Optimization of the extrusion process from physical, physicochemical, and antioxidant characterization of high-fiber breakfast cereals produced with bran and winter squash (Cucurbita moschata D.)

High-fiber breakfast cereals (HFBC) are highly produced, and adding squash is proposed to enhance their nutritional and nutraceutical composition. This study aimed to optimize the extrusion process from the physical, physicochemical, and antioxidant properties of HFBC, evaluating the effect of barrel temperature (BT, 90–120 °C), screw rotational speed (SRS, 110–210 rpm), and squash content (SC, 4–20%). Bulk density and breaking stress increased with high SC and low BT and SRS. The water solubility index decreased with low SC across all BT and SRS ranges. Total color difference decreased at low SC and high SRS. Total phenolic compounds and antioxidant activity (inhibition of low-density lipoproteins oxidation) increased at low BT and high SC. The optimal extrusion conditions were BT 90 °C, SRS 209.99 rpm, and SC 5.35%, and the HFBC obtained in these conditions presented adequate dietary fiber levels and sensory properties. The HFBC exhibited acceptable physical, physicochemical, and antioxidant properties, presenting adequate levels of phenolic compounds and fiber provided mainly by SC.