Bioactive and Nutritional Profiling of Freeze-Dried Pigmented Sweet Potato Powders: Antioxidant Capacity, Phenolic Compounds, and Mineral Composition

Abstract

Freeze-dried sweet potato powders derived from three distinct genotypes—white (Koretta), orange (Ro-Ch-G), and purple (Ro-Ch-M)—were comprehensively characterized with respect to their proximate composition, phenolic profile, antioxidant activity, color attributes, and mineral composition. The purple sweet potato powder showed the highest total phenolic content (5.79 mg GAE/g dw), flavonoid content (0.38 mg QE/g dw), and DPPH, ABTS and FRAP radical-scavenging activity (DPPH: 8.8 μM TE/g dw; ABTS: 11.7 μM TE/g dw; FRAP: 13.32 μM TE/g dw). In contrast, the white sweet potato powder exhibited the lowest values. HPLC-DAD-MS analysis revealed 19 tentatively identified phenolic compounds, with anthocyanins detected exclusively in the purple sample, which might be associated with its higher antioxidant activity. Color measurements showed distinct profiles among the analyzed composite powders. The purple sweet potato powder exhibited the lowest lightness (L) and hue angle values, whereas the orange sweet potato powder showed the highest b and chroma values, consistent with its characteristic orange pigmentation. Mineral and elemental analysis also showed variation in macro-, micro-, and trace-element composition among the composite powders, with the pigmented samples generally exhibiting higher concentrations of several elements, including K, Ca, Mn, P, and Zn. The resulting freeze-dried powders exhibited a diverse profile of quantifiable bioactive compounds, particularly in the purple sweet potato powder, supporting their compositional interest for further investigation in food applications.