Nutritional composition of quinoa (Chenopodium quinoa Willd.) and its use in the elaboration of gluten-free bread of optimised quality

Abstract

En primer lugar, los granos de quinua exhibieron no solo un alto perfil nutricional con grandes contenidos de proteínas y carbohidratos, sino también una composición en moléculas de alto interés (tocoferales y carbohidratos) que promueven beneficios bioactivos para el organismo humano. En segundo lugar, se realizaron seis experimentos separados, los primeros cuatro diseños factoriales completos se realizaron formulando (sobre la base del peso de las harinas) pan GF con dosis de XG (1.5, 2.5 y 3.5%), GC (2.5, 3.0 y 3.5%), HPMC (3.0, 4.0 y 5.0%) o CMC (3.0, 4.0 y 5.0%) con contenido de agua variable (80, 90, 100 o 110%, dependiendo del hidrocoloide), seguido de dos diseños de mezcla D-óptima, realizados mediante la formulación de GF pan con tres hidrocoloides fijados en 4.0%: HPMC (e 2.80 a 3.60%), GC (de 0.04 a 0.60%) o XG (de 0.04 a 0.60%) y 100% de contenido de agua; y luego con tres hidrocoloides establecidos al 5.0%: CMC (de 3.50 a 4.50%), GC (de 0.25 a 0.50%) o XG (de o.25 a 1.00%) y 115% de contenido de agua.

The objectives of this doctoral thesis were: (i) to determine the chemical composition of the most common quinoa colour varieties (red, black and white), (ii) to assess the separate effects of xanthan gum (XG), guar gum (GG), hydroxypropyl methyl cellulose (HPMC) and carboxymethyl cellulose (CMC) and their interactions with water content on gluten-free (GF) bread formulated with a base mixture of rice, maize and quinoa flours; and finally, (iii) to determine the combinations of XG-GG-HPMC and XG-GG-CMC doses that optimise selected consumer-oriented quality attributes of bread. GF batter and bread were characterised by measuring several attributes; namely, stickiness and back extrusion properties of batter; specific volume, baking loss and colour of bread loaves; water activity, pH, texture profile analysis and firmness properties of bread crumb; image analysis from scanned bread slices were also used. Quinoa grains exhibited not only a good nutritional profile with high protein and carbohydrate contents, but also a composition in molecules of high interest (tocopherols and organic acids) known to promote bioactive benefits for the human organism. Four full-factorial designs were conducted by formulating (flours weight basis) GF bread with doses of XG (1.5, 2.5 and 3.5%), GG (2.5, 3.0 and 3.5%), HPMC (3.0, 4.0 and 5.0%) or CMC (3.0, 4.0 and 5.0%) with varying water content (80, 90, 100 or 110%, depending on the hydrocolloid); followed by two D-optimal mixture designs, conducted by formulating GF bread with three hydrocolloids set at a total dose of 4.0%: HPMC (from 2.80 to 3.60%), GG (from 0.04 to 0.60%) and XG (from 0.04 to 0.60%) with 100% of water content; and then with three hydrocolloids set at a total dose of 5.0%: CMC (from 3.50 to 4.50%), GG (from 0.25 to 0.50%) and XG (from 0.25 to 1.00%) with 115% of water content. XG and GG rendered gluten-free batter and bread of similar quality, although GG, particularly at a high dose, produced smaller loaves of harder and more resilient and cohesive crumb than XG. Compared to XG and GG, HPMC yielded batters of higher stickiness, consistency and firmness, which, when baked, rendered loaves of higher volume, softer crumb, and larger pores. Compared with HPMC, CMC rendered less sticky and firmer batters that translated into baked loaves of smaller volume, harder crumb, and denser crumb appearance. The interactions that take place between XG, GG and HPMC, or CMC, GG and XG mixtures, affected the quality of the final gluten-free bread. From a desirability approach, GF breads of greater specific volume with softer and more open crumb appearance were obtained with combinations of 0.24% XG, 0.60% GG and 3.16% HPMC, or 4.34% CMC, 0.41% GG and 0.25% XG.