Physical Modification of Starch in Plant-Based Flours: Structural, Physicochemical, and Pasting Property Changes and Potential Applications in Baked and Extruded Products

Unmodified starches and flours have physicochemical and functional limitations that include low solubility, limited swelling power, low water absorption, and a high tendency to retrogradation and syneresis—characteristics that restrict their use in the agri-food industry. To overcome these limitations, several physical modifications have been proposed, such as hydrothermal treatments (heat-moisture treatment, HMT; dry-heat treatment, DHT; and annealing, ANN), as well as extrusion and the use of microwaves. HMT, DHT, and ANN are processes that are performed at low, intermediate, and high-moisture content, respectively. Extrusion employs high temperatures, pressure, and shear forces, whereas microwaves use photon irradiation and dielectric heating. This review focuses on the importance of physical modifications of flours and their effect on the physicochemical, structural, and rheological properties of starch. Flours subjected to these treatments show improvements in their physicochemical characteristics, including a higher content of slow-digestion starch and resistant starch fractions. When applied in the production of baked and extruded products, they enhance texture and extend shelf life, while maintaining acceptable sensory qualities. In addition, these processes increase the versatility of flours from non-conventional sources, such as gluten-free cereals, legumes, roots, and tubers, expanding their possibilities of use in the agri-food industry.