein-rich flour fractions from amaranth have been investigated by several researchers, for example, roller mill and plansifter by Berghofer and Schoenlechner (2002) or differential milling process, sieving, and pneumatic separation by Tosi et al. (2000). Abrasive milling seems to have potential for such small seeds. In earlier studies barley pearlers were studied (eg, Betschart, Wood, Shepherd, & Saunders, 1981) and in more recent studies, Roa, Santagapita, Buera, and Tolaba (2014) applied a combination of abrasive milling and planetary ball milling, and found that milling energy influenced the rheological and thermal behavior of amaranth flour (Roa, Baeza, & Tolaba, 2015).

16.2.2 Wet Milling for Production of Starch-Rich, Fiber-Rich, or Protein-Rich Fractions (Protein Concentrates and Isolates) Wet milling is mainly applied to isolate starch, but other coproducts that are interesting for food applications are the protein-rich and fiber-rich fractions. Typical wet milling includes the following steps: 1. 2. 3. 4. 5.

Cleaning of the grain; Soaking in an aqueous solution (often including alkali); Several milling steps to pulverize the particles; Filtration through a series of screens with decreasing mesh sizes (mainly to remove germ and fiber); Separation of starch and protein by centrifugation (mainly for lab scale) or table method (for industrial scale).

The protein fraction (lighter fraction) is then concentrated and dehydrated. The starch suspension is washed and concentrated. The two mentioned separation techniques are based on density differences between starch and protein. For amaranth seeds these separation methods cause problems due to the already mentioned tight starch protein bonds and small seed size (Middlewood & Carson, 2012a; Wilhelm, Themeier, & Lindhauer, 1998). Thus, screening, microfiltration, or tangential flow filtration (pressure-driven separation process) is more feasible (Middlewood & Carson, 2012a, 2012b).

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Wet milling of amaranth has been investigated on a laboratory scale and many methods have been developed, more or less similar to corn wet milling (eg, Calzetta Resio, Aguerre, & Suarez, 2003, 2006; Calzetta Resio, Tolaba, & Suarez, 2009). However, the efficiency of the process has not yet reached a level that may be applied on an industrial scale. There is no commercial wet milling process for amaranth yet. Alkaline soaking has been proposed for amaranth wet milling, in order for easier removal of the protein, but it has to be considered that starch granules might be damaged or lost (decreasing yield) (Perez, Bahnassey, & Breene, 1993). Acid wet milling (Loubes, Calzetta Resio, Tolaba, & Suarez, 2012), use of enzymes (Radosavljevic, Jane, & Johnson, 1998), or sodium metabisulfite (Calzetta Resio et al., 2009) might eventually be alternatives. If the specific aim of separation is to produce protein concentrates or isolates, the process is performed analogous to the described wet milling methods. This commonly applies alkaline steeping of defatted flour, in order to increase the yield and purity of isolated or concentrated protein. Optimal pH for this alkaline extraction is pH 11 and usually the glutelin, albumin, and globulin proteins are isolated (Martinez & Anon, 1996). On a laboratory scale, Conde´s, An˜o´n, and Mauri (2015) used alkaline steeping at pH of 11 (using NaOH) and achieved a yield of 2 g isolate/100 g defatted flour with a purity of approximately 90%. Bejarano-Luja´n and Netto (2010) found that modification of the standard wet milling process of amaranth, by including an acid washing or heating step during alkaline extraction, changed the composition and functionality of the isolated protein fraction. Consequently, this modified the structure and rheological properties of gels obtained from this protein. Pilot-scale or even industrial-scale processing to obtain protein isolates or concentrates has not been investigated much. Castel, Andrich, Netto, Santiago, and Carrara (2012) performed a pilotscale study to isolate protein from amaranth (Amaranthus mantegazzianus). They compared the application of alkaline extraction or acid pretreatment in combination with isoelectric precipitation or ultrafiltration processes on protein yield, protein concentration, and physicochemical characteristics of the protein concentrates. Protein yield was higher after alkaline extraction in comparison to acid pretreatment, but protein concentration was lower. Acid pretreatment, and in particular ultrafiltration, improved protein concentration and its nutritional quality (an improved amino acid composition). For full exploitation of dry and wet milling processes to obtain defined fractions, isolates, or concentrates of amaranth components, research has to be intensified, in particular for subsequent scaling-up to an industrial level. With respect to nutritional and physicochemical properties, amaranth and its constituents present a valuable alternative to other sources like meat, dairy, or soy.

