Relationship between nitrogen fertilizer and structural, pasting and rheological properties on common buckwheat starch

•Increased nitrogen level reduced amylose content but increased ash content.•All the common buckwheat starches showed typical A-type XRD pattern.•High relative crystallinity were observed under high nitrogen level.•Samples had higher gelatinization enthalpy with increasing nitrogen level.•Nitrogen fertilizer led to a decrease in the storage modulus and loss modulus. Nitrogen is an essential element for the yield and quality of grain. In this study, the structural and physicochemical properties of two common buckwheat varieties under four nitrogen levels (0, 90, 180, 270 kg N ha−1) at one location in two years were investigated. With increasing nitrogen level, the contents of moisture and amylose decreased but the contents of ash and crude protein increased. Excessive nitrogen application significantly increased the granule size, but reduced the light transmittance, water solubility, swelling power, absorption of water and oil. All the samples showed a typical A – type pattern, while high relative crystallinity and low order degree were observed under high nitrogen level. The samples under high nitrogen level had lower textural properties, pasting properties and rheological properties but higher pasting temperature and gelatinization enthalpy. These results indicated that nitrogen fertilizer significantly affected the structural and physicochemical properties of common buckwheat starch.