Abstract
The objective of this study was to investigate the process engineering behavior and physicochemical characterization of extruded snacks produced from purple corn flour (PCF) enriched with black nightshade (
Solanum nigrescens
) powder (BNP). The combined effects of extrusion temperature (ET = 125–175 °C), feed moisture content (FMC = 18–25 g/100 g), and BNP/PCF ratio (0–50 g/100 g) were evaluated using response surface methodology to determine their influence on process parameters (residence time, torque, and specific mechanical energy), structural properties (expansion index, bulk density, and hardness), functional properties (water absorption index, water solubility index, and pH), and color parameters (
L*
,
a*
, and
b*
). The results showed that the BNP/PCF ratio was the most influential factor affecting most of the evaluated responses, exceeding the effects of ET and FMC. Increasing BNP significantly modified melt rheology, reduced expansion, and increased bulk density and hardness of the extrudates. Likewise, functional properties (WAI, WSI, and pH) exhibited nonlinear responses primarily governed by formulation, reflecting interactions among starch, protein, and fiber. Lightness (
L*
) was the color parameter most sensitive to BNP substitution. These findings demonstrate that incorporating BNP into PCF-based extruded matrices represents a viable technological strategy for developing functional extruded snacks with natural pigmentation and suitable technological properties, providing relevant evidence for the design of cereal-based snacks enriched with value-added plant ingredients.