Effects of Nitrogen Rates on the Physicochemical Properties of Waxy Maize Starch

Appropriate nitrogen fertilization is essential for improving grain yield and starch quality, while reducing N fertilizer costs. The starch physicochemical properties of two waxy maize hybrids, namely, Suyunuo5 (SYN5) and Yunuo7 (YN7), under N rates of 0 (zero N application [N0]), 150 (low N rate [LN]), 225 (moderate N rate [MN]), and 300 (high N rate [HN]) kg ha(-1) are elucidated. Grain starch content initially increases, peaks at MN, and decreases as N rate is increased. N fertilization reduces the starch granule size of YN7. The starch granule size of SYN5 increases under MN. SYN5 exhibits high short/long amylopectin chain ratios under LN and MN. The short/long amylopectin chain ratio of YN7 is unaffected by MN but is increases by LN and HN. The swelling power of YN7 is similar among different N levels, whereas that of SYN5 increases under N fertilization. N fertilization changes starch pasting and thermal properties. Starch with large granules exhibit high trough, final, and setback viscosities and gelatinization temperatures. Starch with high long-chain ratios is susceptible to retrogradation. In conclusion, appropriate N application (225 kg ha(-1) for SYN5 and 150 kg ha(-1) for YN7) favors starch accumulation, and starch has high viscosity and low retrogradation tendency.