Multifactorial Characterization of Quinoa Varieties Based on Chemical, Functional, and Morphological Parameters

This study aims to characterize the chemical, functional, color, and morphological properties of different quinoa (Chenopodium quinoa Willd) varieties from the Andean region of northern Argentina. The nutritional composition, including dietary fiber, was analyzed using AOAC methods; antioxidant activities were assessed with DPPH, ABTS, and FRAP assays. Functional properties such as water absorption index (WAI), water solubility index (WSI), and swelling power (SP) were also determined. Additionally, digital image analysis via laser confocal microscopy was employed to evaluate morphometric parameters like area, perimeter, Feret's diameter, circularity, roundness, aspect ratio, and solidity. The results showed statistically significant differences (p < 0.05) among quinoa samples linked to the variety. Among the evaluated parameters, the color component a* exhibited the greatest coefficient of variation (71.54%), followed by WSI (41.58%) and insoluble fiber content (23.50%), indicating high relative variability in functional and compositional properties. Total polyphenol content ranged from 2.13 to 4.02 mg Gallic Acid Equivalents (GAE)/ g, while total flavonoids ranged from 0.32 to 0.74 mg Quercetin Equivalents (EQ)/ g. Antioxidant activity varied significantly among samples, with mean IC₅₀ values for DPPH at 13.8 mg/mL, and for ABTS and FRAP at 2.11 and 5.3 mg Trolox Equivalents/ g sample, respectively. The first two factors (F1 and F2) of principal component analysis (PCA) explained 58% of the total data variability. Variables most influential for differentiation included antioxidants, color, and nutritional parameters. The variables used in the analysis enabled the grouping and differentiation of the samples, with contributions from morphological, color, compositional, and antioxidant parameters.