Extrusion-Cooking as an Effective Processing Method of Instant Gluten-Free Corn–Buckwheat Blends: Impact of Composition and Extrusion Conditions on Selected Physical Properties

This study aimed to produce gluten–free extruded instant products based on corn and corn–buckwheat blends in a 75:25 and 50:50 mass ratio, respectively, processed at moisture levels of 12, 14, 16, and 18% and at screw rotation speeds of 80, 100, and 120 rpm. In this study, the extrusion–cooking process stability was determined, including energy consumption and efficiency. Additionally, physical properties of extrudates were determined, including density, color, the volumetric gel index, the water absorption index, the water solubility index, and dynamic viscosity. It was shown that increasing the extruder screw speed results in increased process efficiency and energy consumption and properties (gelling ability, water solubility, and a decrease in water absorption, density and yellowness) of the final product. With increasing moisture content, increased bulk density, volumetric gel index, water absorption, and redness and yellowness values and a decrease in solubility were observed. Increasing the buckwheat content resulted in increased efficiency, water absorption, red tint, and dynamic viscosity. However, the opposite observations were noted for bulk density, gel formation, lightness, and yellowness of extrudates. The results showed the extrusion–cooking processing is an appropriate and easy-to-use method for the modification of corn–buckwheat blends and the preparation of innovative products.