Optimization of Single-Screw Extrusion Processing Variables to Develop Valorized Breakfast Cereals Using Brewers’ Spent Grain (BSG) and Cranberry Pomace with Soy Flour and Rice Flour

This study optimized extrusion conditions for breakfast cereal production using brewers’ spent grain (BSG), soy flour, and rice flour, and investigated the effect of cranberry pomace incorporation on textural and sensory properties. Thirteen extrudates using a central composite rotatable design (CCRD) with the variation of extrusion temperature (131–159 °C) and extruder’s screw speed (258–342 rpm) were developed. Response surface methodology (RSM) was applied to model physicochemical properties such as expansion ratio, hardness, crispness, density, porosity, rehydration ratio, water solubility index, L-value, and total color difference. Both temperature and screw speed significantly (P < 0.05) affected these properties with model prediction accuracies ranging from 80 to 97%. Optimal conditions (135–138 °C and 290–300 rpm) produced extrudates with desirable structural and textural characteristics. Cranberry pomace (0–15%) was subsequently incorporated to observe the influence of coprocessing multiple fiber-rich byproducts on the textural and sensory properties. Textural and sensory evaluation indicated that up to 5% cranberry pomace could be incorporated while maintaining consumer preference. These findings demonstrate the feasibility of coutilizing food byproducts to develop valorized extruded breakfast cereals.