Interaction between the seaweed Sargassum filipendula and rice flour in the production of ready-to-eat foods by thermoplastic extrusion

This study aimed to evaluate the effects of partially substituting rice flour (R) with 1.5 % dehydrated Sargassum filipendula (S) flours, using three processing methods: oven-dried flour (SD), freeze-dried flour (SL), and commercial flour (SC). The formulations prepared included a control (R) and three with substitutions (R + SD, R + SL, R + SC), which were processed in a twin-screw extruder with the temperatures of the four zones set at 70 °C, 90 °C, 120 °C, and 115 °C, a screw speed of 200 rpm, and 15 % moisture. The properties were comparatively using the Scott-Knott Test (p ≤ 0.05). The substitution of R affected the torque and specific mechanical efficiency (SME) during the extrusion process. The hardness of the extrudates was higher in the R + SD, R + SL, and R + SC formulations, while porosity did not show significant differences. Microstructure analysis revealed more homogeneous surfaces for the rice-only extrudates (R), while the R + SD, R + SL, and R + SC samples showed visible areas of roughness. X-ray diffraction demonstrated the presence of type V starch and showed that the extrusion process influenced the structural organization of the materials analyzed. All pre-gelatinized flours formed cold paste, with the R + SL formulation showing the highest capacity for DPPH radical scavenging, indicating antioxidant activity potential. In the color analysis, through imaging, it was observed that extrudates and pre-gelatinized flours containing only rice were white, while the formulations with seaweed exhibited brownish tones with dark spots distributed across the sample. The results indicate that differences in composition, origin, and drying methods of seaweed influence the physicochemical properties of the rice extrudates.