Study of the Impact of Operating Parameters and the Addition of Fat on the Physicochemical and Texture Properties of Extruded Snacks

This study investigated the effects of extrusion parameters (barrel temperature, screw speed) and oil content on the physicochemical and textural properties of corn flour-based snacks, using a Box-Behnken response surface design. Significant predictive models (adjusted R² > 90%) were established for specific mechanical energy (SME), expansion ratio, bulk density, hardness, compression work, water activity (aw) and dry matter content. The results showed that increasing oil content dramatically reduced SME (from 229.5 Wh/kg at 5% oil and 110 °C to 68.2 Wh/kg at 10% oil and 180 °C) and expansion ratio (maximum 3.73 at 145 °C, 150 rpm, 0% oil), while increasing bulk density (up to 0.271 g/cm³ at 10% oil). High oil content also led to a sharp increase in hardness (from 67.9 N at 0% oil to 466.9 N at 10% oil). Conversely, higher barrel temperature (up to 180 °C) and screw speed (up to 250 rpm) generally improved snack texture by reducing hardness and density and increasing expansion. Water activity ranged from 0.24 to 0.50 and was positively influenced by oil content and negatively by temperature and screw speed. Overall, oil content had the strongest detrimental impact on snack properties, but optimizing temperature and screw speed allowed the production of snacks with acceptable qualities.