Unraveling in-kernel starch multiscale structure and nutritional profiles of thermal remodeling whole grain black tartary buckwheat

Thermal treatments can improve the processing suitability and nutritional utilization of cereals. In this study, the effects of three thermal treatments, namely heat fluidization, microwave, and baking, on the physical, nutritional, and structural properties of whole grain black Tartary buckwheat (BTB), as well as the multiscale structures and digestive characteristics of in-kernel starches, were evaluated. Thermal treatments induced grain expansion, surface cracking, and porous internal structures, with heat fluidization causing the most significant reduction (32.06 %) in kernel hardness. Heat fluidization also enhanced rutin extractability by 68.00 % and antioxidant activities. Volatile compound analysis revealed heat fluidization reduced aldehyde and hydrocarbon levels, especially reducing hexanal from 27.06 to 3.86 mg/kg. For in-kernel starches, heat fluidization increased cold-water viscosity (56-fold), disrupted A-type crystallinity (relative crystallinity dropped to 8.49 %), reduced short-range ordered structure (R_993/1018 decreased by 2.21 %), and enhanced resistant starch content (33 %). The study highlighted heat fluidization as the most effective method for enhancing processing and nutritional properties of whole grain BTB, offering insights for developing nutrient-dense whole grain products.