Effect of extrusion conditions on the physical and chemical properties of bean powders

This study aimed to investigate the effects of three extrusion parameters (i.e., feed moisture, feed rate, and die temperature) on expansion volume, moisture, starch digestibility, pasting properties, and solvent retention capacities of two bean varieties (Fuji and Medalist). A Box–Behnken Design of Experiment and Response Surface Methodology were applied, considering three levels for each factor: 20, 27.5, 35 g/100 g for feed moisture; 2, 2.5, 3 kg/hr for feed rate; 70, 100, 130°C for die temperature. Feed moisture significantly affected (p < .05) all the measured characteristics of extruded bean powders, while feed rate resulted often not significant (p > .05). Genotype had a relevant effect on the considered properties; in fact, significant models fitted different response variables for Fuji and Medalist beans. The calculated models are a valid tool for the design of bean powders with specific qualities, to be used as new ingredients in food formulations. Practical applications This study investigates the effects of extrusion feed moisture, feed rate, and die temperature on some physicochemical properties of two bean varieties (Fuji and Medalist) largely available and characterized by a plain taste, thus appreciated by both children and elderly people. The results demonstrate that different starch digestibility, pasting properties, and solvent retention capacities can be obtained by modulating the extrusion conditions and taking into consideration the effect of bean genotype. The application of a Box–Behnken Design of Experiment elaborated by Response Surface Methodology allowed to calculate the reliable models to be used as valid tools for the design of extruded bean powders with specific qualities. Targeted extruded bean powders can be efficiently exploited as new ingredients in food formulations, with advantages for both consumers focused on healthier foods (e.g., diabetes, athletes, and children) and industries willing to better valorize their products.