Structural characterization and Pickering emulsifying ability of Tartary buckwheat starch prepared by natural deep...

In this study, a betaine-ethylene glycol natural deep eutectic solvent (NADES) system was evaluated as a model extraction medium for preparing Tartary buckwheat starch (TBS). The extraction performance, granule morphology, selected physicochemical properties, and Pickering emulsion-forming behavior of NADES-extracted TBS (NADES-TBS) were compared with those of alkali-extracted TBS (AE-TBS). The highest starch content was obtained at a betaine/ethylene glycol molar ratio of 1:4, water content of 15%, and extraction time of 4 h. Under these conditions, the starch content of NADES-TBS was 87.34 ± 0.81%, which was not significantly different from that of AE-TBS (87.84 ± 0.66%), whereas the apparent amylose content was lower (22.95 ± 0.08% vs. 24.14 ± 0.38%). NADES-TBS showed a slightly larger mean particle size (9.194 μm) than AE-TBS (8.329 μm), while both samples retained the A-type crystalline pattern. The relative crystallinity changed only slightly from 30.39 to 31.11%. Compared with AE-TBS, NADES-TBS showed a higher pasting temperature, lower peak viscosity, and lower setback viscosity. In an MCT-water model system, NADES-TBS showed lower oil-water interfacial tension and a contact angle closer to 90° than AE-TBS. Pickering emulsions stabilized by NADES-TBS showed smaller droplet sizes than those stabilized by AE-TBS under the tested short-term conditions. These results indicate that the selected NADES extraction process was associated with changes in granule morphology and selected physicochemical/interfacial properties of TBS. However, because residual ethylene glycol, molecular-level structure, and long-term emulsion stability were not fully evaluated, food-related application and mechanistic conclusions require further verification.