Physical, Functional and Process Characteristics of Corn Extrudates Enriched with an Ultrafiltration Retentate from Rose Wastewater

In this study, the potential of extrusion for producing functional food from corn semolina enriched with an ultrafiltration (UF) retentate obtained from rose wastewater was investigated. Extrudates were produced using a single-screw laboratory extruder (Brabender 20DN), and their physical (expansion ratio, bulk density, and moisture content), functional (water absorption and solubility indices), and process characteristics (specific mechanical energy and mass flow rate) and phenolic content were investigated. The effect of the UF retentate’s amount (4 or 11%), the temperature in the third zone of the extruder (150 or 170 °C), and the working screw speed (180 or 220 min−1) on the physical, functional and process characteristics was examined using a full factorial design. Increasing the retentate’s amount led to a decrease in the expansion, water solubility index, specific mechanical energy, and mass flow rate, as well as an increase in the bulk density, moisture content, and water absorption index of extrudates. The augmentation of temperature led to a decrease in the bulk density, water solubility index, specific mechanical energy, and mass flow rate and had no significant effect on the other characteristics. The increase in the screw speed resulted in extrudates with a lower water solubility index, water absorption index, and specific mechanical energy and a higher expansion and moisture content, while it had no significant effect on the density and mass flow rate. The UF retentate enhanced the total phenolic, phenolic acid, and flavonoid contents of the extrudates. Optimal conditions for producing high-quality extrudates were found at 5.02% UF retentate, 150 °C, and 207.8 min−1.