Understanding the relationship between multi-scale structures and functional properties of starch from wheat grains stored for different periods

The multi-scale structure and functional properties of starches isolated from wheat grains stored for different periods (1–3 years) were estimated, and the relationship between starch hierarchical structure and functionalities was elucidated. Results indicated that the activities of α-amylase and debranching enzyme reduced after storage, but the continuous action of amylase may degrade the molecular structure and destroy the intra- and inter-molecular hydrogen bonds within starch granules, thus generating elevated ratios of short A chains and amorphous fractions, which caused the decline of double-helix content (44.8%–39.4%), short-range ordered degree (R_1045/1022, 0.91–0.82), relative crystallinity (25.23%–22.53%) and crystalline lamellae thickness (d_c, 7.03–6.73 nm), along with noticeable erosion on granular surface. The disorganizations or disordering of ordered hierarchical structures may weaken the interactions and entanglements among starch molecular chains, thus reducing the peak and final viscosity of aged starches but facilitating their enzyme hydrolysis. These changes were more evident with prolonged storage (from 1 to 3 years). These findings may provide an in-depth understanding on the structure-functionality relationship of starch in wheat grains during storage and improve the utilization of aged wheat.