Effects of nitrogen and sulfur fertilizer treatment on the structure and physicochemical properties of resistant starch in buckwheat

Abstract

This study investigated the combined application of nitrogen and sulfur fertilizers on the structural characteristics and physicochemical properties of buckwheat resistant starch. The results showed that combined fertilization did not change the crystalline diffraction pattern of the resistant starch samples (exhibiting a B-type crystalline structure), but significantly (p < 0.05) increased the relative crystallinity (35.07–44.36 %). In addition, combined fertilization enhanced resistant starch content (28.36–35.22 %), apparent amylose content (20.50–35.06 %), particle size, pasting temperature (50.30–50.66 °C) and gelatinization enthalpy (2.77–4.65 J g⁻¹). Conversely, higher fertilization levels were associated with lower light transmittance, water solubility, swelling power and viscosity. Pearson's correlation analysis revealed that buckwheat resistant starch and apparent amylose content were significantly (p < 0.01) positively correlated with particle size and gelatinization temperatures, while negatively correlated with viscosity. This study provides a theoretical basis for optimizing the application of nitrogen and sulfur fertilizers to improve the properties of buckwheat resistant starch.