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ABSTRACT

Quinoa (Chenopodium quinoa Willd.) is a native of the Andes that has sparked a worldwide interest due to its unique nutritional value. Quinoa grains have higher protein content than other cereal grains, as well as a better distribution of important amino acids. It can be used as a substitute for dairy proteins. Quinoa is also gluten free which make it used by celiac disease patients. Quinoa seeds contain polyunsaturated fatty acid (PUFA) which has positive effect on improving insulin sensitivity and cardiovascular diseases, also having antioxidant property, which reduces the risk of cancer. It is rich in fatty acids, minerals, vitamins, dietary fibers, and carbohydrates that have favorable hypoglycemic effects. Furthermore, the quinoa plant is cold, salt, and drought resistant, which is why it is known as the "golden grain." This article presents an overview of the nutritional, antioxidant and antinutritional aspects of quinoa plant.

Keywords: Chenopodium quinoa Willd., Golden grain, Gluten free, Quinoa, Superfood

Quinoa (Chenopodium quinoa Willd.) is herbaceous plant. Quinoa belongs to the class Dicotyledoneae, Chenopodiaceae family, Chenopodium genus and quinoa species. Chenopodium quinoa Willd species include both domesticated and free-living weedy forms (Wilson, 1988). It has cereal botanical characteristics such as presence of panicle-type inflorescence but it does not belong to the Gramineae family, its exceptional nutritional balance of protein and lipids, high protein content, sulfur amino acids and lysine, and hence designated  as pseudocereals (Cusack, 1984; Koziol, 1993; Farro, 2008; Vega-Gálvez et al., 2010; Repo-Carrasco-Valencia and Serna, 2011). It is a granifer species native to South America and domesticated by Andes people mainly in Andean regions of Chile, Peru, Ecuador and Bolivia. It was one of the staple food crop of Incas community, they called quinoa as ‘‘the mother grain’’, sustained the Inca community and was considered sacred. During 2013, it was declared as the international year of quinoa, and as a result production and consumption of quinoa increased exponentially (Bazile and Baudon, 2015). It got lot of interest around the world, not only because of its nutritional and functional benefits but due to its ability to grow in adverse climate. Quinoa has ability to tolerate frost, salinity, drought, and can be grown grow on marginal soils. These characteristics are particularly significant in areas where food insecurity is a concern. Quinoa’s aptitude to produce high protein grains and grain yield under ecologically extreme conditions makes it important for the diversification of agriculture as in high-altitude regions of the Himalayas and North Indian Plains (Bhargava et al., 2005).

Nutritional and Functional Perspectives of Quinoa

Protein and amino acid content: As reported by Abugoch et al., (2008) and USDA (2005), the total protein content of quinoa seeds [16.3% dry basis (db)] is higher than barley (11% db), rice (7.5% db), or corn (13.4% db) and comparable to wheat (15.4% db). Protein nutritional quality is determined by the proportions of essential amino acids, which cannot be synthesized by animals and hence must be provided in the diet. Quinoa seeds contain all nine essential amino acids (EAA) for proper human health are: phenylalanine, isoleucine, leucine, lysine, methionine, threonine, tryptophan, valine, and histidine (Abugoch James 2009). Quinoa also provides a protein value which is similar to casein from milk (Vega-Gálvez et al., 2010). Moreover, due to its high protein content and amino acid profile, quinoa is suggested to be an alternative to dairy products. Quinoa protein is also considered as high quality protein as it provides sulfur amino acids, lysine and tryphtophan, which are deficient in cereals and legumes. Quinoa is suitable for the creation of "gluten-free" food products since it lacks gliadins (gluten-forming proteins found in wheat) and suitable for the patient of celiac disease. Thus, quinoa is one of the few plant foods that provide all essential amino acids at per with the Food and Agriculture Organization (FAO) recommendations, with an excellent amino acidic balance (Mujica et al., 2001; Alves et al., 2008).

Table 1: Proximate analysis of quinoa (g 100 g ^-1 fresh weight)

References
Component	Nowak et al., 2016	Vidueiros et al., 2015	Varli et al., 2016	Pereira et al., 2019
Protein	13.1	16.8	14.12	14.6
Fat	5.7	5.9	6.07	6.8
Ash	3.3	4.7	2.7	2.7
Carbohydrate	59.9	51.4	64.16	76.1

 

Carbohydrates

The carbohydrate content of quinoa seeds ranges between 52% and 69% (dry matter weight) (Filho et al., 2017). Starch is the main biopolymer constituent of plant organs, and it is the most abundant carbohydrate present in the seeds. Quinoa possess higher viscosity, water absorption capacity, and greater swelling power (Filho et al., 2017) compared to the starch of wheat and barley. Native quinoa starch consists of uniform small granules less than 3 µm in diameter (Bhargava et al., 2006). The extremely small size can be beneficially exploited and used in blends with synthetic polymers in the preparation of biodegradable packaging and also used as dusting starches in cosmetics and rubber type mold release agents. Its excellent freeze-thaw stability makes it an ideal thickener for condiments, sauces and soups due to its low gellation temperature and storage stability at low temperatures and it can also be used to produce a creamy and smooth texture similar to fats in other applications where resistance to retrogradation is desired (Lorenz, 1990; Tari et al., 2003; Abugoch James, 2009; Vega-Gálvez et al., 2010).

