Effect of supercritical carbon dioxide on physicochemical and techno-functional properties of amaranth flour

Amaranth flour is a foodstuff with good quality protein that could be used to manufacture different products. The supercritical carbon dioxide (SC-CO₂) treatment allows intensifying the extraction process for obtaining a flour without toxic residues and high-quality oil, replacing the use of organic solvent and reducing the extraction time. In this study, physicochemical and techno-functional properties of amaranth flour (Amaranthus hypochondriacus) defatted with SC-CO₂ at different pressure conditions (2900-4350 psi) and temperatures (40-60°C) were determined. It was observed that extraction pressure and temperature had a significant effect (p<0.05) on the extraction yield and protein content, as well as the components present in the flour particles, causing differences in the physicochemical and techno-functional properties. The amaranth flour defatted with SC-CO₂ at 50°C/3630 psi was the most outstanding as it had the best extraction performance (70.2 mg oil/g flour), the highest protein content (16.17 g protein/100 g flour), the swelling (SC) (2.263 g H₂O/g flour), water absorption (WAC) (126.33 g H₂O/100g flour), and oil absorption (OAC) (119.09 g oil/100g flour) capacities, high luminosity (L*) (82.89) and a high total color difference (ΔE*) (5.93). The fatty acid composition of the oils obtained by SC-CO₂ showed high content of polyunsaturated fatty acids (PUFA). Physicochemical and techno-functional properties of amaranth flour changed by SC-CO₂ treatment, flour defatted by SC-CO₂ under intermediate conditions of temperature and pressure (50°C and 3630 psi), was able to produce a high-protein and low-fat amaranth flour as well as with good hydration techno-functional properties, which can be an alternative to defatting process with organic solvents.