Structural, thermal and energetic properties of Andean-pseudocereal flours with high nutritional values

Abstract

Structural, thermal and energetic properties of quinoa, kiwicha and kañiwa native Andean-pseudocereal flours have been studied. Moisture, protein and fat contents and also metallic and semi-metallic levels were, in general, within of the range values reported in the literature. Empirical formulas of quinoa, kiwicha and kañiwa flours have been determined as CH1.87O0.81N0.06S0.0015, CH1.90O0.82N0.05S0.0019 and CH1.76O0.73N0.06S0.0017, respectively. The elemental carbon concentration (Cflour) in organic matter follows the trend, Ckañiwa (45.6%) > Ckiwicha (43.2%) ≈ Cquinoa (43.3%), which reflects the greater structural similarity between the quinoa and kiwicha flours, with respect to kañiwa flour. Regarding thermal and energetic properties: (i) in the temperature range of 261.15–343.15 K, we found no significant differences among the specific heat capacities of the three flours, which are ranged between 1.3 and 1.9 J g−1 K−1; (ii) the organic matter decomposition temperature (T dec) followed the trend, T dec,kañiwa (489.8 ± 1.6 K) > T dec,kiwicha (479.1 ± 1.5 K) ≥ T dec,quinoa (477.1 ± 1.5 K) indicating a greater thermal stability range of kañiwa flour; (iii) the gelatinization temperatures and also the gelatinization enthalpy of kañiwa flour (4.3 ± 1.6 J g−1) were lower than corresponding thermal gelatinization parameters of quinoa and kiwicha flours; and (iv) the standard massic energy of combustion (− Δc u°) or its associated net calorific value (q NCV) of kañiwa flour (18.77 ± 0.15 kJ g−1 or 4487 ± 36 kcal kg−1) was slightly greater than for kiwicha (18.47 ± 0.11 kJ g−1 or 4415 ± 26 kcal kg−1) and quinoa (18.60 ± 0.16 kJ g−1 or 4445 ± 39 kcal kg−1) flours. Taking into account the associated uncertainties, q NCV trend is similar to the Cflour and T dec trends. Accordingly, our results indicate a greater range thermal stability and greater net calorific value for kañiwa flour than for kiwicha and quinoa flours.