Characterization of quinoa defatted by supercritical carbon dioxide. Starch enzymatic susceptibility and structural, pasting and thermal properties

Abstract

Quinoa has recently been considered as an alternative oilseed crop due to the quality and quantity of its lipid fraction. Supercritical fluid extraction (SFE) was used as a green process to extract quinoa oil without solvent residues. Defatted quinoa flour is a potentially valuable raw material whose performance as food ingredient needs to be established. Structural, physicochemical, pasting, and thermal properties of quinoa (cv. Titicaca) defatted by supercritical CO2 extraction (DQ-SCCO2) were characterized. In vitro starch enzymatic susceptibility was also evaluated. Full fatted quinoa (NDQ) and quinoa defatted by hexane extraction (DQ-HX) were also evaluated in parallel. DQ-SCCO2 showed a disrupted and microporous structure due to the pressurization/depressurization of CO2 in SFE. However, its viscometric profile was very similar to that of NDQ, while that of DQ-HX was significantly lower. This denotes a physical/thermal modification of the flour as a result of the higher temperature applied during hexane extraction, 68 degrees C, versus 40 degrees C in SFE. Defatted samples showed lower pasting temperatures (4-5 degrees C) and higher amylopectin retrogradation extent than NDQ. Quinoa showed a very high enzymatic susceptibility regardless its lipid content; 90% of the starch was hydrolyzed by digestive enzymes in 20 min in the three samples. However, defatted quinoa had lower slowly digestible starch content than NDQ, being the lowest value for DQ-SCCO2 sample. The work confirms the feasibility of using DQ-SCCO2 as a raw material in food applications, free of solvent residues, and with a technological quality superior to that obtained by extraction with organic solvents.