16.3 FOOD APPLICATIONS Amaranth can be used in many food applications like cooking, popping, extrusion, fermentation, bread baking, or pasta. Whole seeds can be consumed directly after cooking in threefold water or they can be popped by short and dry heat (without fat addition). These two processes present the oldest forms of consumption that have been traditionally applied. Popping of amaranth is a very interesting alternative use of amaranth because popped amaranth presents a nutty flavor, and thus, may enhance the palatability of food products. In particular, popped amaranth offers a nutty compliment to sweet products such as cakes, cookies, mueslis, or granolas. Popped amaranth grains are quite soft in texture and are ready to be eaten as is or to be incorporated (after milling) into existing or new food formulations. During popping, the embryo stays intact and a partial gelatinization of the starch granules occurs (in the perisperm) and due to the short processing time of only seconds, the nutritional profile of the grain is more or less maintained. For amaranth processing, the absence of gluten should be considered, therefore, it has no dough-forming properties. A strategy to use amaranth is to blend it with other (gluten-containing) cereals in existing products in order to enhance their nutritional value. Up to 20% amaranth addition does not really ask for intensive adaptation of preparation processes. This has been investigated for different products (eg, bread, pasta, cookies, biscuits, beverages) by several researchers. The main aim of adding amaranth to such cereal products is usually their nutritional enhancement. Alternatively, the absence of gluten makes amaranth suitable for the production of gluten-free products. The production of gluten-free bread and bakery products or pasta using amaranth flour is of great interest now, since the need for gluten-free products is increasing due to an increased prevalence of celiac disease and gluten-sensitivity. Summarizing all affected persons together, the market can be estimated to be around 8 10% of the global population. Besides being gluten-free, the challenge of gluten-free food is to offer an adequate nutritional balance. As amaranth, as well as other pseudocereals, is nutritionally superior to many gluten-free raw materials, its use is a logical consequence. In fact, the growing gluten-free market can be seen as one of the main driving forces for the increased production and use of amaranth. Production of gluten-free products in general, and including amaranth in particular, is a great challenge and cannot be carried out without addition of further ingredients or without specific adaptation of relevant processing steps.

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Gluten-free products like bread and pasta with amaranth have been studied by some researchers (Calderon de la Barca, 2010; Schoenlechner, Drausinger, Ottenschlaeger, Jurackova, & Berghofer, 2010), but still remain under-researched compared to major crops. In addition to its nutritional advantages, amaranth and isolated fractions or components thereof offer unique properties and technological functionality in food applications that have not been exploited to a large extent. Amaranth proteins, concentrates, or isolates are characterized by excellent solubility, as well as foaming, emulsifying, and stabilizing properties (Bejosano & Corke, 1998; Fidantsi & Doxastakis, 2001) and thus have a high potential for functional foods, in particular where gel formation is desired. Amaranth starch is characterized by the small size of granules, low amylose content, high water-binding capacity, good freeze thaw stability, resistance to mechanical shear, and excellent gelling and thickening properties (Wilhelm, Aberle, Burchard, & Landers, 2002; Zhao & Whistler, 1994). These functional properties offer a wide range of uses in food applications.

