Protein quality evaluation of amaranth in adult humans


This study was carried out to determine the nutritional quality of the protein of amaranth grain submitted to extrusion and popping processes, using cheese protein as reference. For the biological evaluation, the short-term nitrogen balance index method was followed with 12 experimental adult male human subjects. A Latin square series 3×3 was used (three periods, three subjects) as an experimental design balanced to minimize residual effects by randomly ordering treatments, columns and rows. The study consisted of three periods of nine days each.

The first period started by feeding all subjects a low nitrogen diet, followed by increases of the protein level every two days. The levels were 0.2, 0.4, 0.6/g protein/kg/day, keeping other nutritional elements constant and adequated, including calories, minerals and vitamins. All subjects received all their meals using as a sole source of protein extruded amaranth, popped amaranth or processed cheese. Water intake was kept at a rate of 0.8–1.0 ml per calories consumed. During the study, the subjects maintained regular physical activity.Amaranthus cruentus was utilized. The extruded amaranth was prepared with the Brady Crop Cooker under conditions previously established in other studies. The popped amaranth was prepared at a 250°C temperature during 15–20 sec.

The extruded and popped amaranths were provided as a sweet puree and, as all the other foods conforming the diets of each subject, they were weighed with 0.1 g of accuracy. Diet samples, as well as faeces and urine, were collected daily, which were ordered according to period and level of protein, conforming pools to determine their nitrogen content by the Kjeldahl method. True digestibility results of the protein were 101.4, 89.8 and 85.5% for cheese, extruded amaranth and popped amaranth, respectively. The statistical analysis according to the Tukey test showed that the true digestibility of the protein was the same for the two products of amaranth and different than the digestibility of cheese. Nitrogen balance index values from the equation between nitrogen intake and nitrogen retained, were 0.97, 0.86 and 0.79 for cheese, extruded amaranth and popped amaranth, respectively. The respective values between nitrogen absorbed and nitrogen retained were 0.97, 0.98 and 0.96. The Tukey test indicated that for NI to NR cheese was statistically different for the two amaranth products, which were similar between them. For the relationship NA to NR all values were statistically the same. The calculation of nitrogen intake for nitrogen equilibrium indicated that the amaranth protein is among the highest in nutritive quality of vegetable origin and close to those of animal origin products.

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  1. 1.

    AOAC (1975) Official Methods of Analysis, 12th ed, Washington DC

  2. 2.

    Becker R, Wheeler EL, Lorenz K, Stanford AE (1981) A compositional study of amaranth grain. J Food Sci 46: 1175–1180

    Google Scholar 

  3. 3.

    Bender AE (1978) Food Processing and Nutrition. Academic Press, Great Britain, pp. 59–79

    Google Scholar 

  4. 4.

    Bressani R (1977) Human assays and applications. In: Bodwell, CE (ed) Evaluation of Protein for Humans. Chap. 5. Westport CT: The AVI Publishing Company Inc. pp. 81–117

    Google Scholar 

  5. 5.

    Bressani R (1979) Nutritional evaluation in humans. Food Nutr Bull 2: 160–166

    Google Scholar 

  6. 6.

    Bressani R (1979) The potential of grain amaranth. Food Rev Internat 5: 13–38

    Google Scholar 

  7. 7.

    Bressani R, Elías LG (1984) Development of 100% amaranth foods. In: Third Amaranth Conference. Rodale Press Center, Kutztown, Pennsylvania Sept. 11–14, pp. 8–19

  8. 8.

    Bressani R (1981) A short-term procedure to evaluate protein quality in young and adult human subjects. In: Bodwell CE, Atkins JS and Hopkins DT (eds) Protein Quality in Humans. Assessment and in Vitro Estimation. Westport CT: The AVI Publishing Company Inc. pp. 98–117

    Google Scholar 

  9. 9.

    Bressani R, Elías LG, De Bosque C (1988) The supplementary value of amaranth leaves to cereal grain-based diets. Amaranth Newsletter No 1

  10. 10.

    Bressani R, Elías LG, García-Soto A (1989) Limiting amino acids in amaranth grain protein from biological tests. Plant Foods Human Nutr 39: 223–235

    Google Scholar 

  11. 11.

    Bressani R, González JM, Elías LG, Melgar M (1987) Effect of fertilizer application on the yield, protein and fat content and protein quality of raw and cooked grain of flour amaranth species. Plant Foods Human Nutr 37: 59–67

    Google Scholar 

  12. 12.

    Bressani R, Elías LG, Olivares J, Navarrete DA (1978) Comparación del índice de balance de nitrógeno de tres proteínas calculado de períodos de balance de nitrógeno diarios o de 4 días. Arch Latinoamer Nutr 28: 318–336

    Google Scholar 

  13. 13.

    Bressani R, Kialinowski LS, Ortiz MA, Elías LG (1987) Nutritional evaluation of toasted, flaked and poppedA. caudatus. Arch Latinoamer Nutr 37: 525–531

    Google Scholar 

  14. 14.

    Bressani R, Navarrete DA, De Daqui VAL, Elías LG, Olivares J, LaChance PA (1979) Protein quality of spray-dried whole milk and of casein in young adult humans using a short-term nitrogen balance index assay. J Food Sci 44: 1136–1140

    Google Scholar 

  15. 15.

