Functional, rheological, microstructural and antioxidant properties of quinoa flour in dispersions as influenced by particle size.

Nutritionally, particle size has significant impact on food digestibility in the gastrointestinal system. Controlling the rheological behaviors of particles in dispersion has been of major interest in the industry. In this work, the quinoa seed was ground into flour, followed by fractionating into a selected particle size [+30-mesh (>595-μm) to +200-mesh (>74-μm)]. The effect of particle size on composition, antioxidant, and several functional and mechanical properties of all particle fractions were studied. The protein, crude fat, crude fiber, dietary fiber contents increased with decreasing the particle size while the starch content decreased. The water holding capacity and sediment volume fraction increased with the reduction of particles. Rheological measurement indicated that there were significant differences among rheograms between coarser and finer particles of QF. The finest particles produced a lower complex viscosity and lower mechanical rigidity. The final and setback viscosities decreased as particle size decreased. Microscopy showed irregular-shaped polygon structure for the QF. The particle fractions ranged between +100 and +200-mesh showed compositional resemblances and, subsequently, the properties. The highest extractability of phenolics and antioxidant properties were observed for the finest particles. The information generated from this work would help the industry to develop products with the desired particle size with optimum functional and nutritional properties.