Effect of Dry Roasting on the Physicochemical, Nutritional, and Techno-Functional Properties of Tri-Color Quinoa Flours

Quinoa (Chenopodium quinoa), a gluten-free pseudocereal of increasing interest in food applications, remain underutilized due to limited knowledge of its nutritional and techno-functional properties, particularly following processing. This study investigated the impact of roasting on these properties of tri-color quinoa. Roasting resulted in non-significant increases in the content of protein, lipid, and starch fractions, while carbohydrate and energy contents increased significantly (p < 0.05) by 3.74 and 3.30%, respectively, compared to native tri-color quinoa flour (NTQF). Notably, total dietary fiber, phytic acid, and oxalate contents were decreased by 13.11, 36.05, and 28.78%, respectively, contributing to improvements in in vitro protein digestibility and in vitro protein digestibility-corrected amino acid score in roasted tri-color quinoa flour (RTQF). Although lysine remained the limiting amino acid, its content increased in RTQF. Techno-functional properties were also affected by roasting; water and oil absorption capacities increased by 24.26 and 2.76% (p < 0.05), while emulsifying, foaming, and swelling capacities declined by 47.58, 34.96, and 17.74%, respectively (p < 0.05). RTQF exhibited consistently lower protein solubility across all pH tested, and higher a least gelation concentration, likely due to protein denaturation. Color analysis showed darker (L*), redder (a*), and more yellow (b*) hues in RTQF, with minor but perceptible color difference (ΔE = 1.26) relative to NTQF. Scanning electron microscopy revealed greater starch disruption, increased porosity and fragmentation in RTQF than NTQF. FTIR confirmed structural alterations, with the spectrum of RTQF showing less intense bands and higher transmittance compared to NTQF, associated thermal modification of carbohydrate, moisture content and other components. These findings suggest that dry roasting can be used to modify the nutritional and techno-functional properties of tri-color quinoa, offering expanded opportunities for tailored food applications.