Effects of hydrothermal pretreatments on thermodynamic and technological properties of red bean starch

Abstract The aim of this study was to investigate the effects of hydrothermal pretreatments (HPs) on the thermodynamic and technological properties of red bean starch. The HP chosen included cooking and autoclaving processes and were applied to beans and red bean starches. To obtain powdered starch, the starch pastes were dried at temperatures of 50, 60, and 70°C in an electric oven with 1,200 W. The diffusion model with boundary condition of the third type was fitted to the experimental data and the thermodynamic properties were calculated. The starches obtained were analyzed for extraction yield, color, and technological properties (apparent viscosity, X‐ray Diffraction (XRD), and DSC). Effective diffusivity values ranged from 7.621 × 10 −9 to 9.815 × 10 −5 m 2 min −1 , which reduced drying time by up to 480 min. Starches submitted to HP showed a decrease in activation energy and an increase in Gibbs free energy. It was observed that for an extraction yield >30%, the highest values were found for the treatments submitted to 70°C, especially for the starch submitted to cooking (SC). Red bean starch presented type A crystalline structure, where its crystallinity index ranged from (27.32%–33.41%) and thermal properties were affected by the application of HPs. Using autoclave HP in starch, it is possible to reduce process costs by reducing drying time, as well as changing the crystal structure and thermal properties. Practical Applications The results obtained contribute to optimize the hydrothermal modification using autoclave and cooking in the grains and starch of several cereals. The HP technique influenced the drying time, consequently reducing the cost of the process. The rheological, thermal, and structural properties were affected, thus being considered a viable treatment for starch modification for large‐scale application, due to the technique being easy to handle, low investment, and not using reagents harmful to the environment.