Upgrading Extrusion Process for the Production of Croutons: Optimization and Quality Characteristics

The present study is aimed at standardizing extrusion conditions for producing croutons from whole wheat. Wheat grits, the raw material, were analyzed for their physicochemical characteristics. A central composite rotatable design (CCRD) within response surface methodology (RSM) was employed to design experiments and examine the effects of various independent variables on the dependent variables. The selected range for independent variables included feed moisture (16%–20% on a dry basis), screw speed (400–550 rpm), and temperature (130°C–170°C). No interactions were found between the independent variables and the dependent variables: specific mechanical energy (SME), expansion ratio (ER), bulk density (BD), water absorption index (WAI), and water solubility index (WSI). Feed moisture negatively affected SME, ER, WAI, and WSI while positively influencing BD. Screw speed displayed a contradictory relationship with feed moisture. Temperature had an inverse relationship with SME and BD but was directly proportional to ER, WAI, and WSI. From the overlay plots, the optimized parameters obtained from the extrusion experiments were a feed moisture of 18.9%–20%, screw speed of 400–550 rpm, and a temperature of 150°C. These optimized extrusion parameters provide a balanced approach for achieving desirable crouton quality. The findings contribute to the advancement of extrusion technology for whole wheat-based snack products and can serve as a reference for further research and industrial applications.