    Bressani R, Navarrete DA, Elías LG, Braham JE (1979) A critical summary of a short-term nitrogen balance index to measure protein quality in adult human subjects. In: Wilcke HL, Hopkins DT and Waggle DH (eds) New York: Academic Press Inc, pp. 313–324

    Google Scholar 

  16. 16.

    Bressani R, Sánchez-Marroquín A, Morales E Chemical composition of amaranth grain cultivars and effects of processing in its nutritional quality and supplementary value in experimental animals and children. A review (Submitted for publication in Economic Botany)

  17. 17.

    Bressani R, Viteri F, Elías LG, Zaghi S de, Alvarado J, Odell AD (1967) Protein quality of a soybean protein textured food in experimental animals and children. J Nutr 93: 349–360

    Google Scholar 

  18. 18.

    Bressani R, Viteri F, Wilson D, Alvarado J (1972) The quality of various animal and vegetable proteins with a note on the endogenous and fecal nitrogen excretion of children. Arch Latinoamer Nutr 22: 227–241

    Google Scholar 

  19. 19.

    Cheftel JC (1986) Nutritional effects of extrusion-cooking. Food Chem 20: 263–283

    Google Scholar 

  20. 20.

    Cochran WG, Cox GM (1976) Diseños Experimentales. 4a Reimpresión. México. Trillas (ed), pp. 114–176

  21. 21.

    Conkerton L, Frampton R (1959) Reaction of gossypol with free E-amino groups of lysine proteins. Arch Biochem Biophys (USA) 81: 120–134

    Google Scholar 

  22. 22.

    Imeri A, Elías LG, Bressani R (1987) Amaranto: una alternativa tecnológica para elimentación infantil. Arch Latinoamer Nutr 37: 147–159

    Google Scholar 

  23. 23.

    Imeri A, Flores R, Elías LG, Bressani R (1987) Efecto del processamiento sobre la calidad proteínica de Amaranthus caudatus. Arch Latinoamer Nutr 37: 160–173

    Google Scholar 

  24. 24.

    Mendoza-Montano CE, Bressani R (1987) Nutritional and functional characteristics of grain amaranth flour produced by extrusion cooking. Cereal Chem 64: 218–222

    Google Scholar 

  25. 25.

    Morales E, Lembcke J, Graham G (1988) Nutritional value for young children of grain amaranth and maize-amaranth mixtures. Effects of processing. J Nutr 118: 78–85

    Google Scholar 

  26. 26.

    Navarrete DA, Bressani R (1981) Protein digestibility and protein quality of common beans (Phaseolus vulgaris) fed alone and with maize, in adult humans using a short-term nitrogen balance assay. Am J Clin 34: 1983–1988

    Google Scholar 

  27. 27.

    Navarrete DA, Elías LG, Braham JE, Bressani R (1979) The evaluation of the protein quality of soybean products by short-term bioassays in adult human subjects. Arch Latinoamer Nutr 29: 386–401

    Google Scholar 

  28. 28.

    Navarrete DA, Roque De Daqui V, Elías LG, LaChance PA, Bressani R (1977) The nutritive value of egg protein as determined by the nutrition balance index (NBI). Nutr Repts Int 16: 695–704

    Google Scholar 

  29. 29.

    Organizacíon Mundial de La Salud (OMS) (1985) Necesidades de energía y de proteínas. Serie de Informes Técnios 724. OMS. Printed in Spain, pp. 15, 58–74, 107–119, 127–139, 143–144

  30. 30.

    Pedersen B, Hallgren L, Hansen I, Eggum BO (1987) The nutritive value of amaranth grain (A. caudatus). Plant Foods Human Nutr 36: 325–334

    Google Scholar 

  31. 31.

    Sánchez-Marroquín A (1985) Industrial corn flour enrichment with whole amaranth flour and milling fractions in corn-based products. Arch Latinoamer Nutr 25: 518–535

    Google Scholar 

  32. 32.

    Sánchez-Marroquín A (1980) Potencialidad agroindustrial del amaranto. México, D.F. Centro de Estudios Económicos y Sociales del Tercer Mundo

    Google Scholar 

  33. 33.

    Scrimshaw NS, Hussein MA, Murray E, Rand WM, Young VR (1972) Protein requirements of man. Variations in obligatory urinary and fecal nitrogen losses in young men. J Nutr 102: 1595–1604

    Google Scholar 

  34. 34.

    Scrimshaw NS, Wayler AH, Murray E, Steinke FH, Rand WH, Young VR (1972) Nitrogen balance response in young men given one of two isolated soy proteins or milk proteins. J Nutr 113: 2492–2497

    Google Scholar 

  35. 35.

    Soriano JS (1987) Valor nutritivo de semillas de amaranto procesadas mediante un sistema de lecho fluidizado. In: Memorias del Coloquio Nacional del Amaranto. Querétaro, México, p. 233

    Google Scholar 

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Bressani, R., De Martell, E.C.M. & De Godínez, C.M. Protein quality evaluation of amaranth in adult humans. Plant Food Hum Nutr 43, 123–143 (1993).

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Key words

  • Protein quality
  • processed amaranth
  • extrusion
  • expanding
  • humans