Quinoa. Atul Bhargava
(Jellen et al., 2011). The emergence of quinoa to prominence in organic food markets of the developed world has led to scientists giving increasing attention to the crop’s unique nutritional benefits, and potentially novel abiotic stress-tolerance mechanisms.
Quinoa is a native of the Andean region and has been cultivated in the region for around 7000 years (Garcia, 2003). Quinoa was known by a number of names in local languages. The people of the Chibcha (Bogota) culture called quinoa ‘suba’ or ‘supha’, while the Tiahuancotas (Bolivia) called it ‘jupha’ and the inhabitants of the Atacama desert knew it by the name ‘dahue’ (Pulgar-Vidal, 1954). León (1964) is of the view that the names ‘quinoa’ and ‘quinua’ were used in Bolivia, Peru, Ecuador, Argentina and Chile. The crop has been an important food grain source in the Andean region since 3000 BC (Tapia, 1982) and occupied a place of prominence in the Inca Empire only next only to maize (Cusack, 1984). However, after the conquest of the region by the Spaniards in 1532, other crops, such as potato and barley, relegated quinoa to the background (Bhargava et al., 2006a). However, the sporadic failure of green revolution in the Andes and enormous destruction of other crops by droughts, once again brought native crops like quinoa to the forefront as it showed much less fall in the yields in severe conditions (Cusack, 1984). In the mid-1970s, the exceptional nutritional characteristics of quinoa were discovered and its popularity began to increase (Maughan et al., 2007). Andean countries established small but effective breeding programmes and several new varieties were released. Efforts were made to collect diverse landraces to prevent genetic erosion, resulting in national quinoa germplasm banks in many Andean countries, with the largest banks being in Bolivia and Peru (Maughan et al., 2007).
Quinoa is grown in a wide range of environments in the South American region (especially in and around the Andes), at latitudes from 20°N in Colombia to 40°S in Chile, and from sea level to an altitude of 3800 m (Risi and Galwey, 1989). Recently it has been introduced in Europe, North America, Asia and Africa. Many European countries are members in the project entitled ‘Quinoa – A multipurpose crop for EC’s agricultural diversification’, which was approved in 1993 (Bhargava et al., 2006a). The American and European tests of quinoa have yielded good results and demonstrate the potential of quinoa as a grain and fodder crop (Mujica et al., 2001; Casini, 2002; Jacobsen, 2003; Bhargava et al., 2006a).
1.3.1 Nutritional importance of quinoa
The nutritional excellence of quinoa has been known since ancient times in the Inca Empire. The importance that quinoa could play in nutrition has been emphasized not only in developing countries but also in the developed world. Quinoa seeds have a higher nutritive value than most cereal grains and contain high-quality protein and large amounts of carbohydrates, fat, vitamins and minerals. Perisperm, embryo and endosperm are the three areas where reserve food is stored in quinoa seed (Prego et al., 1998).
The mean protein content reported for quinoa grain is 12–23% (González et al., 1989; Koziol, 1992; Ruales and Nair, 1994a, 1994b; Ando et al., 2002; Karyotis et al., 2003; Abugoch, 2009), which is higher than that of barley, rice or maize, and is comparable to that of wheat (USDA, 2005; Abugoch, 2009). Moreover, the essential amino acid balance is excellent because of a wide range of amino acids, with higher lysine (5.1–6.4%) and methionine (0.4–1%) contents (Prakash and Pal, 1998; Bhargava et al., 2003, 2006a; Abugoch, 2009). Quinoa protein can supply around 180% of the histidine, 274% of the isoleucine, 338% of the lysine, 212% of the methionine + cysteine, 320% of the phenylalanine + tyrosine, 331% of the threonine, 228% of the tryptophan and 323% of the valine recommended by FAO/WHO/UNU in protein sources for adult nutrition (Vega-Gálvez et al., 2010). Starch is the most important carbohydrate in quinoa grains, making up approximately 58.1–64.2% of the dry matter (Repo-Carrasco et al., 2003). Quinoa starch consists of two polysaccharides: amylose and amylopectin. The amylase content of quinoa starch varies between 3% and 20%, while the amylose fraction of quinoa starch is quite low (Abugoch, 2009). The starch of quinoa is highly branched, with a minimum degree of polymerization of 4600 glucan units, a maximum of 161,000 and a weighted average of 70,000 (Praznik et al., 1999). Granules of quinoa starch have a polygonal form, with a diameter of 2 μm, being smaller than starch of the common grains (Vega-Gálvez et al., 2010). The total dietary fibre of quinoa is near that of cereals (7–9.7% by difference, db), and the soluble fibre content is reported between 1.3% and 6.1% (db) (Ranhotra et al., 1993; USDA, 2005).