Another carbohydrate group present in quinoa seeds is dietary fiber. The total dietary fibers content of quinoa seeds is close to cereals 7.0% to 9.7 % dm (Filho et al., 2017). Dietary fibre has a lot of positive effects in the small intestine due to its indigestibility. As a result, the high fibre content of quinoa may aid digestion by promoting the absorption of the other nutrients included in quinoa in the large intestine (Ogungbenle, 2003).

 

Fat

The fat content of quinoa seeds varies between 2 to 9.5%, which is higher than maize and other cereals but less than soybean (Filho et al., 2017). It has an oil content (7% dm) higher than corn (4.7% dm) and other cereals, but lower than soybeans (19.0% dm). Quinoa oil is rich in essential fatty acids such as oleic [C18:1] (19.7%–29.5%), linoleic [C18:2] (49.0%–56.4%), and linolenic [C18:3] (8.7%–11.7%). The portion of (poly-) unsaturated fatty acid accounts to 87%–88% of total fatty acids of the seed (Ando et al., 2002; Ryan et al., 2007). These compounds have gained importance as it has positive effects on the immune system, cardiovascular diseases, cell membrane function, and increased insulin sensitivity (Präger et al., 2018; Filho et al., 2017).

Minerals

The ash content of quinoa (3.4%) is greater than rice (0.5%), wheat (1.8%) and most other cereals (Angeli et al., 2020). Thus, quinoa grain contains large quantities of minerals higher than that of most grain crops (Vega-Gálvez et al., 2010). Quinoa has a high content of calcium, magnesium, iron, potassium, phosphorus and zinc (Table 2).

 

Table 2: Mineral content of quinoa and other grains (FAO 2013; Vega-Gálvez et al., 2010)

Mineral (mg 100 g−1 Seeds DM)	Quinoa	Maize	Rice	Wheat
Calcium	148.7	17.1	6.9	50.3
Iron	13.2	2.1	0.7	3.8
Magnesium	249.6	137.1	73.5	169.4
Potassium	926.7	377.1	118.3	578.3
Phosphorus	383.7	292.6	137.8	467.7
Zinc	4.4	2.9	0.6	4.7

 

Vitamins

Quinoa is rich source of vitamin B, E and C. Quinoa contains vitamins B, namely thiamine (B1), riboflavin (B2), pyridoxine (B6) and folic acid (B9). The values of thiamine (B1) are lower than those of oats or barley, but riboflavin (B2), pyridoxine (B6) and folic acid (B9) are higher than most cereals such as wheat, oats, barley, rye, rice and maize. Furthermore, quinoa is an good source of vitamin E having higher value than wheat (Ruales and Nair 1993; Abugoch James, 2009; Alvarez-Jubete et al., 2010). Ruales & Nair (1993) have reported considerable levels of thiamine (0.4 mg 100 g^-1), folic acid (78.1 mg 100 g^-1) and vitamin C (16.4 mg 100 g^-1).

Antioxidant aspects

Quinoa is good source of bioactive compounds such as flavonoids and phenolic compounds that have antioxidant and anticancer qualities. Because of their anti-oxidative properties, plant polyphenols, phenolic, and flavonoids content are beneficial to human health. It has been suggested that such compounds can aid the risk reduction of cardiovascular diseases, neurodegenerative disorders, and diabetes (Arts and Hollaman 2005; Gawlik-Dzikie et al., 2013). Quinoa extracts contains considerable amounts of ferulic, sinapinic, and gallic acids, kaempferol, isorhamnetin, and rutin. These named compounds were linked to an inhibitory effect on prostate cancer cell proliferation and motility (Gawlik-Dzikie et al., 2013).

Antinutritional aspects

Saponins are secondary metabolites - steroid or triterpenoid glycosides that had been extensively investigated due to their biological effects. They are the main anti-nutritional component in quinoa seeds, acting as a natural defense against diseases and herbivorous animals. Quinoa plant parts contain about 30 different forms of saponins (Ahumada et al., 2016). To distinguish between `sweet` genotypes (with saponin content of 20–40 mg g^-1 dry weight) and `bitter` genotypes (with saponin content of >470 mg g^-1 dry weight), saponin content must be quantified (Pulvento et al., 2010). Saponins are predominantly located in the seed coat`s outer layer and responsible for the bitter flavour. Post-harvest processing processes like cold water washing, abrasion, and dehulling remove the chemical (Rao and Shahid 2012). Saponins derived from quinoa seeds can also be employed in other industries like cosmetics and pharmaceuticals.

Conclusion

Quinoa is a fascinating food to study because of its nutritional, antioxidant and antinutritional properties. It contains all essential amino acid higher than wheat, and soyabean and making it more complete protein food. It is gluten-free, therefore it can be eaten by both celiac disease patients and those who are allergic to wheat. It is a good source of carbohydrates and fats. It also contains calcium, iron, magnesium, phosphorus, and zinc higher than wheat, rice, and maize as well as vitamin E and some B vitamins (thiamine (B1), riboflavin (B2), pyridoxine (B6) and folic acid (B9)). Quinoa has been discovered to contain substances such as polyphenols, phytosterols, and flavonoids having antioxidant properties. These compounds have potential benefits to fight against cardiovascular diseases, neurodegenerative disorders, and diabetes. Although some antinutritional elements are present in quinoa grains, these can be easily removed during the manufacturing process or by using proper handling procedures and home preparation, as is the case with most grains consumed as food.Therefore, quinoa has a great nutritional content and has recently been exploited as a novel functional food, making it a very potential alternative crop.

 

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