REFERENCES AMRC (Agricultural Marketing Resource Center). (2011). Amaranth: ,http://www.agmrc.org/commodities__products/specialty_crops/amaranth.cfm/.. Bejarano-Luja´n, D. L., & Netto, F. M. (2010). Effect of alternative processes on the yield and physicochemical characterization of protein concentrates from Amaranthus cruentus. LWT Food Science and Technology, 5, 736 743. Bejosano, F. P., & Corke, H. (1998). Protein quality evaluation of Amaranthus wholemeal flours and protein concentrates. Journal of the Science of Food and Agriculture, 76, 100 106. Berghofer, E., & Schoenlechner, R. (2002). Chapter 7: Grain amaranth. In P. S. Belton, & J. R. N. Taylor (Eds.), Pseudocereals and less common cereals. Grain properties and utilization potential (pp. 219 253). Berlin Heidelberg: Springer-Verlag. Betschart, A. A., Wood, I. D., Shepherd, A. D., & Saunders, R. M. (1981). Amaranthus cruentus: Milling characteristics, distribution of nutrients within seed components, and the effects of temperature on nutritional quality. Journal of Food Science, 46, 1181 1187. Breene, W. M. (1991). Food uses of grain amaranth. Cereal Foods World, 36, 426 430. Brenner, D. M., Baltensperger, D. D., Kulakow, P. A., Lehmann, J. W., Myers, R. L., Slabbert, M. M., & Sleugh, B. B. (2000). Genetic resources and breeding of Amaranthus. Plant Breeding Reviews, 19, 227 285. Calderon de la Barca, A. M., Rojas-Martinez, M. E., Islas-Rubio, A. R., & Cabrera-Chavez, F. (2010). Gluten-free breads and cookies of raw and popped amaranth flours with attractive technological and nutritional qualities. Plant Foods for Human Nutrition, 65, 241 246. Calzetta Resio, A. N., Aguerre, R. J., & Suarez, C. (2003). Study of some factors affecting water absorption by amaranth grain during soaking. Journal of Food Engineering, 60, 391 396. Calzetta Resio, A. N., Aguerre, R. J., & Suarez, C. (2006). Hydration kinetics of amaranth grain. Journal of Food Engineering, 72, 247 253. Calzetta Resio, A. N., Tolaba, M. P., & Suarez, C. (2009). Correlations between wet-milling characteristics of amaranth grain. Journal of Food Engineering, 92, 275 279. Castel, V., Andrich, O., Netto, F. M., Santiago, L. G., & Carrara, C. R. (2012). Comparison between isoelectric precipitation and ultrafiltration processes to obtain Amaranthus mantegazzianus protein concentrates at pilot plant scale. Journal of Food Engineering, 112, 288 295. Chaudhari, P. P., Patel, P. T., & Desai, L. J. (2009). Effect of nitrogen management on yield, water use, and nutrient uptake on grain amaranth (Amaranthus hypochondriacus) under moisture stress. Indian Journal of Agronomy, 54(1), 69 73. Conde´s, M. C., An˜o´n, M. C., & Mauri, A. N. (2015). Amaranth protein films prepared with high-pressure treated proteins. Journal of Food Engineering, 166, 38 44. Cramer, C. (Ed.). (1988). Montana releases new amaranth line. Amaranth Today, 4(2 3), 6. Elbehri, A., Putnam, D. H., & Schmitt, M. (1993). Nitrogen fertilizer and cultivar effects on yield and nitrogen-use efficiency of grain amaranth. Agronomy Journal, 85, 120 128. Emokaro, C. O., & Ekunwe, P. A. (2007). Efficiency of resource-use and marginal productivities in dry season amaranth production in Edo South, Nigeria. Journal of Applied Sciences, 7, 2500 2504. Fidantsi, A., & Doxastakis, G. (2001). Emulsifying and foaming properties of amaranth seed protein isolates. Colloids and Surfaces B: Biointerfaces, 21, 119 124. Graham, M. W. (2010). Grain amaranth production and effects of soil amendments in Uganda. Ph.D. thesis. Iowa State University. ,http://lib.dr. iastate.edu/cgi/viewcontent.cgi?article52462&context5etd/.. Gupta, V. K. (1986). Grain amaranths in Kenya. Proceedings of the third amaranth conference. Emmaus, PA: Rodale Press, Inc. Gupta, V. K., & Thimba, D. (1992). Grain amaranth: A promising crop for marginal areas of Kenya. Food Reviews International, 8(1), 51 69. Henderson, T. L., Schneiter, A. A., & Johnson, B. L. (1993). Production of amaranth in the northern Great Plains. Alternative crop research: A progress report (pp. 22 30). Fargo: North Dakota State University. Johnson, B. L., & Henderson, T. L. (2002). Water use patterns of grain amaranth in the northern Great Plains. Agronomy Journal, 94, 1437 1443. Joshi, B. D. (1985). Annapurna, a new variety of grain amaranth. Indian Farming, 29 31. Joshi, B. D. (1986). Genetic variability in grain amaranth, Amaranthus hypochondriacus Linn. Indian Journal of Agricultural Science, 56, 574 576. Joshi, J. D., & Rana, R. S. (1991). Grain amaranths: The future food crop. India: National Bureau of Plant Genetic Resources.

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