Enhancing starch leaching and structural reconfiguration of rice through spatial separation and microwave-assisted cooking

Non-continuous rice-water contact (NRWC) cooking has emerged as a promising strategy for regulating starch leaching and improving the quality attributes of cooked rice. However, the mechanisms by which different spatial separation architectures influence starch migration and structural evolution remain poorly understood. This study aimed to investigate the effect of emerging non-continuous rice-water contact strategies on the starch leaching behavior and morphological properties in cooked rice. Cooked rice and rice soup were prepared using various spatial separation cooking methods, including full immersion, percolation, steam-lift cooking, and microwave-assisted steam-lift cooking (MW-SC). The microstructural characteristics, particle size distribution, starch-protein framework, short-range ordered structure, crystal structure, thermal property, and water migrations were analyzed. Compared to the control rice treated with traditional immersion, MW-SC significantly intensified starch leaching and water content. Examination of rice structure revealed the cooking rice treated by MW-SC displayed a three-dimensional porous network characterized by pronounced surface roughness, with decreased average particle size. Confocal laser scanning microscopy analysis demonstrated that the starch-protein framework was pronounced damaged. Crucially, while the crystalline polymorph and functional groups of rice starch remain intact, MW-SC induces a marked reduction in relative crystallinity and short-range order. Macroscopically, the hardness, and adhesiveness of cooking rice was reduced by MW-SC with water absorption and starch solubilization. Our findings establish a direct causal link between spatial separation architectures and starch leaching behavior, providing a mechanistic basis for next-generation cooking appliances designed to precisely engineer rice texture and nutritional profile.