Impact of Hydrothermal Treatment on the Cell Wall Integrity of Tartary Buckwheat Endosperm Cells and Resulted Starch Digestion Properties

The cell walls in whole grains, acting as capsules, significantly affect the nutritional property of whole grain products, particularly the rate and extent of starch digestion that is associated with glucose homeostasis, but the exact mechanism is still not completely understood. In this study, Tartary buckwheat endosperm cells (TBC), representing cell wall-enclosed starch, were used to examine the relationship between starch gelatinization and in vitro digestibility. Consistent with previous reports, both the digestion rate and extent of starch within intact endosperm cells were significantly lower than those of Tartary buckwheat isolated starch (TBS). Structurally, starch in hydrothermally treated endosperm cells (TBC series) exhibited markedly reduced crystallinity compared with isolated starch, reflecting the constraining effect of the cell wall on starch structures. Additionally, the short-range order of intracellular starch was further disrupted, with crystallinity decreasing to 3.81% in TBC-100. Thermodynamic analysis revealed that the gelatinization temperatures (T₀, T_p, and T_c) of intracellular starch increased along with treatment temperature, while the enthalpy changes were significantly lower than that of free starch, indicating that the cell wall matrix might constrain the enclosed starch, leading to a reduced degree of gelatinization and decreased digestibility. Overall, both cell wall integrity (acting as a barrier) and biochemical factors (soluble inhibitors such as phenolic compounds) might act synergistically to limit amylolytic enzyme activity and decrease starch susceptibility, implicating the central role of cell walls in regulating starch digestion in whole grain foods.