Effects of nitrogen level on structure and physicochemical properties of rice starch

Abstract

Nitrogen application is an important agronomic measure affecting rice growth, yield and grain quality. This study investigated physicochemical properties and the structure of two rice varieties under three different nitrogen levels (0, 150 and 300 kg/ha) at one location in one year. The increasing nitrogen level decreased starch granule size. The granule surface at high nitrogen level was more uneven and pitting compared with non and medium nitrogen level. The apparent amylose content decreased with increasing nitrogen level. The starch samples of all nitrogen levels were in conformity with the characteristics of A-type crystallinity. High relative crystallinity was observed at the high nitrogen level. Starch had lower degree of order at short-rang scale with increasing nitrogen level. Starch samples at the high nitrogen level had higher swelling power and solubility, gelatinization enthalpy, lower pasting properties, gelatinization temperature. This study indicated that nitrogen level significantly affected the structure and physicochemical properties of rice starch, and would provide some information for applications of starch in food and non-food industries.