Effects of Nitrogen Rate on Granule Size Distribution and Gelatinization Characteristics of Starch in Corn Kernels

Purpose Effects of nitrogen fertilizer on the granule size distribution and gelatinization characteristics of corn starch were determined by different nitrogen rates.

Method Corn cultivar, ‘Zhengdan 958’, was used to investigate the effect of nitrogen application rate pure nitrogen 0 (N₀), 135 (N₁), 270 (N₂) and 405 (N₃) kg/hm² on the starch granule size distribution and gelatinization properties in corn kernels.

Result The size of starch granule was in the range of 0.40−19.5 μm for ‘Zhengdan 958’. The volume and surface area distribution of starch granules showed the typical two populations of starch granules. The corn starch granules were divided into three groups including small (<1.5 μm), medium (1.5-12 μm) and large (>12 μm) starch granule groups at the maturity. A typical population of number distribution of starch granules was showed in this study. More than 98% of the total number came from small starch granules, which indicated that the corn endosperm starch granules are mainly composed of small starch grains. Under the conditions of increasing nitrogen fertilizer, the percentage of medium starch granules increased significantly. The medium nitrogen led to a significant increase in volume percentage of small and medium starch granules and decline in those of large starch granules, respectively. In addition, medium nitrogen led to a significant decline the peak and trough viscosities in corn kernels. Correlation analysis showed that the peak, trough and final viscosities were negatively related to volume percentage of small and medium starch granules, and positively related to volume percentage of large starch granules. It indicated that large starch granules had more the values of gelatinization parameters.

Conclusion The results suggested that appropriate nitrogen fertilizer increased the volume percentage of small and medium starch granules, and decreased volume percentage of large starch granules, and thus decreased peak, trough and final viscosities in corn kernels.