The ash content of quinoa (3.4%) is higher than that of rice (0.5%), wheat (1.8%) and other traditional cereals (Cardozo and Tapia, 1979). Quinoa grains contain large amounts of minerals like Ca, Fe, Zn, Cu and Mn (Repo-Carrasco et al., 2003). Calcium (874 mg/kg) and iron (81 mg/kg) in the seeds are significantly higher than most commonly used cereals (Ruales and Nair, 1992). Minerals like P, K and Mg are located in the embryo, while Ca and P in the pericarp are associated with pectic compounds of the cell wall (Konishi et al., 2004). The abundant mineral content makes the grains valuable for children and adults who can benefit from calcium for bones and from iron for blood functions (Konishi et al., 2004).
The oil content in quinoa ranges from 1.8 to 9.5%, with an average of 5.0–7.2% (DeBruin, 1964; Koziol, 1990) that is higher than that of maize (3–4%). Quinoa oil is rich in essential fatty acids such as linoleate and linolenate (Koziol, 1990) and has a high concentration of natural antioxidants like α-tocopherol and γ-tocopherol (Repo-Carrasco et al., 2003). The antioxidant activity of quinoa could be of particular interest to medical researchers and needs more attention (Bhargava et al., 2006a).
Few reports are available on the vitamin content of quinoa grain. Ruales and Nair (1992) reported appreciable amounts of thiamin (0.4 mg/100 g), folic acid (78.1 mg/100 g) and vitamin C (16.4 mg/100 g). Koziol (1992) gave riboflavin and carotene content as 0.39 mg/100 g and 0.39 mg/100 g respectively, and concluded that quinoa contains substantially more riboflavin (B2), α-tocopherol (vitamin E) and carotene than wheat, rice and barley. In a 100 g edible portion, quinoa supplies 0.20 mg vitamin B6, 0.61 mg pantothenic acid, 23.5 μg folic acid and 7.1 μg biotin (Koziol, 1992). Recent reports have also confirmed that quinoa is rich in vitamins A, B2 and E (Repo-Carrasco et al., 2003).
However, several antinutritional substances such as saponins, phytic acid, tannins and protease inhibitors have been found in quinoa seed, which can have a negative effect on the performance and survival of monogastric animals when it is used as the primary dietary energy source (Vega-Gálvez et al., 2010).
The leaves of quinoa contain ample amount of ash (3.3%), fibre (1.9%), vitamin E (2.9 mg α-TE/100 g) and Na (289 mg/100 g) (Koziol, 1992). Prakash et al. (1993) reported that leaves have about 82–190 mg/kg of carotenoids, 1.2–2.3 g/kg of vitamin C and 27–30 g/kg of proteins. A recent study on the leaf quality parameters in quinoa has shown that the leaves contain ample amount of carotenoids (230.23–669.57 mg/kg), which was higher than that reported for spinach, amaranth and C. album (Gupta and Wagle, 1988; Prakash and Pal, 1991; Shukla et al., 2003; Bhargava et al., 2006b, 2007).
1.3.2 Stress tolerance
Quinoa exhibits high levels of resistance to several of the predominant adverse factors such as soil salinity, drought (Jensen et al., 2000; González et al., 2009, 2011; Jacobsen et al., 2009; Fuentes and Bhargava, 2011), frost (Jacobsen et al., 2005, 2007), diseases and pests (Jacobsen et al., 2003a; Bhargava et al., 2003). Due to its durability under adverse climate conditions, quinoa may be one of the options for food production under various adverse abiotic constraints (FAO, 1998).
Quinoa is a halophytic species that is regarded as having an unusually high tolerance to salinity. Some varieties of the crop show remarkable resistance to salt during germination. Many varieties of this crop can grow in salt concentrations as high as those found in seawater (40 mS/cm) (Jacobsen et al., 2001, 2003a; Wilson et al., 2002; Jacobsen, 2007; Delatorre-Herrera and Pinto, 2009; Adolf et al., 2012). These characteristics make it an attractive crop for regions where salinity has been recognized as a major agricultural problem (Prado et al.,