Postharvest UVB treatment of amaranth leaves produces a bioactive powder ingredient that improves the phenolic signature and bioactivity of nixtamalized maize tortillas

Postharvest UVB treatment was evaluated as a sustainable strategy to improve the functional value of Amaranthus hybridus leaf powder and its use in nixtamalized maize tortillas. Untreated (AP) and UVB-treated amaranth powders (SAP) were produced and incorporated into tortillas at 7.5% substitution. UVB treatment increased L-phenylalanine in SAP and selectively changed its phenolic profile. After tortilla processing, tortillas containing SAP (SAT) showed the highest phenolic content among tortilla samples, with 3.29-fold more quantified phenolics than tortillas containing AP (AT) and a 10.5-fold increase in rutin. Amaranth incorporation improved protein and dietary fiber contents, reduced rapidly digestible starch, and lowered the predicted glycemic index. SAT also showed the highest cellular antioxidant activity and nitric oxide inhibition. The enriched tortillas maintained microbiological quality, low anti-nutritional burden, acceptable physical properties, and moderate sensory acceptability. These results support UVB-treated amaranth powder as a sustainable ingredient for functional maize-based staple foods.