Microwave-induced complexation between sorghum starch and caffeic acid: Structural modulation and its impact on digestive and retrogradation properties

Microwave-assisted technology offers an efficient and eco-friendly method for starch modification. In this study, sorghum starch (SS) was treated under varying microwave durations and complexed with caffeic acid (CA) to form SS-CA complexes. Microwave treatment significantly reduced crystallinity (24.07 % to 3.51 %), disrupted short-range order, and caused granule swelling, aggregation, and decreased thermal stability. Complexation induced a <i>V</i>-type inclusion structure. The SS-CA (120 s) complex showed a 9.17 % reduction in rapidly digestible starch (RDS) and a 14.40 % increase in resistant starch (RS). Molecular docking and DFT analyses confirmed that hydrogen bonding and van der Waals forces dominated SS-CA interactions. During 0-7 days of storage, free water content in the SS-CA gel increased only 1.58 % compared to 5.93 % in native SS, indicating reduced retrogradation. The SS-CA complex displayed lower gelatinization enthalpy and improved phase stability. These findings suggest the potential of microwave-assisted SS-CA complexes in developing low-glycemic starch-based foods.