Impact of Extrusion Conditions on Quinoa (Chenopodium quinoa) Flour Properties

Abstract

Quinoa flour retains the excellent nutritional attributes of its grains. Additionally, thermo-mechanical processes such as extrusion could be used to modify the properties of traditional ingredients. Hence, the objective of this work was to evaluate the effect of extrusion conditions on the physicochemical, techno-functional, microstructural, and nutritional properties of white quinoa flour (QF). Four extruded quinoa flours (EQFs) were obtained by combining two nozzle geometries (circular or flat) with two different extrusion protocols, which varied in heating profiles and feed rates. In general, the extrusion process did not drastically affect the macronutrient content of the samples or their fatty acid profiles. However, losses of lysine and phenylalanine were observed, depending on the extrusion conditions. The most relevant changes caused by extrusion were in the techno-functional properties of EQFs. This process enhanced their water and oil retention capacities; a phenomenon likely linked to starch gelatinization (evidenced by DSC and LV-SEM) and changes in protein conformations (evidenced by FTIR). Additionally, extrusion induced color changes attributed to Maillard products, and either reduced or preserved the antioxidant capacity, with both effects depending on the nozzle geometry. In general, starch digestibility increased, but EQFs maintained a good proportion of slowly digestible starch. This effect was also more pronounced when the flat nozzle was used. Mixolab assay indicated that the EQFs had a low tendency to retrograde. Consequently, extrusion proved to be a suitable process for obtaining novel ingredients with properties appropriate for a wide range of applications, thereby expanding the potential uses of quinoa flour.