Energy-driven structural transformation in rice starch: A multi-scale rheological investigation of rice flour systems

Rice flour exhibits broad-spectrum applications in gluten-free and texture-engineered foods. However, its functional attributes remain difficult to predict due to fragmented understanding of the relationships among milling effects, starch structure and rheology, particularly under industrially relevant thermal and mechanical processing conditions. The current review presents a reinterpretation of rice milling as an energy-dependent structural preconditioning phenomenon, rather than treating rice milling as a simple particle-size reduction step, where energy is defined in terms of specific mechanical energy, stress intensity and stress history. It integrates current evidence on how mechanical energy input, moisture availability and thermo-mechanical coupling influence hierarchical starch transformations. These energy dependent changes regulate the development of damaged starch, crystalline-amorphous equilibrium, redistribution of polymers and starch-protein-lipid interactions, leading to orchestration of elastic-viscous transitions and temporally modulating rheological behavior including structural recovery. Evidence from multiscale rheological techniques such as Rapid Visco Analysis (RVA), Small-Amplitude Oscillatory Shear (SAOS), Large-Amplitude Oscillatory Shear (LAOS), and recovery tests, indicates that rice flour rheology cannot be adequately explained by individual compositional or structural parameters alone without accounting for processing history and stress-induced structural changes. On this basis, this review proposes a conceptual framework for rheology-oriented milling that links energy input, structural transformations and rheological responses, providing a foundation for the rational selection of milling conditions to obtain rice flours with defined processing behavior and targeted nutritional functionality.